Flash: Very light rain (R–) falling at 5:30 AM! Amazing… Won’t measure though, as thickest clouds are already sliding away. But still, great to see, to smell the scent of rain in the desert, and feel the drops in this little surprise sprinkle!
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Forgetting about that last big bust, namely the last big trough of the season that let us down by producing no measurable rain, let us now consider tropical finches, or rather, FETCHES, since an example is coming soon, one that might well bring rain. (I know what you’re thinking; you’ve heard that before, wrongly, I might add as in the LBT-LBB). Hope springs eternal I guess, though rain is predicted by both the USA and Canadian models, so there is some mathematical backing to this hope. See below, as rendered by IPS MeteoStar:
Green pixelation approaches Tucson-Catalina urban complex on Friday, May 29th at 5 PM,
5:59 AM. Virga falls from Altocumulus opacus. This can also be seen as like a little slice of the tops of many rainy days when cloud tops aren’t below about -30 C or so. As here, those tops are usually still comprised of mostly liquid droplet clouds in which ice crystals form, grow, and fallout. If the air is not rising to replenish the doplet clouds, then you will be left with a patch of ice and virga, a patch that will eventually die. Estimated top temperatures, -12 to -15 C, a little colder than shown on the TUS sounding for yesterday near this time because we are farther into the cold air aloft than TUS is. Also, it would be unlikely that clouds like these would produce ice at the indicated TUS balloon sounding top of Altocumulus at -11 C. With their geerally small droplets, it needs to be colder than that. Egad! This is way too much info! But what kind of ice crystals would you expect in a water-saturated enviroment at around -13 to -15 C? Yes, that’s right, pretty Christmas tree stellar crystals, maybe some aggregates of dendrites. Remember, too, for aggregattes to form that concentrations of the crystals must be more than about 1 per liter. Too, since they are falling through a droplet cloud with droplets larger than 10 microns in diameter, you would expect those stellar crystals and aggregates of dendrites to exhibit some riming, that is, have impacted some of the cloud drops as they grew and fell through the cloud, though keeping in mind that the crystals must attain a diameter of about 200-300 microns in diameter before riming commences, helped by the fact that stellar crystals (planar ones) fall face down like a clown does when he’s trying to make people laugh and trips over something. Also, I think someone in that big house on the right is about to have a baby.9:40 AM. With all the cool air over us, it wasn’t long before Cumulonimbus clouds began boiling upward, giving someone some rain.9:53 AM. While Cu boiled up quickly on the Catalina Moutains, and iced-out a plenty, they never really got the depth required to produce much more than sprinkles and virga. Can you spot the little bit of ice on the right side of this Cumulus mediocris?10:30 AM. Nice example of the tremendous amount of ice being produced by such modest clouds (see right side here–nothin’ but ice).1:01 PM. By early afternoon it was all over, the clouds too shallow, the tops too warm to produce ice even though they were still well below freezing. Just the way it is. Guess warmer than -10 C (14 F) at cloud top when you see a sky like this with no ice.6:47 PM. Sunset so-so as high clouds to the NW blocked the sun so it didn’t under light these clouds. Here, Cu flatten as the heat of the day, such as it was at 85 F, cold for late May, dies away,
From your Pima County ALERT gauges, these 24 h totals ending at 3 AM this morning (covers the whole storm):
Gauge 24 Name Location ID# minutes hours —- —- —- —- —- —- —————– ——————— Catalina Area 1010 0.04 Golder Ranch Horseshoe Bend Road in Saddlebrooke 1020 0.20 Oracle Ranger Stati approximately 0.5 mile southwest of Oracle 1040 0.08 Dodge Tank Edwin Road 1.3 miles east of Lago Del Oro Parkway 1050 0.20 Cherry Spring approximately 1.5 miles west of Charouleau Gap 1060 0.55 Pig Spring approximately 1.1 miles northeast of Charouleau Gap 1070 0.08 Cargodera Canyon northeast corner of Catalina State Park 1080 0.08 CDO @ Rancho Solano Cañada Del Oro Wash northeast of Saddlebrooke 1100 0.04 CDO @ Golder Rd Cañada Del Oro Wash at Golder Ranch Road
Santa Catalina Mountains 1030 0.75 Oracle Ridge Oracle Ridge, approximately 1.5 miles north of Rice Peak 1090 0.00 Mt. Lemmon Mount Lemmon 1110 0.75 CDO @ Coronado Camp Cañada Del Oro Wash 0.3 miles south of Coronado Camp 1130 0.24 Samaniego Peak Samaniego Peak on Samaniego Ridge 1140 0.83 Dan Saddle Dan Saddle on Oracle Ridge 2150 0.12 White Tail Catalina Highway 0.8 miles west of Palisade Ranger Station 2280 0.20 Green Mountain Green Mountain 2290 0.24 Marshall Gulch Sabino Creek 0.6 miles south southeast of Marshall Gulch
The absence of precip at Mt. Lemmon is not because the storm went around it, but rather because it fell as snow.
