Woke up to Cumulonimbus clouds NW-N of Catalina. Hmmm. Here’s the unexpected, pretty sight just after sunrise:
7:24 AM. “Pretty, but will likely die much after sunrise.” Cumulus and Cumulonimbus clouds along a windshift line moving toward Catalina continued to develop throughout the morning while getting closer.9:34 AM. Odd line of Cumulus congestus growing into Cumulonimbus clouds with major rainshafts is getting closer still. “What’s keeping this going so early in the day?”
10:00 AM. “Upon closer inspection….”, a windshift line is detected via photography! Arrow point to shred cloud below base of the turret at left. This is a great example of how clashing winds build clouds. Above the shred clouds is that vigorously growing turret trying to reach the glaciation level.10:06 AM. It made it! (to the glaciation level) Maybe it means that the line of fat Cumulus-Cumulonimbus might make it here to Catalina and rain on me! I’m getting excited. Arrow points to icy top, though as cloud maven juniors you would already recognize that icy top, so I left the arrow out since I forgot add it anyway. These are the best kinds of icy tops to study with an airplane because they near the threshold temperature where ice forms in clouds on this day. That threshold level changes from day to day, strangely believe it, and the warmer the BOTTOM of the cloud, the HIGHER the temperature at which ice forms, strangely believe it#2. Even stranger, Mr. Cloud-maven person thought he had discovered this interesting fact back in 1988 and then he found that this guy, the Englishman, Frank Ludlum, one of the best we’ve ever had in cloud studies, and I should have known better, had reported the SAME THING 36 years earlier in 1952! There is nothing new under the sun, Ecclesiastes said, and I guess I found out first hand. Darn. I laughed bitterly when I saw that Science mag cartoon about stuff like this, posted below because it won’t fit in this caption. Darn. You can see I still have some feelings about having something to report but then finding out that it had already been reported. I thought maybe I was gong to be famous, perhaps win a prize of some kind, but no. (See second cartoon)
Well, the end of the story (told in the captions) is that a windshift producing this line of heavy Cu and a Cb or two and it “struck” Catalina about 11 AM; the wind turned from the SW to the N, but the heavy line of clouds riding it were nowhere to be seen at that time; the last Cumulonimbus cloud disappearing beyond the Charoleau Gap. Tough to take after hopes up.
Only in the early afternoon did a gift of a few drops from a towering Cumulus directly overhead produce the final surprise. The drops fell from 1:22 PM to 1:23 PM. I rushed outside to see what the heck was doing it and here that cloud is (last two photos) from the bottom up.
1:23 PM. Its raining! 1:23 PM also. Arrow points to ice, showing that this little guy got to the ice-forming level, and would have been another great subject for an aircraft study of ice formation.
4 AM to 4 AM 24 h totals ending today, ones that catch that morning rain (except where noted):
2.12 inches near Chrysotile, AZ, NE of Globe.
2.06 inches Wet Beaver Creek, Oak Creek Canyon area.
1.85 White Tail, just west of Palisade RS off Catalina Highway.
1.39 Oracle Ridge near Oracle in Cat Mountains
PHX set daily record ending at midnight last night, 0.80 inches.
Here’s the AZ radar-derived rain from 5 AM to 5 AM from WSI Intellicast:
Catalina? A crummy 0.07 inches. Well, no rain is technically “crummy”.
Good chance that some or all of that rain yesterday morning fell from clouds not having any ice in them, that is, formed rain due to the “warm rain” process, a rarity in AZ. But, without an aircraft, its a dicey call.
1 PM Catalina temperature and dewpoint: 86 F and 73 F. Miami, FL, at the same time: 90 F, 72 F. Warmer and dryer in Miami at the same hour. Our dewpoint was higher here than in Miami, quite something. Our high dewpoints were helped by all the rain water evaporating yesterday against a background of already very moist tropical air.
The air was extremely humid here, but not hazy like back East on humid days. Interpretation? The air was very clean.
