Category Archives: Ice crystals

Wintertime cold Cumulonimbus clouds erupt with sprinkles and snow flurries; no damage reported

One passed over at 9:19 AM with a hard multi-second, surprise rain shower.  One person reported a couple of graupel, or soft hail particles. Tipped the bucket, too; 0.01 added to our Sutherland Heights storm total.  Its now at 0.23 inches.  Of course, there was no damage, but putting that word in a title might draw “damage trollers”, increase blog hits….

The rest of the day was clouds withering, getting mashed down on tops as bases rose and tops settled back, then suddenly, about 3:30 PM, small areas of ice crystals began to show up in a couple of spots, and, boy, did things take off after that.  Tops were lifting to higher temperatures, likely due to an approaching trough, one that otherwise is too dry to do much else.

Honest to goodness cold, wintertime Cumulonimbus clouds formed, though not very deep ones.  Probably of the order of 2-3 km thick is all (eyeball estimate).

But with our cold air aloft, tops were well below -20° C (4° F), lots of ice formed in them and produced streamers of ice and virga across the sky, and in tiny areas, the precip got to the ground.

And with “partly cloudy” conditions, there were lots of gorgeous, highlighted scenes around the mountains.

Let us review yesterday’s clouds and weather and not think about the future too much, starting with an afternoon balloon sounding temperature and dew point profile from IPS MeteoStar:

The Tucson balloon sounding ("rawinsonde" in weatherspeak) launched about 3:30 PM yesterday. Takes about an hour to reach 60,000 feet, but goes higher. Cloud bases were just about at the top of Ms. Mt. Lemmon. Tops were only around 18,000 feet above sea level, but were extremely cold for such small clouds.
The Tucson balloon sounding (“rawinsonde” in weatherspeak) launched about 3:30 PM yesterday. Takes about an hour to reach 60,000 feet, but goes higher. Cloud bases were just about at the top of Ms. Mt. Lemmon. Tops were only around 18,000 feet above sea level, but were extremely cold for such small clouds.  Hence, they were only about 9,000 feet thick at their maximum.

So what do clouds look like when they have tops as cold as -28°Ç?

Well, I really didn’t get a good profile shot of those clouds, they were either too close, obscured by other clouds, or too faraway, so instead let us look at two dogs looking at something as a distraction:

4:11 PM. Dogs observing a plethora of glaciating Cumulus clouds, transitioning to Cumulonimbus.
4:11 PM. Dogs observing a plethora of glaciating Cumulus clouds, transitioning to Cumulonimbus.

Well, let’s start this when the ice first appeared in a cloud, much later in time than what was thought here yesterday morning.  If you logged this “first ice” you are worthy of a merit, a star on your baseball cap:

3:24 PM. FIrst ice of the day, finally, spotted on the SW horizon. The file size is huge so that you can see it for yourself. I had just about given up on ice in clouds, Notice, too, how small the clouds are at this time.
3:24 PM. FIrst ice of the day, finally, spotted on the SW  and WSW horizon in two little areas. The file size is huge so that you can see it for yourself. I had just about given up on ice in clouds, Notice, too, how small the clouds are at this time.

Well, while flawed from a cloud profile sense, here’s what they were looking at, it was the best I could do:

4:19 PM. Note sunlit shower reaching the ground.
4:19 PM. Note sunlit shower reaching the ground.  The hazy stuff is ice crystals, a lot of them all over the place.
4:22 PM. A close up in case you don't believe me that the rain was reaching the ground.
4:22 PM. A close up in case you don’t believe me that the rain was reaching the ground.  I sometimes find that credibility is lacking here.
4:39 PM. Eventually a cluster of precipitating clouds developed near the Catalina Mountains and here are dropping snow and graupel trails.
4:39 PM. Eventually a cluster of precipitating clouds developed near the Catalina Mountains and here are dropping snow and graupel trails.

Let us go zooming:

4:39 PM. Shaft up close. That dark, narrow line in the middle is without doubt a soft hail (graupel) strand. THere might be others, but this one is obvious. The verticality is due to faster falling particles, which graupel are because they are ultimately snowflakes that have captured cloud droplets on the way down, making them much heavier than just a snowflake.
4:39 PM. Shaft up close. That dark, narrow line in the middle is without doubt a soft hail (graupel) strand. THere might be others, but this one is obvious. The “verticality” is due to faster falling particles comprising that strand, which graupel are because they are ultimately snowflakes that have captured cloud droplets on the way down, making them much heavier than just a snowflake.
4:48 PM. Just snow falling out, no real "verticality", a sign of graupel falling out.
4:45 PM. Just light snow falling out here on the Catalinas, no real “verticality” in this shaft, which would be a sign of graupel falling out.
4:46 PM. An opening allowed this distance cross section of a cold, wintertime Cumulonimbus (capillatus) cloud streaming a shield of ice and virga downwind.
4:46 PM. An opening allowed this zoomed cross section of a cold, wintertime Cumulonimbus (capillatus) cloud streaming a shield of ice and virga downwind.  On the left sloping-upward part, the Cumulus turrets still contain liquid droplets (have that ruffled, hard look associated with the higher concentrations that go with droplet clouds compared to all ice clouds).  Sometimes, in spite of the low temperature, here, from the sounding the top is likely approaching the minimum temperature of -28°C, droplets can still survive for a short time before freezing, giving way to lower concentrations of ice crystals.   That appears to be the case here at the tippy top. of the cloud in the back  What is interesting here, an enigma, is that the foreground cloud in front of the cloud I was just discussing,  is clearly all ice from the smallest element to its top and mimics the cross section of the background cloud.  Could it be that its simply older and ice generated in the colder regions has permeated the whole cloud?

Below, diagrammed:

Same photo with writing on it since the written explanation didn't seem very satisfactory.
Same photo with writing on it since the written explanation didn’t seem very satisfactory.
5:07 PM. Graupel in the Gap (the Charouleau one). Well, maybe its a little beyond the gap.
5:07 PM. Graupel in the Gap (the Charouleau one). Well, maybe its a little beyond the Gap, but it sounded good to write that..  This started to fall out of a Cumulus congestus transitioning to a Cumulonimbus.  The first particles out the bottom are always the heaviest, hence, graupel or hail.

Looking elsewhere, there are snow showers everywhere!

5:08 PM. Nice shafting over there near Romero Canyon. Pretty straight up and down, so likely has a lot of small graupel in it.
5:08 PM. Nice shafting over there near Romero Canyon. Pretty straight up and down, so likely has a lot of small graupel in it.
5:08 PM. Looking down Tucson way, this is NOT a graupel shaft. Sure the particles are large, but look at how they're just kind of hanging, getting mixed around by a little turbulence. Guess aggregates of dendrites, ice crystals that grow like mad around -15° C, and because of being complex, often lock together when they collide. Its not unusual to have 20 or more single stellar. dendritic fern like crystals locked into a single snowflake and that would be a good guess about what this is. Where the bottom disappears, likely around 3000 feet above sea level, is where those big aggregates are melting into rain drops
5:08 PM. Looking down Tucson way, this is NOT a graupel shaft, but rather gently falling large snowflakes.. Sure the particles are large, but look at how they’re just kind of hanging there getting mixed around by a little turbulence, almost forming a mammatus look. There are likely aggregates of dendrites, fern-like ice crystals that grow like mad around -15° C, and because of being complex forms, often lock together when they collide. Its not unusual to have 20 or more single stellar. dendritic crystals locked into a single snowflake. Where the bottom disappears, likely around 3000 feet above sea level, is where those big aggregates are melting into rain drops.
5:10 PM. Interrupting the tedium with a nice neighborhood lighting scene as a sun poked between clouds.
5:10 PM. Interrupting the tedium with a nice neighborhood lighting scene as a sun poked between clouds.  We’re not completely cloud-centric here, but close.
5:26 PM. This strange scene of a very shallow snow cloud, completely composed of ice and snow, obscuring the tops of the Catalinas, but being very shallow, hardly above them may explain the cross section enigma. The snow cloud here is all that remains of a much deeper cloud that converted to all ice, then those crystals just settling out, the whole cloud dropping down as a snow flurry. It may well have been as deep as the cloud top on the left or higher before converting to ice and just falling to the ground en masse. Or is it, en toto?
5:26 PM. This strange scene of a very shallow snow cloud, completely composed of ice and snow, obscuring the tops of the Catalinas, but being very shallow, hardly above them may explain the cross section enigma. The snow cloud here is all that remains of a much deeper cloud that converted to all ice, then those crystals just settling out, the whole cloud dropping down as a snow flurry. It may well have been as deep as the cloud top on the left or higher before converting to ice and just falling to the ground “en masse.” Or is it, “en toto“?  What makes this odd is that there is usually some “cloud ice” (ice particles too small to have much fall velocity) at the level from which the precip fell from. You don’t see that here; just a belt of light snow.   Maybe this is why there was that shallow, glaciated cloud  in the Cumulonimbus cross section shot…..  That shalllow cloud was not a new portion, but rather a tail dragger like this stuff, once having been much higher and was actually ice settling out, not new rising, glaciated cloud.  From the back side, you can see that this ice cloud would appear to slope up  if viewed from the east instead of the west like our cross section iced out cloud.  Setting a record for hand waving today.  IS anybody still out there?  I don’t think so.  Maybe I need another dog picture….
5:34 PM. Here's the last of that unsual snow cloud as its last flakes settled to the ground.
5:34 PM. Here’s the last of that unsual snow cloud as its last flakes settled to the ground.

