Cirrocumulus clouds – Page 3

About ice-in-clouds and APIPs (or high temperature contrails)

6:55 AM. A surnrise glow from receding CIrrus spissatus highlights Samaniego Ridge. Very pretty and dramatic.

8:19 AM. Forming uncinus, CIrrus that is. Note trails of precip beginnng to form under these tufts of Cirrus castellanus clouds.

9:06 AM. Jet contrails begin to show up in a Cirrocumulus cloud. You know what going to happen.... — 9:06 AM. Jet contrails begin to show up in a Cirrocumulus cloud composed of supercooled cloud droplets. You know what going to happen….something special for you to log in your cloud diary.

9:20 AM. Another patch of supercooled, very supercooled Cirrocumulus with evidence of a jet contrail. But, is the jet above or IN the Cirrocu? TIme will tell. — 9:20 AM. Another patch of supercooled, very supercooled for that matter, Cirrocumulus with evidence of a jet contrail. But, is the jet above or IN the Cirrocu? TIme will tell.

How cold were those Cc clouds? See below.

(Begin technical module)

The Tucson balloon sounding for 5 AM AST, November 19th with writing on it. — The Tucson balloon sounding¹ for 5 AM AST, November 19th with writing on it. The height of these clouds was slightly lower in the mid-afternoon, but (as Altomumulus then) were still about -23 C. As we know, cloud bottoms almost always get lower with passing time because the higher parts of cloud shields are moving faster.

In the mid- -20s C, around -15 F. Height, about 21,000 feet above the ground here in Catalina. Hope you got that estimate of cloud height right.

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Continuing…

9:21 AM. ANOTHER jet streaks by! This is going to be darn interesting, a rarity, like see a grey parrot in Catalina! — 9:21 AM. ANOTHER jet streaks by! This is going to be darn interesting, a rarity, like seeing a grey parrot in Catalina! The secret about what height the first jet was flying at is beginning to be revealed. Can you see what’s happening to that first contrail a little below the new one? This is a great test to see how far you’ve come as a CMJ (cloud maven junior)!

Here’s what happened in the Cirrocumulus cloud layer in yesterday’s special day, a pretty rare one, after the jets flew through it:

9:30 AM. OK, mystery's over. Even the average CMJ Joe can see that 1) the jets were IN the Cirrocumulus cloud, and more importantly, the aircraft contrails consist of ice. Yes, that's right, the passage of the aircraft has caused a phase change from liquid drops to ice crystals, a lot of them. — 9:30 AM. OK, mystery’s over. Even the average CMJ Joe can see that 1) the jets were IN the Cirrocumulus cloud, and more importantly, the aircraft contrails consist of ice. Yes, that’s right, the passage of the aircraft has caused a phase change from liquid drops to ice crystals, a lot of them.

9:47 AM. Now those contrails are looking like real and icy Cirrus clouds. In this case they're called "ice canals" but sometimes, when aircraft are ascending or descending and do this, they make round clear holes with ice in the middle, called "hole punch" clouds. — 9:47 AM. Now those contrails are looking like real and icy Cirrus clouds. In this case they’re called “ice canals” but sometimes, when aircraft are ascending or descending and do this, they make round clear holes with ice in the middle, called “hole punch” clouds.

Lessons to be learned from yesterday’s supercooled clouds and the aircraft interactions inside them:

Cloud seeding works! You CAN make a supercooled, non-precipitating cloud produce a little precipitation that would not otherwise have occurred.

But in those situations where the clouds, say, are topping the Catalinas, they are often quite thin, and whether there is an economically worthwhile amount of precip is not known. However, an experiment targeting those clouds would be the perfect “baseline” one in cloud seeding to establish how much we can wring out of non-precipitating clouds. Things become kind of a mess when even randomized seeding takes on already precipitating clouds.

“Overseeding”, as here in these clouds when aircraft produce prolific numbers of ice crystals in a small volume, it leads to tiny ice crystals with low fallspeeds. Sure, they fall out and leave a hole, but they virtually never reach the ground except in one a in billion cases when the very cold clouds are real low, practically on the ground.

The Wegener-Bergeron-Findeisen mechanism produces precipitation.