Its not the end of summer rain season even though a few dry days are ahead after today.
Cloud bases in the morning clouds were running 16-17 C, about 62-64 F, which means those clouds had about as much water condensed in them near their tops as any cloud could possibly have here.
AZ mod (here) thinks it can rain here in the late afternoon today. Excellent.
Some of my big fat Cumulus cloud shots from yesterday, ones that were just like ones in Florida and Gulf Coast this time of year.
7:24 AM. Warm-based Stratocumulus clouds with embedded Cumulus build ups produce intermittent rain along the Catalina Mountains.9:36 AM. As the Stratocumulus layer dissipates, gigantic, low-based, Florida-style Cumulus clouds begin arising NW of Catalina.9:48 AM. I can hardly speak, these clouds are so HUGE! How many inches of rain might fall from them? Note glaciated tower protruding above the mass; top, right of center.10:04 AM. Larger yet! Note low scud clouds, seemingly just above Saddlebroke rooftops.10:09 AM. While these were wonderfully tall and low-based Cumulus congestus clouds, something was going wrong. Why weren’t there Cumulonimbus clouds, anvils scattered here and there to the SW-W?11:15 AM. It was getting worse. It was clear that drier air was moving in aloft and dessicating growing clouds. Cumulonimbus were still peppering the area just NW of Catalina, but they were shrinking in size as cloud bases rose.1:23 PM. The Cumulus congestus clouds lined the tops of the Catalinas, and occasionally produced a glaciated turret, but nothing gigantic as had been expected earlier in the morning.1:32 PM. Glaciated turret (center) pokes up behind Cu congestus tops over the Catalinas. Would have been raining like “heck” under it.2:26 PM. Though a big rain did not come through as I thought it might, it was a fabulously photogenic day with scenes of our now green desert topped by those puffy, roiling Cumulus clouds dotting the sky, ones providing thoughts of rain.
Now THAT was a monsoon-like day yesterday, one right out of the western state of Kerala, India; the thick rain of mid-morning, seemingly thicker than most here, the clothes-gripping humidity outside, the strip of fog on the side of the western Ghats, oops, Catalina Mountains, the relatively gentle breezes in the rain, the subdued green hues under the overcast of light rain at the end of the unusual morning drencher, aspects that, en toto, made the morining seem so India-like to me (and I’ve been there in those Kerala rains). Take a look at our green state and State.
10:37 AM, after 0.76 inches of thick rain with occasional thunder. Nimbostratus up top, Stratus fractus along the Samaniego Ridge.10:53 AM. Looking toward Charoleau Gap.
In the Ghats, India, 1975, in case you didn’t believe that I have been in ACTUAL monsoon rains.
And while the rest of the day was sunny, humid and cool for us, the rain wasn’t over with another thunderbludgeoning last night after 9 PM that brought 0.25 inches and the day’s Catalina rain total to 1.02 inches. Drink up, desert!
We also had a nice Altocumulus lenticularis at sunset, suggesting some wind aloft. Seemed almost fall-like seeing this because they are more common with our winter troughs.
6:53 PM.
Another Big Day ahead
3 AM, Arizona obs. Several stations have dewpoints in the low 70s, with TUS reporting, along with light rain, a shockingly high dewpoint of 72 F, really extraordinary.
Get ready! A disturbance over southern California will help organize our storms into ones like those that occur in central Florida today, grouping them into large clusters, with some eye-popping rain amounts likely somewhere in the State (“eye-popping”, 3 plus inches). Don’t be too surprised if you hear about a “tube” somewhere as well. Tubes happen in conditions like these.
After today, its “mostly” dry through the end of September, with the best chance of rain on the 27th-28th.
