Ice crystals – Page 4

Cold slam

That’s your weather forecast for today. There’s nothing you can do about it. Why go on about it?

Next, these from yesterday–was under control, only took 127 photos. Every thousand or so shots I take is NOT of a cloud, and yesterday there were two exceptions, which I will post here as an anomaly; a quirk really:

5:48 PM. Sun broke through the Cumulus and Stratocumulus clouds for this orangy foreground as the white light of the sun is burned orange at low sun angles by passing through a denser portion of the atmosphere. The shorter wavelengths (blueish) are scattered out leaving reddish hues to come shining through. Banner cloud remains in its same crevice on Samaniego Ridge like a trap door spider or a piece of lint in a corner of the room you haven't vacuumed for awhile. — 5:48 PM. Sun broke through the Cumulus and Stratocumulus clouds for this orangy foreground as the white light of the sun is burnished orange at low sun angles due to having passed through a denser portion of the atmosphere and the shorter wavelengths (blueish) are scattered out leaving reddish hues to come shining through. Banner cloud remains in the same crevice as yesterday on Samaniego Ridge like a trap door spider or a piece of lint in a corner of the room you haven’t vacuumed for awhile.

2:55 PM. Horse demonstrating that the appearance of water in a tributary to the Sutherland Wash was real, not an illusion. Thanks, horse. The bit of water in the Sutherland dried up just down from the private land fence opposite the rusty gate. — 2:55 PM. Horse demonstrating that the appearance of water in a tributary to the Sutherland Wash yesterday was real, not an illusion. Thanks, horse. The bit of water in the Sutherland Wash itself dried up just down from the private land fence opposite the rusty gate on the east side. (Horse people know where this is.)

5:56 PM. Gritty view through wires and a telephone pole of the highlight color of yesterday's sunset. Sometimes I think you're here only for the eye candy. — 5:56 PM. Gritty view through wires and a telephone pole of the highlight color in Stratocumulus clouds of yesterday’s sunset. Sometimes I think you’re here only for the eye candy.

Yesterday’s rare ice-forming anomaly

I was hoping you wouldn’t read this far. Something incredible happened, rarely seen here in Arizona. Our slightly supercooled clouds, with top temperatures between -5 and -10 C, formed ice. When I first saw the indication of something falling out of those shallow clouds on the Catalinas, I was beside myself. Here’s what I saw, not taken while driving¹:

11 AM. A shopped photo of the ice fall on the Catalinas to make it look like it was taken from a car, the way you might have seen this. — 11 AM. A shopped photo of the ice-fall from these Stratocumulus clouds on the Catalinas to make it look like it was taken from a car, the way you might have seen this ice fall. Note how I cleverly tilted the image to make it look like it was taken in a hurry before the light changed.

Same image with writing on it. — Same image with writing and an arrow on it to help you out.

I thought it was some kind of fluke since it was indicated just yesterday from this keyboard, based on prior experience in Arizona, that ice rarely forms in our clouds at temperatures above -10 C (14 F). Maybe someone was nefariously cloud seeding I wondered…. Or had flown an ice-producing aircraft through these clouds upwind somewhere. (Its about what cloud seeding would do in marginally supercooled clouds like these, too, not much but something.)

———academic discussion—–

Ice appearance in clouds with tops warmer than -10 C is common in “clean” environments like over the oceans (see the works of Mossop in the Australian Pacific, Borovikov et al in the Atlantic, Hobbs and Rangno in the Washington State coastal waters and the Chukchi Sea offn Barrow, AK, or Rangno and Hobbs in the Marshall Islands) in clouds with warm bases (ones substantially above freezing for the most part) that can be anywhere even in “continental” environments far inland where cloud droplet concentrations are high due to natural and man-produced aerosols (see Koenig in Missouri, Hallett et al in Florida, Rangno in Israel) among many others). We sometimes have those warm-based clouds here in the summer, too.

——-end of academic interlude——–but not really——

These fuzzy very light snowshowers soon ended and the day went on as foretold, no ice in the clouds.While out on Old Jake, shown above, I was taking photos of particularly dark based clouds and was going to tell the story about why they looked so black, and yet did not precip–to warm and cloud top, and drop sizes near the top, too small for ice initiation. Just about every case in which aircraft measurements have been made in such clouds that form ice at top temperatures above -10 C (14 F), inside them are cloud droplets larger than 30 microns AND a few drizzle drops (liquid drops between 100 and 500 microns in diameter, or rain drops. Droplets larger than 30 microns and substantial concentrations lead to collisions where the drops that collide can coalesce into a single drop. Let us not forget Hocking or, later, Jonas and Hocking and the 38-40 micron drop size limits they found for this to happen from lab experiments. Below that 30-40 micron diameter size, the little cloud droplets act like marbles; too much surface tension.

OK, there’s that little discussion preparing you for what comes next. Continuing with the story…was there one? Well, anyway, Mr. Cloud Maven person, riding on his own forecast made that early morning for no ice in the clouds (meaning no rain), decides to also ride on his old horse, Jake, who needs some more of that exercise.