Alfred Wegener, 1911, and later Bergeron³ and Findeisen in the 1930s, came up with the hypothesis that adding ice to a supercooled cloud results in the growth of the ice crystal at the expense of the droplets. They’ll tend to evaporate while ice is being added to the crystal via deposition of water vapor that was once liquid. So, an awful lot, maybe most of the precipitation that falls on earth, involves “mixed phase” clouds. This process has also been called the “cold rain process.”

However, let us not forget the two other processes that produce precipitation, the all ice process (no liquid required–helps produce “powder snow”, and the all liquid process, where cloud drops collide and grow into raindrops–the biggest measured drops in the world (about 1 cm in diameter) have formed soley through this process. It is likely that most of the rain that falls in tropical locations like the Hawaiian Islands and in hurricanes is due to this process even when ice is present in the top part of storms.

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Later, we had some Altocumulus castellanus clouds with virga as the moist level lowered, though they were long gone before they could provide us with a nice sunset:

2:32 PM Bands of Altocumulus castellanus approach from the west. These clouds, while based at just about the same level as the Cirrocumulus clouds earlier in the day had three things going to produce so much ice, and really, convert to Cirrus clouds. The cloud bases were slightly warmer, meaning more water was available to the cloud, the tops were higher and colder, likely around -30 C (-22 F), and perhaps as importantly, the drops near the top of the Ac turrets were larger than those in the earlier Cc clouds. The larger the droplets, the higher the temperature that they freeze at. — 2:32 PM Bands of Altocumulus castellanus approach Oro Valley from the west. These clouds, while based at just about the same level as the Cirrocumulus clouds earlier in the day had three things going for them to produce so much ice (right side of photo–and really, convert to Cirrus clouds). The cloud bases were slightly warmer (the TUS sounding suggests, -22 C), meaning more water was available to the cloud, something that would impact the drop sizes in the turrets of the Altocumulus clouds (left side of photo); 2) the tops were higher than the Cc clouds (ones that were paper thin) and therefore, slightly colder (probably about -28 C) than those of the Cc clouds, and perhaps as importantly, the drops near the top of the Ac turrets before they converted to ice, were larger than those in the earlier Cc clouds. The larger the droplets, the higher the temperature at which they freeze. So, ice is more likely to form in a cloud with larger droplets in it than one with tiny droplets in it even though they are the same temperature. That might explain the difference ice-forming behavior of yesterday’s very thin Cc clouds which mostly had no ice (until an aircraft came along in them) and these prolific ice-producing Altocumulus clouds, ones that converted to all ice. Just educated guesses here.

Still looking for scattered very light showers in the vicinity tomorrow as a Mr. Troughy goes by.

The End.

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¹Through the oral history tradition I learned while viewing the Washington Husky meltdown² at AZ stadium on Saturday from a Mr. Mark Albright that the Tucson weather balloon launch site has been moved from Davis-Monthan Airbase to the University of Arizona campus next to their weather department.

²Late in the proceedings, with about 2 min left and the Huskies starting a play, and in the lead, CM was visibly moved to jump up and say, “Don’t hand the ball off!”, as a gift to Arizona fumble occurred simultaneously. But, being bifurcated in his loyalties now that CM is in Arizona and not with the University of Washington, he had to be somewhat “glad” that the Cats maintained their somewhat suspect but great win-loss record.

³From the Historic Moments in Weather collection:

Tor Bergeron and CM meet in Goleta. His head was gigantic! No wonder he was so smart. CM, not so much. — Your Catalina CM and Tor Bergeron meet for the first time in Goleta, CA, in 1968 at the headquarters of North American Weather Consultants. Yours for $2,100 dollars, today only. I remember thinking that his head was gigantic! No wonder he was so smart. CM, not so much.

Rain to fall in Catalina! (as shown in this latest model run shown below)

Finally found some rain for you. Took awhile. Came from the 11 PM AST global data from last night using the WRF-GFS model, our best. The rain falls around the 19th, “only” 11 days from now and during the “sweet spot” for southern California rain in mid-November, 10-20th, which gives it a few more percent of credibility than it otherwise would have.

BTW, there is virtually no support for this pattern from the NOAA spaghetti factory. So, all of the discussion below about an upcoming rain in Catalina might erroneous, based on a personal hunch about an outlier model run being the correct “solution”, one based on experience, and to HELL with spaghetti¹, a study in forecasting subjectivity, etc.

Got that Bay Area rain timing info originally from C. Donald Ahrens, the big author of Meteorology Today and Essentials of Meteorology, both of which have about 400 editions out by now, while he and I were at San Jose State College University.