Just about. Ended up taking more than 300 photos yesterday (!), first 100 plus of the greenery next to the CDO wash (“its a jungle out there”) during a horseback ride, and of those spindily Cumulus clouds that were rising off Ms. Mt. Lemmon so early in the day (and oddly, with a lower, scattered layer of Stratus fractus clouds along the side of Sam Ridge). Those early skinny towers were full of portent about the day ahead, and those lower St fra, told about the unusually high humidity if you didn’t go outside!
A couple of photos from along the CDO wash and an example of those “stalagmite”-like Cumulus:
Along the CDO near Spirit Dog Ranch.Along the CDO. With the new wetter climate, perhaps new life forms are already arising inside this jungle.Morning glory blossom along the trail, almost a “Husky purple” I thought as the college football season nears and the summer sports malaise ends (hahahah, sort of). In that regard, former Washington Husky pitcher, little Timmy Lincecum, SFO Giants, can’t find himself–we thought for a time he would win the prestigious Cy Young Award every year– but has been a real disappointment this season for those of us who used to watch him throw at Husky Ballpark on Friday nights, so who cares about him or baseball anymore?
The spindily early Cumulus
These were an incredible sight on that early morning ride, truly, because of what they suggested for later on.
You can really get an appreciation for these guys puffing off “Smokestack Lemmon” from the U of AZ time lapse movie, as well as the power that was unleashed in those gorgeous, if volcanic, Cumulonimbus clouds later in the afternoon. I don’t believe I have seen as strong a convection day as we had yesterday before.
One measure of horrific convection, horrific updrafts in clouds is that little or nothing comes out of them. These kinds of Cumulonimbus are well known in the Plains States where giant clouds can form spewing anvils out that can cover much of a whole state. But, then, there is no rainshaft, or its very tiny.
Here’s an example from South Dakota of what is called a weak radar echo, or “echo-free vault” (the Cb seems to be “hollow” with no echo to great heights. sometimes in the middle of it).
The updraft in these severe storms is so strong that almost nothing can fall out, well maybe softball-sized hail; instead the all the water is transported high into the troposphere where only tiny ice crystals form at very low temperatures (liquid drops can be transported to temperatures below -30 C!) in updrafts of 50-60 mph or more in these situations (the measured record is about 100 mph). When this happens, too many ice crystals form and none can grow large enough to fall out until many minutes later, but then are 40,000 feet and can never reach the ground. That appeared to have happened here yesterday.
The South Dakota Cumulonimbus cloud shown was memorable because, like yesterday’s severe thunderstorm west of Catalina in the late afternoon and evening (shown below in its early stage), there was continuous lightning and thunder from overhead, high anvil; no cloud-to-ground strokes anywhere nearby in both situations. Those were likely occurring far off in and near the shafts on the horizons.
Parkston, South Dakota, 1976. This gigantic anvil was rumbling continuously from overhead and to the southwest. Note the tiny rainshaft from the parent Cb on the horizon. Yep, I took this photo WAY back then. I loved South Dakota…in the summertime!5:36 PM. By the time of this shot of this vertical giant, toward the Tortolita Mountaintas, had been thundering continuously from the upper half for over half an hour before this tiny rainshaft FINALLY emerged. It was remarkable, something I had not seen happen here before. It was a measure of how strong the updrafts were in this cloud and many others yesterday. Don’t know for sure whether it had an “echo-free vault.”
Rain amounts
The ALERT precip reports are here. White Tail, by Palisades Ranger Station on Catalina Highway, got another 1.50 inches yesterday and last night. It received 2.44 inches last Friday, and had another 1.25 inches on Sunday for a few day total over 5 inches now. Other local data can be found here and here.
Here in Catalina, we only received 0.08 inches, and that from some steady light rain overnight. Maybe today….
Today?
Well, no surprises for any met man, another strong day of convection. It will be interesting to see if there are more “low echo” Cumulonimbus clouds, ones with lots of high lightning, and a delayed emergence of a shaft, an emergence long after ice has proliferated aloft.
