Lot of great scenes on the 18th, but, ultimately with hopes raised for appreciable measurable rain in Catalina, it was a disappointing day. Nice temperatures, though, for May if you’re a temperature person. Only a sprinkle fell (4:15 PM), and if you weren’t outside walking the dogs you would NEVER have noticed it.
Here is your full cloud day1, as presented by the University of Arizona Weather Department. Its pretty dramatic; lot of crossing winds, as you will see, and an almost volcanic eruption in the first Cumulonimbus cloud that developed near the Catalina Mountains.
That blow up was indicative of an remarkable amount of instability over us yesterday morning, one that allowed really thin and narrow clouds to climb thousands of feet upward without evaporating. Usually the air is dry enough above and around skinny clouds that even when its pretty moist, they can’t go very far without the drier air getting in and wrecking them (a process called, “entrainment”). Here are a few scenes from your cloud day yesterday.
5:45 AM. Gorgeous grouping of Altocumulus castellanus and floccus. They’re coming at you. (If you thinking of soft orchestral music here, you may be remembering well-known orchestra leader, Andre Castellanus.7:37 AM. Here a castellanus turret rises five to six thousand feet above its base. Had never seen one this skinny and THAT tall before. Was really pumped about the mid-level instability at this time. It wouldn’t last. The great height is indicated by the luminosity of the top,Also at 7:37 AM, another amazinging tall turret rises up from quiescent bases, ones not connected to ground currents. The bouoyancy in these clouds is due to the heat released when moist air condenses (latent heat of condensation). When the temperature drops rapidly with increasing height, that bit of heat released is enough to allow weak updrafts to rise great distances, sometimes becoming Cumulonimbus clouds and thunderstorms. These clouds, due to their size, would no longer be considered just Altocumulus andre castellanus, but rather Cumulus congestus. Here’s where our cloud naming system falters some. Later, a couple of these grouping did become small Cumulonimbus clouds with RW- (light rain showers).7:11 AM. The great height of these tops was also indicated by the formation of ice, that faint veil around the edges. Stood outside for a few minutes, thinking I might experience some drops, but didn’t.7:38 AM. The top of this Cumulus congestus has just reached the level where ice will form in the top.10:22 AM. Cumulus congestus clouds began their transitions to Cumulonimbus clouds early and often over and downwind from the Catalinas. Can you spot the glaciating turret in the middle, background? Pretty good skill level if you can.10:23 AM. Here’s a close up of that turret in rapid transition to ice. It was this kind of phenomenon that led Hobbs and Rangno and Rangno and Hobbs to reject the Hallett-Mossop theory of riming-splintering as THE major factor in ice production in Cumulus to Cumulonimbus transitions like these. The high concentrations of ice particles happened faster than could be explained by riming and splintering, or so it was thought. Still think that, but am in the minority, though there have been reports of inexplicable, fast ice development like that Stith et al paper (with Heysmfield!) in 2004 that for a time appeared to put the “icing on the career cake.” Incredible ice concentrations were found in updrafts of tropical Cu for which there was no explanation! That finding hasn’t been replicated by others, casting doubt on the whole damn paper! “Dammitall”, to cuss that bit.11:04 AM. Nice Cumulonimbus capillatus incus (has anvil) pounds up toward Oracle way. Tops are not that high, maybe less than 25 kft.3:41 PM. The air aloft began to warm and an inversion capped most of the convection causing the tops of Cumulus clouds to spread out and create a cloudy mid to late afternoon. Nice, if you’re working outside in mid-May. Since the tops were colder than -10 °C (14 °F) the ice-forming levels, some slight amounts of ice virga and sprinkles came out of these splotches of Stratocumulus clouds. One passed through the Sutherland Heights, but if you weren’t outside you would never have known it!4:38 PM. Isolated rain shafts indicate some top bulges are reached well beyond the ice-forming level. Note grass fire in the distance.7:22 PM. Pretty nice sunset due to multi-level clouds, some Stratocumulus, Altocumulus, and a distant Cumulonimbus anvil.