Don, a grad student then, and me, and undergrad, worked and sang together to Top 40 songs radiating from KGO-FM ^2,3 in a little corrugated metal building there by the San Jose State football stadium back in the late 60s, and it was somewhere between songs that he told me about his findings.

Don had done a rain frequency study for the Bay Area for a local insurance company and it turned out that he found that it was somewhat more likely to rain in the middle of November than earlier or later in the month. That rain fell more more often than earlier was no surprise, but more often than later in the month was. Later I found that it was also true for southern California.

Sometimes oddities like these are referred to by big professors of weather, like Reid Bryson at the U of Wisconsin Badgers, as “singularities”, a weather pattern that tends to recur year after year around the same time of the year, like the so-called “January thaw” in the East which I don’t think happened last year.

So, ever since Don told me about the mid-November peak of rain in the central and southern parts of Cal, I have looked for it year after year and it seems to turn out quite often, and this November seems to be no exception, though the models were resisting this pattern for quite awhile before “giving in.”

Well, anyway where was I? It seems that the southern California rain is now being foretold for around 18th of November, and a day or so later it trudges on into Arizona. From IPS MeteoStar, a Sutron Company, whatever that is, this wonderful map:

Valid the night of November 19th-20th. Colored regions denote those areas where the model thinks it has precipitated during the PRIOR 12 h. So, storm has arrived here during the day on the 19th.

Some clouds

we have known over the past few weeks while CM was re-hydrating mentally:

Some ice for you on a warm fall day (virga from Altocumulus castellanus and or floccus)

Pretty iridescence (or irisation) in a Cirrocumulus cloud.

The End

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¹1The non-supportive spaghetti plot from the 00 Z (5 PM model run from last evening):

Valid at 5 PM AST Wednesday, November 19th. Arizona is in a low amplitude ridge, according to most of the "members" of the repeat model runs with itty-bitty errors deliberately put into them. I have rejected this plot and look for validation of this action around the 19th of November. You will not hear about it further if I am erroneous in this action! — Valid at 5 PM AST Wednesday, November 19th. Arizona is in a low amplitude ridge, according to most of the “members” of the repeat model runs with itty-bitty errors deliberately put into them. I have rejected this plot and look for validation of this action around the 19th of November. You will not hear about it further if I am erroneous in this action!

²An odd, almost mysterious Frisco FM radio station with no commercials featuring, “Brother John.” We’d sing along to the Four Seasons, The Five Americans’, “Western Union” (about telegraph, the way people used to communicate before the Internet).

³We both had quite a talent for falsetto it seemed at the time.

While waiting for S, the (NASA) Diary of the Great O

While waiting for the remnants of former H. Simon to pass over us during the next couple of days, bringing some rain, starting overnight, got distracted while looking to see how many rainfall measuring stations they have in Baja Cal, and found this about the Great O from NASA. Its a pretty fascinating read I thought, which you will also find fascinating. Sure, intense hurricane O’s floody remnants missed us here in Catalina/Tucson, but it did produce some prodigious rainfall on its path across Baja and points northeast from there into NM. NASA’s Tropical Rainfall Measuring Mission (TRMM) radar estimates that over the ocean off southwest Mexico that about 33 inches fell over a ten day period while O was meandering around down there with some other disturbances, probably raising sea level that bit. And up to 5 inches per hour was falling in rainbands as it entered Mexico from the Gulf of Cal! O was deemed the strongest hurricane (tied with 1967’s Olivia) to ever hit southern Baja since sat images became available.

You will also see reprised in the “Diary of O” the huge rainfall totals that were expected in the TUS area but rains that missed us, the sad part of the story for some folks, who we will not mention. But, as Carlos Santana said, “Those who do not know history, are doomed to repeat it.”

For that reason, in view of the prodigious rains predicted in southern AZ again, but to the west of us, I thought we should be prepared for disappointment by recalling O’s “terrible” miss for TUS.

Here are some graphics from our very fine U of AZ Weather Department’s Beowulf Cluster computer outputs from just last evening at 11 PM AST, ones that can be found here, in case you don’t believe me again, a seeming theme around here. First, when the computer model thinks it will start raining, Figure 1, and in Figure 2, the expected gigantic totals expected along and near the US border where we really shouldn’t go unless you 1) go in an armored vehicle of some kind, 2) make prior arrangements with the appropriate ruling Mexican drug cartel for that part of the US that you just want to visit some rain, nothing more:

Figure 1. Valid for 2 AM AST tonight. The leading edge of the rain has reached Catalina. You might want to stay up for that. That wet desert aroma as rain begins is so awesome!