The day concluded with a very nice sunset:

5:53 PM. Sunset color with shafts of snow down Tucson way.
5:53 PM. Sunset color with shafts of snow turning to rain down Tucson way.

 

Now, the long dry spell…  Break through flow from the Pacific under the “blocking high”  eventually happens about a week away now, but more and more looks like that flow might stay too far to the north of us, rather blast northern Cal some more,  and not bring precip this far south.  The blocking high needs to be in the Gulf of AK, but now is being foretold to be much farther north…

The End, gasping for air here.  More like a treatise than a quick read!

Sutherland Heights storm total now 0.71 inches as of 7 AM; soil turning green as moss look alike growth reminding one of Seattle spurts from bare ground!

First, in blogging for dollars, this:

3:55 PM. Rainbow fragment and solar home. Yesterday's visual highlight. Yours for $1995.95. If you call now, we'll throw in a exact same photo FREE!
3:55 PM. Rainbow fragment and solar home, an extraordinary combination.. It was yesterday’s visual highlight. Yours for $1995.95. And, if you order now, we’ll throw in a second,  exact copy of this extraordinary, magical scene FREE!

Here’s a nice one from the day before as the clouds rolled in, starting with Cirrus and Altocumulus, lowering to Stratocumulus later in the afternoon.

5:04 PM, 30 Dec.
5:04 PM, 30 Dec.  Sun break amid Stratocumulus.  Stratus fractus topping mountains.

Yesterday’s clouds; an extraordinary day with a little drizzle amid light showers

Hope you noticed the true drizzle that occurred yesterday, namely, fine (larger than 200 microns, smaller than 500 microns in diameter), close TOGETHER (critical to the definition of “drizzle”) drops that nearly float in the air. They may make the least impression, or none, when landing in a puddle.

When you see drizzle, you have the opportunity of chatting up your neighbor by educating them informally to what drizzle really is (many, maybe most,  TEEVEE weatherfolk do NOT know what “drizzle” is, btw), and 2) by telling your neighbor, if he/she is still listening to you, that the droplets in the clouds overhead must be larger than 30 microns in diameter, or better yet, “larger than the Hocking-Jonas diameter of 38 microns, at which point collisions with coalescence begins to occur” and  “drizzle is not produced by ice crystals in the clouds overhead; they’re not enough of them to produce ‘fine, close together drops.'” Your neighbor has likely left the building at this point, but, oh, well, you tried.

Here, in Arizona, shallow clouds, such as we had yesterday, hardly ever can produce the broad droplet spectrum in which clouds have droplets larger than 30 microns in diameter.  Its because this far inland from the ocean, where the air is very clean,  the air has picked up natural and anthro aerosol particles that can function as “cloud condensation nuclei” (CCN).   As a result of ingesting dirt and stuff, clouds have too many droplets here as a rule for the droplets in them to grow to larger sizes.   They’re all mostly less than 20-25 microns, sizes in which even if they collide, they can’t coalesce.

In “pristine” areas, if you go to one, such as on a cruise out in  the oceans, droplet concentrations in clouds are much lower, and even a little water that might be condensed in a shallow cloud can produce a broad spectrum, one that extends to droplet larger than 30 microns.

So even little or shallow layer clouds can precip over the oceans, produce drizzle or light rain showers (in which the larger drops are bigger than 500 microns in diameter).  Of course, here we recall that the (whom some consider “villainous”) geoengineers want to stop drizzle out over the oceans so that clouds have longer lifetimes, are darker on the bottom, and reflect more sunlight back into space.

Those guys can be lumped into the same ilk as those who want to change the color of the sky from blue to whitish or yellowish by adding gigantic amounts of tiny particles in the stratosphere, again for the purpose of cooling the planet!  Unbelievable.  Please ask before doing this!!!

A Pinatubo sampler for what “geoengineering” would do to our skies,  say, sunsets in particular.  I took this photo from the University of Washington’s research aircraft in 1992 off the Washington coast in onshore flow.  But we saw these same sunsets, sunrises, yellowed by the Pinatubo eruption of June 1991 everywhere we went, including in the Azores in June 1992.

AB469_mf9193_1517_ontop Sc_Pinatubo above

OK, pretty boring, whiney, really, so inserting picture of a nice horse here to make people feel better if you’ve been depressed about what our scientists have been pondering to do about global warming other than controlling emissions:

8:57 AM. Zeus. Led cloistered life for 13 years; likes to bolt now that he's getting out.
8:57 AM. Zeus. Led cloistered life for 13 years; likes to bolt,  now that he’s getting out on the trails.
7:40 AM, yesterday, Dec. 31st.
7:40 AM, yesterday, Dec. 31st.  The low hanging Stratocumulus clouds, about 1500 feet above Catalina, and the mountains had a bit of an orange tinge.  It was probably due to sunrise color on a separate much higher layer.

Later….drizzling Stratocumulus, same view:

10:30 AM. Stratocumulus praecipitatio, if you want to go "deep" into cloud naming. "Stratiformis", too, covers a lot of the sky.
10:30 AM. Stratocumulus praecipitatio, if you want to go “deep” into cloud naming. “Stratiformis”, too, covers a lot of the sky. Note misty-like view, lack of shafting.
12:48 PM. More Stratocu P., an example of those clouds in the distance that kept dropping little and light rain showers on Catalina.
12:48 PM. More Stratocu P., an example of those clouds in the distance that kept dropping little and light rain showers on Catalina.
1:01 PM. Highlighting amid the RW-- , (weather text for "very light rain showers").
1:01 PM. Highlighting amid the RW– , (weather text for “very light rain showers”).  Stratcu P., with maybe Stratus fractus or Cumulus fractus below.  The shadowed,  dark shred clouds  in the mddle would be Stratus fractus IMO.
3:55 PM. Zooming in on that pretty rainbow. You know, this is a cloud heaven here. I hope you all appreciate it!
3:55 PM. Zooming in on that pretty rainbow. You know, this is a cloud heaven here. I hope you all appreciate it!  Maybe that’s why I get upset over “geoengineering” and changing the sky anywhere.
3:57 PM. Between showers, but new ones erupted upwind. This one have a shaft, implying a higher cloud top than the prior, non-shafting clouds that brought us semi-steady RW--.
3:57 PM. Between showers, but new ones erupted upwind. This one have a shaft, implying a higher cloud top than the prior, non-shafting clouds that brought us semi-steady RW–.

