“Alas”, now there’s a word to don’t see every day…probably a little stiff from laying around so long.
Those Cumulus that shot up over the Catalinas early yesterday morning were a magnificent sight, and so full of promise. And while thunder was heard here just after 11 AM here in Sutherland Heights-Catalina, the showers just did not get off the mountains around here as hoped, though there were a few big boys (or “gals”, to be gender neutral) around to the NW-N and down to the S-SW during the afternoon. Here are the Pima County ALERT totals for the past 24 h. Lemmon had a good drop of 1.46 inches; that’ll surely keep those mountain streams going. But as you will see, not much elsewhere. Just a trace here, our mode for this summer in Sutherland Heights-Catalina area it seems.
BTW, all available model outputs (U of AZ 11 PM run not available at this time) show fewer showers than yesterday, though to CM, it looks like a very similar day to yesterday in sat imagery and such1. So, it would seem we have a another day with a chance for a good rain in the afternoon or evening, about like yesterday when some showers did form off the mountains and could have landed on us. Besides, even without rain, it was a pretty day anyway. Its all great.
Here is yesterday’s cloud history with its early promise, ultimately only fulfilled only on the Catalinas around here:
1BTW, if you want a really GREAT forecast by a true expert, rather than a “shoot from hip” kind of one that CM so often offers, you have to read what Bob has to say today when he posts it. U of AZ experts also often refer to his careful analyses.
2Here they sing about something we probably don’t want to happen to Catalina, Arizona.
Running out of material, which is quite interesting because I haven’t been doing much, so am reprising these….
We had a little uptick in rainfall last year mostly due to that four and half inches in July. Very nice. No trend is evident in the summer rainfall here, global warming aside.
When it falls in summer….
Hmmm. Just noticed a discrepancy in the years of record. Huh. Must investigate later.
Some of yesterday’s clouds
One of my specialties is cloud bottoms, and there were several opportunities to photograph them. Here’s a quite nice one, hoping one day it might appear in a gallery, it’s that good I think. It was just starting to unload its watery burden onto the unsuspecting folks in south Catalina and Oro Valley (see next shot):
Models chock full of moist days for at least a week ahead, so “let the games begin”. Certainly we Catalinans will get nailed one of those days. Extreme SE AZ has been pretty wet so far, with Douglas having almost 2.5 inches already. Will be green down there soon! Might be worth a trip to see how things are coming along.
The End, except for this shot of the prior day’s really dramatic sunset:
That’s your weather forecast for today. There’s nothing you can do about it. Why go on about it?
Next, these from yesterday–was under control, only took 127 photos. Every thousand or so shots I take is NOT of a cloud, and yesterday there were two exceptions, which I will post here as an anomaly; a quirk really:
Yesterday’s rare ice-forming anomaly
I was hoping you wouldn’t read this far. Something incredible happened, rarely seen here in Arizona. Our slightly supercooled clouds, with top temperatures between -5 and -10 C, formed ice. When I first saw the indication of something falling out of those shallow clouds on the Catalinas, I was beside myself. Here’s what I saw, not taken while driving1:
I thought it was some kind of fluke since it was indicated just yesterday from this keyboard, based on prior experience in Arizona, that ice rarely forms in our clouds at temperatures above -10 C (14 F). Maybe someone was nefariously cloud seeding I wondered…. Or had flown an ice-producing aircraft through these clouds upwind somewhere. (Its about what cloud seeding would do in marginally supercooled clouds like these, too, not much but something.)
Ice appearance in clouds with tops warmer than -10 C is common in “clean” environments like over the oceans (see the works of Mossop in the Australian Pacific, Borovikov et al in the Atlantic, Hobbs and Rangno in the Washington State coastal waters and the Chukchi Sea offn Barrow, AK, or Rangno and Hobbs in the Marshall Islands) in clouds with warm bases (ones substantially above freezing for the most part) that can be anywhere even in “continental” environments far inland where cloud droplet concentrations are high due to natural and man-produced aerosols (see Koenig in Missouri, Hallett et al in Florida, Rangno in Israel) among many others). We sometimes have those warm-based clouds here in the summer, too.
