First, a water year (Oct-Sept) update. You won’t like it:
One caveat about February’s total: It might be as much as 0.25 inches higher since a good bit of snow during the historic February 20th storm probably did not get into the Davis Vantage Pro gage located some six feet above ground level where wind raises havoc with snow measurements in particular. Gauges day had more all around mine. You can go to the U of AZ rainlog.org home, plug in the date (in this case the 20th, and see what other folks had compared to the crummy 0.52 inches the gauge here got following the meltdown. Generally, while there are a couple of goofy obs on the rainlog site, the amounts around here were 0.70 to 0.90 inches. Thus, our February 2013 total is more likely around 1.20 inches, not 0.95 inches as shown in this graph. Dang.
Here’s the March daily measurable rain climo:
Current and just passed weather
Traced last night, I’m sure you logged it. Drops were falling, pretty big ones, at 2:42 AM. Only lasted about a two minutes. If you want to see what happened in radar and clouds, go here. Shouldn’t be surprising that it traced here given all the virga, and isolated spots where drops were already hitting the ground last evening.
Here are some shots after I got back from PHX-Anthem late yesterday. Some drops hit the window, too. First, I thought I would share with you a wildlife response to coming changes in the weather, something you’ll begin to notice as you traverse the long road to cloud maven juniordom. Here, shelled creatures demonstrate a preoccupation with the sky over due to increasing Cirrus cloudiness in Anthem, late on March 2nd, the day BEFORE all the heavy virga. Its something to note when these creatures do this. They are telling you something about the coming weather. Well, anyway, that’s what you should say when you see this turtle formation; your neighbors will then think you’re some kind of turtle “whisperer” AND a weather guru all in one.
At the Anthem Community Park: Wildlife shown here were clearly becoming increasingly concerned about the thickening cloud cover late on the 2nd.
3:53 PM. Tentacles of virga from deep Altostratus clouds reach down toward the Tortolita Mountains.5:53 PM. Altostratus with virga and mammatus (left side), a term reflecting certain female mammalian characteristics. As I have reported here in the past, some of the female grad students at the U of WA weather department were offended by such nomenclature, asking why such clouds couldn’t have have been termed, “testicularis” (quite an unseemly term, really) and drew lines through a label of a wall print of “mammatus” on a fifth floor hallway. The culprit was never caught, and the “graffiti” was never removed. Makes you realize the kind of issues that budding, bright female meteorologists at the U of Washington are thinking about. BTW, this also demonstrates that the notion of “mammatus/testicularis” are always associated with, or indicating a thunderstorm, is quite goofy.6:30 PM. Had a late “bloom” as a distant hole in the overcast let the sun under light our Altostratus clouds with virga. Only lasted a few minutes. Nice.
The weather ahead
Of course, the big media weather stars with their gigantic salaries are all over this next storm, I am sure. Its mind boggling how much money they make having fun with weather on TEEVEE…
Here’s is the latest forecast from our friends in Canada, most of whom want to live here in the good ole USA!; that’s why the entire population of Canada is so clustered near the US border. You can feel them up there (hahah, I like to tease my Canadian relatives):
Valid for 5 AM AST, Friday, March 8th. “Vorticity maximum poised to strike AZ from low over central Cal. “Vorticity maximum”? Cloud and weather maker. There’s some writing on this; hope you can read it.“Bee” sting! LOOK at all the precip indicated for AZ! THis is so great, one of the great model forecasts of our time, well, this winter anyway.
Range of amounts with this next storm: I think in view of the wetting up of the models, I too, will wet it up. Bottom amount, almost surely in the bag, 0.25 inches now, up from 0.10 inches. Top? Wow, in view of passage of this system in the afternoon, you have to think about enhanced convection, thunderstorms here and there, and with those, and luck, the top has to be around 1.00 inches now. Notice how similar the track of this in the Candadian model is to our historic Feb. 20 storm, one in which amounts over half an inch to an inch were the norm. Can’t wait to see this go by, no matter what!