Confidently, though dark Cumulus clouds underlying a broken to overcast deck of Stratocumulus, looked even exceptionally dark in places, Mr. Cloud Maven person smiled at this darkness of the cloud bottoms, knowing that the darkness in the bases of shallow Cumulus only spoke to how high (and small) the cloud droplets were in those clouds; they had to be highly “continentalized”clouds, ones with tremendous droplet concentrations in them and because of that, all of the droplets in them have to be tiny, being so great in number. And, in being a Cumulus cloud with an appreciable updraft, even more droplets are activated in “continental” air than are at the bottom of a layer cloud like Altocumulus.

When the drops are tiny, more sunlight is reflected off the top of the cloud and the darker they get on the bottom, and the more removed they are from producing a drizzle drop, or are in having the precursor droplets to drizzle drop formation, cloud drops larger than 30 microns.

This is what a Cloud Maven person thinks before he gets on a horse….

So, as I am riding along near the Sutherland Wash, these patches of dark bases form nearly upwind…. I watch them for awhile, quite unconcerned, and smiled again, thinking about the other horseback riders, people on bikes out there that likely turned back in fear of a terrific downpour, not really having the knowledge they need about clouds.

Then suddenly I noticed ice streamers coming down NW of Catalina only a couple of miles away! It was falling from the downwind part of these darker clouds, where after a period of time, ice, if it was going to form would be. But, how could this happen?!!!! Before long, the thicker regions of the cloud began to emit stranded precip, a sure sign of graupel up top in the cloud. Graupel in clouds with supercooled droplets only 23-25 microns in size, much smaller than those required for coalescence, and the present of those droplets leads to ice splinters when they are banged by a graupel particle. A coupla graupel (soft hail) and after awhile, (10-30 minutes) a cloud can have a lot of ice, 10 per liter or more in concentration, plenty enough for precip beside the graupel-melting to rain stranded part. Here is a shot of the further, SHOCKING development:

3:06 PM. First graupel strands emit from base of Cumulus congestus. More ice aloft can be seen on the right. Horse's ears show that he, too, is surprised by this sight. — 3:06 PM. First graupel strands emit from base of Cumulus congestus. More ice aloft can be seen on the right. Horse, too, noting precipitation in the distance, is surprised by this sight. “It’s OK, Jake, its over there and moving away from us.”

3:18 PM. I smiled, a sardonic one, as the drops began to fall (see smudge, lower center). A dark-looking complex of Cumulus topped by Stratocumulus had formed ice upwind of me, and now, me and horse were going to get wet. — 3:18 PM. I smiled, a sardonic one, as the drops began to fall (see smudge, lower center). A dark-looking complex of Cumulus topped by Stratocumulus had formed ice upwind of us (see upper right), and now, me and horse were going to get wet.

I had to laugh at myself on the way back, the rain drops wetting us down, when I thought about being quite confident yesterday morning about no ice would form in our clouds. When you have an occupation that tends toward error, its good to have a sense of humor. There’s nothing worse than a humorless meteorologist at a party, one whose likely obsessing over his error-filled life.

So, why ice? The TUS sounding at 5 PM AST did not suggest tops colder than -10 C Z(moisture top was about -5 C is all), but where the moisture ended, the air was incredibly dry, reported as “1 percent” relative humidity. Here is that 5 PM TUS sounding:

Arrows point to main top height, and where the highest Cumulus tops might have gotten to as they momentarily, due to inertia, mounded above the main moisture level. Normally, they plop back down because they get chilled, and the tops are cold relative to the surrounding air.

So, an overshooting top COULD have gotten to -10 C, and certainly, with that incredibly dry air just topside, those drops in those evaporating turrets would have chilled a couple of more degrees C. So, maybe that’s it, in fact, the overshooting moderate Cumulus tops DID reach to, or below, the -10 C normal ice-forming temperature here.

However, the concentrations that developed in these clouds HAD to be due to other processes beyond just the run of the mill ice nuclei since there are so few of them at -10 C, and that where drops larger than 23 microns come into play. Without those, there would never have been showers yesterday, only a very isolated drop or two. Those larger than 23 micron size drops lead to “ice multiplication” where just a couple of initial ice particles can “multiply” like rabbits in clouds because of ice splinters shed when hit by graupel. However, as we speak, the full understanding of how ice forms in clouds with these “high” temperatures has not been pinned down. Some researchers, the present one included, believe that ice splintering alone is not sufficient to explain the rapidity in the appearance the high concentrations (10s to 100s per liter) that develop in clouds like we had yesterday. You probably don’t care about what I think, but rather go with the majority opinion… Oh, well, it always safer that way.

As a test of even deeper knowledge that an aspiring cloud maven junior might have, this question:

What kind of ice crystals and other frozen particles would have been in those clouds yesterday?

Quiz music here No help from the audience, that other person who reads this blog.

No cheating; don’t get out your Magono and Lee (1966) translated-from-a-Hokkaido-University monograph on ice crystals and the temperatures and humidities that control their shape.

Answer1: What is a (hollow) sheath?

Answer2: What is a needle?

Answer3: What is a graupel (more a lump around a pristine ice crystal or frozen drop than just an ice crystal?