More troughiness and winds ahead during the next week as has been foretold in our models, and reinforced by weather “spaghetti” plots, after our brief warm up today. No rain here, though. Seems now like rain can only occur at the very end of the month where weaker upper troughs coming out of the Pac appear to be able to reach down and fetch some tropical air.
The End
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1Its gone now because I couldn’t finish yesterday. Went off to Benson for horse training with Zeus.
Its the way they do it now days, part retro, part modern. Next? Drones, of course. In the meantime these interesting scenes from yesterday:
12:51 PM. Cowpokes herding cattle, distant center.12:52 PM Monday. Can you find the copter? Pretty hard. Its a little one person job. Look on left side, center.12:57 PM Copter in flyby.
No clouds? Well today were “Cow-maven”….
The End
PS: Nice rows of Cumulonimbus clouds now (1:58 PM, Tuesday) distant N-NE from Catalina, toward the M-Rim.
Back to weather and yesterday’s microburst with three minutes of sheets of unbelievably heavy rain with rice-sized hail, 50-60 mph gusts, blazed across Sutherland Heights between 4:06 PM and 4:13 PM. It was a memorably violent storm, comparable in those worst 2 minutes or so to anything we see in the summer, and it was completely un-predicted for Catalina the day before (0% chance of rain here) though showers WERE predicted for the higher terrain of eastern AZ yesterday). For the full story, see Bob M’s excellent discussion. For just clouds and stuff, here is OK.
Looks like the Sutherland Heights got the most of anyone anywhere near here. No reporting station in the Pima County ALERT system in Catalina or in the Catalina Mountains got measurable rain, that’s how local our storm was. Rarely if ever do you see that happen.
Stuff blew everywhere and I felt lucky not to lose some branches of trees in the yard. Here’s yesterday’s cloud diary. First the background about what was happening, the TUS balloon sounding of the atmosphere:
The TUS sounding at 5 PM AST (launched around 3:30 PM). Classic inverted sounding associated with downbursts. Cloud bases are at 0 °C (32 °F) at 14 kft above sea level, or about 11,000 feet above us in Catalinaland. Lots of turning of the wind, too, helpful for stronger storms. So, rain and hail had a long ways to fall, cool the air, drag it down and blast the surface.9:43 AM. Castellanus of the morning. Patch Cirrus on top. Recall that in my cloud chart it says when you see this cloud, it might rain within 6 to 196 h. Pretty accurate yesterday since it rained about 7 h later here.2:11 PM. Cumulus were reaching mediocris stage around here while off to the horizon, Cumulonimbus tops could be seen over the higher terrain of the Mogollon Rim.2:11 PM. However, a single Cumulus congestus just past the Tortolita Mountains was transitioning into a little Cumulonimbus. Precip is fall out of that lofted flat side of the cloud to the left of the main base. What a surprise to see that! But it was clearly too small to do anything.