AKA, Cumulus humilis virgae, or, with virga. While there were plenty of small Cumulus around yesterday, it wasn’t until after 1 PM that trace amounts of virga could be seen starting to emit from them as they got colder during the day. I think I did, too. By the end of the day, cloud BOTTOMS of those little clouds were about -20 C (-4 F)! Poor guys. Tops were likely only a little cooler, at -22 or -23 C. Those Stratocumulus bottoms topping the mountains in the third photo were about -5 C (23 F) already.
Here’s what happened yesterday. First, the tail of the frontal cloud band came by, dropped a few flakes on the Catalinas before rushing off. Here is that precip, barely detectable on the Tucson radar:
1. 7:43 AM. A haze caused by falling snow tops Samaniego Ridge. Ms.Lemmon is obscured.2. 8:43 AM. The dramatic looking backside of the frontal cloud band (looks like merged different layers of Stratocumulus) closes the book on precip. The lack of precip suggests cloud tops are warmer than -10 C.3. 9:06 AM. Final goodbye. Crenelated tops of castellanus, kind of cute, nice looking I thought. Stratocumulus clouds now top Samaniego Ridge, no precip evident, just cloud bases, but you knew that. I think its great I’ve taught you SO MUCH!4. 12:01 PM. Cumulus fractus amid the dust. Twin Peaks were obscured briefly in dust as the gusty winds developed later in the morning.5. 12:41 PM. Pancakes over the Catalinas, hold the ice.6. 1:16 PM. Then the ice! Can you find it? More educational than “Where’s Waldo”, though both are good for the brain. 15 points.7. 1:24 PM. Some more of that ice. This should be a little easier to find, but not really easy. Remember, ice means precip in these clouds! 15 points.8. 1:31 PM. Its still dusty, windy, I’ve been sitting out in it now for almost 2 h making this ice ID test up. This is the next level of detection. Can you find the ice amid a dusty sky? 10 points.9. 2:12 PM. Another tough one worth 10 points. The Catalinas are still so pretty with those cloud shadows traversing across them.10. 2:42 PM. A lot more ice, but farther away. This was part of a southward moving snow band that dissipated before reaching the Catalinas. 5 points.11. 4:45 PM. Where’s the ice? 1 point.
Extra credit:
What are the concentrations of ice particles in those clouds shown at 1:16 PM through 2:12 PM, photos Nos. 6-9? How about in the last two photos? 25 points.
Answer: Probably less than 5 per liter of those larger than, say, 150 microns in maximum dimension in 6-9, likely 10s per liter in photos Nos. 10-11.
Why know something as arcane as this?
Because it impresses the neighbors, for one thing, because then you can go on and on about the Wegner-Bergeron-Findeisen precipitation mechanism in “mixed phase” clouds, or simply impugn them, with the words from the Walt Disney Studios science song lyric in “Water Cycle Jump1“;
“Your brain is on vacation/if you don’t know about precipitation.”
Second, if you’re into “vigilante science”, as Mr. Cloud Maven person was in parts of his science career, knowing concentrations of ice in clouds by sight will help you clean up some of the messes in the domain of cloud seeding when people report concentrations of ice that are too low. But an extra low ice concentration report benefits them because it helps make the clouds seem like they need some of that seeding to make ice and then more precipitation. Then a big contract is let based on bogus cloud reports, ones that you damn well know are goofy just by looking at the clouds, or checking out rawinsonde cloud tops when its raining from them… I could go on, and on, and on….. Someday…will tell those stories.
I hope that helps explain why this is important. If not, oh well.
The weather way ahead.
Well, you all know about the hot ahead. Now some rain pixels have shown up on March 10th. Not worth showing, but will keep an eye on them.
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I am euphoric that this song is now online! I loved that song! Gritty but great, except the part where it is asserted that condensation leads to precipitation. Condensation (and the ice form of “deposition”) is only the first step. Also, if you like easy listening, boring music, don’t go to this site; it might be too much for you.
