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!

Cold clouds and pretty, wintry scenes as long as they don’t last too long

What a gorgeous day yesterday was with deep blue skies dotted with Cumulus and one or two shallow Cumulonimbus, highlighted by our snow-capped Catalina Mountains.  After the brief warm up, more storms ahead for Catalina!

Yesterday’s clouds

DSC_0487
10:23 AM. By this time Cumulus were popping up all over, and with the temperature at just 10,000 feet above sea level (7,000 feet above Catalina) cloud mavens everywhere were pretty sure ice would eventually form in lots of Cumulus.
DSC_0490
10:24 AM. Shallow Cumulus congestus (left side) converting into an equally shallow Cumulonimbus capillatus (right half of cloud). This scene from a fairly primitive area of Arizona.
10:26 AM.
10:26 AM.  Pretty scene over Saddlebrooke.
DSC_0494
10:37 AM. Ice, there it is. Even shallow clouds spewed ice crystals and or small snowflakes (clusters of individual ice crystals.

Explanatory module below

The TUS balloon sounding, launched at about 3:30 AM yesterday morning from the campus of the University of Arizona Wildcats.
The TUS balloon sounding, launched at about 3:30 AM yesterday morning from the campus of the University of Arizona Wildcats.
DSC_0496
10:27 AM. Wintry scene #1, view toward the Charouleau Gap, and why do the French make spelling so hard?
11:04 AM. "Ice, there it is!", to paraphrase a song from "In Living Color."
11:04 AM. “Ice, there it is!”, to paraphrase a song from “In Living Color.”
DSC_0508
11:12 AM. Wintry scene #2. View is toward the Charouleau Gap.
DSC_0510
11:12 AM. Icy, but shallow Cumulonimbus cloud heads toward Catalina spewing a light rain shower and soft hail called “graupel.”
11:44 AM. Wintry scene #3.
11:44 AM. Wintry scene #3.
DSC_0526
12:32 PM. Not an advertisement for the University of Washington Huskies sports powerhouse, but rather a demonstration and graupel did, in fact,  fall from our shallow Cumulonimbus clouds yesterday.  BTW, the Washington Huskies play the NFL-ready, #1 Alabama Crimson Tide on New Year’s Eve at 1 PM AST in a fubbal playoff game.  It would be great if you watched, raising viewer numbers, and possibly therein,  the revenue stream flwoing into the University of Washington (from which I emanated). Oh, there appears to be a conical graupel there on the left. Graupel falling through a cloud of droplets often stays oriented with one face down, and that face collects all droplets that are freezing on it making that downward  facing side, as you would imagine,  bigger than the rear part, and so you get a pyramidal-shaped piece of soft ice. If it mainly tumbled on the way down through the cloud, it would be pretty spherical.  That white streak on the right is one that’s falling.
11:45 AM. Another ice producing candidate forms in cloud street aligned with Catalina.
11:12 AM. Another ice producing candidate forms in cloud street aligned with Catalina.  Couple of drops is all that came out of this.
DSC_0552
3:18 PM.  Very shallow, ice-producing clouds.  Few in the area had ice at this point in the afternoon, and a very tedious inspection of these clouds, comparing them with surrounding clouds,  suggested that their tops were just a bit higher than the ones around it that did not spew a little ice.
The TUS balloon sounding launched at 3:30 PM AST, also with writing on it.
The TUS balloon sounding launched at 3:30 PM AST, also with writing on it.
5:06 PM. Wintry scene #3 Pretty, eh?
5:06 PM. Wintry scene #4 Pretty, eh?
5:32 PM. Stratocumulus with red liner. Nice.
5:32 PM. Stratocumulus with red liner. Nice.

After the brief warm up ahead, still looks  “troughulent” and stormy in the SW as December closes out,  continuing into January.

The End

0.52 inches here, 1 to 1.5 inches on the CDO upper watershed; will it run?

May take Jake Horse out to see if the Sutherland Wash is running, anyway, if the CDO is not running here in Catalina.

Thunderstorms (at least 4 separate ones yesterday), with hail, graupel, wind, rain;  what a nice day for Catalinans and our environs.  Lightning was still visible as of 7:52 PM last evening, and close enough that  thunder could be heard, technically meaning a thunderstorm is in progress in weather parlance.  Here’s some pea-sized hail for you, sent by a listener, “Dave”, in Sutherland Heights:cropped IMG_20130308_104705_630

Was awakened by a moderate rainshower just before 3 AM.  Dropped 0.03 inches in a few minutes, to bring the total to 0.40.  Another shower followed within half an hour, but bucket didn’t tip for even 0.01 inch.  May have to jiggle it to get that extra 0.01 inch that I KNOW fell. Hahahah.