Nice sunset yesterday, one consisting of_______, _________, ________ clouds, ones that always give us one of those “glad to be here” in Catalina, CDP, feelings. I might give the answers tomorrow, but please try to name these clouds and maybe get that, “Its fun being a cloud-maven, junior” T-shirt you’ve always wanted. It has clouds all over it, maybe even ones you’ve seen and logged!
Only got a trace of rain here in Catalina, though there were a few “be-a-moth” (as we used to say as kids) Cumulonimbus clouds here and there yesterday. Check the U of AZ time lapse movie at about 2:30 PM yesterday for a giant. A couple of examples from around here below:
3:55 PM. Now if we were talking pancakes, this would definitely be a “tall stack.” It was quite a sight, and I hope one of you out there got under this and have a rain report for us today. I would estimate, as you would now, in view of the little movement of the storms yesterday, bases about 8 C (pretty warm), that this giant gave someone 1-2 inches in the peak core.5:44 PM. Here’s a complex of Cumulonimbus clouds SW of Tucson (left of Twin Peaks). The television got pretty worked up about these, as did the TEEVEE weather presenters last evening.
As we know, we are beginning the overall decline in chances of rain each day now; the summer rain season is winding down gradually. Doesn’t mean that in any particular year like this one that it will, BUT you have to give credibility to longer term models outputs that are on the dry side because we’re not dealing with an unbiased coin. The head on the quarter getting flipped for the choice of kicking or receiving in a football game is getting heavier; go for the tail since the heavy head might cause tails to come up more often.
Lately the model runs have had a complete break in the summer rain season around the 25th for a couple of days, then a slow return to wetter conditions alternating with breaks. Go here, to IPS MeteoStar, to see their rendering of the WRF-GFS outputs from last night’s global data, concentrating on the Arizona portion of these maps.
So, what are the chances THIS output, with a reasonable amount of “green” (meteorologists love to color areas of precipitation green; always have and always will) in Arizona at the end of August and the first day or two in September will have summer rains lingering on?
Go next to the NOAA spaghetti factory here. Examine the contours for the end of the month and the first of September…. And, there you have it! Eureka! The confidence level you’ve been looking for.
The late afternoon yesterday was like a Carpenter’s song, i.e., “easy listening” interrupted by Metallica, Megadeath, Slayer, Black Flag, Helloween, The English Dogs (“She Kicked Me in the Head and Left Me for Dead”), etc.
A day filled with moderately promising Cumulus congestus and brief area Cumulonimbus clouds, was suddenly overrun by a black steam roller with a watering tank behind it, and also having a big fan, to wind up a semi-ludicrous metaphor, coming down out of the northeast bringing an early nightfall, blinding rains, and winds of 60-70 mph. It was an astonishing change, and if you weren’t watching, but rather watching TEEVEE: “Ka-blam! What the Hell?” (More on TEEVEE later; see last caption.)
Some rain totals, ones up to 2.64 inches (!) can be found here in the listing of Pima County ALERT gages. More results will be available during the morning from the U of AZ network here, and from the CoCoRahs network. BTW, if you haven’t joined up, it would be good if you joined up with both of these latter “rain gangs.”
Of course, neurotic-compulsive cloud-maven person was watching for you. I only wish I had a huge microphone yesterday evening so that I could have alerted the people of Catalina, “CDP”, to its impending weather doom.
Non-weather side note: “Catalina: its not a town”, but rather, a “Census Designated Place” (CDP) where people are clustered, according to the Census Feds. Namely, we’re Catalina, CDP, Arizona, 85739. Its quite amazing the kinds of things you might read here, and its usually right after I find them out myself.
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Enough collateral information.
The day, had a tranquil but portentful beginning filled with potentiation, with those low, warm cloud bases. However, with the rising temperatures, ones into the mid-90s, so, too, did cloud bases rise. This is normal. As the daytime relative humidity falls, the cloud bases form at higher and higher levels. I hope you didn’t get upset seeing that the afternoon bases were above the top of Ms. Lemmon. Still, those higher, cooler bases did mean that the rain had farther to fall through dry air, not as good as having them down on the Sam Ridge line.