Condensation by itself can NEVER lead to precipitation. You got to have ice or those larger cloud droplets (again, let us call to mind, Hocking, 1959, Jonas and Hocking 1970 was it?) that cloud droplets do not stick together UNLESS they are around 38 um in diameter and larger, and then there have to be quite a lot of those that size and larger to “bump and stick” (sounds like volleyball) to form a true raindrop (mm sizes). You see, cloud droplets pretty much stop growing due to condensation at sizes TOO SMALL to fall out of a cloud as precip! They’d evaporate in the first 50 feet out the cloud bottom. NEVER forget that as a cloud maven junior!
I smiled seeing the groundskeepers scurrying about, sweeping and scraping snow off the courses and environs at the Dove Mountain golf tournament yesterday. I was smiling because the golf culture here is so different from that in Seattle, Washington, much more “pampering” here. Due to frequent inclement weather in Seattle, we have to toughen our skins against weather if we want to play golf. Rain? Snow? No problem.
In Seattle, golf season begins on March 1st. That’s because in March in Seattle, its only raining (or occasionally snowing) on every other day by then, not every day, as earlier in the winter.
So we’re going golfing on March 1st, dammitall, no matter what!
So shop keepers like this one below on Aurora Avenue in the north end of Seattle, knowing that Seattle golf culture, exult with big signs like this one when March 1st arrives!
The golf weather culture in Seattle, Washington, as represented by this sign. Photo by the writer, March 1st, 1990.
Inaccuracy in media re Catalina snowfall or maybe it wasn’t: a tirade
I was thinking that maybe a tirade would be a nice change of pace for you before some cloud discussions.
First, since I heard a weather presenter report that “2 inches” of snow fell in Catalina, a visual correction to that report. There was FOUR inches on the ground after settling/melting during the day and night of the 20-21st. If there is FOUR inches the following morning, it HAD to have snowed quite a bit MORE than FOUR inches! (The total depth of snow that fell was 5.5 inches here on Wilds Road).
Here is the proof, 4 inches of depth as measured by a raingauge dip stick, one tenth inch markers are 1 inch in length–I didn’t have a regular ruler. Some of the labels indicating light amounts of rain have worn off while the stick was being used in Seattle for 32 years, so you’ll have to count down from the 1.00, 90, 80 hundredths labels, ones clearly visible. For added proof I have added a second photo, and if you call now, you’ll get a third photo free plus for $75 for handling and shipping…
7:02 AM, February 21st. A raingauge measuring stick protrudes from a FOUR-inch depth of snow on a hitching post (where some snow could have even slipped off, or blew off!)7:04 AM. A slightly higher depth on a second hitching post–oh, yeah, leading the big western life here in Arizony with a horse and hitching posts.
I felt sad, though, remembering the words of humorist Dave Barry, speaking to the National Press Club back in ’91 I think it was, when he diverged from humor into a serious note, admonishing his Press Club Audience: “Why can’t we get it right?1”
Maybe in our case of the missing snow, it was because the person that called in the report was not a Cloud Maven Junior, and did not know how to measure snow. Maybe less actually fell where that person was (unlikely). Let us not forget that the snow on a flat board in Sutherland Heights, above Catalina proper, measured at nearly the same time as this, was SIX inches!
Yesterday’s clouds, and those snow-covered mountains
While it was sad to see so much snow disappear so fast, it was, overall, another gorgeous day in a long nearly continuous series of ones since the beginning of time here in Arizona, except maybe for those days of upheavals and dinosaurs and then when it was underwater, a remnant of the latter epoch as shown here in this fossil of a hydrosaurus, a precursor to grain eating critters like the Perissodactylas we have today…(horseys and such). As you can see, the teeth here were for eating something like mueslix, not for ripping flesh. I can’t believe all the information I am providing you today!