3:00 PM. However, those cloud over there kept shooting up turrets, becoming larger and larger until we had us a full blowed Cumulonimbus and something in the way of a rain shaft (Code 2, transparent, except for that one strand–almost certainly a hail or graupel shaft).3:54 PM. While CMP had to be inside for an hour, this surprise happened just to our SW, with rain falling on this side of Pusch Ridge! Wow, WHAT an interesting day this is turning out to be! Not only was there rain, but thunder! Didn’t think it would get here, well, maybe a sprinkle is all.4:02 PM. The rain shaft had gotten denser, and there are tendrils of heavier precip. Thunder is a remarkable every minute. Didn’t look vigorous enough for that kind of electrication rate. What’s really promising now is that darker round blob in the upper right hand corner of the photo indicating new cloud growth. That raining part of the cloud would hardly make it here even if it came right at us, given the light winds up there; needs to be replaced by new cloud growth. Was thinking now, “Gee, it might measure!” No thought of wind yet since that shaft looked kind of weak..4:04 PM.4:04 PM. Looked down on Catalina to see this remarkable site, a surface dust plume racing through town, rain just behind it! At this point you could see that it was going to blast the Sutherland Heights, so was a pretty exciting moment, and the rain was certainly going to be measurable if the gauge didn’t blow over!4:04 PM. Another view of this shaft just before the wind came roaring over the hill in the foreground. From the incredible but very short-lived torrential rain, Sutherland Heights must have gotten one of those narrow strands, but again it would not be one of those you see there, but something dropping out almost on top of us.4:06 PM. Here it comes, just over the hill. You can see the surface dust plume advancing north into Catalina where no rain fell!4:06 PM. Here’s something you rarely see, dust blowing off the little hills above the Sutherland Wash, Baby Jesus Trail area. Rain was just starting here.4:09 PM. Just about the peak of the rain shaft. Horsey retiree Jake shows that the wind si blowing away from the corral. The visibility is relatively high in this extremely heavy rain because the shaft was so tiny.4:09 PM. Just seconds later the shaft had moved a few blocks away and down the hill (whitish area running from left to right). Note expanse of blue sky in the background, too.4:13 PM. Storm is virtually over and here you can see the amount of water that came of the roof, and some wind damage (cushion out of place). Some cushions went down the hill.4:43 PM. The day ended peacefully enough with more Cumulus and distant Cumulonimbus clouds around. Great sunset scene of clouds over the Catalinas, but was enjoying live classic rock music at a friend’s house with some 50 others; no camera.
Too dry today for rain. Next chance for rain around the 17-19th as that bigger (but maybe drier) cold trough settles in. Temps will be nice, though. Lots of intermittent trough action indicated in 06 Z mod run through the rest of May, so May should continue to be pretty interesting and likely devoid of never-ending heat month as sometimes happens here. This scenario pretty well supported in those crazy NOAA spaghetti (or Lorenz) plots.
The End
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Photos not loading in WordPress now, so quiting here, dammitall! Must go on to other chores now. Not happy!
OK, photos finally went in. Happy now, though too many photos as usual.
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1I doubt that happened…. Really, this was a song about people who don’t like to go to work, kind of anti-capitalist which is ironic because it was that system that allowed the boys to make their millions (billions if they had invested wisely into Microsoft in the early 1980s) and gone on to help the world with their billions like Bill and Melinda.
Oh, me. So much wind, so much bluster, so gigantic aloft, but so little rain. Well, actually none here. Review of troughy’s last day on Sunday, Mom’s Day, where it tried to rain here:
5:35 AM.5:35 AM. With light showers around to the NW-NE, was clinging to hope that a sprinkle might fall from one of this clouds if it could grow that bit deeper, colder on top. But, no.6:25 AM. Gone, all hope of even a sprinkle.6:24 AM. Light shower from a weak Cumulonimbus cloud passes just to the north of Saddlebrooke. So close…. Note rain shaft is transparent, something we would refer to as a Code 2 rain shaft.
6:35 AM. Another longing look at that shower, drifting off to the east. Note the icy plume on the downwind side on the right. Since this Cumulonimbus cloud’s not very deep, and cloud top temperature likely -10 °C (14 °Ï) or even a little warmer, you should guess that those crystals up there are columnar in shape, hollow sheaths (seems redundant) and needles. Its a little unusual to see those kinds of ice crystals in Arizona, especially from a few miles away, since they are only millimeters and fractions of millimeters in size. Normally it take lower temperatures to have ice in our clouds. The cloud drops have to be larger than usual at that aforementioned temperature for those high temperature crystals to form. Only on especially clean aerosol days could that happen, or if there are large dust particles. Since there was no sign of dust, and the visibility was at least 100 miles, one guesses that it was the unusually clean conditions with weak updrafts at cloud base (i.e., ones result in only the best and biggest cloud condensation nuclei to activate) that led to larger than normal drops at temperatures warmer than -10 °C. Well, killed that audience. But sometimes you just get carried away with how much you THINK you know… Remember, my demand to stop blogging for a million dollars is still on the table if you want to strangle yourself at this point due to content overload.