The second extraordinary thing about yesterday was that the top temperatures of these clouds was around -10° C (14° F), temperatures that ice does not form act as a rule in Arizona.  To get ice at temperatures that high, you also need larger cloud droplets, and they have to occur in the -2.5° C to -8° C range.  In this range, it was discovered that falling ice crystals, mostly faster falling ones like “graupel” (aka, soft hail) when colliding with larger drops, ice splinters are produced.  The cloud droplets must be larger than 23 microns in diameter in THAT particular temperature zone, something that would occur more often in our warm,  summer clouds, but would rarely be expected in our winter ones.

Why?

Again,  it goes back to clouds in inland regions ingesting lots of natural and anthro aerosols that cut down on droplet sizes in clouds (by raising droplet concentrations in them).  Our recent rains have helped cut down on that process on ingesting dirt, for sure, and was a likely player yesterday.  Furthermore, our winter clouds are moisture challenged relative to the summer ones with their tropical origins and high cloud base temperatures, a second reason not to expect larger droplets in our winter clouds.

Here  is the TUS sounding with some writing on it for yesterday afternoon from IPS MeteoStar.  (Satellite imagery was also  indicating warmer than usual tops for precipitating clouds yesterday.):

The TUS balloon sounding ("rawinsonde" in techno speak) launched at about 3:30 PM yesterday afternoon. Balloon rises at about 1,000 feet a minute, FYI. Typically they pop up around 100,000-120,000 feet! Instruments are parachuted down. Sometimes they are found and returned to the NWS and re-used! How great is that?
The TUS balloon sounding (“rawinsonde” in techno speak) launched at about 3:30 PM yesterday afternoon. Balloon rises at about 1,000 feet a minute, FYI. Typically they pop up around 100,000-120,000 feet! Instrument package is parachuted down so it doesn’t conk somebody on the head. Sometimes they are found and returned to the NWS and re-used! How great is that?

Here’s the punchline:  If clouds are drizzling, then they are ripe, if the tops get to lower temperatures than about -4° C for what we’ve termed “ice multiplication” or “ice enhancement”.  A very few natural ice nuclei at temperatures between -4° and -10° C, say, starts the process, those forming “soft hail” which then leads to ice splinters.  This is the leading theory of this anomaly of ice in clouds at temperatures only a little below freezing, if you think 23° to 14° F fits that definition.

There are exceptions where this process did not explain the ice that formed at such high temperatures, so standby for further elucidation about how in the HECK ice forms in clouds at some point in the future.

As usual, no time to proof, so good luck in comprehending what’s been written.

The weather just ahead:

The second main rainband is just about here at 9:25 AM.  Cloud tops will be deeper and colder than in the prior rains, raising the possibility of some thunder today, and maybe another third of an inch of rain.  Watch for an windshift line cloud (“arcus” cloud) might well be seen today.  That’s always dramatic and exciting here in Catalina cloud heaven.

The End at last!

And a happy, weatherful year to all!

An unbelievably long blog about a surprise afternoon sprinkle of rain

A very few small, isolated drops fell between 4:50 and 5 PM here in Sutherland Heights from what appeared to be nothing overhead. You’d have to be really good to have not been driving, and to have anticipated the possibility (by recognizing ice in upwind clouds) and then having observed it.  You would be recognized, given some extra adulation,  at the next cloud maven junior meeting if you did observe it, that’s for sure.

So, a long blog about anticipating and observing a sprinkle of rain (RW—, “RW triple minus” in casual weatherspeak or text).

We start with some nice, but inapplicable to our main story photos from yesterday.

3:14 PM. Another one of those, to me, memorable, dramatic shots just because of cloud shadows on our pretty mountains caused by Cumulus humilis and mediocris clouds; Cirrus uncinus on top.
3:14 PM. Another one of those, to me, memorable, dramatic shots just because of cloud shadows on our pretty mountains caused by Cumulus humilis and mediocris clouds; Cirrus uncinus on top.
3:15 PM. Pretty CIrrus uncinus, "Angel's hair."
3:15 PM. Pretty CIrrus uncinus, “Angel’s hair.”
3:15 PM. Looks like a cloud street off the Tucson Mountains, one that streamed toward Catalina. Hope you were unbusy enough to notice it. Its a pretty common one here when the lower level winds are out of the SSW, and the clouds shallow.
3:15 PM. Looks like a cloud street off the Tucson Mountains, one that streamed toward Catalina. Hope you were “unbusy” enough to notice it. Its a pretty common one here when the lower level winds are out of the SSW, and the clouds shallow.
3:50 PM. Shadow quirk. The cloud shadow follows the terrain line. Wow. Never seen that before, but I suppose if you had an infinite number of monkeys watching, they'd see it all the time. Maybe they would type out some Shakespeare as well in time.
3:50 PM. Shadow quirk. The cloud shadow follows the terrain line. Wow. Never seen that before, but I suppose if you had an infinite number of monkeys watching, they’d something like this all the time. Maybe they’d type out some Shakespeare as well in time.
3:54 PM. While busy watching the cloud-sahdow dappled mountains, some honest-to-goodness Cumulus congestus arose in a line to the southwest! Not at all expected! Looks like they're tall enough to form ice, but don't see any. Will take too many photos to see if any develops though.
3:54 PM. While busy watching the cloud-sahdow dappled mountains, some honest-to-goodness Cumulus congestus arose in a line to the southwest! Not at all expected! Looks like they’re tall enough to form ice, but don’t see any. Will take too many photos to see if any develops though.
3:56 PM. That poor turret that first extruded from this line (center raggedy one) is being ravaged by "entrainment", that cloud killing process wherein the surrounding dry air gets in and kills off the droplets. Pretty sad when you think about. It also shows you just how friggin' dry the air was just above the main tops. No ice visible here.
3:56 PM. That poor turret that first extruded from this line (center raggedy one) is being ravaged by “entrainment”, that cloud killing process wherein the surrounding dry air gets in and kills off the droplets. Pretty sad when you think about. It also shows you just how friggin’ dry the air was just above the main tops. No ice visible here.
3:56 PM. Let's zoom in to be sure. Anyone saying they can see some ice in this is either an ice-detecting genius or just play lying.
3:56 PM. Let’s zoom in to be sure. Anyone saying they can see some ice in this is either an ice-detecting genius or just plain lying. BTW, that turret on the left, partially visible, is much taller, so its got a good chance to convert to ice.

Ann DSC_7808

3:58 PM. Now even little tiny babies can see the ice that formed in that now dessicated turret. This means some rain fell out of it! Wow, did not see that coming today.
3:58 PM. Now even little tiny babies can see the ice that formed in that now dessicated turret. This means some rain fell out of it! Wow, did not see that happening today.
3:58 PM. Pulling back to grab the whole scene, those Cumulus congestus clouds converting to small Cumulonimbus clouds that will bring those few tiny drops to Catalina in an hour.
3:58 PM. Pulling back to grab the whole scene, those Cumulus congestus clouds converting to small Cumulonimbus clouds that will bring those few tiny drops to Catalina in an hour even as the dry air up there wasted them. Real cloud mavens would be thinking about the possibility of rain here, seeing the ice form in clouds upwind of us, that right at that time! Congratulations!
4:09 PM. Doesn't look that great now, but areas of ice visible, and its heading this way with a light shower falling out of it! Maybe we'll pick up another trace!
4:09 PM. Doesn’t look that great now, but areas of ice visible, and its heading this way with a light shower falling out of it! Maybe we’ll pick up another trace! But what cloud name would you put on this scene? Well, its kind of embarrassing to call them “Cumulonimbus”, but we do have a suitable moniker for weakly-producing Cumulus ice clouds with a little precip, Cumulus congestus praecipitatio. Yep, that’s the name I would use here since the rain is reaching the ground (is not just producing virga).
4:30 PM. Code 1 rain shaft, a transparent one. We're going to a LOT of trouble for a trace of rain here! But, you should have been really excited by this time. The possiblity of rain is just minutes away, but you'll have to be outside to notice it!
4:30 PM. Code 1 rain shaft, a transparent one. We’re going to a LOT of trouble for a trace of rain here! But, you should have been really excited by this time. The possiblity of rain is just minutes away, but you’ll have to be outside to notice it!
4:40 PM. Drawing back to look at the whole scene, which is not that great. Bottom of sprinkle cloud has evaporated leaving that big patch of ice, left side of photo. Can the sprinkle heading toward us survive? Your heart probably was really pounding at this point since you wanted to see some drops so BAD, report that trace the next day, one that maybe only you would have noticed.
4:40 PM. Drawing back to look at the whole scene, which is not that great. Bottom of sprinkle cloud has evaporated leaving that big patch of ice, left side of photo. Can the sprinkle heading toward us survive? Your heart probably was really pounding at this point since you wanted to see some drops so BAD, report that trace the next day, one that maybe only you would have noticed.
4:47 PM. Three minutes to first drops, though here no drops would be reaching the ground from the condition the cloud is in now, its too high, just really anvil ice, and the ice crystals too small, The drops that are going to be intercepted are surely the last ones reaching the ground, the top of the sprinkle shaft, above which there are no more drops.
4:47 PM. Three minutes to first drops, though here no drops would be reaching the ground from the condition the cloud is in now, its too high, just really anvil ice, and the ice crystals too small, The drops that are going to be intercepted are surely the last ones reaching the ground, the top of the sprinkle shaft, above which there are no more drops.
4:55 PM. Drops are collecting on the windshield a few hundred yards from the house with almost no cloud aloft at this point!
4:55 PM. Drops are collecting on the windshield a few hundred yards from the house with almost no cloud aloft at this point! A trace of rain has been logged!