Possible hydrosaurus fossil encountered on a hike in Catalina State Park (still checking on what it is). Finding was reported to park rangers.
Here are some shots with some notes on them or in the captions. First those MOUNTAINS!
8:21 AM, February 20th, looking east from Sutherland Heights, which had SIX INCHES of snow on the ground at this time. Stratocumulus clouds top Samaniego Ridge.9:13 AM. The snowy Tortolita Mountains with some Altocumulus perlucidus above.
2:25 PM. With most of the snow already gone around Catalina, the majestic Catalina Mountains remind us of our great February 20th snowstorm and why we live here.
2:26 PM. While it was serene-looking over the Catalinas, to the southwest the sky was filling in with Cumulus and slightly higher Stratocumulus clouds. Why don’t you see virga even though we know they are at below freezing temperatures? In unison: “NO ICE!” (Tops too warm and cloud droplets likely on the small side.) This was to change in the next couple of hours.
3:24 PM. But first, another look at the Catalinas from Shroeder Ave in Catalina because I think its worth it before continuing. Golder Ranch Drive is on the far left.
5:25 PM. Clearly there has been a change in the temperatures at the tops of these clouds, likely now colder than -10 C. A trough of colder air was approaching aloft, and that likely lifted and cooled cloud tops. The cloud layer was due mostly to the spreading out of Cumulus tops (Stratocumulus cumulogenitus). The TUS sounding indicated cloud tops were about -13 C, capped by a very strong stable layer. There was a fall of sparse drops around this time, so some of it was getting to the ground.
The weather ahead
Cold then HOT. Hot when? Heat’s on already by March 1st for sure. Look at this “signal” in our trusty NOAA “ensembles of spaghetti” from last night:
Valid for 5 PM AST, March 1st. You won’t see a signal stronger than this one for 8 days from now. Likely will reach into the 80s when this ridge of warm air is fully developed.
The End, at last. Anyone still there?
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1Deadlines have a way of getting in the way of “truth.”
On a movie-sounding title theme again today, or this title could be the title of a bedtime story for kids, one that alludes to the Greek citizen bee keeper, Perlucidus, due to his early work in distributing hives, honey and honeycombs. Some cloud patterns resemble honeycombs, and so when Luke Howard decided to create a Latin system of names for clouds around 1802-03, he wanted to pay homage to Perlucidus1. Yesterday morning we had Altocumulus perlucidus and those clouds are discussed in detail below the lengthy “historic learning module” below.
——historic learning module————
Our Latin cloud naming system follows the tradition of Latin names first established in the hard sciences like botany and biology. After they did their naming thing, we weather folk decided, under leadership of Luke Howard, to “join the club”, to sound like the other scientists of the day when we were talkin’ clouds, that is, pretend to be on as solid a foundation as, say botanists, whom we likely envied, by creating a similar Latin naming system for clouds. That would show them!
Unfortunately, we really didn’t know what clouds had in them in those days, there were no aircraft measurements. Were they ice clouds or liquid droplet clouds, a mixture of both? And so the naming system that was developed came out a little fuzzy; flawed really. I guess “fuzzy” is appropriate for clouds. As the singer said, “I really don’t know clouds at all2.”
OK, after that “side lobe”…an example of fuzziness and flaws in our names: while Stratus and Altostratus have virtually the same name, and can look VERY similar on occasion, one (Stratus) is completely composed of droplets, and the other (Altostratus) is almost always completely composed of ice particles and snowflakes (aggregates of ice crystals, bunches locked together). No doubt Howard saw the visual resemblance from the ground, and may have thought they were composed of the same stuff.
Yet, from the name of Altostratus, you would think it is a droplet cloud like Stratus, but just located at a higher level (“alto” meaning “high” in Latin). Even our scientists confuse Altostratus in their peer-reviewed papers with something else because of this naming problem. A better name, since Altostratus is full of ice precipitation (unknown when Howard was making up his names, of course) would have been, “Altonimbostratus”. Nimbostratus, by definition, is a precipitating layer cloud, too.