Answer4: What is an amorphous ice fragment?

Congratulations and adulation! You are now officially a cloud maven junior. Don’t forget to order that CMJ Tee.

Below, examples from the “ice crystal bible”, Magono and Lee 1966:

Needles, followed by sheaths, followed by “lump” graupel, and then some ice fragments in the last two panels.

——————–

Only a crazy person would take photos while driving, like that crazy woman I once knew whose hobby was taking photos of dust devils while driving! Oh, my.

Creepin’ Cirrus; pedantry on display

“Storms” at 30,000 feet, single ice crystals falling from various varieties and species of Cirrus clouds. That’s about all we got for “weather” in the next few days as Cirrus creeps up from the tropics into Arizona. But those Cirrus produce great sunrises and sunsets, so have camera ready. And while not much is happening, you should practice logging what you see up there.

Cirrus clouds are the first clouds we see when something is up with the weather, even when it stays up high, but even in these “storms at 30,000 feet”, the moist level tends to decline over time, meaning there might be a chance for mid-level clouds to appear….such as, you guessed it, say, Altocumulus clouds, clouds mainly comprised of droplets, in the near future. That would be pretty exciting; mo’ better sunsets!

Maybe if it was a “cold one”, an Altocumulus cloud with virga hanging out of it, would give you a great opportunity to talk with your neighbors about the Wegner-Bergeron-Findeisen¹ precipitation mechanism (be sure to use all three names to attain the greatest personal stature with them).

——–Warning! Beginning pedantic unit———-

What’s “WBF”, you say?

Hell, you see it all the time! Well, actually only once in awhile here in Arizona. Below, in a pictogram, is a representation of “WBF in action” from a few days into our cold spell just passed so you’ll know when you see ice virga hanging from a droplet cloud you’ll know what the HELL has happened up there. (Dry spells, such as we are in now, make me want to cuss that bit more.)

The background.

Your car has been parked outside all night, and the air was moist. You finally wake up and go outside and you see that dew has formed on your car windows, well, all over. But even though its a bit below freezing, not too much because we’re in Arizona, you also see that in a couple of spots, ice has formed; “horror frost” crystals as we call them here in Arizona because we don’t like frost and cold air of any sort. (The real name is “hoar frost”, and watch out how you use that in a sentence.) The remainder of the drops you see on the car are still in the liquid phase, or have JUST frozen.

But here’s the exciting, magical thing that happens around those “horror frost” ice crystals, demonstrated with a photo through a car window. I’ve added stuff on this jpeg to help explain the magic show going on when the two, liquid and ice, mingle.

And what you see that has happened here is the same thing that happens in clouds when ice and droplets mingle, are co-located so-to-speak. When an ice crystal forms in a droplet cloud, it becomes a vapor hog, water molecule hoarder, because at water saturation, the condition that results in the drops forming in the first place, its SUPERSATURATED with respect to an ice crystal! Amazing, and CRITICAL for life as we know it on this planet because most of the precipitation that falls in mid-latitudes is related to this process. We would have virtually no precip here in Catalina ever without this process.

What does that mean? When the two phases are in proximity as here, the droplets nearest the crystal evaporate, and the ice crystal grows and falls out, usually, as precipitation. Most rain on this planet is due to that process! There are two others that are also important, all ice, all liquid, but today I’m only talkin’ WBF, the “mixed phase” process.

In a cloud, especially a flat one like Altocumulus, this “mixed phase” condition results in ice crystals that grow too heavy to stay in it–its kind of like a “Thanksgiving-for-ice-crystals” inside a mixed phase cloud, and they fall out in those fine strands because they are so fat.

In another way, the ice crystals in a mixed phase cloud are like a low pressure centers, the droplets high pressure centers and the molecules move from high to low pressures.

Mixed phase clouds would go away completely, of course, UNLESS there was some upward motion to keep new droplets forming. But, as in “Ghosts of the Perlucidus” blabbed about here a couple of days ago, sometimes there isn’t enough upward motion to keep the droplets “alive” and only a ghostly remains of the droplet cloud can be seen in a thin patch of ice.

Further detective work re the above jpeg.

Those ice crystals has to have formed when the drops around them were still liquid, probably just as the window reached a freezing temperature or a hair below. If all the dew drops had frozen at once as clear ice, you would not have seen this crystal growth happen because everybody is in the solid phase, no “high or low pressures.” So, while dew drops were forming and growing while the temperature dropped below freezing, there was something quite unique about a particle on the window that caused ice to form when most other places were quite happy to be liquid. We call those special particles that might have triggered an ice crystal, “ice nuclei”, though, too, there may have been a window surface imperfection that did it.

Anyway, ice nuclei are always much rarer in clouds than “cloud condensation nuclei”, particles that the cloud droplets form on. A demonstration of that is in that photo above.

Cirrus clouds, almost never having water, “don’t need no water” because its often supersatured with respect to ice above 30,000 feet without having a droplet cloud. So, even without the water phase, an ice crystal can get fat and fall out in many Cirrus clouds, such as the revered, Cirrus uncinus with its pretty trails. Veil clouds like Cirrostratus? Not so much growth.