Valid for 3 PM tomorrow afternoon. One small area around Organ Pipe National Park is forecast to exceed TEN inches by then! — Figure 2. Valid for 3 PM tomorrow afternoon. One small, mountainous area around Organ Pipe Cactus National Monument is forecast have more than TEN inches by then, likely slowing the amount of incoming drugs. Organ Pipe Cactus NM is a US national park that you are warned not to visit, or if you do, you might be shot or have some other untoward happenstance if you go hiking. So you probably shouldn’t drive down there to see this once in a century rain. How sad is THAT?

Right now, as of 4 AM AST on Thursday, this model thinks Catalina and vicinity will get less than half an inch. Be prepared for more, though, rather than less. Note the streamer of heavy precip associated with Simon in Figure 2. Well, recall that O’s heavy precip streamer was going to be right over us, but then shifted eastward in the models and in real life at the last minute. The above prediction would only have a bit of a “westward bias” (the real streamer is EAST of where its shown now) to give TUS and vicinity a memorable, drenching October rain. This is what occurred with O’s streamer of torrential rain which was expected to pass over TUS, but ended up a little east of us. So, anyway, given all the little uncertainties in model predictions at this point, the watchword here is “watch out” which is actually two words. The view from here, incorporating a positive rain bias as you know, is somewhere around an inch for Catalina. The grassy green is gone, most annuals in serious wilt or crispy now, but could an inch bring some green back? Clueless on that score.

Yesterday’s Clouds

6:06 AM. Nice Cirrus sunrise. — 6:06 AM. Nice Cirrus sunrise, maybe some Cirrocumulus at far right, and off on the left horizon.

5:05 PM. Altostratus translucidus with an Altocumulus layer on the horizon.

5:07 PM. A “classic” view of Altostratus translucidus (sun’s position can be discerned through it), and here, an all ice path to the sun. Liquid cloud elements would appear as dark flakes, or would obscure the sun’s position. Sounding indicated that this layer was 26 kft above the ground in Catalina!

The End.

Interesting optics yesterday; substantial rains just ahead

Pretty boring lately…. No motivation here, even after caffeinating royally every morning. Have had some pro work to work on, too, like reviewing a manuscript for a journal–loosely translated, work that’s largely comprised of “finding fault in the work of others,” which I am pretty good at, to be a little immodest. Due this weekend, too…

11 PM U of AZ mod has late afternoon and evening rains in Catalina! Yay. Looks pretty wet, too, through the middle of next week, some lucky places (Catalina/Oro Valley) might get 1-3 inches during that time I suspect. (Neck out pretty far here.)

But…another longish dry spell takes hold after that. Seems to be the character of our summer; a couple good, wet days, then a long dry spell.

Still there were some great cloud sights yesterday, and I wanted to share them with my reader, wherever you are.

Down at second from the bottom is the rare sun pillar, and the last photo, a kind of an odd parhelia (sun dog) since the clouds were mainly Altocumulus ones in which it was occurring and it was darn bright.

Parhelia normally occur in icy Altostratus clouds. I would guess that this one might have been caused by ice crystals produced by an aircraft that passed through that Ac layer toward the horizon, right.

The End, back to work….

Some recent clouds that have floated over Catalina, AZ

Many of you are starved to see some low clouds rather than a few Cirrus or Altocumulus clouds under a blazing sun, about 27 million degrees F in the core, only 10,000 F at the surface we call the “photosphere”, what we see up there. (And you think its hot in Arizona!)

So, I thought I would provide some relief in this time lapse video of the clouds of Seattle from yesterday, as provided by the University of Washington’s Weather Department. You’ll see some great Stratus, maybe some Stratocumulus, and later, little bulging Cumulus that rise up to as much as 5,000 feet (!) above the ground. Maybe some of your neighbors are temperature refugees in Seattle now, so it will be great to see what they are experiencing and logging in their cloud diaries. And, we’ll be checking this day when they get back, for sure.

The current dry spell begins to fade as the days go by now.. In the meantime, since this site is mainly for the display of pretty clouds and not of any other value, here are some shots from the past few days. Have left the captions for you to formulate in silence.