9:20 AM. Nice Cirrus of many varieties and species, fibratus (fairly straight tendrils) is one, maybe some uncinus (hook or tuft at the top) in there, too.6:55 PM. One of those visual treasures that occurs on our mountains when we have some clouds around.7:08 PM. The two eyes of a fearsome sun blaze at Catalina as it split into two parts going over the horizon, the foreboding angry face of the hot days just ahead before another big cool down. In that regard, that is about a big cool down coming, it is well to remember that it was also foretold here that the big cool down we just had would also be accompanied by some rain, a quarter to half an inch, a forecast that was in error by a quarter to half inch.
Yesterday was another great humilis day for you, with quite a phase twist at the end. I am sure most of you out there saw the surprising final touch to a warm day with high-based shallow Cumulus.
11:52 AM.11:52 AM. Cumulus humilis and fractus over the Catalinas, in case you think I was hiding bigger clouds that might have been over the mountains.5:15 PM. 95 and 25, temperature and dewpoint. What is the height of the cloud bases above ground level given a 70 degree F difference? Hint: divide difference by 5 and that’s the hieight above the ground in thousands of feet. So they were way up there at about 17,000 feet above ground level!
Let’s see how close that using that old estimator technique was yesterday by examining the Tucson sounding for 5 PM AST (launched around 3:30 PM, goes up about 1,000 feet a minute). From the Wyoming Cowboys, this:
Wow! LCLP was 515 millibars, just about exactly at 17,000 feet. Also, look how darn cold bases were, almost -10 °C or 14 ° F, tops around -14 °C or just 7 °F, and yet we see no ice…yet.
6:06 PM. Which way is the wind blowing at cloud level? Ans: at you. Nice cloud street streaming off the Catalinas over Catalina. Clouds not looking so much like Cumulus humilis anymore but rather more like Altocumulus opacus. No signs of any ice…yet.6:09 PM. Hint of ice in this photo of clouds far downwind of the Catalinas (looking north over Saddlebrook and beyond. Can you find it?6:52 PM. By this time, there was ice EVERYWHERE! It was an amazing transition from cloud lurking up there with no sign of ice, to ice in almost every cloud. Have hardly ever seen such a dramatic transformation in clouds that seem to be unable to produce ice most of the day. What happened? I don’t know. But will guess. These clouds, part of a moisture slug moving around the big trough coming in, were actually being lifted in time so that minute by minute they were getting a little colder until ice concentrations suddenly onset. Ice seems to depend on droplet sizes (the larger ones freeze at higher temperatures, AND temperature, the same size drop will freeze as the temperature falls. In clouds like this, the largest droplet sizes were likely the same before and after the transition to ice, so one would guess that the temperature at which they would freeze was reached as the tops rose due to a layer being lifted, not because some tops were higher and colder. The transition was too widespread and affected small clouds as well as the larger groupings. Well, lotta handwaving here, but it was an amazing change that transpired last evening.7:07 PM. Noticeable virga is now dropping out of those clouds, ice concentrations probably up to a few to tens per liter!7:07 PM. Looking toward the Charouleau Gap. Icy looking cloud over there, too. What is going on?7:08 PM. Nice sunset, though. Ice barely visible at right.
While waiting for some rain in the days ahead, not backing off that in any way, though models generally have not had any (bad models!), will pass along a horse prank that happened.
Two days in the morning, as I went to fill “Zeus” water tank in the dawn hours, there was something dark at the bottom of it. I thought maybe some poor little animal or bird had drowned in his tank that night. I reached down, and found it was my State Park baseball cap! I had left it on the top of a panel, maybe above the water tank, wasn’t sure, so it likely blew off the panel into the water tank. But then again, I wasn’t sure that Zeus hadn’t put it in there on purpose.
But that was a crazy thought.