The End

(What about those gorgeous Cumulus congestus and Cumulonimbus calvus clouds over toward and well beyond Charouleau Gap about this time? Maybe later or tomorrow.)

Evening thunderstorms roll across Catalina with apocalyptic cloud scenes

Some apocalyptic cloud scenes can be Cumulus that explode suddenly into Cumulonimbus,  and Cumulonimbus clouds with their foreboding (unless you live in a desert)  rain shafts,  and their predecessor shelf clouds like “swirly dark Stratocumulus”, and arcus clouds, the latter, a lower line of clouds just above and a little behind the wind shift at the ground, usually just ahead of the main rain shaft.  While we didn’t get to see an arcus cloud yesterday, we had some dramatic swlrly dark Stratocumulus clouds to scare us.  I say “swirly” because if you looked up yesterday evening as they passed over, you would have seen rotation in them.

These can combine, as they did yesterday, to make you think someone might drop out of the clouds and fix the world1.  See those scary photos below, way below as it turns out.

This monster collection of Cumulonimbus clouds (“mesoscale convective system” or MCS in weather lingo) with swirly shelf clouds preceding it barged over Catalina later yesterday afternoon after it appeared that not much was going to happen all day.  Heck, there wasn’t even a decent Cumulus over the Catalinas until after 2 PM!

The result of this system slamming Catalina was the usual strong preceding winds roaring down from Charouleau Gap way and points north or northeast.  The winds were not as damaging as three days earlier.

Then the rain!  So nice!   Got 0.55 inches of rain here in Sutherland Heights, an inch and half on Samaniego Ridge, and 1.65 inches on Ms. Lemmon.

Worth watching is the U of AZ weather departments time lapse video, especially beginning at 2 min 50 s into it.  That’s when the big group of Cbs begins to make its presence known from the east.  What is interesting, and what I have not seen before, is that you will see the tops of a thunderhead farther west, that icy part up around 30,000 to 40,000 feet, shoved backwards (back toward the west) by outflow at the tops of the huge incoming system.  Very dramatic.

Yesterday’s clouds

1:30 PM. Yawn. Its 103 F, dewpoint 60 F.
1:30 PM. Yawn. Its 103 F, dewpoint 60 F. Baby Cu begin dotting the Catalina Mountains.
DSC_5616
2:14 PM. Cumulus congestus finally arises within the local cloudscape. Looks like the top is high enough to convert to ice.

Detour:  detecting ice in clouds….some practice shots

As the burgeoning cloud maven junior person you, of course,  know how important the appearance of ice in our clouds is.  You got ice; you got precipitation, which is snow up there, soft hail, hail, frozen drops.

DSC_5623
2:19 PM. The declining right side of this cloud has ice in it, but its hard to detect for most observers. Only the BEST of the cloud-mavens could scream out, “there it is!”, before its more obvious to the less gifted CMJPs.
2:22 PM. Well, too easy now to see that there's ice in those little fingers extruding out from the body of the cloud; evaporation of the cloud drops has left the slower evaporating ice "naked" so-to-speak. It also in the higher turret, and would be termed a "calvus" topped Cu, properly, Cumulonimbus calvus, though not much fell out of it.
2:22 PM. Well, too easy now to see that there’s ice in those little fingers extruding out from the body of the cloud; evaporation of the cloud drops has left the slower evaporating ice “naked” so-to-speak. It also in the higher turret, and would be termed a “calvus” topped Cu, properly, Cumulonimbus calvus, though not much fell out of this one, close to Saddlebrooke.
3:31 PM. In the meantime while I wasn't looking, Mt. Lemmon erupted sending a plume of cloud droplets which converted to ice skyward to at least 35,000 feet ASL.
3:31 PM. In the meantime while I wasn’t looking, Mt. Lemmon erupted sending a plume of cloud droplets,  higher up,  ice,  skyward to at least 35,000 feet ASL. Indicated a phenomenal amount of instability afternoon, instability that was about to be realized in a line of mammoth Cumulonimbi.
3:49 PM. "Eruption" just about over. Notice how skinny the root is now, AND that the top of the stem of convection is now only about half as high as in the first shot. Like a wild fire plume that has cooled off, the plume height goes down. Still formed ice on the right side, as you SHOULD be able to see. You should also be guessing that those were likely warmer habit crystals, like needles and sheaths. I did, if that's any help.
3:49 PM. “Eruption” just about over. Notice how skinny the root is now, AND that the top of the stem of convection is now only about half as high as in the first shot. Like a wild fire plume that has cooled off, the plume height goes down. Still formed ice on the right side, as you SHOULD be able to see.   You should also be guessing that those were likely warmer habit crystals, like needles and sheaths. I did, if that’s any help.
4:38 PM. Another cloud jack (Cumulonimbus eruption indicating a whole lotta instability), tops probably far above 40,000 feet.
4:38 PM. Another cloud jack (Cumulonimbus eruption indicating a whole lotta instability), tops probably far above 40,000 feet.  A lower portin of the anvil drifts southward toward Catalina.  This one was dumping somewhere near the Biosphere 2 landmark.  Note that anvil, lower right. That was our incoming major complex of Cum
5:17 PM. WOW! This was magnificent, and just one of the many large Cumulonimbus clouds racing toward the Catalina Mountains. This is the one that in the video, the crown of it can be seen forcing the air over us in the opposite direction.
5:17 PM. WOW! This was magnificent, and just one of the many large Cumulonimbus clouds racing toward the Catalina Mountains. This is the one that in the video, the crown of it can be seen forcing the air over us in the opposite direction.  Still, it was not certain at this time these storms would make it here.  And, this is looking ESE, while the storm movement was from the ENE.
5:25 PM. The "Menace of Charouleau Gap". Many of our worst storms roll in from the ENE, toward Charouleau Gap, and many who have lived here will tell you and this is the archetypical seen for those storms. A sudden blackening of the sky beyond Charouleau Gap. These darker clouds are rarely the ons producing the storms, but are riding a strong NE wind surging toward Catalina, about to produce some mayhem. The winds always arrive before the rain. And, as a few days ago, there are times when ONLY the wind arrives, there is not enough instability aloft to allow the storms to drift past higher terrain without falling apart.
5:25 PM. The “Menace of Charouleau Gap”. Many of our worst storms roll in from the ENE, toward Charouleau Gap, and many who have lived here will tell you and this is the archetypical seen for those storms. A sudden blackening of the sky beyond Charouleau Gap. These darker clouds are rarely the ons producing the storms, but are riding a strong NE wind surging toward Catalina, about to produce some mayhem. The winds always arrive before the rain. And, as a few days ago, there are times when ONLY the wind arrives, there is not enough instability aloft to allow the storms to drift past higher terrain without falling apart.  On this day, they will make it.
5:48 PM. I am going to work this scene over because it is associated with one of the more spectacular storm sequences here in Catalina, one that comes up usually a few times every summer.
5:48 PM. I am going to work this scene over because it is associated with one of the more spectacular storm sequences here in Catalina, one that comes up usually a few times every summer.  The anvil outflow aloft is thickening and lowering, and the outrider shallow Stratocumulus are racing out and along the Catalina Mountains.  Things are changing incredibly fast and the NE wind is about to hit.
6:05 PM. Walking the dogs to beat the rain, The NE wind has hit, the power line wires are howling. The sky continues to darken and look ominous, but....no rain shafts have come over the mountains, a cause for concern.
6:05 PM. Walking the dogs to beat the rain, The NE wind has hit, the power line wires are howling. The sky continues to darken and look ominous, but….no rain shafts have come over the mountains, a cause for concern.
6:21 PM. The shallow clouds ahead of the rain area continue to spread down and out from the Catalinas. A small opening in the clouds allows this dramatic highlight. I like highlights.
6:21 PM. The shallow clouds ahead of the rain area continue to spread down and out from the Catalinas. A small opening in the clouds allows this dramatic highlight. I like highlights.
6:22 PM. Let's look a little closer at this spectacular highlight.
6:22 PM. Let’s look a little closer at this spectacular highlight.  Wow!  This is just as good as a bolt of lightning.
6:33 PM. Maybe time to get the Good Book out, cram for the finals.... This was really quite the sight, considering it had been so sunny just a couple of hours before. Again, these are fairly shallow clouds riding the outflow winds, now gusting 35-45 mph in Sutherland Heights. The mottled bases here indicate that there is no organized wide updraft to launch them into deep Cumulonimbus clouds at this moment, anyway.
6:33 PM. Maybe time to get the Good Book out, cram for the finals…. This was really quite the sight, considering it had been so sunny just a couple of hours before. Again, these are fairly shallow clouds riding the outflow winds, now gusting 35-45 mph in Sutherland Heights. The mottled bases here indicate that there is no organized wide updraft to launch them into deep Cumulonimbus clouds at this moment, anyway.
6:34 PM. Finally, a major new rain shaft emerges over Samaniego Ridge, upstream of Catalina!
6:34 PM. Finally, a major new rain shaft emerges over Samaniego Ridge, upstream of Catalina!
6:35 PM. Looks like more and more people are dropping off Word Press as these files are going in pretty easy now. Here, the apocalyptic cloud formation rolls down and out across Oro Valley, with heavy rain just to the left.
6:35 PM. Looks like more and more people are dropping off Word Press as these files are going in pretty easy now.Here, the apocalyptic cloud formation rolls down and out across Oro Valley, with heavy rain just to the left.
6:43 PM. A rare sight, wind driven rain streaming off the tops of the foothills of the Catalinas. The winds were likely hurricane force (>64 mph) to do this.
6:43 PM. A rare sight, wind driven rain streaming off the tops of the foothills of the Catalinas. The winds were likely hurricane force (>64 knots, 74 mph) to do this.  Samaniego Peak received 1.50 inches during this storm.
7:21 PM. Sunset in Catalina, July 29th. The sun does not have a sharp disk because the light is being scattered by large particles like rain drops. When its smog, the particles are of the order of micrometers and a sharp disk will be seen.
7:21 PM. Sunset in Catalina, July 29th. The sun does not have a sharp disk, is rather blurry,  because the light from the sun is being scattered by large particles like rain drops which bend the light so that we can’t see the disk’s outline. When its smog, the particles are of the order of micrometers and a sharp disk will be seen because the sunlight is not bent around large particles.  I think Einstein said that…
7:21 PM. Orange and rainy as sunset procedes as usual.
7:21 PM. Orange and rainy as sunset procedes as usual.