Best not to do too much with this caption.

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The End.

A day with Cirrocumulus, Cirrus and Cumulus; summer rain season looks to start on time

What a day, Mr. and Mrs. Catalina, except for that last second “header”:

7:57 AM. Cirrocumulus with exceptionally fine granulation (left center). You might feel a little chop if you were flying in it, but it would be hardly anything. More chop, lower right, where you have something akin to ocean waves rolling along from left to right.

8:04 AM. Pretty Cirrus fibratus (strands are pretty straight in Ci fib).

4:47 PM. Pretty scene over the S-Brooke population complex. — 4:47 PM. Pretty Cu humilis and fractus scene near the S-Brooke population complex.

5:05 PM. Nice shadow bounding the Catalinas, — 5:05 PM. Cu hum and fractus over the Catalinas, Nice shadow bounds the mountains I thought.

The weather way ahead, 10 days and beyond; dreaming green pixels

Rain showing up around these parts beginning overnight on July 3rd-4th, kind of a normal time for a summer rain season onset. This from last evening’s global model crunch. Prior model runs have been dry, so it could be bogus, of course. But, its a hopeful sign. Rains every day after that in this run. Below, the titillating start as rendered by IPS MeteoStar:

Valid at 5 AM AST July 4th. Green areas show those ones where the model has calculated some rain in the prior 12 h.

Valid at 5 PM AST July 8th. Raining all over Arizona by this time. How great would that be? Com'on model! — Valid at 5 PM AST July 8th. Raining all over Arizona by this time. How great would that be? Com’on model! Don’t let me down! A feel a really old song coming on about being let down.

Let’s look at some spaghetti and see if the “solution” above has any credibility at all:

Valid at 5 PM July 4th. Note gaps in red lines in northern Arizona and NM. Errorful mod runs are therefore pretty confident the necessary ridge of high pressure aloft WILL be centered to the north of us. So, there is a fair amount of confidence from spaghetti that the summer rain season will start pretty much on time. — Valid at 5 PM July 4th. Note gaps in red lines in Arizona and NM. Errorful mod runs (deliberately so, recall) are therefore pretty confident the necessary ridge of high pressure aloft WILL be centered just to the north of us at this time, extruding all the way from the central Atlantic. So, there is a fair amount of confidence from spaghetti that the summer rain season will start pretty much on time. What’s also supportive is the bulge in the jet stream to the north in southern Canada, as indicated by the bunching of those bluish lines. Pac NW looks cool and rainy with this pattern, BTW. You can enjoy more spaghetti here.

So, right or wrong, you heard it here first because I got up early; summer rain season looks to start on time.

The End.

Another hurricane (“Cristina”) forms off Mexico; can AZ rain be far behind?

Looks pretty good…. Two completely different computer models show tropical moisture getting into Arizona in about 5-6 days a resulting preview of the summer rain season. You can find quite a bit of “green pixies” (areas of rain denoted by areas of green pixels) in Arizona here from IPS Meteostar’s rendition of our best model, the WRF-GFS. And, the Smoking Canadians have rain in our area in their model, too. This is going to be the best chance for measurable rain in Catalina since early April!

In the US model linked to above, you can also see the residual low pressure center from today’s Hurricane “Crissy” moving up the coast of Baja Cal in five days. Finally, could we have a month with above normal rain after not having one since November 2013 (or was it 2012?) Might happen, after all we deserve it. So, I will now predict that June will be above normal in rain in Catalina, AZ.

You can keep track of Crissy here. I will be tracking Crissy, that’s for sure.

Below, an example of rain (with drizzle) in case you’ve forgotten what it looks like in a research aircraft with laser beam imagery of all the stuff you’re flying through:

Rain as seen by aircraft instrumentation, arranged in order of small to larger, left to right. — Rain (and drizzle drops) as seen by aircraft instrumentation, arranged in order of small to larger, left to right. The horizontal lines are just about a millimeter apart, so the biggest drops here, one that aren’t breaking up, are about two millimeters in diameter. Drizzle drops, as CMJs know, are those between 0.2 to 0.5 millimeters in diameter, so there are a lot of those. BTW, these were collected while the aircraft was flying at about 160 knots (80 meters per second). Pretty amazing you can image these drops as they go by so fast!