As a test, yesterday morning I decided to put the cap back on top of the end of a horse corral panel, but much farther away where it could not possible fall into the tank, just in case Zeus was telling me what he thought of me by dunking my cap.
9:41 AM May 4th.
Here’s what I found when I came back in the afternoon to feed Zeus:The same scene as the prior morning!
It’s been very “West Coasty in the spring” here lately. Cool days, 70s, with do-nothing Stratocumulus splotches all over. I couldn’t take it anymore in SEA, and bailed largely due to the dominance of Stratocumulus as a cloud type there. Yes, I would be termed a “stratophobe.” A lot of us refugees from the West Coast suffer from “latent stratophobia”, and aren’t really running from crime, smog, traffic congestion, or high prices on the West Coast. You can only take so much strato, and I know many of you out there are reaching your limit here as well. You’ve seen enough “June gloom” days throughout the year.
I hate to punish you with more photos of Stratocumulus clouds, but to document yesterday, it has to be done. Concentrate on the scenery below the Stratocumulus in the following photos as a way of calming down. Fortunately today we should see only small Cu, and little Stratocu.
However, early on, those with expert cloud-maven eyes probably noticed the development, if briefly, of shallow Cumulonimbus clouds to our north. Tops really didn’t protrude much above the overall tops of ugh, must I say it again, those Stratocumulus clouds so prevalent elsewhere. Of course, there were some Cumulus, too, most underneath the spreading layer of ugh, Stratocumulus. Hmmm. I like that; “Ugh Stratocumulus.” Everyone would know instantly what that cloud type is! Low, gray, lumpy; nothing really redeeming about it. I’ll try to work around the shots of Stratocu as much as I can.
Yesterday’s clouds
6:00 AM. Tops of weak, residual Cumulonimbus clouds, still going after the prior evening’s thunderstorm, poke up above Altocumulus castellanus clouds9:23 AM. Cumulus piled up early over the Catalinas, but tops hit a strong stable layer and were already spreading out here fortelling the kind of day it would likely be. Didn’t get as warm as expected, either, which helped keep the cloud flatter, too.11:30 AM. Light rain showers developed to the north from shallow Cumulonimbus clouds (above horizon, center and right), but hardly deemable as those by most folks. Could be labeled “Ugh Stratocumulus praecipitatio”, too, I guess.11:30 AM. Light rain showers developed to the N about this time, raising hopes that showers might develop over the Catalinas, too.11:30 AM. Zooming for ice. Yep, though barely detectable with confidence.11:30 AM. Backing off a little for more perspective; ice a little more evident in the soft mushy look of those turrets. In some cases the updrafts, as in this case, are so weak, that the heavier ice particles have a tough time staying at cloud top as in cases like this.11:30 AM. Looking a little more to the right for icy tops. Can you make them out? You will get quite a commendation at the next club meeting if you can.12:16 PM. Showers all over. Not to the spreading tops of Cu and Stratocu that produced so much cloud cover, but were too warm to form ice any longer. Very Seattle spring look here. Nicely formed Cumulus bases with tops that go nowhere.3:46 PM. Skipping over a lot of time and the same kinds of clouds are shown in the prior photo; just another shot here to show you nothing has changed.5:35 PM. Big dark stretches of Stratocumulus clouds are still lurking over Catalina and environs.6:39 PM. Stratocumulus clouds dissipating now, holes in the sky allow interesting shadow and light patterns.7:04 PM. Not a great sunset, but not a bad one, either, as the last remnant of Stratocu clouds fades away into the night.
The weather ahead
From IPS MeteoStar’s rendering of our WRF-GFS model output, this:
Valid on Friday, May 6th, 11 AM AST. Quite the Big Mama trough drifts toward us. Its this kind of situation that southern and central Cal get hail, TSTMs, and even a weak tornado. This situation goes on for a few days. For us, we’re on the cusp of rain, according to our best model. But, still hanging solidly at this keyboard that a decent, measurable rain (0.25 inches or more) will occur in Catalina during the passage of this behemoth trough. This map looks promising. The jet at this level has gone by, and “rain follows the jet”, more than less here in the cool season.