——-end of academic interlude——–but not really——
These fuzzy very light snowshowers soon ended and the day went on as foretold, no ice in the clouds.While out on Old Jake, shown above, I was taking photos of particularly dark based clouds and was going to tell the story about why they looked so black, and yet did not precip–to warm and cloud top, and drop sizes near the top, too small for ice initiation. Just about every case in which aircraft measurements have been made in such clouds that form ice at top temperatures above -10 C (14 F), inside them are cloud droplets larger than 30 microns AND a few drizzle drops (liquid drops between 100 and 500 microns in diameter, or rain drops. Droplets larger than 30 microns and substantial concentrations lead to collisions where the drops that collide can coalesce into a single drop. Let us not forget Hocking or, later, Jonas and Hocking and the 38-40 micron drop size limits they found for this to happen from lab experiments. Below that 30-40 micron diameter size, the little cloud droplets act like marbles; too much surface tension.
OK, there’s that little discussion preparing you for what comes next. Continuing with the story…was there one? Well, anyway, Mr. Cloud Maven person, riding on his own forecast made that early morning for no ice in the clouds (meaning no rain), decides to also ride on his old horse, Jake, who needs some more of that exercise.
Confidently, though dark Cumulus clouds underlying a broken to overcast deck of Stratocumulus, looked even exceptionally dark in places, Mr. Cloud Maven person smiled at this darkness of the cloud bottoms, knowing that the darkness in the bases of shallow Cumulus only spoke to how high (and small) the cloud droplets were in those clouds; they had to be highly “continentalized”clouds, ones with tremendous droplet concentrations in them and because of that, all of the droplets in them have to be tiny, being so great in number. And, in being a Cumulus cloud with an appreciable updraft, even more droplets are activated in “continental” air than are at the bottom of a layer cloud like Altocumulus.
When the drops are tiny, more sunlight is reflected off the top of the cloud and the darker they get on the bottom, and the more removed they are from producing a drizzle drop, or are in having the precursor droplets to drizzle drop formation, cloud drops larger than 30 microns.
This is what a Cloud Maven person thinks before he gets on a horse….
So, as I am riding along near the Sutherland Wash, these patches of dark bases form nearly upwind…. I watch them for awhile, quite unconcerned, and smiled again, thinking about the other horseback riders, people on bikes out there that likely turned back in fear of a terrific downpour, not really having the knowledge they need about clouds.
Then suddenly I noticed ice streamers coming down NW of Catalina only a couple of miles away! It was falling from the downwind part of these darker clouds, where after a period of time, ice, if it was going to form would be. But, how could this happen?!!!! Before long, the thicker regions of the cloud began to emit stranded precip, a sure sign of graupel up top in the cloud. Graupel in clouds with supercooled droplets only 23-25 microns in size, much smaller than those required for coalescence, and the present of those droplets leads to ice splinters when they are banged by a graupel particle. A coupla graupel (soft hail) and after awhile, (10-30 minutes) a cloud can have a lot of ice, 10 per liter or more in concentration, plenty enough for precip beside the graupel-melting to rain stranded part. Here is a shot of the further, SHOCKING development:
I had to laugh at myself on the way back, the rain drops wetting us down, when I thought about being quite confident yesterday morning about no ice would form in our clouds. When you have an occupation that tends toward error, its good to have a sense of humor. There’s nothing worse than a humorless meteorologist at a party, one whose likely obsessing over his error-filled life.
So, why ice? The TUS sounding at 5 PM AST did not suggest tops colder than -10 C Z(moisture top was about -5 C is all), but where the moisture ended, the air was incredibly dry, reported as “1 percent” relative humidity. Here is that 5 PM TUS sounding:
So, an overshooting top COULD have gotten to -10 C, and certainly, with that incredibly dry air just topside, those drops in those evaporating turrets would have chilled a couple of more degrees C. So, maybe that’s it, in fact, the overshooting moderate Cumulus tops DID reach to, or below, the -10 C normal ice-forming temperature here.