Another problem in our naming system is that unlike in botany, where a redwood tree does not become a pine tree over time, clouds are always morphing into new forms.
And then we have to come up with silly expressions such as “Altostratus opacus cumulonimbomutatus”, what might pass for the remains of a Cumulonimbus cloud that has lost its base and only the heavy, higher level ice-cloud anvil (Altostratus) remains.
So, as Howard was attempting to follow the Latin scientific naming conventions of the day for clouds, up popped the descriptor, “perlucidus” for clouds patterned like a honeycomb in homage to Perlucidus1.
Two cloud genera (there are TEN3-I really like footnotes. They give a piece a really erudite feel even when its not), have the descriptor, perlucidus attached to them because they can attain a honeycomb pattern. These are Stratocumulus and Altocumulus, to repeat.
——-End of historic learning module———–
Yesterday we had some very cold Altocumulus perlucidus, some cloud elements shedding ice and disappearing because of it. The TUS morning sounding indicated these were in the range of -25 to -27 C. Here’s what these clouds looked like when they were still mainly composed of liquid droplets:
7:29 AM. Classic Altocumulus perlucidus (honey-combed pattern) with fine veils of ice crystals falling from many of the droplet cloud elements.
9:15 AM. Here, in brighter light, one can see the droplet clouds at left, while there are patchy, hazy regions in between. Those are the ice crystal remains, “ghosts” of the perlucidus cloud elements that have completely changed into ice (glaciated).
9:24 AM. Ovalized shot of the icy ghosts of perlucidus. There really is no cloud name for this grouping.
Strange Brew yesterday
There were also some very strange looking lower clouds as dry convection, associated with that little warming we had yesterday afternoon during this historic cold wave, bulged upward into a pretty moist laminar stable layer that resisted like heck being pushed up. When it was pushed up by that convection, which with greater moistness you would have seen as small Cumulus, instead you got slivers of clouds on top of where the Cumulus should have been. Those slivers of moist air that just reached the condensation level where droplets form in the air sliding over the top of the “invisible Cumulus.” The result, these odd forms shown below, resembling lenticular clouds with ragged bottoms in some cases:
12:15 PM. This dome shaped oddity. Was only there for a minute or two. Jumped out of car to get it. I hope your happy.12:38 PM. Then over the Catalinas, these strange forms of lenticularis clouds likely forced by dry convection rising up from underneath.
The last photo of a band of Stratocumulus with a ton of ice in it is worthy of a comment. A few days ago, the models had this day having significant precip, precip that would have been snow, followed by the same vast clearing we had later yesterday. Imagine last night and this morning’s cooling air augmented by a snow cover! Yikes. Woulda been 5 degree colder than what is already a pipe bustin’ cold morning. Wouldn’t have had so much afternoon melting because the ground has been chilled for several days now.
Wishing you happy pipes this morning. They’re freezing up here, temperature now 22.x here.
BTW, the list of Arizona low record temperatures will grow substantially today, as if you didn’t know it.
The weather ahead? Warmer. Can it be otherwise?
Also at 12:38 PM, looking farther down the Catalinas. Strange indeed.1:23 PM. The end of the clouds was at hand when this band heavily glactiating and higher-than-normal-based Stratocumulus clouds came over. (The elements were too large to be Altocumulus.) Some flurries could be seen falling from these clouds on Mt. Lemmon at little later.
The End
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1Shockingly, this part has been completely made up.
2She also said, “Ice cream castles in the air”, followed by, “Feathery canyons everywhere.” And finally, “Clouds got in my way.” (BTW, “Clouds got in my way”, too, as if you couldn’t tell!)
3The the ten are: Cumulus, Stratocumulus, Nimbostratus, Altostratus, Altocumulus, Stratus, Cirrus, Cirrostratus, Cirrocumulus, and the mighty most of the time, Cumulonimbus.