More troughs pummel the SW into mid-May, but other than bringing fluctuating temperatures and wind, look a bit on the dry side. Dang.
Day started out as expected, but instead of Cu fluffing up into congestus and Cumulonimbus clouds yesterday as expected, a higher layer of Altocumulus (with ice plumes) filled in the sky indicative of “slab lifting” due to our incoming trough, and with the strengthening winds mixing things all up, the Cu went flat on us. So about three days in a row, the kind of clouds expected didn’t happen. First time this has happened since four days ago.
But, we did have Cumulonimbi in the area, those deeper clouds indicative of the cooling aloft that had occurred during the day, if you noticed the OCNL LTG to the NW-N after dark. Thought, too, for a moment around 8 PM a cell was erupting overhead as sparse large drops fell, always the melted remnant of graupel (soft hail) aloft indicating a Cumulus turret up there, but it didn’t mature into a full blown Cumulonimbus. So, only a trace of rain from all those many sprinkles yesterday afternoon beginning just after 2 PM through about 9 PM. Darn.
Mike joins “Bob” in doing some great, professional-style weather discussions for TUS and vicinity, not at all like the ones found here.
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Yesterday’s clouds
11:42 AM. First Cu begin to take shape.11:43 AM. From Romero Ruins Trail. Small Cu begin to form to our SW-W.1:20 PM. Cu continue to grow and expand in coverage as wind picks up and small cloudlets of Altocumulus shedding ice roll over on top. Getting pretty cloudy at this point. No congestus anywhere.1:36 PM. Lots of ice dropping out of those Cu now merging with a higher layer of Sc. But no sign of anything deep.2:20 PM. Really looking kind of bleak as the overcast thickened with no sign of a strong shaft (which would indicate a buildup), just “gentle” virga and light rain showers reaching the ground.3:14 PM. Shafts of virga and rain reaching the ground are more evident, but suggest “mounding tops” not ones jutting up much.6:50 PM. Strong TSTMs had erupted by this time to our NW toward PHX and vicinity. Here the darkness on the horizon is a dust plume, not a rain shaft, a plume generated by heavy precip to our NW. It wasn’t long that some LTG was observed NW-N of us.6:50 PM. Close up of a weak ‘boob-like feature driven by strong outflow winds. Spread out and flattened racing toward Avra Valley.6:51 PM/ Dust cloud riding a wind shift to the N approaches Catalina. The temperature here dropped about 10 °F in half an hour about this time when the wind turned to the N. So much promise, so little production.
Should see some nice Cu today, though, as our upper puddle of cold air slips away from us. Early birds may have noticed some lingering Cumulonimbus tops to the NW-N at dawn. Probably won’t see any more of those except off in the distance to the N during the day.
The weather way ahead
Notice that the red lines are in Baja and this strongly suggests troughing (cooler than normal air aloft) in our region. Looks pretty Niño-ish. So, it would appear that we’ll continue to have an occasional blast of cooler days, rather than just a long series of clear, warm days.
Still looking for significant rain next week, between the 6th and 8th, but our best model from last evening’s (00Z, 5 PM AST) global data thinks that rain in AZ will mainly be to our north with little if anything here. However, I have rejected that analysis and am clinging to the thought that at least 0.25 inches will occur in Catalina next week during the aforementioned window. I recommend that you be kind of clingy, too.
Valid May 15th at 5 PM AST. Those who are able to look into spaghetti and read the strands know that this map promises a pretty nice spell of weather, temperatures often below normal, through at LEAST the middle of May.
Punctuation: its hard. Not sure about that in the title. Oh, well. Kind of sad that English is my first language, too.
Yesterday was definitely more Stratocumulus-ee (clouds flatter than expected) than anticipated, which hurt since it was foretold here that it would be Cumulus-ee day. And there was but the slightest evidence of any ice around, something that was also expected. So the record of almost always being right on weather and clouds (i.e., >50% of the time) took a hit, which hurt, to repeat something about personal feelings.