However, the concentrations that developed in these clouds HAD to be due to other processes beyond just the run of the mill ice nuclei since there are so few of them at -10 C, and that where drops larger than 23 microns come into play. Without those, there would never have been showers yesterday, only a very isolated drop or two. Those larger than 23 micron size drops lead to “ice multiplication” where just a couple of initial ice particles can “multiply” like rabbits in clouds because of ice splinters shed when hit by graupel. However, as we speak, the full understanding of how ice forms in clouds with these “high” temperatures has not been pinned down. Some researchers, the present one included, believe that ice splintering alone is not sufficient to explain the rapidity in the appearance the high concentrations (10s to 100s per liter) that develop in clouds like we had yesterday. You probably don’t care about what I think, but rather go with the majority opinion… Oh, well, it always safer that way.
As a test of even deeper knowledge that an aspiring cloud maven junior might have, this question:
What kind of ice crystals and other frozen particles would have been in those clouds yesterday?
The U of AZ models got pretty excited about yesterday’s rain potential, even the WRF-GFS run AFTER the one I looked at and got me excited about yesterday’s rain potential. The model one that followed the one I saw when posting yesterday’s blog, one that comes out around mid-morning based on 5 AM data, also had a big rain day in these parts. (Sometimes the two runs don’t agree so well, so when they did, it seemed like a “done deal.”) Take a look, for example, at the total rain predicted in that later model run that came out yesterday morning, and take a look at what it thought Mt. Lemmon, would receive in the 24 h ending at midnight last night in this pdf:
Yep, 3-4 inches (!) was to have fallen from the skies on Ms. Lemmon in the 24 h ending at midnight last night. You can also see that we here in Catalina were supposed to see at least half an inch (that greenish area to the west of the orangy area). We got 0.14 inches. Better than zero, though.
Catalina mountains max: 0.55 inches, at White Tail, near Palisades Ranger Station (on the highway to Mt. Lemmon).
Probably as much as half an inch fell “over there” under this sudden late afternoon thunderstorm by Samaniego Ridge shown in the photos below.
Two places, though, one in the Rincons, and once again over in Avra Valley, did get drenched with more than 2 inches yesterday, so large amounts did fall in some areas. Very appropriate for the really warm cloud bases and humidity we have these days.
That late night model run (based on 11 PM data) has another active day today, though not as active as yesterday. The model thinks showers will roll off the Cat Mountains this morning. Not so sure about that, but surely, there will be some giant clouds around and some tremendous falls of rain here and there with the humidity we have. 69 F dewpoint here now (5 AM) in Catalina. Enjoy, as we know these spectacular rain days are numbered, and sooner or later, the westerlies will creep down here and wash all this humidity away with dry Pacific air, and we’ll start to feel those cooler mornings associated with drier air overhead, that dry air that lets all that night warmth escape into space.
GW moisture factoid
One possible cause about why global warming has pretty much halted over the past 10-15 years (well, up to 2010, anyway, when this paper I am going to mention was published), was that the moisture in the stratosphere (the layer above where clouds and precip form) had declined over the period when the temperature stopped rising. With less moisture up in the stratosphere, more heat was escaping into space from the earth since water vapor is the biggest greenhouse gas of all, and when it changes a little, a lot happens to the radiation characteristics of the earth. This decrease in water vapor “topside” since the late 1990s was enough, it was calculated, to offset the effects of increasing anthropogenic greenhouse gases since then. Whether such a drying will continue, or why it happened, is not known.
This finding was from Susan Solomon’s group, work that appeared in the illustrious journal, Science. Solomon is the scientist that did so much work on explaining the ozone hole in the 1980s.
While we here in Catalinaland only received a “trace” of rain again from a thunderstorm that sudddenly formed just before 3 PM to our SE-S, there were some tremendous rains in the area yesterday afternoon and evening. Some examples:
Pima County ALERT precip, max observation: 2.09 inches, Brawley Wash at Highway 86
U of AZ rain map, maximum, as of 7 AM (more reports will filter in during the day): 0.90 inches, N Tucson, see this dump in the movies.
Cocorahs, Pima County max, as of 7 AM (more reports will filter in during the day): 0.64 inches, 2.5 WNW Tucson
USGS, Statewide max 1.2 inches, JD Cabin near Williams.