———-End of pedantic unit———

Yesterday’s clouds

You may have spotted those creepin’ Cirrus at sunset yesterday. If not here they are, a classic example, ones that kind of drift up to the north out of the tropics into Arizona that from weak circulations down there, even in drought times here, periodically passing overhead, keeping our skies from being boring, particularly for those many of you who out there who are cloud-centric, head-on-a-swivel when outdoors:

5:48 PM. Disant Cirrus, loaded with a few contrails, creeps toward Catalina. Outta be here by now but its dark and I think I can make out something so this is not really a forecast because I kind of cheated by looking at the sky just now. — 5:48 PM. Distant Cirrus, loaded with a few contrails because there’s an airway down there, creeps toward Catalina. Outta be here by now. Its dark and I think I can make out something so this is not really a forecast because I kind of cheated by looking at the sky just now but I WOULD have said that without looking… And if those clouds did get here, there might be nice sunrise for you.

What ahead?

Of course, there’s some rain on the model “horizon” (IPS MeteoStar rendering of WRF-Goofus model), but like that “puddle” on a desert highway on a hot day that you never get to, and I’ve tried, because it moves away as you speed down the road, the “puddle” staying the same distance away, our model rains seem to do the same thing. I’ve used this metaphor before, but I can’t think of a better one. I think its pretty good, too; damn good, really, to cuss a bit more. :} Here are a couple of examples of rain in southern Arizona from last night’s global model run to get your hopes up, most likely to be dashed:

Valid for 5 PM AST, January 28th, Monday. Green areas denote the rain the model thinks has fallen in the prior 12 h. Yeah, right! — Valid for 5 PM AST, January 28th, Monday. Green areas denote the rain the model thinks has fallen in the prior 12 h. Yeah, right.

Valid for 5 PM AST, February 1st, Friday. I would gladly eat my words with whipped cream on them if this happens.

The END, FINALLY!
—————————-

¹They’re not “mostly dead” now, but “all dead”, to crib a line from “The Princess Bride.”

“The Seeds of Uncinus”; a review

Starring Justin Bieber as Harry Potter in the upcoming 12th Harry Potter movie, the musical….

(There, that should grab some attention. But then people would be disappointed, maybe mad, but still they might see something here about Cirrus uncinus clouds that they didn’t know before.)

Had some great Cirrus uncinus clouds yesterday! I was not thinking about uncinus at all yesterday, but rather amorphous blobs of Cirrus, but there they were. Maybe you saw those “Ci unc” with their great tails hanging down, streaking across the sky. And there was something “wrong”, too.

What was it? Its rare when it happens.

The tails were going the “wrong” way, evident later in the day. As streamers of crystals from the “head” of Ci unc trail out, the wind nearly always decreases going downward, and the tails fall back behind the head TOWARD the west, or toward whichever way the wind is blowing FROM. Yesterday, the tails went in front of the head, a real odditity telling you the wind was a little stronger below the head. Hope some of you logged that anomaly. Its hard to get your CMJ T-shirt without having noticed that.

Some photos, too many, no doubt, but that’s what I do, and I’m quite good at it:

9:07. "Angel's hair" passes to the south of Catalina. Cirrus uncinus and Cirrus fibratus, maybe a thin layer of Cirrostratus above it. — 9:07. “Angel’s hair” passes to the south of Catalina. Cirrus uncinus and Cirrus fibratus, maybe a thin layer of Cirrostratus above it. Note the long tails streaming away from Catalina (center).

9:21 AM. Cirrus fibratus (no hook/tuft visible at top because you can't see it here) and Cirrus spissatus eject toward Catalina. Just thought this was pretty, nothing to do with today's discussion. — 9:21 AM. Cirrus fibratus (no hook/tuft visible at top because you can’t see it here) and Cirrus spissatus eject toward Catalina. Just thought this was pretty, nothing to do with today’s discussion.

12:38 PM. Arrows all over in this mainly batch of Ci unc shows seed cloud specks that lead to them much later.

12:15 PM. The heavier Cirrus forms have departed and these delicate ones were to dominate the rest of the day. So pretty. The hooky ones are Ci unc.

But how do these long-tailed Cirrus get that way? How do they start?

With seed clouds, cloud specks with tiny quasi-spherical ice crystals in them, sometimes the ice called “germs” because they’re so small, maybe 10-20 microns in size; tiny dots.

Next is a sequence showing the fleck seed cloud stage to the tail growing stage of Cirrus uncinus, in which the larger ice crystals start to fall out. Unfortunately, by the time the tail is as long as those seen in these shots, those original Cirrus fleck clouds might be a 100 miles away.

Now, is any of this information useful for everyday life? Of course, not! But, let’s say you get on Jeopardy, the TEEVEE program and you have chosen, “Clouds” as your category and the hose (oops, “host”, damn autospeller!) asks you, “This kind of ice crystal is found below the tops of CIrrus clouds.”

You’re answer from today’s “lesson”:

“What is a bullet rosette?” Some kind of prize happens when you say that, and you’re happy for the first time that you read all this.