Here in the Heights, 0.08 inches fell between 1 PM and 3 PM. Clouds accompanied the rain.
But what kind? That’s why I am here for you. See way below.
First, some techno-babble. Rain was an on and off event for Catalina and environs in the models run after run. A forecaster friend sent many e-mails that went from “looks good for rain” here, and just about as many that said, “doesn’t look good for rain.” In fact, the (WRF-GFS) model run for just 12 h before it rained, had no rain here, but just a bit to the north. What happened?
Extra sag.
Here’s the amount of trough “sag” (“amplitude”, as we would say) over Arizona predicted just 14 h before it started raining in Catalina yesterday afternoon:
12 forecast valid for 11 AM yesterday morning. Note that the wind maximum is NORTH of Catalina, and over central AZ.
Areas of rain forecast to fall in the 6 h ending at 11 AM AST yesterday morning. Rain just a tad north of Catalina.A computer analysis of the actual winds at 5 PM AST yesterday showing that the trough had more amplitude (sag, droop, etc.) as it crossed Arizona yesterday than was forecast just a day or so in advance. That meant we in Catalina were more embedded in the deeper, and colder clouds with this trough. The jet stream circumcribes those clouds during the cool season here in AZ and most of the SW US. See rain totals at top of blog.
In case you think I am lying again, just because I am a meteorologist and say a lot of wrong things, below is the REAL map for last evening with wind data from rawinsonde balloons on it.
From the Huskies, this 500 mb map over satellite imagery. Strongest winds in our trough run from San Diego, Tuscon, to El Paso, with the tightest spacing of contours and strongest winds at this level in extreme northern Mexico
I hope you’re happy now.
Here’s what the temperature did as the windshift and rain began, in case you missed it:
Yesterday’s temperature trace for Sutherland Heights.
Yesterday’s clouds
The sequence: cloudy, sunny “sucker hole” (one of Biblical proportions), cloudy, raining, sunny, dusty.
6:06 AM. Altostratus and Cirrus combine to produce a gray start to the day.9:44 AM. Lower level moisture layer produces an Altocumulus lenticularis just beyond Pusch Ridge. Seems sky will cloud up real good at this point.Also at 9:44 AM. Looks real bad off to the N, too, in dense Altostratus and lower Sc or Ac.
10:57 AM. Sucker hole! Its real sunny, warming up. You’re thinking as you ride your horse as I was, “What a bad weatherman we have! Said would be windy, cold, and might rain, and yet here is the sun and warmth. What a bad weatherman we have!” (Weatherman is laughing in the background.)11:44 AM. Sucker hole starts to fill in… Haha! “Dreamer” is the horse there.12:10 PM Sucker hole filling in more and more! You’re starting to feel real bad that you made fun of your weatherman, but he’s still laughing at you.
1:17 PM. Rain showing up to west-southwest, upstream. Wind shift hits and ten degree cool off begins. You’re glad you finished your horseback ride none too soon.3:54 PM. A remarkable thing is happening. While there’s plenty of dust in the air. it is also still raining slightly, almost from drizzle-sized drops. Eyeballing the cloud depth at the backside of the rainband clouds from which the drops MAY have fallen from, your CM opined that these drops originated with melted aggregates of needle or sheath ice crystals that, as single crystals before aggregating, were in high concentrations (10s to 100s per liter) in those clouds, implying that a strong ice multiplication phenomenon was at work inside them. Was really a weird scene to have so much SUN and drops falling from clear sky overhead. I would be very proud of you if you noticed this few-minute event at the end of our little rain.
Rawinsonde balloon temperature and dewpoint profile near the time that it rained in clear air from the backside of our rainband. As you can see, cloud tops were around -10 C or a little cooler, pretty warm for raining clouds here. The main part of the rainband likely had somewhat cooler cloud tops. Thought you like to know. This sounding supports the idea that an ice multiplication process was at work, at least on the back shelf of these clouds that rained. I wanted to confirm prior ground speculations with more speculations from the sounding at rain time, though it was launched around 3:30 PM AST way over there by Davis Monthan Airbase. Wondering now if I will finish this blog today….4:34 PM. Shelf of rainband exits the Catalinas. Nice lighting, though.6:32 PM. While the rain may have washed a lot of dust out of the air, more dust invaded the area as soon as the rain ended.
Don’t really need me anymore. Everyone’s on top of this ” incoming” now, set to begin in the area overnight on Thursday, the one you’ve been reading about here since maybe last October I think. So, feeling sad today, also because it looks like its going to be a bit too warm for snow, which I think I mentioned about a dozen times. Maybe I will take it out on you by boring you with a science story, one about ice in clouds…but one featuring such stalwarts as Sir Basil Mason, Stan Mossop, John Hallett, Pete Hobbs, Alexei Korolev, and others. Interested now?