10:23 AM. Turrets begin shooting upward from bases topping Samaniego Ridge. This is good.1:37 PM. Weak Cumulonimbus (Cb) finally forms in the area. Getting a little concerned at the lack of “progress”, and much higher bases now.1:56 PM. Another weak Cb forms over the Tortolita Mountains.
3:43 PM. Another weak Cb forms this side of the Tortolita Mountains. That promising dark base above Catalina unleashed a sprinkle! (Sarcastically spoken).3:18 PM. Finally, something close! Looks promising, but fizzled out.4:14 PM. Not looking good. The Catalinas are back to producing shoots, not Cbs.
5:25 PM. Then “The Man” showed up, a gigantic Cb, one like the model had been suggesting would occur in the prior evening’s run.6:28 PM. The “black steamroller” appears, about to blow over lawn furniture everywhere.6:56 PM. Rolling into Sutherland Heights above Catalina, CDP, this 30-minute “incher”. I wonder who was watching TEEVEE, perhaps planning a TEEVEE party tonight, and not watching?
For a great movie of yesterday’s clouds from the U of AZ, go here.
Oddity
An as yet inexplicable odditity to yesterday’s stupendous storm. The lack of cloud to ground strokes; I didn’t see ONE, and I was looking. Second, the frequency of lightning was as high as it gets. In the dusky light, a new flash within the Cb in less than ONE second at the peak. Its was remarkable. That same kind of activity could be seen last night as the storms receded from us with almost continuous in cloud lightning, but no strokes to the ground (at least during the time I watched.
Today?
Still humid, still unstable aloft. Mods say another active day, so watch it (not teevee)!
7:12 AM. Action shot of bird with morning Altocumulus perlucidus translucidus.11:50 AM. Clouds topping Samaniego Ridge. Get ready for sprouts!12:38 PM. Amid the Cumulus “rubble” a glaciated top has emerged representing a Cumulonimbus calvus. Can you find it? Only the BEST cloud-maven juniors will be able to locate this tip of a tall cloud. Maybe you’ll get that special badge… If you don’t believe me that there was an extra tall top in this photo, you can go to the movies and see it here: http://www.atmo.arizona.edu/~leuthold/yesterday.mov.4:23 PM. While it was pretty and placid here, ominous Cumulonimbus clouds pile up on the S-WSW horizon.6:49 PM. Closer, spectacularly tall and pretty, but still over there, not here.7:05 PM. Time to give up and go to bed. Finely granulated virga from Cirrus/Altostratus deck was a bit of a treat. Suggests tiny cells of rising currents within that layer that produced tiny areas of larger ice crystals now falling out after the “updraft” (maybe 1ft a minute) weakened. The crystals? Likely “bullet rosettes”, of course, to extend the guesswork.
OK, enough of yesterday, a bit of a disappointment unless you looked at the models and saw that there wouldn’t be much here.
But TODAY….oh my. Those models have a MUCH more active day! Be ready; have camera charged, video as well. Don’t forget, you loggers out there, to note the time of your first Cumulonimbus sighting.
Should be a “fun” day with once again our very warm cloud bases (topping Sam Ridge now as I write at 6:02 AM) giving us, in essence a cloud travelogue to normal condtions in tropical countries near the Equator.
How much rain can fall from in these tropical boys? As we saw two days ago, 2 inches in an hour can fall; three is possible. 2-3 inches in an hour? Happens all the time in Florida in the summer. And with our upper sixties and low seventies dewpoints this morning, we are one with them (taking into account our higher elevation).