2:45 PM. As the end of the Cirrus approached, as often happens, you get to see how they looked when they first formed, and here's a shot of that. — 2:45 PM. As the end of the Cirrus approached, as often happens, you get to see how they looked when they first formed, and here’s a shot of that.

2:57 PM. Its got writing on it. — 2:57 PM, just 12 min later. Its got more writing on it.

3:07 PM, ten more minutes go by. I was watching, standing there in a lot of cold air so I could get this sequence. What were you doing? Watching the Seahawks lose to Atlanta? — 3:07 PM, ten more minutes go by, trails lengthen further. I was watching, standing there in a lot of cold air so I could get this sequence. What were you doing? Watching the Seahawks lose to Atlanta in the last 30 s of the game after they just had gone ahead? How could that happen? Its OK, I understand. Clouds don’t always come first for you.

3:19 PM. Last one, was getting too far away.

4:07 PM. The afternoon finished out in an undercutting-the=Cirrus Cirrocumulus clouds, maybe Altocumulus lenticularis in the distance due to having shading. Had some great, delicate patterns as well.

4:10 PM. Cirrocumulus. These are droplet clouds and did not form ice at any time. They were lower and warmer than the Cirrus fleck clouds. Shows how similar the formation process is of Cc and Ci, flecky, dotty, tiny updrafts, maybe 0.1 meters per second. — 4:10 PM. Cirrocumulus. These are droplet clouds and did not form ice at any time. They were lower and warmer than the Cirrus fleck clouds. Shows how similar the formation process is of Cc and Ci, flecky, dotty, tiny updrafts, maybe 0.1 meters per second or less updraft forms them.

Today’s clouds?

COLD, cold trough going over us again today and this evening. Air should moisten up some in the lower levels as this happens allowing for some Cumulus to form, ones likely to develop a little ice in them, which means a little virga here and there is likely. There are also likely to be a couple of Altocumulus or higher based Stratocumulus patches, too, during the day. U of A has predicted soundings over TUS here.

The weather ahead

Temperature extremes pattern still ahead in just a few days now; warm in the West, darn cold in the East. Rain has shown up here on the afternoon of the 27th in last evening’s 5 PM AST global data model run.

Speaking of extremes

A number of low temperature (not “cold” temperature) records have been broken in AZ. Here are a few, as reported by the NWS. Some of these records that were broken go back 100 years, such as the 7 F at Wilcox, set two days ago, breaking the 8 F in 1913, the same time as when the TUS low temperature record was set. The two patterns must have been similar, 1913 and now. Makes you feel special, doesn’t it?

SXUS75 KFGZ 140119
RERFGZ
RECORD EVENT REPORT
NATIONAL WEATHER SERVICE FLAGSTAFF, AZ
600 PM MST SUN JAN 13 2013
...RECORD LOW HIGH TEMPERATURES FOR NORTHERN ARIZONA ON JAN 13 2013...
CITY (PERIOD OF RECORD)          NEW LOW HIGH    PREVIOUS RECORD/YEAR
GRAND CANYON NP N RIM (1926 - 2013)    11          16         IN  2007
PAYSON (1949 - 2013)                   33          35         IN  1960
...RECORD LOW TEMPERATURES FOR NORTHERN ARIZONA ON JAN 13 2013...
CITY (PERIOD OF RECORD)            NEW LOW       PREVIOUS RECORD/YEAR
FLAGSTAFF (1899 - 2013)                -7          -6         IN  1963
GRAND CANYON NP N RIM (1926 - 2013)   -12          -5         IN  1926
THESE RECORDS ARE PRELIMINARY PENDING OFFICIAL REPORTS.
$$

SXUS75 KFGZ 132320
RERFGZ
RECORD EVENT REPORT
NATIONAL WEATHER SERVICE FLAGSTAFF, AZ
1000 AM MST SUN JAN 13 2013
...RECORD LOW HIGH TEMPERATURES FOR NORTHERN ARIZONA ON JAN 12 2013...
CITY (PERIOD OF RECORD)          NEW LOW HIGH    PREVIOUS RECORD/YEAR
FORT VALLEY (1909 - 2013)              20          23         IN  1963
MCNARY 2N (1921 - 2013)                22          27         IN  1964
SUNSET CRATER NM (1970 - 2013)         21          25         IN  1985
...RECORD LOW TEMPERATURES FOR NORTHERN ARIZONA ON JAN 13 2013...
CITY (PERIOD OF RECORD)            NEW LOW       PREVIOUS RECORD/YEAR
FLAGSTAFF (1899 - 2013)                -7          -6         IN  1963
THESE RECORDS ARE PRELIMINARY PENDING OFFICIAL REPORTS.
$$

SXUS75 KTWC 131605 CCA
RERTWC
RECORD EVENT REPORT
NATIONAL WEATHER SERVICE TUCSON AZ
841 AM MST SUN JAN 13 2013 
...RECORD LOW TEMPERATURES SET FOR JAN 13...
LOCATION                  RECORD  OLD RECORD
BISBEE-DOUGLAS AIRPORT      07    15/1975 
FORT THOMAS                 11    12/1962 
SIERRA VISTA                16    18/1916
WILLCOX                     07    08/1913
$$