Thought I would run down to Golden Goose Plaza here in Catalina to catch some sunset shots after I thought of this headline; “gold on gold” :{ Here are three shots from the GGP for your viewing pleasure:
5:48 PM. Altocumulus, no virga showing.5:49 PM. A hot more to the southwest with Altocumulus opacus on the horizon showing snow virga.5:50 PM. Zoomed shot to show remarkably heavy snow virga shaft (left of GGP sign) falling from that distant patch of Altocumulus. Another shaft is visible above the white car.
Lesson time… The clouds in the first shot aren’t producing virga. Why? Not cold enough you would guess, AND, the liquid cloud drops in them very tiny. The smaller the drop, the more freezing is resisted in clouds, the larger the drops, and the lower the temperature, the more likely it is that ice will form.
When ice does form in a droplet cloud, the drops around the ice crystal evaporate and the vapor appears on the ice crystal, depositing on it as new molecules of ice. Under a microscope on a glass slide, the crystal magically gets larger while a liquid drop next to it gets smaller and disappears. This process occurs in clouds that are comprised of both liquid droplets and ice crystals and the crystals eventually fall out as precipitation. The folks who described this “mixed phase” process, and at one time thought to be the only one that produced rain at the ground, was Alfred Wegner1, Tor Bergeron2, and Walter Findeisen. We won’t mention “riming” an additive to that process today, which is the collection of instant freezing of drops by the falling ice crystals making them heavier…
This “mixed phase” (liquid and solid together) process is ALWAYS described in weather text books from elementary to graduate ones. It requires the presence of droplet clouds and the introduction of ice to get the ball rolling. Altocumulus clouds are always mostly comprised of droplets, and so virga coming out of them is ALWAYS due to the “mixed phase” precipitation process. Tell your friends.
Here’s some surprising facts about yesterday’s Altocumulus clouds, even to me.
How high were those clouds? Well, according to the TUS balloon sounding they were no less than about 27,000 feet above sea level, or about 24,000 feet above us here in Catalina, and along with that, they were extremely cold, with tops indicated to be about -30 C (-22 F). The thinner ones on the right side of these photos would have been only slightly warmer, and as you can plainly see, had no virga, no ice in them even at those low temperatures! Pretty remarkable. In thin clouds like those not producing ice, you can bet the droplets were very, very small, likely smaller than 10 microns in diameter, and that small size of droplets is associated with a resistance to freezing. Such clouds also tell you that there is a lack of what we call, “ice nuclei” up there, substances around which ice can form, usually soil particles.
In the clouds with virga off on the horizon (3rd photo), they are clearly deeper, meaning the drops were larger near the top of the clouds, AND likely a bit colder as well, both factors leading to prolific ice formation and heavy virga trails. Hope this makes some sense. Pretty skies, anyway.
The TUS sounding for last evening at 5 PM AST:
Today’s clouds and weather?
Some mid-level moisture is still around, and so more Altocumulus clouds, along with some Cirrus should move in during the day and evening hours with virga possible, since they’ll likely be cold again. The U of A mod also sees lower, but very shallow Cumulus clouds likely, ones too warm to rain via the “mixed phase” process that you now know about. So, rain chances are pretty dismal later today and tomorrow. Nothing in the longer term, two week view either. Man, this is a LONG dry stretch!
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1Remember Wegner? The meteorologist that came up with the idea of plate tectonics around the turn of the century? But the geographers/geologists laughed at him for about 50 years until they saw that he was right. Why did they laugh at him? He was a weatherman, not a paleogeographer/geologist ( i. e., not a member of the club).
2Here’s a photo of Tor Bergeron from 1968 in case you wanted to see what he looked like. I don’t know who that is standing next to him…looks like someone who might have been influenced by Buddy Holly.