In the meantime, exulting over the large amounts, so well foretold by the U of AZ Beowulf Cluster run from 24 h ago.  Truly amazing!  Our total here was also well=predicted by that model; amounts in this storm increase northward reaching 0.87 inches at Oracle State Park, 0.55 inches at the NE corner of Saddlebrooke.  We SO needed a good rain.  Here’s where the totals are:

201303091030_pptreport

Here are some mind-boggling statewide totals from the USGS, some approaching two and a half inches of water content at Sunflower near Payson!  How great is that?!  Really, this has been a billion dollar storm in dropped water and snow. Maybe it should have a name now.

2013030911_AZ pcp USgS Sheet1

You will can also access rainfall data from the U of AZ rainlog.org network here, and from CoCoRahs national network for Arizona here.  As always, its necessary to point out that in the rainlog network, the measurements reported this morning will be assigned to yesterday’s date, while the ones in the CoCoRahs system will be assigned to today, March 9th.

Since its unlikely to rain for at least 10 days, I thought I would overdo the precipitation data for our billion dollar storm.

Sadly, as you will see in this Pima County ALERT gauge totals above,  we in the north end of the County really got the nice rain; most of the county did not.  We were lucky we were that bit farther north because it wasn’t the wind direction helping us out in most of the storm; that “help” is taking place now because the wind is more from the west at cloud levels.   Going into yesterday yesterday evening the wind at cloud/mountain top levels was from the south-southwest rather than from the west, and normally that more southerly flow helps the south facing sides of the Catalinas, as much as us.  So, it was more to do with cloud top temperatures and those clouds being a bit too warm to the south, while northward and to the northwest (perpendicular to our jet stream), the temperatures decreased rapidly at the same level in the atmosphere, and that in turn, allowed cloud tops to deepen more as they went nortward.  Make any sense?  Here’s a map of temperatures aloft for yesterday, two graphics to try to explain this:

A 500 millibar map at 5 PM AST.  Center of coldest air is to the northwest of us at that time, gets colder over you as you take Highway 79 to Florence and beyond.  Cloud tops do, too.
A 500 millibar map at 5 PM AST. Center of coldest air is to the northwest of us at that time, gets colder over you as you take Highway 79 to Florence and beyond. Cloud tops do, too.  The full loop is here.

 

Mapm for the same time with colors showing temperatures getting colder to the NW of us.  More likely to have deeper clouds and thunderstorms as you go NW.
Mapm for the same time with colors showing temperatures getting colder to the NW of us. More likely to have deeper clouds and thunderstorms as you go NW.  Full loop is here.

First, here’s last evening’s TUS sounding, as rendered by the Cowboys of Wyoming.  Its got some writing on it:

The Tucson sounding at 5 PM AST, yesterday, March 8th.
The Tucson sounding at 5 PM AST, yesterday, March 8th.  Cloud tops marked by asterisks to represent ice crystals, and bottom by little “o’s”.  The arrows in roughly an “R” shape is an attempt at replicating the thunderstorm sign used by NOAA.  Even though the clouds were topping out at less than 25,000 feet, they still contained enough ingredients such as hail and updrafts to generate enough static electricity for lightning.

———begin tedious stream of consciousness again, probably worth skipping——–

Graupeling hard here at 3:38 AM!  Third shower since getting up!  Pounding roof.  Very small, like rice grains.   Just quit, like someone turned a light off at 3:41 AM.   Tells me its a new cell that just formed with narrow strands of precip/graupel.   Investigating…no echo at 3:36 AM nearby… waiting for next 6 min sweep…    2:42 AM:  No echo!  I have not seen this happen before.  Could it have developed and died in less than 5 min?  Did not tip bucket!  Its just like yesterday, we had no less than four hail/graupel episodes and I was beside myself thinking of those balls of ice bouncing OUT of my rain gauge collector!  I was being short-changed in the amount of precip I could report.   I think I am going to have to add to my rain total, maybe 0.03 inches due hail balls that bounced out

——————–end of tedious stream———————-

OK, now up to 0.13 inches in rain that has fallen since about 3 AM.  This is great, because now the total amount in the storm is 0.50 inches here!

Yesterday’s clouds

After a few sprinkles-its-not-drizzle amid brief sunbreaks yesterday morning, the first thunderstorm rumbled across Marana and the Oro Valley at 9:30 AM.