While “only” 0.42 inches fell here (a great rain, really), and 0.43 inches at the ALERT gage on the CDO bridge at Lago Del Oro, Sutherland Heights got whooped with a whopping 1.75 inches yesterday afternoon in a remarkably dense and windy rainshaft. But I am getting ahead of myself with this report and this sunset photo. First some more precip reports, here (ALERT gages) and here (U of AZ network). “And the winner is…” (as of 9:18 AM) for the greatest 24 h amount in ALL of Arizona, Bonita Canyon near the Chiricahua NM (2.06 inches) followed by Sutherland Heights!
Check the rainlog amounts above and here for CoCoRahs!
On to our story of the day, to be interrupted later by another learning module…
The day started like any other one, with our often observed morning Altocumulus perlucidus translucidus deck covering most of the sky. With the rising sun, Cumulus began to appear and grow rapidly with bases of those clouds topping the Samaniego Ridge line, something that is a rare occurrence. By 10 AM, showers were already appearing on the Cat mountains; those towering Cumulus clouds had already reached the precip forming level.
By 10 AM, you should have been VERY excited, talking to the neighbors about the low and warm cloud bases; alerting them to possible exceptional rains.
6:49 AM.9:29 AM.10:11 AM. Little acorns are turning into giant sequoias already!
At this point, I feel I have to insert a diversionary learning module. If you’re one of those people who doesn’t care about what’s going on “way down inside” these Cumulus clouds, as Robert Plant might put it if he was a nephologist instead of with Led Zepelin, then skip this module.
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Begin learning module.
With cloud bases as warm as 15 degrees C (close to 60 F!) almost certainly the first precip to form in yesterday’s clouds were drizzle drops (remember, to keep Cloud-Maven from getting mad at you, having “rain rage”, you have to remember that drizzle drops are between about 100 and 500 microns in diameter and that at that size, a few human hairs in diameter, they almost float in the air; umbrellas can be useless when it is drizzling.
Dirzzle is NOT a sprinkle of larger drops, dammitall, and its important to me that you know that!
Here’s the interesting part (he sez). Before drizzle and raindrops can form in a cloud without ice being involved, the droplets inside the clouds must reach 30-40 microns in diameter, maybe a third of a human hair in diameter.
Until they reach that size in the clouds, they will bounce off each other like itty bitty marbles or ping pong balls. After that “magical” size greater than 30 microns, they can coalesce, merge into one larger drop, which then falls faster, collects more drops, and, if the cloud is deep enough, fall out as a raindrop.
In the olden days, this was called a chain reaction process by cloud seeding nut and Nobel Laureate in chemistry, Irving Langmuir, who published a nice paper on this in 1948. Today most folks call it the “warm rain” process, because ice is not involved. Happens a LOT in the tropics, and places like Hawaii, but its rare here because our cloud bases are so warm as they were yesterday, and our clouds, being “continental”, that is, having high droplet concentrations (hundreds of thousands per liter of air) makes it hard for cloud droplets to grow up to be 30 microns in diameter. BTW, raindrops as big as 1 cm in diameter, the biggest known size, came out of a cloud in Hawaii that had no ice in it.
So, for me, a cloud-maven, it was quite interesting yesterday to see that our cloud bases yesterday were “Floridian”, and likely had a good deal of “warm rain” in them, even before they towered up to 50,000 feet, -60 C, and had a ton of ice in them. Its often the case that those raindrops are carried up to levels where they freeze and jump start the ice/hail forming process higher in the cloud via splintering (banging into drops and leaving fine ice shards in their wake) and shattering (they break up upon freezing).
End of learning module; you can wake up now…
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The payoff by those low, warm cloud bases? Exceptional looking clouds, a travelogue in the sky really, more like ones you’d see in Florida in the summertime, Bangladesh, Phillipines, Jakarta, etc. Here they are, before and during the Big Dump on the Sutherland.