Oh, me. I guess its great to be big enough to congratulate a people smarter than your people. The Canadian model, a version of that used by the people of Europe, has seemingly won the battle of the Arizona rain question. Almost no rain in Arizona is now predicted through the end of September in the last several runs of the USA! model, which now has the last of hurricane Meriam dying a quiet death off Baja, her moist remnants staying in Mexico, not getting here. This was the “solution” the Canadian model had predicted for several days for the end of September in Arizona that made a prediction of rain here very dicey anyway if you read what I had been blabbing about.
BTW, along with abandoning our tropical rains, the USA WRF_GFS model has the “usual” heavy rains 10-15 days out. I laughed out loud when I saw these new predicted rains in today’s run from 5 AM AST data. I guess we can hope again.
Well, congratulations to my relatives in Canada for “winning” the battle of the models, but I will NEVER go there again! I loved those now bogus rain maps for Arizona that the USA! model produced for several days anyway; SO much rain! Going to save them, and mope around about what could have been because that’s who I am.
In the meantime, we had some nice cloud patterns yesterday morning, and I will grudgingly post those as though I am quite happy and feel normal after looking at the latest model runs:
6:29 AM.Probably Cirrocumulus is the best name for this though it is all ice here and the dappled pattern won’t last as the ice spreads out. A little patch of Altocumulus is on the left.6:30 AM. Now this was interesting, a little patch of Altocumulus, tops about -10 C, maybe -11 C according to the TUS sounding, and there is some snow virga coming out on the right side. Cool.
10:07 AM. Gorgeous example of Altocumulus “floccus” (no or ragged bases), though “castellanus” could also be used since somewhat of a base is still present. You have to get your camera out quick because skinny isolated ones don’t last for more than a couple of minutes. Check the next photo a few minutes later.
You probably don’t believe me, but at 2:08 PM, a few drops came down from this Cumulonimbus debris cloud, one that drifted off the Catalinas. Likely you were inside watching fubball or something instead of checking on a possible trace of rain. Oh, well. I understand. You had more important things to do than see if it was raining and note it in your weather log book. You are keeping one aren’t you?
2:08 PM. Rain is falling. Most of you will notice that this cloud is full of ice, so it COULD have rained out of it since ice means precip.
The proof?
Here, on the “trace detector”, a 1985 Corolla four-door, hatchback mini-SUV, mileage like a Prius before ethanol, some drops. BTW, yours for $12,000, comes with University of Washington Husky “W” insignia, also shown here, because I worked for the University of Washington and was a loyal company employee, i. e., supported all the company sports teams. Its just who I am.
2:09 PM. This photo was taken in case people didn’t believe me that it had rained yesterday. After all, this is the internet and you never know for sure what’s true.5:31 PM. Late afternoon Cumulonimbus spawns a rainbow for desert.
BTW#2, the Pima County ALERT raingauge at White Tail, near Palisades Ranger Station, just off Catalina Highway on the way to Mt Lemmon, had more than an inch of rain yesterday from our isolated Cumulonimbus clouds! It seems to register the highest rainfall time and again. It might be a fun Sunday drive to go there and see what all that rain has done. They must be over 10 inches for just August alone!
Today?
U of AZ mod (11 PM run) is predicting an uptick in thunderstorms this afternoon, then dry tomorrow. Hoping for one more dump…. You never know when the last one will be this time of year.
Some more visual ice cream, this morning’s pretty virga:
5:54 AM. What are these rays called?2:14 PM. Where am I? The heaviest rain in all of Arizona fell here yesterday.5:29 PM. Why wasn’t it raining on the Catalinas from these dark clouds?6:16 PM. Where is virga and snow falling out? “If you miss one more, you’ll be out.”7:19 PM. “Who was buried in Grant’s Tomb?” A nice sunset, as almost always here, with a little snow virga hanging down from dense Altocumulus clouds
The weather ahead.
Rain in the area, the models say, every day for the next few days. Check here and with Bob (our local expert), who seems to be mad a lot, even titling his blog, “madweather.” I guess he’s not afraid, like some men, of showing his emotions. I get mad myself, but usually its when it doesn’t rain on me that day.
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.