Too, with noticeable breezes at times, the sky almost completely overcast at mid-day as well, and the temperature well below 80 °F, it seemed darn COLD for late April.
Today, looking ahead, the air cools over us again as it did two days ago as a puddle of cold air slams down the interior of the West Coast and into AZ, and we should see some nice, photogenic Cumulus/shallow Cumulonimbus this afternoon, and, since the coldest tops will be well below -10 °C, there should be some virga and light showers around. So, another chance today for a little measurable rain here in Catalinaland before April closes out. The jet stream at mid-levels remains south of us, too, a critical aspect for cool season rain in the Great SW.
With more instability today than yesterday, there should be some more sun around compared to yesterday since holes due to downward moving air around the upward moving air in cumuliform clouds will be out there. Looking forward to today!
Still looking for the good rains next week as extra jumbo-for-May trough crashes into Cal from the Pac.
Yesterday’s clouds
In reverse order, today. They imported that way, and am too lazy to move them all.
6:49 PM. Looking toward Romero Canyon. Very nice lighting and shadows on our beautiful Catalina Mountains. Hard to believe that enough folks voted to cut off views like this when Oracle was widened and sound walls were put up in front of their homes to save, oh, 2-3 decibels is all, AZDOT said.6:49 PM. Nice lighting on Samaniego Ridge as the sun went down.4:23 PM. Nice “muffin-like” Cumulus over Ms. Mt. Lemmon producing a huge shadow. (hahah; its the cloud overhead left that’s causing the shadow. Kind of a dramatic shot I thought.3:15 PM. Lots of cloud coverage by those flattened tops (Stratocumulus cumulogenitus) with small to moderate Cumulus clouds below.3:12 PM. Thought I saw just that slight veil of ice (center), but maybe “grasping for a seed and swallowing a camel” here.1:06 PM. Looking NNW at Cumulus cloud with flattening tops due to an inversion lurking north of Saddlebrooke village.1:06 PM. A mix of Stratocumulus with small Cumulus clouds below lurk over and west of the Catalinas.7:35 AM. “Regular” Altocumulus with underlying Stratocumulus lurk to the north.7:29 AM. Altocumulus lenticulars lurk behind the Catalinas.
0.02 inches of it, anyway, as the core of the jet stream at 18,000 feet or so passed by Catalina yesterday afternoon. Keep your eye on the orange and reddish streak in these progs from IPS MeteoStar yesterday morning beginning at 5 AM AST and how it slides over us as the clouds began to ice up:5 AM yesterday. Jet at this level races across central AZ. 11 AM yesterday. Maximum winds getting closer! Tiny Cumulus clouds begin to appear over the Catalinas and on the west to north horizon.
11:40 AM.
The jet separates deep cold air on the left side, looking downwind, and deep warm air on the south side. The deep warm air prevents Cumulus clouds from getting very deep due to inversions and stable layers where the temperature does not change much with increasing height, or even rises. The temperature at 500 millibars or 18,000 feet above sea level dropped from -17.7 °C to -21.1° C over TUS yesterday between 5 AM and 5 PM, while the temperature about which ice begins to form in our clouds dropped about 400 meters during that time. With the temperatures at the ground rising into the mid-70s as the colder air moved over us, Cumulus clouds deepened, reaching the ice-forming level between 1 and 2 PM.
Also with patterns like this, the cyclonic rotation (vorticity) in the air above us is increasing like mad, and that leads to a gentle upglide motion in the atmosphere, one that also helps cool the air aloft and usually produces sheets of clouds like Cirrus, Altostratus, Altocumulus and NImbostratus. But yesterday the air was too dry for sheet clouds to form.
First ice was noted just after 1 PM. Can you find it?