SXUS75 KTWC 131542
RERTWC
RECORD EVENT REPORT
NATIONAL WEATHER SERVICE TUCSON AZ
841 AM MST SUN JAN 13 2013 
...RECORD LOW TEMPERATURES SET FOR JAN 13...
LOCATION                  RECORD  OLD RECORD
BISBEE-DOUGLAS AIRPORT      07    15/1975 
...RECORD LOW TEMPERATURES SET FOR JAN 12...
LOCATION                  RECORD  OLD RECORD
FORT THOMAS                 11    11/1962 
KITT PEAK                   12    19/1989 
$$

SXUS75 KTWC 131458
RERTWC
RECORD EVENT REPORT 
NATIONAL WEATHER SERVICE TUCSON AZ
0746 AM MST SUN JAN 13 2013
...RECORD LOW TEMPERATURE SET AT DOUGLAS AZ...
 A RECORD LOW TEMPERATURE OF 7 DEGREES WAS SET AT DOUGLAS AZ TODAY. 
THIS BREAKS THE OLD RECORD OF 15 SET IN 1975.
$$

Flatlined

The recording raingauge, that is. A coupla drops is all that fell here in Catalina after some indications of cores around us later yesterday afternoon that were producing measurable rain. You can go to the U of AZ rainlog site to see some local amounts–the Pima County ALERT site is down right now. They’ll have some reports in the mountains and elsewhere, providing it wasn’t snow. The most I’ve seen so far is 0.05 inches, lucky dogs.

Some nice cloud sights on a day of dramatic, icy development. I wonder if you say the first Cumulus/Stratocumulus blob glaciating far to the WSW, beyond Twin Peaks? I thought it would happen first toward the NW-N because the air got colder if you headed in those directions. Yesterday’s cloud highlights, once again pioneering here the “novella-sized”, explanatory caption:

SONY DSC — 8:24 AM. Altocumulus overspreads the sky, briefly. Ac perlucidus translucidus (thin). Someday I think I will make you memorize ALL of the cloud names and their species and varieties.

: 3:58 PM. By this time it looked very promising for a few hundredths of rain.

The weather ahead: measurable rain!?

I am sure, that due to our fine array of weather practitioners on TEEVEE (ones that make an incredible amount of money, mind-boggling really, and ones that have the same kind of fun doing weather forecasting as I do) that rain is in the offing for Catalina in the days ahead. So why bludgeon the topic here? Well, let’s guess a range of amounts that could occur, bottom and top, based on SOP-eyeball of weather patterns and goofy, variable progs:

Last night’s Canadian run, has a near miss now, rain partitioned to the SE of us. Booo! But, then rain with a follow up system on Jan. 1st, maybe with some snow in it here. So between the first threat and the second, both happening between the evening of December 30th and the evening of the 1st, the range has to be wild, maybe not useful. At the bottom, we could be completely bypassed in measurable rain from two strong troughs (we’re still in a “trough bowl” BTW), but I guess if you’re in a drought, you only get misses. But, being the optimist, AND with our own USA! model indicating measurable rain as of last night’s run, the range of amounts over the four days of chances, has to be from a trace to 0.50 inches at most. So, a range with all the factors at play is not too useful.

The average of those two, 0.25 inches, often works out as the closest estimate. Let’s see what the U of AZ has this morning… Oops, no update, budget cuts strike some more!

The End.

Lots of bluster, little rain except at Sutherland Heights where 0.39 inches fell last evening

Another day with hours of thunder, but with those high and cold cloud bases, not much rain reached the ground. Also hurting the rain situation, too much ice. An afternoon sprinkle, a very close, rogue lightning strike, followed by an early nighttime “chaser” storm that, with all of its bluster, wind and vivid lightning, produced only 0.02 inches here, but a lot more at Sutherland Heights, a robust 0.39 inches (new knowledge, gained after dip sticking gage up there at around 7:30 AM) To see how remarkable that Sutherland Heights rain amount is, go here to the U of AZ rainlog network.

Here’s a smaller, but typical example of yesterday’s generally “low output” Cumulonimbus clouds:

Here’s another quite bad cloud (shown below), though it was good one one hand, because it was an early afternoon, frequently thundering cloud which gave promise of rain later in the day. But that rainshaft? Pitiful.

It was also a forerunner of the kinds of storms we would have. Again, with high and cold bases (and oddly to me), there seemed to be an awful lot of lightning for the size of the Cumulonimbus cloud at 1:55 PM, much of it in vivid cloud to ground strokes. You may have seen a another example of that last evening around 9 PM on the Catalinas when there were a series of frequent and spectacular cloud-to- ground strokes, but little rain. The most that fell up there was 0.28 inches at Oracle Ridge. Map here. BTW, you can see the “1:55 PM”
Cb in the U of AZ time lapse movie at the far left beginning around 1:40 PM.

Well, how high were cloud bases? Rendered by the Cowboys, this 5 PM sounding for Tucson:

Reading this sounding, it makes bases appear to be around 16,000 feet Above Sea Level (subtract our elevation for above ground level) and a few degrees C below freezing. With bases that high and cold, the amount of water condensing at the bottom of the cloud is less than on days with bases, say, at 5 C and at 10,000 feet ASL.