9:55 AM.  Thunderstorm with hail and heavy rain moves into Oro Valley.
9:55 AM. Thunderstorm with hail and heavy rain moves into Oro Valley.
10:21 AM.  Looking upwind toward Pusch Ridge at the bases of  a line of rapidly moving Cumulus congestus clouds.
10:21 AM. Looking upwind toward Pusch Ridge at the bases of a line of rapidly moving Cumulus congestus clouds.
10:25 AM.  Hail-producing cloud has passed by, but shaft increases in size and visibility.  This is a time when tremendous amounts of ice is forming in the cloud, ultimately leading to its demise as a fluffy area looking area of only ice crystals.  Without the liquid droplets, that disappear during this stage where ice forms explosively, no graupel or hail can form. Its a normal life cycle event for cells like this.
10:25 AM. Hail-producing cloud has passed by, but shaft increases in size and visibility. This is a time when tremendous amounts of ice is forming in the cloud, ultimately leading to its demise as a fluffy area looking area of only ice crystals. Without the liquid droplets, that disappear during this stage where ice forms explosively, no graupel or hail can form.
Its a normal life cycle event for cells like this.
12:12 PM.  Another line of young Cumulonimbus clouds races toward Catalina and Sutherland Heights, a recurring theme yesterday.
12:12 PM. Another line of young Cumulonimbus clouds races toward Catalina and Sutherland Heights, a recurring theme yesterday.
12:23 PM.  Passage of that complex of Cumulonimbus clouds shown in the prior shot resulted in this hail shaft trail on the foothills of Samaniego Ridge.  Hail shafts are very narrow.  If it had been snow, there would have been much greater coverage.
12:23 PM. Passage of that complex of Cumulonimbus clouds shown in the prior shot resulted in this hail shaft trail on the foothills of Samaniego Ridge. Hail shafts are very narrow. If it had been snow, there would have been much greater coverage.
2:30 PM.  But the day wasn't done then, was it?  Here something in the way of an arcus cloud rolled across Oro Valley and onto the Catalinas.  Thought maybe a tube might form.
2:30 PM. But the day wasn’t done then, was it? Here something in the way of an arcus cloud rolled across Oro Valley and onto the Catalinas. Thought maybe a tube might form.
4:55 PM.  Just kept on giving.  Here yet another line of developing Cumulus congestus, just reaching the precip stage a little upwind of Catalina, dropped a few more graupel particles while going on to dump heavily farther north.
4:55 PM. Just kept on giving. Here yet another line of developing Cumulus congestus, just reaching the precip stage a little upwind of Catalina, dropped a few more graupel particles while going on to dump heavily farther north.  This recurring pattern of clouds developing,  able to become deeper with colder cloud tops is the primary reason the north part of Pima County did so well yesterday and this morning,

Today’s clouds

These early morning stratiform (flat) clouds will disperse into Cumulus and Stratocumulus in clumps. They’ll be cold enough at cloud tops for ice and virga, but clouds likely will be too shallow for more than a hundredth or two in the heaviest precip areas around Catalina. Things dry out later in the day, the Cu becoming smaller, so the best chance of measurable rain is before, say, 2 PM.

Get camera out fast, too. THere was a huge dump of hail or snow on Charoleau Gap last night or this morning I suspect, and it looks spectacular even now at 6:53 AM. Its local, because its not seen at the same elevations to the south on Samaniego Ridge. But, it will just be gorgeous with those deep blue skies and white Cumulus clouds all around.

The End, finally, I think.

Thundery trace; expect more than that today

(A note:  I am not getting WYSIWYG in what I am writing and what is posted in WP.  This is SO FRUSTRATING!  True I am a bit of an amateur at WP,  but those spaghetti plots that start the blog are SUPPOSED TO BE AT THE END OF IT as I see them in the draft, not absorbed in the “gallery” as well, dammitall!)  Computers and sofware are going to kill me, I am sure.  Where are my pills?!

Another promising start to a summer day today in Cat Land, as was yesterday since we have another cloud filled morning, some clouds having weak rainshafts indicating glaciation in the turrets sprouting from today’s layer.  And, there’s been a slight uptick in moisture over us, which raises the chances for measurable rain in Catalina today.  We also have support for this contention in the great U of A local model forecasts here, based on last night’s 11 PM AST run!  Yay!