Only the largest hailstones up there can make it to the ground as such here in Arizona due to our high summertime freezing levels.  The rest melt into raindrops, some of which are large enough to reach the ground.  Those downpours that suddenly emit from cloud bases were always  hail or graupel (soft hail) aloft.

Sometimes in deep stratiform clouds attached to clusters of Cumulonimbus clouds, and with especially moist air from the base of the stratiform layer to the ground, clusters of ice crystals we call snowflakes make it to the ground without evaporating as steady light or very light rain.

Last night as our storm was coming to an end, it is likely that THOSE drops were once snowflakes rather than soft hail or graupel.

The End (finally)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

————————————–

1Huh.  Maybe that wouldn’t be a bad thing.  I am very concerned about microplastics (particles 5 millimeters and smaller) in our oceans,  resulting from the breakup of larger plastic items we’ve been throwing in the oceans for decades.  Seems those tiny particles are getting into everything, including the fish out there!  It would be great if someone could get rid of them.

Passages: an upper low one on the 18th disappoints; today is the 20th

I got behind….

Lot of great scenes on the 18th, but, ultimately with hopes raised for appreciable measurable rain in Catalina, it was a disappointing day. Nice temperatures, though, for May if you’re a temperature person.  Only a sprinkle fell (4:15 PM), and if you weren’t outside walking the dogs you would NEVER have noticed it.

Here is your full cloud day1, as presented by the University of Arizona Weather Department.  Its pretty dramatic; lot of crossing winds, as you will see, and an almost volcanic eruption in the first  Cumulonimbus cloud that developed near the Catalina Mountains. 

That blow up was indicative of an remarkable amount of instability over us yesterday morning, one that allowed really thin and narrow clouds to climb thousands of feet upward without evaporating.  Usually the air is dry enough above and around skinny clouds that even when its pretty moist, they can’t go very far without the drier air getting in and wrecking them (a process called, “entrainment”).  Here are a few scenes from your cloud day yesterday.

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5:45 AM. Gorgeous grouping of Altocumulus castellanus and floccus. They’re coming at you. (If you thinking of soft orchestral music here, you may be remembering well-known orchestra leader, Andre Castellanus.
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7:37 AM. Here a castellanus turret rises five to six thousand feet above its base. Had never seen one this skinny and THAT tall before. Was really pumped about the mid-level instability at this time. It wouldn’t last. The great height is indicated by the luminosity of the top,
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Also at 7:37 AM, another amazinging tall turret rises up from quiescent bases, ones not connected to ground currents. The bouoyancy in these clouds is due to the heat released when moist air condenses (latent heat of condensation). When the temperature drops rapidly with increasing height, that bit of heat released is enough to allow weak updrafts to rise great distances, sometimes becoming Cumulonimbus clouds and thunderstorms. These clouds, due to their size, would no longer be considered just Altocumulus andre castellanus, but rather Cumulus congestus. Here’s where our cloud naming system falters some. Later, a couple of these grouping did become small Cumulonimbus clouds with RW- (light rain showers).
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7:11 AM. The great height of these tops was also indicated by the formation of ice, that faint veil around the edges. Stood outside for a few minutes, thinking I might experience some drops, but didn’t.
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7:38 AM. The top of this Cumulus congestus has just reached the level where ice will form in the top.
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10:22 AM. Cumulus congestus clouds began their transitions to Cumulonimbus clouds early and often over and downwind from the Catalinas. Can you spot the glaciating turret in the middle, background? Pretty good skill level if you can.
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10:23 AM. Here’s a close up of that turret in rapid transition to ice. It was this kind of phenomenon that led Hobbs and Rangno and Rangno and Hobbs to reject the Hallett-Mossop theory of riming-splintering as THE major factor in ice production in Cumulus to Cumulonimbus transitions like these. The high concentrations of ice particles happened faster than could be explained by riming and splintering, or so it was thought. Still think that, but am in the minority, though there have been reports of inexplicable, fast ice development like that Stith et al paper (with Heysmfield!) in 2004 that for a time appeared to put the “icing on the career cake.” Incredible ice concentrations were found in updrafts of tropical Cu for which there was no explanation! That finding hasn’t been replicated by others, casting doubt on the whole damn paper! “Dammitall”, to cuss that bit.
DSC_4062
11:04 AM. Nice Cumulonimbus capillatus incus (has anvil) pounds up toward Oracle way. Tops are not that high, maybe less than 25 kft.
DSC_4075
3:41 PM. The air aloft began to warm and an inversion capped most of the convection causing the tops of Cumulus clouds to spread out and create a cloudy mid to late afternoon. Nice, if you’re working outside in mid-May. Since the tops were colder than -10 °C (14 °F) the ice-forming levels, some slight amounts of ice virga and sprinkles came out of these splotches of Stratocumulus clouds. One passed through the Sutherland Heights, but if you weren’t outside you would never have known it!
DSC_4084
4:38 PM. Isolated rain shafts indicate some top bulges are reached well beyond the ice-forming level. Note grass fire in the distance.
DSC_4109
7:22 PM. Pretty nice sunset due to multi-level clouds, some Stratocumulus, Altocumulus, and a distant Cumulonimbus anvil.