1:11 PM. Looking N toward the Charouleau Gap. Tiny puff of ice ejects from a Cumulus humilis cloud based at about 8 thousand feet above ground level. Bases were running about -5 °C
2:31 PM. Cumulus and Stratocumulus clouds launched off Pusch Ridge and the Tucson Mountains stream toward Catalina. The sky begins to fill in rapidly.3:44 PM.3:49 PM.3:57 PM. A horse eating as it clouds up.4:33 PM.5:09 PM. Light rain falls in Catalina/Sutherland Heights.6:04 PM. RW- (light rain showers) continue in Oro Valley.
5 PM yesterday. Just passed! B y this time, Sutherland Heights had 0.02 inches as the tops of Cumulus and Stratocumulus complexes continued to cool and ascend. The sounding from TUS at 5 PM AST (launched about 3:30 PM AST) indicated the coldest tops had reached -20 °C or so, plenty cold enough for ice, virga, and light rain showers. Too bad the bases were so high since we could have had some real rain if they had been lower.
But, we were “lucky” to get that. Even the great U of AZ model had no rain anywhere near us late yesterday afternoon when it fell! THAT does not happen very often.
Looking ahead….today:
Nice Cu, ice, too.
Farther out:
Substantial rains, maybe half an inch or so, still on tap between May 6th-8th as previously foretold here. Yay! May averages 0.38 inches here in Catalina. More rain likely after that episode, too. So an above normal May in rain is pretty much in the bag now. Could be an especially great May, too.
Partly its because I can’t think of anything else, brain pretty empty, but check this out:
Valid for May 9th. Shows the kind of “split flow” we expected from the Big Niño, storms dividing in the central Pac or so, parts going northeast, often just grazing the Pac NW, so that area ends up drier than normal, whilst a southern branch from the CenPac carries storms to lower latitudes of the West Coast, drenching southern Cal and the Great American Southwest that we live in. Was that too long for one sentence? Well, moving ahead, you can see this pattern in how the non-political red lines diverge in the eastern Pacific from the non-political blue ones to the north, which there is quite a bit of in politics today as well. Well, anyway, it was kind of interesting of me to point this classic “Niño” pattern out to you, even though it is seen in a computer output form that is largely incomprehensible to most. What does it mean for AZ and Sutherland Heights? The red lines down thisaway on most of these maps to this point mean that there will be chances for rain, AND lower than normal temperatures for the first 10 days of May. Nice! The resultant headline is below:
Measurable rain to fall in the Sutherland Heights, Catalina, in May 2016!
OK, got that “scoop” out…. Here’s the link to NOAA from whence the above map came.
BTW, here’s what a split flow storm looks like as it comes into southern Cal. Man, if it was January or Feb, this would be a real gully washer, a “get the sandbags out” kind of storm. I love this map so much!
Valid just ahead, really, for May 4th 11 PM AST. This is the best example output lately and its from yesterday, but who cares. We should see something resembling this come out of the lower latitudes of the Pac. From IPS MeteoStar.
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Now a little more on these kinds of crazy ensemble maps (“Lorenz”, as named here, or more known more generally as “spaghetti” plots)
This kind of map was telling us we had rain threats at this time in April and at the end of the month some 10-15 days in advance, so far in advance that media weather folk would likely consider it unprofessional to make such a prediction so far in advance. Since we’re not worried about being unprofessional here, we have leapt into the void! Just go ahead and say things! Get the story out now!
Today a strong upper level trough with precip in the mountains of central and northern AZ will indeed be occurring today and tomorrow as was indicated by those crazy maps so long ago. The hoped for rain here will not occur.
However, the storm near the end of the month, also indicated way back then, looks even stronger than the present one, and it will reach farther south than today’s, and so will not only bring some rain and very cool air to the central and northern AZ mountains, but likely around us, too!
The same scene as the prior morning!
5 AM yesterday. Jet at this level races across central AZ.
11 AM yesterday. Maximum winds getting closer! Tiny Cumulus clouds begin to appear over the Catalinas and on the west to north horizon.