But first, a few nice cloud shots from yesterday so you don’t get too mad at me for boring you first:
2:07 PM. CIrrostratus fibratus (has detail, not just an amorphous veil).4:21 PM. Two dense patches of Cirrus spissatus patches and dog, Zuma (named after the acclaimed dramatic series, Baywatch, which took place at Zuma Beach; also where the author, whilst not storm chasing, spent a LOT of time.
5:22 PM. Cross section of a Cirrus uncinus (hooked at the top). This shows how the ice crystals forming at the top first get heavy enough to fall out, but if encountering drier air, start to evaporate, slow in fallspeed, and as in this case, form a flat layer of tiny crystals at the bottom of the head of Cirrus uncinus. Likely a little moist again at that bottom location so the tiny guys don’t away very fast.5:29 PM. Sunset in Cirrus (spissatus and others).
Cloud ice science story
(drink some coffee, maybe take an extra swig of an “energy drink” if venturing forward)
Kind of takes the fun out of it when other people are saying what you want to say by yourself, lilke today’s forecast for Friday’s storm. Kind of like being second when you publish “new” results behind other researchers who “got in” a little a head of you (like Korolev et al.-with Hallett!) did in 2004 reporting the FIRST image of a shattered frozen drop they said.
Drop shattering during freezing; what about it?
It was thought not to happen in natural clouds after that embarrassing episode back in the 1960s when the Great Knighted, Sir B. J. Mason1 and his student, Swinbank (1960), reported drops exploded with they froze. Liquid centers tried to get out of the ice shell as the drop froze from outside in, as you would expect, but then blew up when the freezing water expanded inside the shell. Looked pretty good.
There was only one thing wrong, their findings weren’t valid for real clouds.
They put too much CO2 in their cloud chamber (that’s right, the very SAME stuff that’s supposed to make the earth warmer and warmer year after year but has been sitting around lately, about 15 years actually, not doing anything) and that CO2 in the experiments turned out to make the outer ice shell real weak, and also the CO2 came out of solution in the water in the liquid center to make matters worse by expressing gas through the shell. I wonder how many people have done that?
This was found out by researchers in my very own group before I got there, Jim Dye and Peter Hobbs, a few years later. When real air was used, the drops didn’t explode. So, down that hypothesis went that exploding drops caused a lot of ice to form in natural clouds.
End of story? Nope.
Later, Hobbs with grad student, Abdul Alkezweeny, repeated the experiments with freezing drops, but this time instead them just sitting there, had them rotate as they froze and they DID shatter some, but not a lot! This was back in 1968.
But no one was reporting images of shattered drops.
In those days, there was a HUGE amount of unexplained ice in clouds. Cloud chambers on the ground and in aircraft, found that little ice formed until the air IN THE CHAMBER was at least as cold as -20 C (-4 F), but instrumented aircraft repeatedly found tremendous amounts of ice in clouds that had never been colder than -10 C (14 F). Hence, an enigma.
But the explanation that a few drops exploded, sending out thousands of ice shards never gained any ground because there was never any observational evidence that it happened. Instead, an Australian researcher, originally from South Africa, Stanly C. Mossop, with John Hallett, discovered in 1974 that a bar moving through a cloud chamber between -2.5 C and -8 C, caused ice splinters to eject from SOME of the little drops hitting the bar and freezing on it. But the drops had to be at least 24 microns in diameter, fairly large for cloud droplets, or nothing happened. Also, if they moved the bar too fast or too slow, nothing happened. So, there were a lot of criteria involved in this process, temperature range, drop sizes, speed.
So, the Hallett-Mossop riming-splintering hypothesis was born. They assumed the bar, moving at the fall speeds of soft hail, showed what soft hail did inside clouds: multiply ice content!
It was an exciting time to see that the mystery of all that ice in clouds at higher temperatures was finally explained, not needing, shattered drops or anything else.
But there were some problems. In the early days, it was thought that this process, to raise the ice concentrations in clouds much, would take as long as 1-2 hours because it was a “cascade” process. The few first splinters had to grow to sizes there they fell fast enough to bump into drops and cause ice splinters to eject. Well, that wasn’t right. Natural clouds formed ice MUCH faster than that, as you here in Arizona know so well.
The experiments continued and it was found that shattering helped this process (assuming it occured, but even more important was the freezing of drizzle and raindrops. When those froze, they became instant rimers, splintering objects, and so the time for a cloud, but one having drizzle and raindrops in it, and in the right temperature zone, just between -2.5 and -8 C, was cut down to minutes, something like 10-20, to get ice concentrations from about 1 per cubic meter, to tens of thousands per cubic meter, a real rain cloud.
Except for a single image of a drop half by a researcher using a cloud camera with a glider in the 1970s, no one had reported a shattered drop. Then along come Korolev et al. (with the great Hallett!) in 2004 reporting shattered drop images in a Canadian frontal band using an advanced cloud camera. They wrote that it was the FIRST images ever reported of shattered drops. Rangno and Hobbs (2005) also reported images of shattered drops in clouds around the Marshall Islands, thinking at the time that they were going to be first in line, and then discovered the Korolev et al. report. It was a sad day to find that reference, as a researcher that was thinking about the glorious days ahead, the keynote addresses to important conferences, that would result from being first in line with something and then other people would always have to reference you.