12:49 PM. After a huge storm over the Torts, an ominous line of Cumulus clouds began extruding westward toward Catalina.1:07 PM. This is looking VERY good, but, with all the cool air, can these Cumulus bases really be hiding tall clouds? You never know until you see the streamers. Excitement level probably should have been around a 6-8 of 10 here, holding back that bit so that you’re heart is not broken by a later broken up cloud base.1:29 PM. “Thar she blow”s, though actually, its like an upside down spouting whale; the streamers begin to emerge in the distance.
1:28 PM. Just six minutes later!1:31 PM THREE minutes later. Excitement level 9 of 10.1:36 PM. Full blowed tropical Cumulonimbus shaft. Thinking about that “Rawhide” theme seeing this, after all, this is “Arizony”: Rollin’ rollin’, rollin’, though the streams are swollen, keep them dogies movin’, rawhide” rain and wind and weather, hell bent for leather….’
That last shot is of the one that rolled into the north Catalina area and Sutherland Heights, dropping 1-2 inches.
Tried to beat it up to Sutherland Heights but was late, visibility
was bad, lightning close by, so stayed in car with one of our (wet) dogs, Pepper.
As a result, in no “in the storm” shots. Sorry.
Oops, today?
Latest mod run from 11 PM AST last night by U of AZ here. Surprisingly, this model run thinks today is quite a down day, not much shower action here. Must be due to the cloud cover keeping the temperatures down all day (in the model) Or something else that is not immediately apparent to me, anyway?
But, temperature is NOT everything, as we saw yesterday. When the air is this humid, and deeply humid as yesterday, it doesn’t take blazing temperatures to launch Cumulonimbus clouds.
So, it seems likely, with the usual daytime thinning of these clouds, perhaps not enough of that in the model, that tropical Cumulonimbus clouds will once again arise here and there. I think Bob, our local scientist expert in these matters, will fill in some of my blanks on this later. He’s probably not up yet.
Only a marked change in the flow pattern at near the top of our Cumulonimbus clouds can really do much, and its not obvious any thing much is changing up there (is it helping air to rise, or to descend and dry out?) The latter can put a real damper on cloud development even if there is initial good humidity, and right now, it doesn’t get any wetter in AZ than it is right now, this morning!
Five consecutive days of afternoon and, or, evening rains are ahead. If you don’t believe me, go here, to the University of Washington’s model run from last night‘s GLOBAL data, showing where the rain areas will be (in color!) every three hours for the next FIVE days. You will see that EVERY afternoon and evening has regions of color in our area. I hope you’re happy now.
Instead of dwelling on yesterday’s drab conditions; all that water up there, and in the air around us as measured by those high dewpoint temperatures, air that produced almost no rain here in Catalina, I thought I would instead liven things up today with a learning module for you, delimited by a string of dashes for excitement.
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Below, is a link to the Environmental Science Services Administration (ESSA) pamphlet that tells you how to interpret today’s probability forecasts (10%, 40%, etc., chances of rain).
While I have provided this information as a public service, if you would like to obtain one of these pamphlets for yourself, you can get them for ten cents from the Superintendent of Documents, Government Printing Office, Washington, D. C.
Alert: there may be some questions in the days ahead to make sure that you read and understand this information. A sample test question:
“There is a large Cumulonimbus cloud on the Catalina Mountains but you can’t see them through the rainshaft coming out of that cloud. There is a flash flood warning for the CDO wash. The chance of rain is 10%?
True or false?
(The answer to this sample question will be provided in an upside down font when WordPress is able to to that.)
End of learning module. (I hope you’re happy now.)
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OK, here’s is a tiny sample of clouds from yesterday. I hope you recorded them correctly in your log book. Here they are, in case you miss them on some hot day ahead:
12:36 PM Sprinkles are around. Altocumulus opacus, could be labeled Stratocumulus underneath. Above the Altocu, Altostratus, the three layers helping to provide that Seattle drab look.
4:35 PM. Can you spot the Cumulus fractus under this Altostratus translucidus layer?