In the meantime, here’s a nice map of radar-derived rainfall, ending at 5 AM today, from the folks at WSI Intellicast:
The most exciting, predictive aspect of the day, that is, how unstable the air over us was, how ready the atmosphere was to allow plumes of cloudy air to shoot upward, is shown in this U of AZ Weather Department action-packed movie which I shall name; “Dancing Rainshafts”, because they do kind of twist around each other in this movie in the late afternoon. One of those is responsible for that 0.90 inches rain in north Tucson around Sky Line Ave. This is one of the most interesting videos I’ve seen. Nothing much happens until late morning, and then, “Pow!”
If you noticed at the beginning of the day, when Cumulus started to form on the Catalinas, you saw these incredible, tall, thin clouds, something akin to smoke stacks, plumes from geyers, rising off them. It was a sure sign the atmosphere would do something special yesterday. You’ll have to see those tall thin clouds in the U of AZ movie; while I did “document” them in a sense, there was no memory flash card in the camera again, the tiny font alerting me to this fact too small for normal vision.
Still, thanks to the U of AZ Cats, who won their football game on Saturday, you can see it here, to repeat.
OK. now on to the local cloudscape yesterday….
Here’s what I thought was a surprise, this sequence where a modest cloud glaciated. Suddenly, after a period of remission in Cumulus activity, this moderately large cloud welled up SE of the house (first photo).
The weather ahead….
More of the same every day for the foreseeable future, which is about a week now. Check here. They have a lightning icon in every 12 h period! Fantastic!
But, with all those percentage chances of rain over that whole given in 12 h increments, what IS the chance of measurable rain here in Catalina at some time during that FIVE days? IF I have calculated it correctly from an example given to me by Mark Albright, Research Meteorologist at the U of WA, it is…drum roll… 96%!
Pattern clouds: Cirrocumulus undulatus in odd, parallel lines. I had not seen parallel lines like this before. Fragments of Altocumulus are also present.
Though only a few drops hit the ground here in Catalina, the day ended with a pretty sunset. This marked the third day in a row where large Cumuluonimbus clouds cells at least an inch of rain in southern Arizona, but we got missed, something that also happened several times in early August.
Some of the moisture doing this is from old, former tropical storm, Elena, particularly the moist plume that resulted in yesterday’s pretty pattern clouds shown in the first photo. Check the moist plume (whitish stream) from her here.
While Elena was a bit of a disappointment as far as producing rain here in Catalina, her lower level moist plume too far to the west, a sibling storm is arising off Mexico, one that the models (hah!) as they did before, have calculated will cause a renewal of our summer rain season; showers are foretold for several days beginning around the 3rd as that storm trudges up the west coast of Mexico toward Baja. You can see the storm and the showers here in this rendering of the WRF-GFS model by IPS MeteoStar. Remember those green areas on these maps are those in which rain is foretold to have fallen in the previous 6 h (later in the run, in the prior 12 h). There is a LOT of green over SE Arizona after the showers begin to occur by the afternoon of the 3rd.
As is commonly heard these days from people concerned about drought, “think green”!
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.
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.
For a great movie of yesterday’s clouds from the U of AZ, go here.
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.
Still humid, still unstable aloft. Mods say another active day, so watch it (not teevee)!
Another day with hours of thunder, but with those high and cold cloud bases, not much rain reached the ground. Also hurting the rain situation, too much ice. An afternoon sprinkle, a very close, rogue lightning strike, followed by an early nighttime “chaser” storm that, with all of its bluster, wind and vivid lightning, produced only 0.02 inches here, but a lot more at Sutherland Heights, a robust 0.39 inches (new knowledge, gained after dip sticking gage up there at around 7:30 AM) To see how remarkable that Sutherland Heights rain amount is, go here to the U of AZ rainlog network.
Here’s a smaller, but typical example of yesterday’s generally “low output” Cumulonimbus clouds:
Here’s another quite bad cloud (shown below), though it was good one one hand, because it was an early afternoon, frequently thundering cloud which gave promise of rain later in the day. But that rainshaft? Pitiful.
It was also a forerunner of the kinds of storms we would have. Again, with high and cold bases (and oddly to me), there seemed to be an awful lot of lightning for the size of the Cumulonimbus cloud at 1:55 PM, much of it in vivid cloud to ground strokes. You may have seen a another example of that last evening around 9 PM on the Catalinas when there were a series of frequent and spectacular cloud-to- ground strokes, but little rain. The most that fell up there was 0.28 inches at Oracle Ridge. Map here. BTW, you can see the “1:55 PM”
Cb in the U of AZ time lapse movie at the far left beginning around 1:40 PM.