As Ecclesiastes wrote, their is hardly anything new under the sun if you’re slow going about it.
Published another paper on shattered drops back in ’08. But, found they didn’t SEEM to be making a big contribution to the ice content in clouds, less than 10%. You can go here to see that I didn’t make that part up. That was kind of sad finding, too. You want what you find to be HUGE, and it wasn’t so huge as I hoped.
So, riming and splintering remains our best, most accepted explanation for the great amounts of ice in clouds that aren’t so cold, though the author and Hobbs, have mostly found it wasn’t powerful enough to account for the speed of ice development. Only the author’s friends, Stith et al (2004), have reported a lot of ice that couldn’t be explained by the riming-splintering mechanism as have R&H over the years.
But it would be so great if others confirmed the Stith et al findings.
The End for now.
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1Wiki doesn’t do a very good job, and doesn’t even list his outstanding updated, Physics of Clouds text published in 1972, the “bible” of cloud physics in those days! Unbelievable.
2Riming: Think of what happens to an airframe in a liquid drop cloud at below freezing temperatures. HELL, here’s a photo by the author from the author-occupied Lear Jet 35 flying in supercooled clouds over Saudi Arabia, 2006, The weapon-looking things under the wings image precipitation particles like raindrops and snowflakes using laser beams with light sensitive diodes at the other end, one that when shadowed, give you a two dimensional image of what went through the laser beam.
8:01 AM, December 16, 2006.
11:02 AM, December 10th, 2006. Had to land at Hail, a small, pretty town north of Riyadh to pick up some supplies, ones for the randomized cloud seeding experiment underway. It was interesting that we could carry these boxes labeled “Explosive” to the Lear Jet without any notice. Hmmmm. They were there because that’s where another NCAR radar was besides the one at Riyadh, and a plane might have to land to continue seeding if it ran out of the seeding flares like the ones inside these boxes.
An unusual sight yesterday: bulging dawn Cumulus fronted by fog. These Cumulus (not spawned by ground currents) suggest instability aloft, a rapid decline in temperatures with increasing height, which allows the buoyancy of “warmish air” in-cloud surrounded by cooler air to go up, whilst fog1 suggests the opposite; cold, damp, heavy air that can’t go anywhere but down, slip sliding away as it did yesterday because its topped by warmer air, a atmospheric “glass ceiling”. Ground fog like this is colder air that you can see.
7:21 AM. Looking NW from Equestrian Trail Road across Oro Valley. 7:19 AM. Odd multiple layers of ground fog (lowest) and Stratus clouds (“clouds” because they’re not on the ground) with shreds of Cumulus fractus above Samaniego Ridge. 7:07 AM. As above, suggesting a very fine layering of moist air with little temperature caps.
Here in Catalinaland, this kind of layering of cold air, as most of you know, is endemic on clear nights. Those who drive down across the CDO wash from Sutherland Heights or along Lago del Oro from the surrounding higher terrain know. Because of the stupefying amounts of rain in the past three days, the air is damp enough at ground level to form fog and you can see whose colder at night than you are IF you are above it. Also, anyone who walks their dog in the morning passed innocuous looking gullies, is aware of how cold air flows downhill and collects in low places.
The lack of density of this fog indicated that it formed in real clean air, air that didn’t have a lot of junk in it (which would also contain a lot of CCN, cloud condensation nuclei. Pretty hard to get fogs like we had in Bakersfield, CA.
Once things warmed up some, and with Arctic like air up top, Cumulus arose, a couple of which sprouted icy tops and shafts, namely, became small Cumulonimbus clouds, tops around 20-25 kft. Along with these clouds, there was a treasure of sunny highlights and shadows moving across the Catalinas. Here you go:
10:49 AM. Small Cumulus humilis, mediocris begin forming as temperature “warms up” to 50 F (egad).
11:13 AM. There’s water (glinting) on them rocks! One of the prettiest sights we get to see on the Catalinas after some rain. Not enough water was dumped on the mountains during our drought-denting storm to get water into the CDO Wash locally, but the Sutherland Wash developed a trickle. Just too much dry ground up there for much runoff with the relatively steady rains that we had.
12:10 PM. Small Cumulonimbus clouds erupt just north of Saddlebrooke. Thought I heard thunder from this complex later. 2:50 PM. While small Cbs developed to the north, the Cat Mountains were only able to produce Cumulus congestus (“heavy Cu”). Didn’t see any ice; neither did you, or there’s something wrong. But, if you go here (U of AZ time lapse), you WILL see some forming in the downstream portions of clouds over the Catalinas. Sometimes not seeing ice is because the tops are blowing off away from you before they show it, especially when there isn’t a lot.3:48 PM. Last gasp Cu congestus. Will highest turret form ice?3:49 PM. Ice starting to show!3:53 PM. Droplet cloud completely gone. No question now, nice ice plume. You want to target aircraft into densest portions of this ghostly veil of ice; will correlate with densest portions of liquid cloud. Not enough ice for a shaft below the cloud, but someone felt a few drops below it!