Below, the photographic diary for yesterday starts begins with the Altocumulus opacus layer, with more than one layer up there.  Then, after the usual thinning-dissolution of that layer in the morning, the welcome sight of baby Cumulus beginning to appear over Mt. Lemmon by noon.  Those Cu steadily inflated reaching the “glaciation” level by 1:31 PM, a welcome sight after the “dud” Cumulus clouds of the prior two days.

After our first thundery spell, several new thunderstorms developed to the NW and E-SE over the Catalinas late in the afternoon,  but again, produced only another trace in a 20 minute or so of “very-light-rain-its-not drizzle” (one of the recurring themes here).

Since I can’t add more captions after the icy sprout, a WP problem, the times of the last few photos are, 1:53 PM, 2:08 PM, and finally, another great sunset sequence, some distant Cumulonimbus to the NW and another blazing sunset underlighting some virga from the remains of our last thunderstorm, these taken at 7:30 PM.

The Weather Ahead, way ahead:

We’re always on pins and needles this time of year, hoping for the best summer rains we can get, at least I am. The transformation of the desert into green again during the summer, after the spring greening,  is one of THE most rewarding aspects about living here in the summer, flying ant swarms aside.

Below are the “spaghetti” plots from NOAA that give us some clue about the reliability of the longer term model forecasts.  These are for the afternoon of July 19th, some ten days from now, and the afternoon of July 23rd.  Both plots below strongly indicate that the circulation pattern is ripe for good summer rains here between now and the 24th.  Doesn’t mean that every day will have rain, but it does mean recurring summer rains are likely with no long breaks.  That black region over the SW indicates a high probability (not certainty!) that our big fat SW summer anticyclone will be well positioned for good summer rains here.  In contrast, if that black area was OVER southern Arizona, or to the south, it would be a horribly, hot dry spell here that the models were foretelling.


Yesterday’s awful Cumulus clouds; better ones today!

From the University of WY Cowpokes, this awful sounding from yesterday afternoon at Tucson.  Where the two lines first pinch together, around the “500” label, is where the Cumulus cloud bases were yesterday afternoon (marked by the oval)!  To see why those Cumulus were awful ones with too much ice, check the temperature lines, the ones that slope upward to the right with the labels on the bottom, “0”, -10, -20, etc.   Yep, that’s right, the bottoms of those clouds were at 500 mb, and -20 C!  The Weather Cowboy sounding algorithm, the one that produces all the numbers in the column at right, thinks the bottoms of Cumulus clouds were even HIGHER, at 428 mb and nearly at -30 C (that “LCLP” number)!

So, the awful looking, dried out, Cumulus clouds have been explained.

Too high, too cold, too much ice.  Reminded me of the old days in Durango, Colorado, in the early 1970s.  Charming town, but awful place if you wanted to see Cumulus clouds without much ice.  Too high, too cold, and too much ice there, too.

What’s wrong with too much ice?

Too many ice crystals completing for itty bitty amounts of “condensate” (yes, Virginia, even at those temperatures, cloud begin as liquid droplets).  But when they are so cold to begin with, so many of the droplets freeze, that they all try to take the water from the ones that haven’t frozen (cause them to evaporate, the water molecules rushing to the nearest ice spec.

So when nearly ALL the droplets freeze, the ice crystals are all itty bitty as well, and can’t fall out, even though individually they may have a bit more mass in them than the droplets.  They just float up there and gradually die.

Stories from the field interlude

OK, gotta get this out…   In the domain of cloud seeding, where ice-forming nucleants are put into clouds, the phenomenon of having too many ice crystals would be called, “over-seeding”.  Believe it or not, deliberately “overseeding” clouds to make them look like the ones we had yesterday, and so that they wouldn’t rain has been tried!

Yikes.  Why?

The Coors Brewing Company, in the early 1970s,  did not want their hops in the San Luis Valley of southern Colorada (around Alamosa) spoiled by having rain fall on them at the wrong time.  The program was ended when alfalfa farmers in the same area, ones that WANTED RAIN, terminated the program prematurely with sticks of dynamite;  they blew up the seeding contractor’s radar, used to direct aircraft into the clouds to seed them.  Mr. Cloud-maven person, the writer,  was working in Durango in those days, on the other side of the mountains from Alamosa, on a scientific cloud seeding project (a randomized one) to see if seeding could cause more snow to fall from winter storms, so he was close to the “action.”

Yes, everyone gets excited about clouds and weather, especially alfalfa farmers!  Its so great.

Below a few shots of yesterday’s small, ice-ed out Cumulus.