So, less condensed water input means less rain coming out the bottom later.

If there is “too much ice” for the amount of water coming into the bottom of the cloud as we saw yesterday, its like a glass of water filled with ice cubes in which only a tablespoon of liquid water can be contained in it. The analogy is only somewhat representative since with “too many ice crystals” competing for the available water vapor, you end up with high concentrations of smaller crystals that hang in the sky rather than fall out.

So you get big anvils and debris clouds with little rain to the ground even in the peak stage of the storm.

Since the best rains in the shafts we see are due to melted graupel and hail, icy particles that generally start as an ice crystal at high elevations in the cloud, if there is little “supercooled” water there isn’t much graupel or hail, the type of precip that can make it to the ground from high bases (melting snowflakes wouldn’t from bases as high as we had yesterday because they’re essentially like Rice Krispies, there’s not much mass in them).

Well, this is pretty boring, so will end here with a sunset photo from last evening:

Today?

The U of AZ WRF-GFS rendering of rain in the State of AZ sees early afternoon Cumulonimbus clouds breaking out over the Cat Mountains today.

Why not?

Starting out with pretty similar sounding this morning, but a bit more moist than last evenings above 600 millibars (about 14,000 feet ASL).

Longer view?

Hector marches slowly toward the Southwest (Canadian model outputs), promising an enhancement of August’s meager rains so far in southern AZ.

The End.

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¹Reminded one of summers in Durango, Colorado, where high, cold cloud bases and “too much ice” is normal.

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.

1:31 PM. That icy sprout on the top meant a rainshaft was already fully developed inside that cloud. There’s always some of it falling out.

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.

Late bloomers and a dry day; but plentiful rains dead ahead

Here’s a brief reprise of yesterday in photos. Expect a similar day today, late rising Cu over the Catalinas, isolated Cumulonimbus off on the horizon, probably NW-NE over the Mogollon Rim, and to the distant SE-S. None are expected to make it here.

4:02 PM. Really haven’t done much, though some turrets poked up to the ice-forming level. Arrows show some ice falling out of an old, evaporating turret.

4:03 PM. Massive anvil appears over the horizon to the SE-S giving hope something could still happen.

5:52 PM. Getting closer!

7:16 PM. Rain complex stays to the S-SW, but provides a nice summer scene with occasional lightning.

7:37 PM. Cumulonimbus capillatus incus (one with an anvil) punctuates the sunset. Somebody got dumped on out there.

Don’t forget to go to the movies to re-live yesterday here, courtesy of our University of Arizona Wildcats.

The rain ahead

One of the great model forecasts of our time came out yesterday from the 12Z global data, and has been pretty much replicated in its results from the new data that came in yesterday at 00Z. These runs have had plentiful rains in SE AZ for just about every day after our little hot dry spell, and both of those US runs with all that rain ahead are supported by model runs by the Canadians using their brand of the Euro model. Here’s the US full run from last night, whilst the Canadian run can be found here.

What’s intriguing is that a tropical wave, sometimes called an “inverted trough” because its upside down compared to our winter troughs, is foretold to move into the State about the 4th of July. An inverted trough would bring extra organization and clustering of Cumulonimbus complexes, which means bigger areas of rain, often accompanied by a large stratiform rain shield that produces hours of rain. It is also true that these can be our most damaging storms.

OK, this big event is “out there”, and you know that this blog is going to jump on the wetter side of the model forecasts. Still, its pretty darn exciting to think of days of scattered showers beginning in early July, and maybe a real drencher just ahead around th 4-5th. The best part is that even if that doesn’t happen, we are embedded in a flow pattern that would keep up that a hopeful possibility of rain day after day, into mid-July.

More nice clouds

Another nice day of high heat and high, patterned clouds. at times. Here are a few shots of the latter, beginning with another flaming sunrise shot. The U of AZ time lapse movie for yesterday is really informative. The clouds shown in the second shot go by just after 6 AM, soon after the movie begins and you can really see the ice/snow falling out of those guys.

They’re not zero, but the chances of rain twixt now and the end of the month are pretty small. However, a tremendous surge of humid air is indicated as the month closes from the remnant of a tropical storm-hurricane along the Mexican Gulf of Mexico coast. Of course, that’s so far out it can’t be TOO reliable, but its something that would bring substantial rains. Here’s what it looks like in green (moist air) and brown (dry air) from IPS Meteostar. All that “green” air to the east of us is heading our way.

Spinning on down from Glasgow to Rocky Point, a low

This is pretty interesting; don’t see this happen too often where a lobe of low breaks off and spins from Montana, back toward the south-southwest to pretty much over Rocky Point, MX, as you will see in this past 48 h water vapor loop. In a water vapor loop, you pretty much see all that the movement that is taking place in the atmosphere and here you can begin to understand why it takes biggest computers on earth to model it. Here’s a close up from IPS Meteostar.