Below, one of the attributes of our partly cloudy days and low near-winter sun angle; pretty lighting:
5:19 PM.5:06 PM.3:54 PM.
The weather way ahead, first week in December.
Pile of cold air to drive into West Coast and Rockies during the first week in December. Snow even possible here, the air is that cold, but mainly the cold air will likely lead to the first cold spell where temps drop significantly below freezing. The worst days look like the 5th and 6th right now, after the threat of rain and or snow pass. So, if you have an evap cooler, you’ll definitely want to have it drained before then if you haven’t already taken care of it (like me).
Rain threat at the end of the month/first day or so in December is fading some in mods, but I refuse to give up on it!
The End.
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1Fog is “gof” spelled backwards, BTW. Has a lot of meanings and I avoided the obvious juvenile approach (today), “Think I’ll go goffing today” which I wouldn’t say anyway because I don’t play gof.
Some nice CIrrus spissatus and the rare Cirrus castellanus yesterday (something I say a lot here in old AZy). Here is half hour sequence of a patch of heavily precipitating Cirrus spissatus, kind of a cloud oxymoron. I thought it was pretty spectacular even if you don’t care one wit about it. (Hahaha, “wit” instead of “whit.”)
Those Cirrus clouds were up at about 35,000 feet above sea level, at around -50 C (-58 F), but snowing like mad. Don’t let folks tell you its too cold to snow; usually happens that way because here on the surface there’s a high pressure over you, the sky is clear, to wit; a fair weather pattern, and that’s why its not snowing here on the earth when its -58 F, except maybe when there’s a ice haze called “diamond dust“, tiny ice crystals floating/glinting in the air.)
8:48 AM. Cirrus spissatus on the left with the little snowstorm trailing off to the left will pass overhead of Basha’s parking lot there on Oracle in about half an hour, a prediction made in hindsight. 9:07 AM. Taken while not driving down Equestrian Trail Road to Basha’s supermarket.9:21 AM. Basha’s parking lot. Snow, composed of single crystals, not flakes or what we called “aggregates” because they don’t stick together at such low temperatures, pours out of this really cold cloud. The single crystals in the trail would be bullet rosettes, a complex looking crystal consisting of hexagonal columns that stick out from a center point. How much snow falls out? Just a dusting. You could blow it away off any surface. When flying through these icy clouds toward the top where the crystals are simpler, there are sparkles and glints when the sun hits the crystals just right. Very pretty.
The day ended up with lower Cirrus and few Altocumulus clouds with virga as the dry air aloft moved in, providing the clear western horizon that allowed the sun to highlight our clouds. That great sunset, as much as I could see anyway being “on the road” here:
5:37 PM. Heavy Cirrus (spissatus) or Altostratus patch, either name OK, with Altocumulus on the far right horizon.
The weather ahead
Mods still showing rain in the area on Sunday the 17th pretty consistently now. And as we saw from the “errorful” NOAA spaghetti maps yesterday, a trough with cooler weather, clouds and scattered precip is pretty much in the bag for that time period (16th-18th). Can only hope that we get something measurable here. But, even without rain, those days will be pretty ones with Cumulus clouds around.
For those less weather-watchfully-endowed as a CM or CMJ is, these from last evening between 6:02 and 6:10 PM:
6:08 PM. Its raining on me, too, and so I am IN somebody’s rainbow! How cool izzat?
Yes, Virginia, it did rain on the Lemmon yesterday, and that very light rain crept across SH-Catalina just after 6 PM yesterday, eventually crossing Oro Valley with a little baby sprinkle.
Drops were pretty numerous, pretty small, and fairly uniform in size, making me think about what was up there doing it. The shaft was always thin coming down the mountains toward us, and being thin means the top ain’t too high, as you know. Maybe, it was one of those rare ice multiplication days that happens here every so often, ice that forms at temperatures not terribly far below freezing. Going to movies now to see if the U of AZ time lapse can shed light on the buildup–thinking aggregates of needles and sheaths that melted into raindrops and ice multiplication in a top only as cold as -10 C or so.
OK, looked at movie, can’t see a protruding high top and so I am concluding that I am correct in the assertion that an unusual event happened in AZ, ice formation a plenty at temperatures of -10 C. It happens, but requires larger cloud drops in our clouds than usual, maybe some drizzle drops that froze, became graupel (soft hail).
Now I will look at the TUS sounding for yesterday afternoon and see that it confirms my thoughts, tidying up a nice story of cloud microphysics. After looking at it, will post it since it is supportive of the above conjectures, otherwies I would not have posted it. From the Cowboys this for Tucson yesterday afternoon:
The afternoon sounding for TUS, launched around 3:30 PM AST. This profile DOES support the thought that ice formed at high temperatures. Amazing! I really was thinking needles and sheaths as the drops came down.