More troughiness and winds ahead during the next week as has been foretold in our models, and reinforced by weather “spaghetti” plots, after our brief warm up today.  No rain here, though.   Seems now like rain can only occur at the very end of the month where weaker upper troughs coming out of the Pac appear to be able to reach down and fetch some tropical air. 

The End

———————

1Its gone now because I couldn’t finish yesterday.  Went off to Benson for horse training with Zeus.

One of the great humilis days of our time; began with virga above Ms. Mt. Lemmon

I was really happy for everyone out there when the skies were dotted with so many perfect examples of Cumulus humilis.   It was like a numismatist finding a perfect Indian head penny.  If you were like me, and I suspect you are, you were just going CRAZY taking pictures of those flat little pancake clouds.  Those clouds were pretty much limited to about 1,000 feet (300 m) thick at most

Not cold enough for ice in them, of course, since the temperatures at Cumulus cloud tops were only around -3 ° to -5 °C (28 ° to 23 ° F, respectively).  Around here, ice USUALLY does not appear in clouds until the temperature is lower than -10 °C at cloud top.

Yesterday began with some light snow falling on Mt Lemmon…well, it was falling downward TOWARD Ms Lemmon, actually.  Fell out of some thick Altocumulus clouds up there around where the cloud top temperature is… what?  OK, silly question for you, probably lower than -15 °C (5 ° F).

Let’s check the sounding to be sure, remembering that the launch site (University of AZ) was downwind of air flowing from the NW yesterday that went over the Catalinas, so a sounding at the U of AZ might suggest higher temperatures than this cloud was actually at since the air was probably descending before it got there.

Indeed, as just seen by me, the TUS sounding indicates that layer, up around 14 kft above sea level, 11 kft or so above Catalina, not a city, but rather a Census Designated Place or CDP, was “only”at  -10 ° C.

I reject that as the temperature of the virga-ing cloud over Ms. Lemmon!  Its a little too warm IMO.

8:41 AM. That white haze under the Altocumulus cloud is composed of ice crystals, concentrations probably a couple or less per liter of air. Likely stellar or plate crystals, ones that form at temperatures less than -10 ° C.
8:41 AM. That white haze under the Altocumulus clouds is composed of ice crystals, concentrations probably a couple or less per liter of air. Likely stellar or plate crystals, ones that form at temperatures less than -10 ° C.   Almost certainly no aggregates of crystals; concentrations too low to form “snowflakes” which are aggregates of single crystals.  Snowflakes form when higher concentrations of crystals collide and get locked together, as in stellars, and their cousins, dendrites, that grow in a similar temperature regime.  Dendritic crystals are usually seen in deeper clouds than these because those crystals have time to grow extensions in various directions, are not just “planar” ones.  If the cloud is thin like this one, not much growth can take place in the droplet cloud and simpler crystals like hexagonal plates and stellars (Christmas card crystals) fall out.  There is a lot of hand-waving here….
DSC_3273
10:20 AM. A horse named “Zeus” looks to see if any Cumulus clouds are forming over the Mogollon Rim to the NE, or, maybe he’s fixated on the horses in that corral below…

By afternoon, the skies over Catalinaland were spotted and dotted with spectacular Cumulis humilis examples.  (The littlest shred clouds are Cumulus “fractus.”)

I’ve left the time of the photos off today.  After all, there was only one true time yesterday, “perfect humilis time!” or as we like to say, “PHT.”   Immerse yourself.

DSC_3278 DSC_3277 DSC_3276 DSC_3275 DSC_3274

DSC_3288 DSC_3287 DSC_3286 DSC_3285 DSC_3284 DSC_3282 DSC_3281 DSC_3280 DSC_3279

The End

I. Q. Test (“Ice Q”, that is)

Yesterday was a great day both for airborne researchers studying the onset of ice in clouds, and for my followers to test their “ice” Q detecting abilities, to come up with a clever play on words there.

What was so great about yesterday’s clouds?

Well, they were real cold, bases up around 9,000 feet above Catalina (about 12,500 feet above sea level) at -7° C (19° F).   Excellent.  Nice data point.

Cloud tops?

This is what was pretty great for you and me; they didn’t overshoot much, the clouds were pretty flat, not very deep, not a lot of flight time needed climbing to cloud top to see what it was around here.   That means that if you are flying around up there sampling clouds for ice content, that the tops you smashed with your aircraft were pretty much the ones at the temperature that the ice crystals you ran into later formed at.  Remember, when cloud tops first rise up, they usually have little detectable ice (the ice crystals are too small for your instruments, or, they haven’t formed yet, takes a little time.

When there are big overshooting tops,  an inexperienced, well, crummy researcher in an aircraft finding the ice, as it is usually found, lower down in the cloud, might put the origin of the ice at the temperature of the collapsed top, not at the lower temperature where it formed and the original top reached up to.

So, the lack of much overshooting made it a great day to assign the ice you found to the right cloud top temperatures.

What else was great?

It was a marginal day for ice formation here in the Catalina area, so you get a good data point on when ice starts to form in clouds given that base temperature.  As the cloud deepens upward, more ice would be expected with the lower temperatures.

And, as noted by Ludlum way back in the 1950s, and by Prof. Battan right here at the University of Arizona which I did not attend, btw, that level at which ice and precip onsets changes from day to day (largely related to how warm (crazy isn’t it?) the cloud base temperature is.  On days with warmer cloud bases, the ice onset temperature is also higher.    For example, in summer here, its not unusual to have ice onset between temperatures of -5° and -10° C (23° and 14° F) when bases are warmer than about 10° C.

Anybody still out there?

So, yesterday, with the deepest Cumulus clouds around 2,000 to three thousand feet thick right in our area (they were deeper elsewhere), tops were running around -15° C, this temperature, as you know, leads to the formation of plate-like crystals, hexagonal plates, stellars (Christmas card crystals), maybe some spatial dendrites (stick out in different directions) if the latter crystals were in the Cumulus cloud long enough.  If the concentrations of ice get high enough, you’ll get “snowflakes”, interlocking dendritic crystals.   A single, good-sized snowflake might have 20-50 individual dendritic crystals.

Is anybody still out there?

Below some shots from yesterday afternoon when there were traces of ice spewing out of local clouds.  Did you see those regions and note them in your cloud diaries, that’s the important question.

DSC_3037
3:23 PM. A nice view of the overall scene around here with our small Cumulus clouds (Cumulus humilis and mediocris). You see a house in the distance off this dirt road. Pretty say when you think that in America some people still live on dirt roads.
DSC_3040
3:49 PM. Oh, there’s a nice little Cumulus toward the Charoleau Gap. Doesn’t seem to have any ice…. Let us look closer, and, of course, we look for ice to appear at the downwind edge where cloudy air has been in the cloud the longest, see if anything is falling out.
DSC_3041
3:49 PM zoomed view. Oops there it is, a little ice, single crystals, concentrations likely lower than 1 per liter of air. You wouldn’t expect to find any “aggregates” here, since they require higher concentrations of ice to bump into each other and lock together. Wow, this is an incredible amount information based on a little hazy spot in a photograph!
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4:13 PM. Lets look over here toward the south. OK, there’s an obvious ice haze beyond the Catalinas, but what about the cloud in the middle? See anything coming out the downwind (right) side?
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4:13 PM zoomed view of the fall of ice crystals out of this cloud. This patch of ice haze is so obvious it would have been pretty embarrassing for you not to have noticed it, made a note about it.   Of course, we care so much about ice because that’s where nearly all of our rain here in Arizony comes from, as you know, recalling the work of Wegner, Bergeron, and Findeisen, where it was shown that an ice particle in a water cloud will grow at the expense of the droplets around it.  For a time, it was thought that all precip of consequence was due to that process, but not so.  Ask Hawaiians.  Or powder snow lovers about storms consisting only of little dry ice crystals, no water drops in those clouds.