The haze below this little Cumulus fractus cloud is due to ice having formed in it! Bad news from the get go if you're hoping for virga and rain later in the day.
Merely a Cumulus humilis, center, and having a bit of puffery. But its mostly ice. Quite awful-looking, really.

About today’s “better” clouds

Overnight there was an invasion of air from the east carrying increased lower level humidity. How cold will the bases be today after yesterday’s -20 C or so? Around 0 C our TUS morning sounding suggests. While that’s still cold, it should mean rain to the ground here and there in the fatter Cumulonimbus clouds that will be around even though they will be dominated by ice again. With these higher base temperatures, it means more water condensing in the clouds BEFORE ice forms. When that happens, you are likely today to get “graupel” forming in areas of the clouds where the condensation is greatest, and the ice just beginning to form. “Graupel” or soft hail, falls rapidly compared to ice crystals and aggregates of ice crystals (i.e., “snowflakes” to get away from jargon) and those graupel up there are likely to be what MAINLY gets to the ground today, melted of course, into raindrops. This because the “free air” freezing level is about 7,000 feet above us here in Catalina (3,000 feet elevation). Should be a fun day, reminding us of out upcoming summer rain season.

And, what do we think about when we think about graupel/soft hail forming in the clouds overhead?

Electricity, lightning!  Yes, these clouds will be getting “plugged in”, so to speak, this afternoon here and there.  Be watchful.

 

Nice display of Cirrus uncinus in the late morning as Cu began to form.

BTW, if you want a really expert discussion for today, go to Bob’s page here.  (He may weigh in on this later…) And,  of course,  our NWS here.  They seem to be getting pretty worked up and excited about today’s weather and all the wind that might blow out of our afternoon thunderstorms.

BTW, nice flowers out there in the desert now days; this on our “Arizona rose” (took about nine attempts to upload this!  Bad WP!)

 

The End.

All’s well that ends well

What a nice day yesterday was, ending with this fabulous, but run-of-the mill sunsets we get to see here in the Catalina area on a regular basis.  Yesterday was interesting because we had two graupel (soft hail) showers, the first about noon, and the second with a blast of thunder (1) at 1605 PM.   If you weren’t lucky enough to get any, measure it and report it to the National Bureau of Standards, or the NWS, here’s what it looked like on our old chaise lounge a  couple of minutes after it fell (see below).  Some of it was “conical graupel”, pointed on one side, though that is not visible here.  Graupel, soft hail form when there aren’t many ice crystals in the cloud and the cloud is chock full of droplets at below freezing temperatures.  Those droplets freeze instantly onto the ice crystal as it makes it way down to the ground, eventually losing all of its identity as it become a little snowball.  Usually, where this happens in the cloud is in a very limited region, and, it usually doesn’t last for a long time.  So, consider yourself especially “lucky” to see graupel/soft hail, hail.  I do.  If you want to relive yesterday’s clouds, as seen from the U of A, go here.   “Above Catalina” is at the left, beyond Pusch Ridge.

What’s exciting now is that something akin to an atmospheric iceberg is barreling down on us (SE AZ) from the north.  This “cold low” center, representing a column of extraordinarily cold air in this case, goes from the ground all the way up through the “troposphere.”  IN this case, the troposphere is squashed down to less than 20,000 feet over Wy0ming right now. The stratosphere is above that, and above “cold lows”,  the stratosphere dips down over them.  Usually its twice that height at our latitude.

Here’s what I am talking about, shown in this morning’s 500 millibar pressure map (about 18,000 feet above the ground) or usually half way up through the troposphere (map courtesy San Francisco State U.)  The winds flow along the green lines, ones that bend gently toward the west over the Great Basin.  That bend in the wind represents an area where a small low center amid this giant river of wind will form in the next 24 h and that little center of circulation should pass right over us!

Now, not a single model output that I saw from last night’s runs had enough moisture in this forming upper center to have snow even fall on Mt. Sara Lemmon (e.g., the U of AZ regional model from last night).

A few days ago, the Canadian model was suggesting a signficant storm here from this center. I really believe it.   Well, that’s “bye-bye” since the center is not well to the west of us as that Enviro Can model indicated it would be, but rather will end up right over us (which means much drier).    The U of WA model run from this morning’s data says that a little “L” will be right over my house on Thursday morning (see reddish map below) !  Man, it will be cold over me!    Might lose some plants in this one before its over.

However, I am going to stick my neck out and expect (hope) there will be just enough moisture for flurries around here (Catalina area) anyway tomorrow into tomorrow evening.

BTW, the U of A has just issued a special weather discussion here.  You’ll want to check this out!