Gotta go now, ride a horse, more later maybe….looks like we have those pesky Altocumulus clouds, though ones not as thick as yesterday’s which took into mid-afternoon to burn off, and kind of wrecked our rain chances.
Needles and hollow sheath ice crystals only form when the temperatures in cloud are warmer than -10 C (14 F). Normally in AZ we do not see ice forming at those temperatures because the conditions for their formation, generally involving very large cloud drops and drizzle drops in clouds at those temperatures are rare. This is because we usually have high concentrations of cloud droplets and those higher concentrations lead to itty bitty drops, ones less than 30 microns in diameter at temperatures higher than -10 C. So, another thing that we can guess about yesterday’s clouds is that the droplet concentrations might have been lower than usual, and that the drops in the clouds got larger than 30 microns in diameter.
Well, at least much of today anyway. The title for today is from Gershwin, of course, and the version of a song he later changed to “Blue Skies” (really old version here)–this was after he moved from New York, an extremely cloudy state, to southern California (“Hollywood”, in 1936) where weathermen can sleep for six months due to soporifically boring weather, to emphasize that weather aspect there with redundancy since “soporific” means boring as well. I lived there in so. Cal., myself, San Fernando Valley, growing up and I know first hand. Slept out in the backyard with doggie in case a sprinkle fell out of Altocumulus in the summers and didn’t want to miss it1 That’s how bad it was weatherwise.
Continuing, Gershwin didn’t think “Gray Skies” was so uplifting as a song, and he eventually changed the title to something more “accessible” as a popular song (who wants to think about Altostratus, or, Stratocumulus???).
BTW, you won’t find facts like this on other blogs; in fact, to be redundant with the word “fact”, won’t find this kind of information anywhere else at all!
We got us some more of that Altostratus overhead today, and in places, embedded or separate patches of Altocumulus (droplet clouds), and you know what this means. Its snowing up there above 15,000 feet above ground level, and if Ms. Mt. Lemmon was only a few thousand feet higher, there would be PLENTY of snow on top. There could be some spectacular sunrises/sunsets today and tomorrow as this stream of tropical moisture aloft passes by. Be ready.
Yesterday’s clouds
First, a couple of “action” shots, ones where glaciation is taking place:
6:48 AM. You know the drill, (the cloud) used to be this, and now its that. “Droplets to ice; its a natural thing.” The droplet cloud on the right side is Altocumulus perlucidus (looks somewhat like a honeycomb).
6:47 AM. Some more of that over there. Sometimes I have called the icy small patches, “The Ghosts of Perlucidus.” (Happens because the clouds are not only real cold, but damn cold (usually less than -25 C (-13 F).
The weather ahead
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The End.
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1 In case you don’t believe me, maybe I just made that up about sleeping out, only pretending to be some kind of weather fanatic in this blog, this picture for the doubters out there from those summer days with doggie in the backyard; hoping for a drop so I could enter it in my weather diary. Oh, yeah, I had one.
I hope you’re happy now. I put it in full size so that you could see it was me, not someone else.
I thought today I would provide some answers to yesterday’s pop “ice-Q” quiz a new expression I just now made up except that I just now also found out that its already “out there” for a computer graphics card and some refrigerators.
But ignoring that fact completely, you might try using it in a sentence today: “My ice-Q level is gradually getting higher these days. I’ve been working on it for some time now.” Lot easier to say than “ice IQ.” Thanks in advance for using “ice-Q” in a sentence today! You’ll have to make it clear that you’re not referring to a graphics enhancing video card or to overclocking a computer and a refrigerator of some kind.
I thought, too, that maybe I need more science content; maybe I’m kidding around too much, teasing you with droll, well, maybe sophomoric humor, and ludicrously WRONG content, like indicating on a diagram that the Equator goes through Hawaii and that the day of the week changes when you cross the Equator. That was so funny! (Or was it?) ((Well, I laughed…)) (((Hmmmmm…maybe a laugh track1would help, like on all those TEEVEE shows that seem to indicate that America has the sense of humor of a moron.))) ((((Is this too strong?))))
So, today I thought I would ramp up the science content, give you something a little heavier to think about, give the old noggin’ some real exercise. Below, from Agee et al. in the February 15 issue of Science just out. I put it in extra big letters so you won’t miss anything:
Its about a bit of Mars found in Morocco at something like the Tucson Gem and Mineral show. If you ever dreamed of being a spaceperson and wanted to go to Mars to see what’s like, you don’t have to go. Some of its already here. Seems the planet was shooting stuff at us, oh, maybe “2.089” billion years ago. Some of Mars is at lot closer than you think, too. Its just over in New Mexico at the UNM Meteoritic Museum in ABQ! How great is that?
Some answers
Below, some of the very SAME photos you saw yesterday with arrows and writing on them. OK, I am repeating things. But you know what, life is a lot easier when you repeat things rather than have to think up new things.
End of answers.