Stormy weather still ahead as noted here I don’t know how long ago.  April looking more and more to be a generous month of rain here in Catalina.  But will those showers be too late for May flowers?

The End.

Similar maps…

When some of you were weather browsing this morning, and you saw this forecast map from IPS MeteoStar, valid for next Tuesday, which shows a very late in the season tropical storm off Baja heading toward the Southwest US, while a vigorous winter storm bashes the West Coast, I had a feeling that it reminded you immediately of one of your early weather memories of a similar situation.  First, the IPS map.

2015111700_WST_GFS_SFC_SLP_THK_PRECIP_WINDS_186
Valid at 11 AM AST, Tuesday, November 24th.  This from last evening’s 5 PM AST global data. The green and blue areas are regions where the model thinks it has rained during the prior 6 hours.

The map below is from an era when you were a little child and maybe you, too,  were clipping weather maps  out of the Los Angeles Daily News, if that’s where you lived:

Sandwiched between storms 002
Actual map from the Los Angeles Daily News, November 30, 1951, clipped by the present writer.   Note that with isobars the Daily News was not afraid of challenging its readers with a non-Mickey Mouse weather map.  The tropical storm on this map is down there to the lower right where the scale of miles is.  Like this winter season, 1951-52 was a Niño year, though not of the great magnitude of this one.

 

Looking back,  but a little closer,  like yesterday and the day before…..

Nice storm we just had.    0.65 inches fell in Sutherland Heights.  Would not have predicted that much over these past couple of days to be honest.  Total for month now 1.10 inches or a little above the 38 year average of 0.97 inches.

After a long dry spell though at least the next week,  November will close out on a dry or wet note, which is pretty encouraging.

Yesterday’s clouds, ice and sun: a soliloquy on ice

 Fair amount of ice yesterday in our low clouds.  As you would guess on your way to becoming a cloud maven, bases AND tops were especially cold for AZ.  Afternoon cloud bases were running about -8° to -9° C, whilst tops were about -15° C.  Still ice was not plentiful.   How’s come?  Well, it seems the amount of ice in clouds is dependent on both the cloud top temperature and the droplet sizes in the coldest parts of the clouds (see Rangno and Hobbs 1994, Quarterly Journal of the Royal1 Meteorological Society)  (Hell, no one’s going to read this, though it is now available without having to go through a “pay wall” and the page linked to above has been updated  with new pdfs!)

In sum, a cloud with a base of -10° C and a top of -20° C will have LESS ice than a cloud with a base of 0° C with the same cloud top temperature (-20° C) because with a warmer base, the drops near the top of the cloud in second example will be larger.

That seems to be the way it works.  So, yesterday’s thin cloud with cold bases had smallish drops, and ice production was a little limited.

Also, if you monitored Ms Lemmon, and the Catalinas in general, you probably were thinking, “Where’s the ice?”, in those cold Stratocumulus clouds as they piled up against them.

Well, when you have strong winds at cloud level as we did yesterday, and with ice crystals taking a little time to appear from some of the droplets that freeze in the cloud stream, grow, and eventually fall out, you’re not going to see much evidence of ice on the windward side of the mountains in these kinds of situations.  The ice is going to appear and fallout as snow or virga downwind a good distance downwind, and that’s what was happening yesterday to nearly all of those deeper clouds (with slightly colder tops and larger cloud droplets in them) that formed over the Catalinas.

If you don’t believe me, yesterday’s time lapse movie from the our great weather resource, the University of Arizona, shows this.  You’ll see a lot of precip and virga falling of those clouds as they stream eastward from the Catalinas.  So, we didn’t get to SEE much ice from those Stratocu clouds but it was there.

Lastly, the sun, as it appeared yesterday at sunset in the dust-haze kicked up by that powerful low that brought us our rains.  The jet stream, as was pointed out by a friend, was about 200 mph overhead of TUS at 40 kfeet.  Wow.

5:21 PM.  The sun.  Stratocumulus sans virga at top.  Droplets too small, temperature too high at cloud top apparently.
5:21 PM. The sun. Stratocumulus sans virga at top. Droplets too small, temperature too high at cloud top apparently.  Sun seems to be free of blemishes, too.  Are we still in a sunspot minimum,  thought to drive cooler climates, one that might rival the Maunder Minimum?  I don’t know.  I am a weatherman, not an astrologist.

 

The End.

—————————

1″Royal”–that is so funny; “hey”, guys,  wake up, its the 21st century!

0.33 inches so far; more rain on way! Dense blog contains annotated photo!

Looks like CMP is low AGAIN on his prediction!  Thought a third was the most that could fall  in our present storm chapter (10% chance of more, that is), and best estimate, 0.165 inches.  Now it looks like met friend and professor at a major university will be much closer with his half an inch prediction.  Very painful.  Kind of like Stanford with their brainy team beating the Washington Huskies  in fubball .    It really hurts.

Let us begin today with a look at desert grasses from this summer and falls rains.  Pretty deep, knee high in some areas, but as we know here, full of nettles.  Kind of a cool look though.

7:53 AM.
7:53 AM.

Was heading out to see, what from Google Space, appeared to be a new meteor crater near me, one maybe the astro boys missed.  Turned out it was just a house under construction, pretty much underground as well.  Kind of a cool thought to build like this, lots of energy saved, which is always good.  Cell phone service likely compromised.

8:11 AM.  An earth house under construction.
8:11 AM. An example of an earth house under construction here in the Catalina area.

Yesterday’s clouds

…and a dense discussion of detecting ice in them.  I am hoping that my followers noted the time of the first appearance of ice in those Cumulus and Stratocumulus clouds  that began to fill in during the middle and late afternoon.  As that happened, a few raindrops sputtered down here just after 3 PM as that happened.  You should have logged both these events, the first visual appearance of ice, and when those drops fell in your weather diaries.

The whole point of this blog is the detection of ice in clouds by layman and laywomen, or “laypersons” I guess it should be now days.  This is because if you see ice developing in lower clouds, something will be falling out of them soon.  Ice grows in water clouds at below freezing temperatures at the expense of droplets.  Therefore, if they stay in a water cloud long enough, they will get heavy enough to fall out.   Poor droppies disappear, unless the air is really rising fast.

An interesting side note is that the air FLOWS THROUGH  clouds, exiting on the downwind side.  A cloud does not just float along as is.  It is moving slower than the air, even itty bitty Cumulus clouds the cloudy air is being replaced constantly.  The cloud is really moving upwind relative to the air! The POSITION of the cloud moves downwind, but SLOWER than the air that goes into it.

However, if ice crystals form in a small cloud then, they will fall out as single crystals at the downwind edge; they are not going to reach the ground unless you’re on a mountain top.  You saw a fair amount of ice exiting the downwind end of clouds yesterday, falling out and evaporating in the dry air there.   Where the cloud is wide, then they can gain some mass, collide with droplets, or other crystals and fall to the ground.

2:38 PM.  No ice nowhere.
2:38 PM. No ice nowhere.  Windy conditions not shown.
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2:38 PM. Cumulus and Stratocumulus clustering to the south-southwest of Catalina, but no sign of ice.

You need clusters of crystals locked together, called “aggregates”  or ones that have gone through riming, collisions of ice crystals with drops at below freezing temperatures that freeze on the ice crystal making it more massive to get rain drops to the ground.   Riming is what leads to graupel (soft hail) and hard hail (the latter to crystals impacting larger, often precipitation-sized drops that freeze on them).