The discerning reader will want to know what spaghetti sez; what are the chances that the steering winds in the middle of the troposphere will steer Crissy toward us as it moves around off’n Mexico. Will those steering winds help Crissy’s moisture get into Arizona and over Catalina?

We seek help from spaghetti and, indeed, the spaghetti shown below is “supportive”, that is, it shows that the “planets are lining up” for rain here, as an astrologer might say, those people we look to for personal guidance in everyday matters; whose forecasts are so important no newspaper can go without them without causing an uproar on the part of their readers.

See writing on figure below for some additional weather interpretation.

ann spag_f144_nhbg — Valid for 5 PM AST June 16th. Those red lines suggest that Crissy’s remains (RIP) might indeed be directed at eastern Arizona! Big trough for this time of year foretold along West Coast with high confidence, as indicated by “bunching lines”, perfect for drawing tropical storms northward into the Southwest US. If not us, then those dry areas of New Mexico and west Texas virtually guaranteed for some tropical air.

Yesterday’s clouds

10:53 AM. Mostly Cirrus uncinus, bisected by a contrail.

2:38 PM. Cumulus humilis and fractus boiled up out of 100 F plus air at the surface. Tops warmer than -10 C, so no ice, just those thin patches of Cirrus on top. — 2:38 PM. Cumulus humilis and fractus boiled up out of 100 F plus air at the surface.
Tops warmer than -10 C, so no ice, just those thin patches of Cirrus on top.

3:08 PM. Cirrocumulus atop Cumulus fractus clouds.

Nice Altocumulus around this morning, but moisture is really confined to that level, not deep enough for rain at the ground. The Cumulus that form this afternoon will have bases around 14,000 to 15,000 feet above the ground. They should be deeper than yesterday, and so ice is likely to form in the larger ones (and we hope that you will log that in your daily cloud diary), but only tantalizing virga is likely, maybe with some brief windy periods near them.

The End

Nice weather we’re having; snowbirds ejected to the north too soon

Sure, there was a little mischievous wind in the early afternoon, BUT, as a day in late May in Catalina/Sutherland Heights zone of Arizona, wherein the temperature is less than 100 F, well, it was pretty darn great. Another one is on tap today just like yesterday today, too. Feeling sad about the early, northerly ejections of “snowbirds” who thought because of the warm winter, May would be an inferno here and are missing some splendid weather. Doesn’t work that way. You just don’t know.

Lot of interesting clouds yesterday, too, real cold ones. Those Cumulus that formed in the late morning and afternoon started producing ice almost immediately. Wonder if you caught the first ones over there beyond the Charouleau Gap around 11 AM? They did not look as high-based as they were, thus, as cold overall, dad-gum, those cloud bottoms were running around -10 C (14 F)!

How high off the Catalina ground were they? Oh, about 13,000 feet, or about 16,000 feet above sea level (about 550 millibars). I woulda guessed, as you would have, about 8,000 feet off the ground when I first saw them forming (and not looking at the temperature and dewpoints, from which you can make a pretty good calculation of the cloud base height). From the Cowboys at the U of Wyoming, this sounding for TUS yesterday afternoon:

The Tucson balloon sounding for yesterday afternoon, launched around 3:30 PM, ascends at about 1,000 feet a minute.

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Weather Hints for Every Day Use by “Art”: You can calculate the height of a Cumulus cloud base by taking the difference between the temperature and the dewpoint, dividing it by 5, square that number, add the number you started with, and subtract the square root of 2.

DId I get the number you started with?

(Actually, stop at “dividing by 5”, multiply that number by 1000, and you’ll come out just about right. Yesterday, 85 F temp, 20 F dewpoint, leads to 65 F difference, divide by 5, you get 13, and times a thousand is an estimated CUMULUS cloud base of about 13,000 feet above you, not too bad).

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Continuing….. Since bases were so cold, tops were exceptionally cold, too, for shallow Cumulus and started producing ice when they were only about 1,000 to 3,000 feet thick, with cloud top temperatures of -15 C to -20 C (about 4 F to -4 F). Some of the highest tops, all east of us, and mostly on the east side of the Catalina Mountains, were likely as cold as -30 C (-22 F).

You can see yesterday’s small Cu spewing ice in the great U of AZ time lapse movie here. Only plays for one day, though.