Row of Altocumulus castellanus top lower center.
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).
In the distance is Altocumulus opacus virgae, that is considerable precip is dropping out of them.Here the faint whitish cloud ghosts near splotches of the Altocumulus clouds are due to ice crystals, indicating that these clouds are colder than -10 C at cloud top.Our regular neighborhood cloud, an Altocumulus lenticularis formed downwind of the Catalinas in the usual spot after most of the Altocumulus had departed.After the brief clearing, a surge of threatening looking Stratocumulus invaded the sky. Rain can be seen falling above the horizon to the north.
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.
Who can forget those profound words of Aerosmith and Steve Tyler, “I’m BACK in the saddle again”? Just the way he says, “I’m BACK…” is really something. Well, if you can’t remember anything anymore, here’s a reminder. Wasn’t that great “rockumentary” movie by Rob Reiner, “Spinal Tap” about these guys? BTW, pilots on VFR flew through cloud saddles between turrets all the time… So, there really are “cloud saddles.”
First of all to start today, you budding cloud-mavens out there should, as always, be reviewing yesterday’s skies here to make sure you got all the clouds down in your cloud log, a service provided for you by your University of Arizona Weather Department. Since this link is overwritten each day, you probably should go there now.
In the meantime, while you’re scrutinizing that time lapse film, a cool front will go by this morning. Nice, except no rain outside of isolated sprinkles from mid-level clouds like….Altocumulus opacus virgae, you know, those dense loooking clouds with little snowstorms under them meaning their tops were colder than -10 C (14 F).
Later, after a brief gap in those mid-level clouds, some honest to goodness LOW clouds are supposed develop just after the front goes by later this morning. How do I know that? I cheated by going to the Wildcat Weather Department model results produced by the MASSIVE Beowulf Cluster and saw that clouds are supposed to get low enought to top Samaniego Ridge by mid-morning. Check the sounding predictions here if you don’t believe me. You’ll see the temperature and dewpoint lines pinch together at sharply lower altitudes beginning around 9-10 AM AST, with cloud bases predicted to be down to about 7,000 feet!
Haven’t seen cloud bases (bottoms of Cumulus and Stratocumulus) as low as that since the last rain which I missed because I was driving mom all the friggin’ way to Asheville, NC, and back to see my brother in his “new life” there. There’s a lurid story behind that new life, one that you would naturally be quite interested in, but it shall remain hidden from view.
But why don’t those lower clouds that move in and top our Catalina Mountains rain/snow? Tops too warm, predicted to be warmer than -10 C, so, no ice can form, a necessary ingredient for stuff to fall out the bottom. You probably knew that already, and I am beginning to feel a little useless. Oh, well.
Here’s a nice plot of today’s weather around the SW and the satellite cloud scene at 5 AM AST from the U of A (again): Wow! Rain drops hitting roof now, 5:37 AM! Overhead cloud tops still colder than -10 C!
Remember, if you are an intelligent person you will NOT CALL THESE FEW SCATTERED DROPS “DRIZZLE”!!!!!!! Its a rain shower, a very very light one, that you might “code” as RW— (three minuses). Drizzle drops float in the air, and are close together; these are not. There are IMPORTANT cloud reasons for denoting this difference. Some day I will tell you the “science story” about a well-known scientist, really considered the best in his field, who told me to leave his office and never come back after I informed him it had been drizzling outside. So, I Mr. Cloud-maven person has some “drizzle baggage”…..he is carrying around.
Note the gap in clouds over us now and that little scruff to the west. Those are the lower clouds that will move in later. Below this, our Tucson sounding for 5 AM AST, where you can see that the tops of these Altocumulus clouds are around -20 C (-4 F). Bases are indicated to be around 15,000 feet above sea level, or 12,000 feet above Catalina. Poor drops have to fall such a long way in such dry air. No wonder only the biggest ones, likely HUGE snowflake aggregates, or maybe even “graupel” up there, made it down.