For air travelers, or those who examine tree icing after storms, rime ice is white and produced by small cloud drops; clear icing is caused by much larger drops, usually drizzle or rain drop sizes.  If the drops are too small (much less than about 20 microns) they are too small to hit anything and rather go around solid objects.  Let’s say you’re on the top of Ms Mt Lemmon, say at 8.000 feet in the fog.  The temperature is 24° F.  Its windy.  You look around and you see no icing on the pine trees  trees up.

Where are you?

Ans: at cloud base.

That’s because itty-bitty drops, too small to hit on pine tree needles are flowing around the needles.  Some great comments to make that would enhance your stature as a cloud maven junior is to offer your companion the information, “Wow, look at those trees!  Here we are ing the freezing fog, and yet they have no ice sticking to them!  That means the cloud droplets are pretty small, smaller than about 20 microns! I guess we’re at the base of this cloud system above us.”

These would be really great things for you to say.  Of course, as you drove up to Mt. Lemmon, you would know already how far above cloud base you are, but, what the HECK.

You’re at Ms. Mt. Lemmon again,  You like it up there when its in the fog.  This time the temperature is 25 ° F.  Its windy.  The pine trees are loaded with rime icing, the ice juts out in the direction from which the wind is coming.

Where are you?

Answer:  At LEAST a few hundred feet, more likely a thousand feet or more above cloud base.  Drops have reached sizes above 20 microns in size, as they usually do at these heights above cloud base in old Azy.  Later, you notice that the clouds are topping Sam (Samaniego) Ridge at the 6500 foot level.  Now, they can’t be disconnected layer clouds, but rather SOLID from base to where you are.  Drops are tiny again at the bottom of each layer.

Here’s another example.  You get up in the morning after a cold winter storm to see “iced trees” on Ms Lemmon.  Another comment you could be making is that, “Wow (always begin with “wow”), those clouds must have really been low based last night, way down on Sam Ridge!”

Riming on trees is analogous to the collection of fog droplets by trees and vegetation along the west coasts of the continents in onshore moving banks of Stratus and Stratocumulus clouds that intercept hillsides.   These can be significant sources of water.  Some studies of droplet collections by trees have found that under the tree, something like 20-40 inches of “rain” can be collected by a tree in northern California.

Wow, I can’t believe all the information I am providing today!  Its really incredible.

OK, to first visible ice yesterday, 3 PM:and

3:00 PM.  FIrst ice begins to eject out the end of that Stratocumulus complex upwind of Catalina.  When the body of the cloud began to be overhead, a few drops reached the ground!
3:00 PM. FIrst ice begins to eject out the end of that Stratocumulus complex upwind of Catalina. When the body of the cloud began to be overhead, a few drops reached the ground!
3:00 PM.  Close up of ice ejecting out the downwind end of this Stratocumulus complex.
3:00 PM. Close up of ice ejecting out the downwind end of this Stratocumulus complex (that hazy stuff).
3:30 PM.  Classic example illustrating the air flow through a cloud that's producing a little ice.  What kind of ice?  Looks like colder crystal types, plates, stellars, maybe some dendrites.
3:30 PM. Classic example illustrating the air flow through a cloud that’s producing a little ice. What kind of ice? Looks like colder crystal types, plates, stellars, maybe some dendrites; defintely not warm crystal types like needles and hollow columns that form at temperatures above -10° C.
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4:49 PM. Nice lighting.
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5:21 PM. Wind shift clouds, those lowest ones on the horizon, begin to appear to the north-northwest horizon, toward Casa Grande.
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5:31 PM. The sun going down amid Cumulus or could be called, Stratocumulus castellanus.
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5:32 PM. OCNL LTG DSNT NNW at this time.   Again you see those wind shift, frontal passage type clouds here.  A wind shift to the NW didn’t hit here until about 1:30 am when the rains and temperature drop hit.

 

 

The End

“Just another day”, pretty much like the day before

Just Another Day“, btw, one of the many great songs by Oingo Boingo, if you’ve ever heard of them.  We’re not just about clouds here.  Trying to broaden your pop cultural knowledge with distractions like this.

Yesterday was remarkable  in how exact it was to the day before in clouds, but ultimately disappoiting.1  There was supposed to be more cloud action, shafting around, that kind of thing, but there wasn’t.  It was virtually identical in every way, including having only two clouds that got high and cold enough to have ice in them. I am sure you recorded them in your cloud diary, and this will be a little tedious as a result, but….what the HECK.

Here is your cloud day for yesterday, focusing on the detection of ice in clouds:

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1:15 PM. Not much going on.
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1:17 PM. Not much going on.
2:44 PM.
2:44 PM.  Not much going on, but nice cloud street.
3:23 PM.  Suddenly,  a narrow erection of cloud shot out of the larger Cumulus mediocris/congestus.  Would it form ice?  I was thinking so, and with that, maybe a rain shaft that could disrupt the wind field and trigger more buildups.  "Here we go," I was thinking, as you were as well.
3:13 PM. Suddenly, an erection of cloud (center at top)  shot out of the larger Cumulus mediocris/congestus. Would it form ice? I was thinking so, and with that, maybe a rain shaft that could disrupt the wind field and trigger more buildups. “Here we go,” I was thinking, as you were as well.
3:14 PM,  Looks pretty firm yet.  No indication of ice.
3:14 PM, Looks pretty firm yet. No indication of ice.  But definitely a few thousand feet higher  and colder than the surrounding cloud.
3:15:30.  Beginning to soften and fall back!  No sign of ice.  Those ragged edges represent the intrusion of dry air into the cloud called "entrainment."  Entrainment is less as the cloud shoots upward and contains vortex rings.  Worried now that this turret was not as high as initially perceived.
3:15:30. Beginning to soften and fall back! No sign of ice. Those ragged edges represent the intrusion of dry air into the cloud called “entrainment.” Entrainment is less as the cloud shoots upward and contains vortex rings. Worried now that this turret was not as high as initially perceived.
3:17 PM.  Stepping back and looking at the whole cloud, the top has been disconnected from the bottom by very dry air between where the top is now, and the lower part of the cloud.  Entrainment has beheaded this cloud!  And, no sign of ice...yet.
3:17 PM. Stepping back and looking at the whole cloud, the top has been disconnected from the bottom by very dry air between where the top is now, and the lower part of the cloud. Entrainment has beheaded this cloud! And, no sign of ice…yet.
3:18 PM.  Not much good up there, with no body, but ice is now visible, and is likely forming, as more of the cloud head evaporates.
3:18 PM. Not much good up there, with no body, but ice is now visible, and is likely forming, as more of the cloud head evaporates.  See that faint ice  veil below the head?
3:21 PM.  I am sure you can see the wisps of ice that this turret contained quite easily now.  Won't do much good decapitated like that.  Huh?  "Decapitated."  Seem to be on a religious theme today.
3:21 PM. I am sure you can see the wisps of ice that this turret contained quite easily now. Ice won’t do much good being decapitated like that with no cloud body to fall through and grow.. “Decapitated.”  Huh?  Seem to be on a religious theme today.  Must be due to that article I read in the Atlantic recently.
3:30 PM.  Twin towers, but like the one over Catalina, it faded into oblivion.
3:30 PM. Twin towers, and like the one over Catalina, it faded into oblivion after getting a little higher than ours, forming more ice.
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4:13 PM. Ever hopeful, but no, never  saw no ice from this tall boy,  phrasing here mindful of that classic new  old folk song, “Never did no wanderin’ ” by The Folksmen.
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7:26 PM. Nice storms elsewhere. Here, looking NE-E.

Today is another day.  More hope for a shower late today or tomorrow, models say, then likely another dry spell as the summer rain season ebbs again for awhile until that possible super hurricane Dolores drags some moisture up this way.  (Dolores, now just a tropical storm, was just born off southern Mexico near the coast.  Will be interesting to see just how strong she gets.

The End

——————-

1Some fans  like to see misspelled words here.  Amyone see that criminal who was sentenced to “life in person” as described in the AZ Star?  That was pretty grate.