A quiet day most of the day with no sign of the explosive developments that were indicated to occur in the U of AZ models, causing some excitement in the Dept there. Not a shred of Cumulus clouds appeared on the Catalina Mountains until mid-afternoon. Then, fairly quickly things looked more promising for rain, as in shots 2, 3 and 4 showing a Cumulus turret that exploded upward. The instability of the day, indicated in the models, was finally being unleashed! The time lapse movie from the U of A is even more dramatic (here).
But this Cumulus congestus cloud quickly converted into a long, thin Cumulonimbus, and was not followed by others as hoped for. Only its glaciated head survived, drifting non-chalantly across Oro Valley. No rain made it off the Catalinas, either, as can happen with this type as the mid and upper portions dribble light showers away from the mountains.
2:43 PM. First Cumulus clouds begin developing on the Catalinas.3:32 PM. Strongly rising turret gives promise of things to come.4:03 PM. Icy, bottomless Cumulonimbus drifts away from the Catalinas.4:14 PM. While this Cb disappointed, Cb tops on the horizon gave promise.6:54 PM. Now this is looking VERY promising, as a Cumulonimbus (Cb) top approaches from the east.7:00 PM. OK sunset, though.
So, nothing in the daytime…
But then during the early nighttime hours, things began to happen. By nightfall lightning was occurring to the NE, and a cell developed right over Catalina/Oracle Road about 8:30 PM. An extremely close lightning “pop and explode” strike hit here about 8:45 PM, but no rain was falling! Odd, since the radar indicated the edge of the thundercell was in my neighbor’s yard practically.
The cell drifted away toward the west, its intense rainshaft visible in the night light of Oro Valley. You can see from the rainlog.org site that some folks got blasted, one site in Rio Vistoso reporting 0.70 inches. The Pima ALERT data, showing amounts in the mountains, is here. Pig Spring, a little northeast of Charoleau Gap was the “winner” at 0.43 inches.
Sprinkly rain occurred a time or two overnight; in fact, its raining right now (R—, “R triple minus” for exceedingly light rain, 6:07 AM.) And check this cloud-radar 12 h loop from IPS Meteostar. You will see how the rain was all around us last night, though light, something the U of AZ model (WRF-GFS) had picked up on yesterday in forecasting an active night rain situation in SE AZ.
One factor that kept things at bay, and my Seattle friends won’t believe it, was the “cool air” yesterday, the high temperature only reaching 95-97 F here, about 10 degrees cooler than the previous day. Really, it felt quite comfortable I thought. That cool air really put the damper on convection, or, restrained the damper conditions than could have been.
Today?
Of course, these model breakdowns have to do with how accurate the initial conditions are. The U of AZ experts, in their late morning assessments of data that have arrived at 5 AM AST and later, or other local data from water vapor sounders, spend a lot of time seeing which of the two models they run on their Beowulf Cluster had the best starting conditions. They can then estimate what the differences might be in the model output imagery, and which model did the best job given the starting errors, always present to greater and lesser degrees.
Today, the model run from last night’s data have little rain in the Catalina area today, though storms approach from the Ne in the evening hours similar to yesterday. But the mods don’t think they survive the trip from the White Mountains and Rim to here, dying out about the time they reach the Catalinas.
As we have seen, this kind of close call can’t be taken too literally. So, the best forecast has to be generalized, in my opinion, to a chance of a thundershower in the mid-afternoon through the early nighttime hours. If you see Cumulus clouds piling up over the Catalinas by noon, the chances will be much greater for rain in the Catalina area today or early tonight (he sez).
Tomorrow is thought to be a wetter day here. Always, “tomorrow” it seems.
Well, the end of the story (told in the captions) is that a windshift producing this line of heavy Cu and a Cb or two and it “struck” Catalina about 11 AM; the wind turned from the SW to the N, but the heavy line of clouds riding it were nowhere to be seen at that time; the last Cumulonimbus cloud disappearing beyond the Charoleau Gap. Tough to take after hopes up.