Note, too, those white puffs exploding in west Texas as our little low spins thisaway. Those are massive thunderstorms that our low has and will be triggering in west Texas and eastern New Mexico over the next few days. This is great to see that happening due to the drought those poor folks have been experiencing over the past couple of years. This little low, as tiny as it is, will make a huge dent in those conditions in some areas. It really would be great to be there in some little town, like the well-named town of “Plains”, TX, and see how happy the folks are getting as the rains hit. It would be like the end of a Hallmark movie where everyone is quite happy about how things have turned out.

Here are two shots showing what its like now in Plains-Floydada, TX, area, First, you can see that the earth is quite flat there.

DSCN1514 — Note green along highway. It has been raining off and on in these areas for the past month, so things are perking up. There were occasional bursts of wildflowers, too.

DSCN1525 — These aren't horses. What are they?

But while Texans are getting happier and happier (and I hope they don’t complain about flooding because that would be just plain WRONG), what’s in it for us?

Well, the quality of moisture is less here toward the center of the low, maybe about 1/3 as much in the air over us as in Texas. So, what does that mean we will see? Maybe a few Altocumulus in streaks, maybe finely patterned Cirrocumulus, and then as afternoon comes on, some Cumulus with high bases because its so dang dry. I better predict some Cirrus cuz I see some now! Also, I think I will forecast that the low temperature this morning will be about 62 F here in Catalina because that’s what it is now. Maybe some ice optics, too, now in progress! Continuing, these clouds, too, mean some great opportunities for sunrise/sunset color and ice optics now that I see one (parhelia).

But with those high bases goes low temperatures, likely well below freezing, and you know what that means. The tops are likely to be colder than -10 C to -15 C, 14 F- to 5 F), an ice-forming threshold hereabouts for small, high based Cumulus. With the formation of ice, VIRGA, snowflakes and ice crystals come out the bottom. You can see this by the hazy look around the clouds where it is evaporating–ice takes longer to evaporate.

In the higher terrain, the virga will melt into rain and reach the ground, and the clouds will likely get tall enough to produce lightning, but not here today, but to the north of us at least early in the afternoon and evening. Our best chance of rain with thunderstorms in southeast AZ will be tomorrow as the moisture gradually increases over us from the backflow around the north of the low. The low is forecast to pass to the south of us tomorrow and Thursday. You can see all this happening in our local U of AZ weather model here. (Note the local time is in the upper left hand corner. You will see the precip is only forecast to occur in the afternoon and evenings with this system.

So, finally, some weather excitement in the offing!

Clouds of yore, well, those on Thursday, April 26th

Kind of got distracted with chores after the big trip to NC and didn’t get to this until today… If you can remember as far back as April 26th, we had a “FROPA” (“frontal passage” in weatherspeak) that day. The U of A weather model indicated beforehand that the bases of the clouds last Thursday would lower to the tops of Samaniego Ridge.

Well they did, though it seemed in doubt for a time, and occurred a bit later than the model had predicted.

Also, a few drops came down here late in the morning; more precip was visible to the north of us and that was reflected in the NCAR precip estimate for Arizona the following morning, an estimate that suggested the heaviest rains were up to half an inch just 150 miles away.

Here are a few of last Thursday’s clouds with some commentary.

These clouds came in two separate segments, the first batch were at Altocumulus levels, some 12,000 feet above the ground according to the TUS balloon sounding that morning at 5 AM AST. Those were the clouds that produced the sprinkles around 5:30 AM. Poor snowflakes melting into drops had to fall such a long way!

After a brief clearing, a surge of lower Altocumulus and Stratocumulus came in. For a time, they looked awful threatening, and appreciable rain could be seen falling from them to the north. They produced a few sprinkles here in the late morning and early afternoon about the time the clouds had lowered (as predicted by the UA model, to the tops of Samaniego Ridge to the east).

Why didn’t they rain more?

The answer, as always here, is that the tops were much shallower, and therefore warmer, than those early Altocumulus clouds sporting considerable ice at times. You can be sure that those Stratocumulus clouds over us had tops warmer than -10 C (14 F), a general threshold for ice formation around these here parts. (Over the oceans, where the drops inside the clouds are larger, the threshold temperature for ice formation is higher.)

Just to the north of us, where rain was occurring, you can be sure that the tops sloped upward in that direction, becoming colder than -10 C.

That second batch of lower clouds looked dark and threatening, but lots of times with lower clouds its because they have higher concentrations of drops in them, not because they’re especially thick as you might guess at first. The droplet concentrations in those dark Stratocumulus might have been twice as high as in those early higher, Altocumulus clouds.

Drops in clouds with higher droplet concentrations, say due to smog, reflect more of the sun’s light off the top. That makes them darker on the bottom, and because they are then also harder to get precip out of, they last longer.

This is a real problem, BTW, for climate models, since longer lasting clouds reflect more light back into space and in that sense, and help counter the global warming expected from trace gases like CO2. But, would you rather have ugly clouds and smog infested skies and a cooler planet, or clean skies and clouds and a warmer planet?

The weather ahead

No rain in sight. But a big heat wave, probably temps around 100 F now looming toward mid-may. May is our driest month, BTW, averaging only a quarter of an inch.