Now I will look at the weather way ahead…
First, I did see a bunch of NOAA tornado watches out associated with our cold trough, now those watches are for central Florida, so it was good to hear that other than a scare, some big ones didn’t occur. You can get all the warnings and watches here, BTW.
Nothing out there, really, for us for two weeks or more. A close call for precip and another cold surge happens around the 9-10th of March, that’s about it.
Oh, me, another LONG dry spell ahead. Are we REALLY going to have a third drier-than-normal late winter and spring in a row? Sure looks like it now with February on line to be just short of an inch compared with our inch and a half average. Dang.
With no weather ahead, will likely hibernate for awhile. Watch some TEEVEE (hahahaha).
It was hard to see all the smoke around yesterday morning after the two previous stunning days with high visibility. I was thinking I had never seen so much smoke in Catalina as I saw yesterday morning. Here is some photos of that awful event:
7:56 AM. Heavy dark smoke layer evident to SW. Some Stratus clouds also were present.
8:40 AM. Normally, in my experience here, such smoke is husbanded to that region south of Pusch Ridge. But no, not yesterday, its HERE! What an awful view this was!8:45 AM. In this photo not taken while driving1, you can see that there are TWO plumes the lower one drifting south from the area of the Golder Ranch-Sutherland Wash development of expensive custom homes, some of which might have been burning wood for heat, or something else woody, while aloft is a second, separate plume. I could not tell where the higher one came from, even in this time lapse from the U of AZ. Note how in the movie the Stratus clouds in the morning change direction in movement. The movement at first is from the west-northwest (left to right), and those clouds contained the higher smog layer. So, could it have been from PHX??? ———– 1Smokey the Bear reminds drivers that only you can prevent smoky, well, a lot of it anyway.
In the afternoon, the smog was gone, mixed through a greater depth, the layering destroyed by the convection, those rising currents and compensating downward ones, that cream any morning layering. The dilution effect, and it also could have been that the aerosol load (smog) decreased with time, made things look much more clear. To this eye, there was still a lot of smog present, just diluted in the space between the ground and the bases of these small Cumulus clouds shown below. Still, there were so many pretty scenes on this horseback ride with a friend that I took more than 100 photos! Some water was present in some of the little washes, always nice to encounter, and some vividly green spots of of emerging growth (shown last).
The final point worth mentioning for pedantic reasons, is that yesterday afternoon’s TUS sounding indicated the same cloud top temperatures as the day before, about -12 to -13 C. Yet, there was no ice dropping out of those clouds. The day before, with the SAME cloud top temperature, ice and virga were widespread.
What’s up with that?
Ah, the complexities of ice formation in clouds!
When clouds are small and have a lot of droplets per liter in them, likely hundreds of thousands yesterday, given all the smog around, the drops end up being especially small because so many form on some of the smog particles (called “cloud condensation nuclei”).
In repeated flights at the University of Washington, we found that the resistance to form ice is dependent on not just on temperature, once thought to be the sole controller of ice formation, but droplet sizes in clouds as well. Small droplets sizes in clouds meant they were less likely to form ice, given the SAME cloud top temperature. Altocumulus lenticularis clouds are the poster child for ice formation resistance in clouds with their tiny drops, often having to be colder than -30 C before ice forms. On the other hand, clouds in the pristine Arctic around Barrow in the summer time, over the oceans away from continents, and in deep, warm based clouds even polluted ones, form ice at temperatures higher than -10 C when the drops in the clouds are large and have reached precipitation sizes (more than 100 microns in diameter to millimeter sizes).
So, it seems likely that yesterday, our shallower, pollutted clouds had smaller droplets in them than those deeper, less polluted clouds of the prior day in which we saw so much ice form in the later afternoon with about the same cloud top temperatures as yesterday. It is also the case, that when clouds are in large patches as they were the day before, that ice formation has more time to take place, and that, too, may be a factor.
Complicated enough? Yep.
2:52 PM. In the Catalina Mountains on the back from the Deer Camp trail. Cumulus humilis dot skies. No ice evident.
2:18 PM. Cumulus humilis sitting around over Sutherland Heights, and the Oro Valley
The weather ahead
After another round of cold, this one dry cold just ahead for us, the heat is on by early March, and along with that heat in most of the West in early March, likely record cold in portions of the East. Check this 500 mb map out for the afternoon of March 2nd, produced by last night’s WRF-GFS model run at 5 PM AST, rendered by IPS MeteoStar:
Look at the size of that cold trough and low center! Huge!
That isn’t the only weather news ahead, cold in the East, warm in the West in March. Our upcoming cold shock that hits on Sunday, is caused by an unusually powerful upper trough that dips down into Texas after it blows by us, then roars northeastward across the South on Monday and Tuesday. Expect to read about godawful tornadoes in the South on Monday and/or Tuesday.
I wonder if you noticed the blackish smog layer to the south and southwest of Catalina yesterday? Usually it stays down that way, flowing peacefully toward the northwest from Tucson across Marana and Avra Valley, an area where a close meteorologist friend and his wife just bought a house even though they knew this happens in winter and not one in Catalina where we normally escape this characteristic Tucson smog plume. They must like winter smog overhead, but then as the sun heats the ground, it comes down to you. Go figure.