You may also have noted in your cloud diary the bifurcation in the Cumulus array of yesterday. Almost no Cumulus west of Catalina, and plenty in the east half of the sky, appearing to be largest in the distance in the east. We were literally on the edge of the moist plume from the south that was hoped to end up been west, with us deeply embedded in it, and where measurable rain might have fallen here as it did east of us yesterday. Oh, well.

Today, with a low center passing over us tonight and a blob of Pacific Ocean air in it, and while that air is cold and pretty dry aloft, it will be a little more moist and so cloud bases today should be a little lower, and warmer, than yesterday’s. That means a little more water condensing in them than in yesterday’s clouds, and a greater chance of sprinkle here. Hoping for measurable, but its probably less than a 50-50 shot at that. Likely will be some thunder in the area of SE AZ, too. And, as always with high cloud bases, gusty winds that arise due to virga and rain falling through the dry air below cloud base. (Yesterday afternoon’s gales in the Sutherland Heights, momentary blasts of 40-50 mph, were NOT due to virga, but a rather to something I didn’t see coming, maybe a smallish low center–nothing really showed up on the maps.)

You can see the forecast trajectory of that upper low coming toward us, from the University of Washington’s Huskies, whose #14 softball team plays away, really away, at #1 Florida in Gainesville this weekend–how crummy is that except for the great Cu there and its important enough to be on TEEVEE Saturday?) computer output by clicking on this informative sentence.

You will also see in the above loop that our low takes its time moving along, and will keep the skies interesting with Cumulus and weak Cumulonimbus clouds today and tomorrow, along with temperatures below seasonal norms for late May (aka, less than 100 F) ((Snowbirds left too soon; ice still melting off some areas of the Great Lakes!))

From the cloud vault; yesterday’s clouds

10:28 AM. Small Cu began forming in the lee of the Catalinas during a horseback ride with a friend, in case you didn't think someone as cloud-centric as me could have a friend. — 10:28 AM. Small Cu with lenticular type tops began forming in the lee of the Catalinas during a horseback ride with a friend, in case you didn’t think someone as cloud-centric as me could have a friend. Calm winds, then, too.

11:08 AM. First ice! Can you spot it? — 11:08 AM. First ice! Can you spot it in the distance? Horse can’t believe that ice is forming already, and is rolling around in ecstasy, thinking about what it might mean for the afternoon.

1:43 PM. Approaching low with air moving upward ahead of it, triggers a batch of Cirrus and Cirrocmulus lenticularis (really high lenticularis) upwind of Catalina and above some Cumulus fractus.

3:18 PM. One of the more remarkable sights yesterday, were the small Cumulus clouds (humiilis or mediocris) that iced out. Look at ll the ice that formed in this small cloud, exiting on the left side, but dominates the whole cloud from this viewpoint. When you see this, it tells you how COLD those clouds are. First guess should be around -20 C at top when you see this much ice in a cloud this SMALL. Clouds having warmer bottoms, can have warmer tops that look this icy because ice forms in clouds at higher temperatures when the drops in them are larger. — 3:18 PM. One of the more remarkable sights yesterday, were the small Cumulus clouds (humiilis or mediocris) that iced out. Look at ll the ice that formed in this small cloud, exiting on the left side, but dominates the whole cloud from this viewpoint. When you see this, it tells you how COLD those clouds are. First guess should be around -20 C at top when you see this much ice in a cloud this SMALL. Clouds having warmer bottoms, can have warmer tops that look this icy because ice forms in clouds at higher temperatures when the drops in them are larger (see Rangno and Hobbs 1994, Quart. J. Roy, Met, Soc.) Oh, yeah, baby, have some pubs!

6:58 PM. Iced out Cu/weak Cumulonimbus beyond the Gap, the Charouleau one, end the day. Shoot, a slight change in trajectory from the south, and they woulda been here.

7:00 PM. Meanwhile, all quiet to the NW, no Cu whatsoever demonstrating the moisture edge we were on.

The weather ahead and WAY ahead

Now what I think is really interesting, which is almost everything to do with weather, is that the models are suggesting a tropical injection again at the end of MAY into early June, with a chance of a decent rain again. As you can see in the plot below from the NOAA spaghetti factory, a trough to the west of us and over California is a virtual certainty now at the end of May. That means the air above us will be, while quite warm, originating from the deep Tropics with the likelihood of clouds and precip coming up from there. Nice. Will keep me posted on these developments, in case no one else is reading this far.