Here is yesterday’s Tucson smog plume exiting Tucson:
8:47 AM. Smog plume exiting Tucson, moving left to right over Twin Peaks area. This was one of the densest, most awful ones I’ve seen from Catalina.
But then, in the later morning hours, a southerly wind brought that smog bank to our normally clear air oasis of Catalina, infecting the shallow Cu fractus clouds that formed as the sun heated the ground. This was a real disappointment since probably most of us were expecting the kind of pristine view of the Catalinas yesterday morning.
10:09 AM. Smoke-filled Cumulus fractus clouds. The smog looks white here instead of dark because of “forward scattering”; the white light of the sun is being scattered in the viewer’s direction by the smoke particles. (In the first photo, there was no forward scattering and so you can see the actual dark hydrocarbony smoke particles for what they are, dark and sooty.
Fortunately the smog was dispersed as the day wore on. As the layer in which it is contained gets deeper, and without more smog being added to it, the amount of smog, say, per cubic mile diminishes and pretty soon it gets so thin you can’t detect it with your eyes. Still, exactly the same amount might be in the column of air between you and the higher cloud bottoms. Here’s what it looked like in the later afternoon:
BTW, while its easy to see that the Cumulus fractus clouds in the second photo are very low, in the 3rd photo above it’s much harder to detect how high these small Cumulus are. The TUS sounding indicated that they topped out at 9,000 feet, or only about the same height as Ms. Mt. Lemmon! Top temperatures in these smoke-filled clouds were no colder than about -8 C (about 20 F), too warm for ice to form in them, especially when the cloud droplets are reduced in size by smog. The larger the cloud droplets, the higher the temperature at which ice begins to form in them, and so smog generally reduces the chance of rain in shallower clouds.
This is why oceanic clouds in pristine regions lacking smog, even shallow ones, rain or drizzle so easily. The cloud droplets are much larger in those clouds right from the get go than those in smoggy regions. So oceanic clouds can rain either because those larger cloud drops reach sizes where they can collide and stick together, forming larger drops that can fall out (“warm rain process”) or form ice at the highest temperatures known for ice formation, -4 to -5 C (23-25 F). Usually both processes are work in those ocean clouds that rain so efficiently. They’re pretty great, really, such little clouds that rain.
Vacation in Hawaii if you’d like to see some up close (though not downwind of the Kilauea volcano plume and in the lee of the Big Island of Hawaii since that volcanic plume can smoke up the clouds real bad there and they stop being so darn efficient as rain producers. Recall that the biggest drop in the world was measured in clouds in Hawaii (1 cm in diameter, Beard, private communication, received AFTER Peter Hobbs and me got the Guinness record for the biggest drop ever measured, 8.6 mm in diameter–got a lotta publicity around the world, too, calls came from everywhere!).
You see, Beard didn’t publish anything about HIS BIG DROP; we published ours in a refereed journal. “Neeny, neeny, neeny”, I think is what you conclude here. Immaturity: sometimes I think its not valued enough in life.
That’s what its like in academia; you publish or die! Die that slow death as an “Assistant Associate” professor of something, never reaching the exalted “Professor” status.
The “combo” ice seen yesterday morning
We had two forms of ice yesterday morning that you may have noticed, say, on your car if it was parked outside overnight. There were originally rain drops left from the storm that froze in place during the cold night (was 30 F here yesterday morning), and then the deposited ice from water vapor on top of the drops.
The deposition process, as we call it, leads to hoar frost ice crystals growing in time as the molecules of water vapor add to it during the night. This combo ice led to an unusual site on the car before the sun did away with it. Here are a couple of shots of this unusual sight:
9:57 AM. “Strange brew.”
9:58 AM.
The weather ahead
After the “sunny malaise” for 5-6 days, with Arizonans statewide out doing things, its back to the Bowl, the trough bowl. The period we’re in now might be called, “a sucker ridge”, a high pressure ridge that is. You might well think, “Well, that’s it for winter in Arizona!” after a few days of the “sunny malaise”, but you’d be WRONG. I can’t emphasize the word, “wrong” enough. The Bowl comes back with a vengeance, too, when it reforms here in the Southwest; there will be one storm and cold blast after another. If you’re a snowbird, you might start to cry, and wonder why you didn’t go to Costa Rica for the winter.
Well, I am looking forward to storms and seeing more scenes of white mountains deep in snow, and green vegetation shooting skyward. That’s the promise of the “Bowl” ahead, where storms collect, in the weeks ahead right into March.
Taking a few days off now, likely without pay, to replenish mind, get out and do things like the rest of Arizonans will. Will give you time to ruminate on all that’s been said here over the past year or so, correct and incorrect, mature and immature…
The End.
About real clouds, weather, cloud seeding and science autobio life stories by WMO consolation prize-winning meteorologist, Art Rangno