The End.

Late morning cold slam

Its not a breakfast at a restaurant chain, but a sharp cold front passage later this morning, say between 10 AM and Noon. Should be pretty interesting. Temperature will drop about 10 F in an hour. Expecting/hoping, too, for a little measurable rain with this “FROPA” (frontal passage in weatherspeak). The brisk winds, as they always do, have activated a lot of the nighttime wind detector lights in the neighborhood.

The usual post-frontal clearing in the afternoon and a pretty cool day, maybe 20 F cooler than yesterday afternoon which got to 88 F here in the Heights, the Sutherland ones, that is. Of course, our media weather stars are all over this weather situation, so nothing much to be added here.

Still have plenty of higher ice clouds overhead right now at daybreak, but look for an invasion of Cumulus and Stratocumulus within the couple of hours after daybreak. They should appear first on the Lemmon, topping it, then fill in after that as the cold slam gets closer.

Yesterday’s clouds

The full complement of expected clouds was not really observed yesterday. Missing in action for the most part locally were Altocumulus lenticulars downind of Ms. Lemmon. Cirrocumulus clouds were also pretty much a no show. You can see some of those high lenticular formations that did occur WAY downwind of Ms. Lemmon and the Catalinas if you view the U of AZ Weather Department time lapse movie for yesterday between 11 AM and 1 PM, then another pile of Ac len just at sunset (7:15 PM) in their movie.

Below, what we did see, various varieties of Cirrus, and eventually those thickening to Altostratus ice clouds. And a hole was out there that allowed a brief colorized sunset rather than a gray one.

9:20 AM. Main feature is Cirrus spissatus, with Cirrus fibratus (lines at upper right) and some uncinus (center left) also present.

1:13 PM. Looking at incoming Cirrus to the WSW… More Cirrus spissatus (patches) in the distance with some hooked Cirrus (uncinus) upper center.

1:14 PM. Looking N at the traces of Altocumulus lenticularis clouds (e.g., sliver cloud above road in distance), possible Cirrocumulus top center of photo.

6:21 PM. By this time, the leaden look of Altostratus pretty much dominated the sky; dosen’t look good for sunset color at this point.

7:03 PM. Sunset bloom began as bottom of Altostratus got lit up. Note how similar the cloud bottoms are in this photo compared to the one just above.

7:06 PM. Heavy line of Altostratus with a higher overcast of CIrrostratus adds interest to the fading sunset.

Sprinkles in area overnight!

Some sprinkles/radar echoes passed overhead early this morning. Will check, as you will, for drop images in dust on solid outdoor surfaces to possibly report a trace due to drops that reached the ground. Going out now with flashlight, to heck with that coyote over there. Result: looks like there were a few isolated, larger drops that fell last night. Below, confirmation of echoes overhead from WSI Intellicast’s 24 h radar-derived rain for AZ:

Radar-derived precip ending at 5 AM this morning from WSI Intellicast

Nice sunset with late sudden bloom after looking like there might not be any color at all.

6:54 PM. Mammatus shaped virga hangs down from heavy patches of Altostratus providi — 6:54 PM. Mammatus -haped virga hangs down from heavy patches of Altostratus providing sunset highlights. Dimly seen are flakes of Altocumulus clouds, as seen below as well.

6:18 PM. Doesn’t look like much of a sunset will get through this solid-looking cloud cover of Altostratus, Cirrus, with flakes of Altocumulus below.

10:13 AM. Bright patch of CIrrus is from an aircraft; the Altocumulus flakes with virga hanging down are natural. Only a greatest of the Cloud Maven Juniors would be able to make such a discernation, if there is such a word.

10:12 AM. Over this way, a mix of Cirrocumulus and Altocumulus (larger globules).

Expect another middle to high cloud cloudy day with nice breezes. Weak jet stream to south (see map below) as upper level trough passes today, the main criteria for cool season rain in AZ (some 90-95% of all measurable rain in AZ falls only when the jet stream in the middle troposphere (about 18-20 kft above sea level) is south of us. However, while that criteria is met today, just not enough moisture has leaked in over the Baja and southern California mountains for clouds low enough to produce rain. So while its a virtually necessary condition, its not always sufficient.

Forecast winds at 500 mb (18.5 kft ASL) at 11 AM AST. Strongest winds at this level coming onshore in Baja, Cal.

The End.