Well, how high were cloud bases? Rendered by the Cowboys, this 5 PM sounding for Tucson:
Reading this sounding, it makes bases appear to be around 16,000 feet Above Sea Level (subtract our elevation for above ground level) and a few degrees C below freezing. With bases that high and cold, the amount of water condensing at the bottom of the cloud is less than on days with bases, say, at 5 C and at 10,000 feet ASL.
So, less condensed water input means less rain coming out the bottom later.
If there is “too much ice” for the amount of water coming into the bottom of the cloud as we saw yesterday, its like a glass of water filled with ice cubes in which only a tablespoon of liquid water can be contained in it. The analogy is only somewhat representative since with “too many ice crystals” competing for the available water vapor, you end up with high concentrations of smaller crystals that hang in the sky rather than fall out.
So you get big anvils and debris clouds with little rain to the ground even in the peak stage of the storm.
Since the best rains in the shafts we see are due to melted graupel and hail, icy particles that generally start as an ice crystal at high elevations in the cloud, if there is little “supercooled” water there isn’t much graupel or hail, the type of precip that can make it to the ground from high bases (melting snowflakes wouldn’t from bases as high as we had yesterday because they’re essentially like Rice Krispies, there’s not much mass in them).
Well, this is pretty boring, so will end here with a sunset photo from last evening:
The U of AZ WRF-GFS rendering of rain in the State of AZ sees early afternoon Cumulonimbus clouds breaking out over the Cat Mountains today.
Starting out with pretty similar sounding this morning, but a bit more moist than last evenings above 600 millibars (about 14,000 feet ASL).
Hector marches slowly toward the Southwest (Canadian model outputs), promising an enhancement of August’s meager rains so far in southern AZ.
1Reminded one of summers in Durango, Colorado, where high, cold cloud bases and “too much ice” is normal.
Trying to be excited for those around us who got all that rain yesterday while we received a paltry 0.18 inches here in the upper reaches of Catalina. Still it was another good little rain for our local desert.
The 24 h rolling archive from Pima County rainfall gages is here. Most seen here? 2.01 inches at Finger Rock and Skyline, Tucson. You’ll see that storm in the movies.
Also, check the more comprehensive U of AZ rainfall network here. In fact, you might as well join up, too. It would get you out of your rut. Think how exciting it would be to go out in the morning and see how much rain fell in your gage in the previous 24 hours! Maybe someday you might win the “rain lottery” and have the biggest amount anywhere in the State! The most reported so far this morning is a deluge of 3.17 inches over by Picture Rocks again. Good grief, have they been getting hammered.
What a July this is turning out to be!
Here we are in Catalina, its late afternoon, it has just rained again, the temperature is a chilly 70 F, dewpoint 68 F (almost saturated), with Stratus fractus just above eyeball level lining the hillsides! Its an amazing scene for an afternoon in Catalina and vicinity in July. And so DARK! Here is that odd scene from yesterday afternoon:
Relive yesterday, as though you were in the city of Tucson shopping possibly, here in this movie, courtesy of the U of AZ Weather Department. The movie is rated “R”, for violence since the sky goes WILD in the afternoon, winds going every which way.
Also, in this time lapse you will get a sense of how rapidly moist air is flowing across us from the east to east-southeast. This movie, comprised of still shots taken every 10 s shows movement, like the day before, that is phenomenal for summer, more like a winter scene when winds are normally strong. There are even Altocumulus lenticular clouds (almond shaped ones) hovering over and just downwind of the Cat Mountains! Amazing.
But check the CHAOS in the mid and later afternoon. Unbelievable. Areas toward the Catalina foothills, during this chaos, got another 1-2 inches again yesterday.
In contrast, let us now look at the very same day in a time lapse film in Seattle, Washington, where Mr. Cloud-Maven person spent 32 years, most with the U of Washington Huskies Weather Department. Here it is. I sum up the totality of that movie for July 29th below:
Those Seattle skies, for the most part, were like eating plain, cooked oatmeal everyday, all day.
Below, the start of our exciting day, the middle, and the end has already been shown above. Lots of nice rain shafts SUDDENLY collapsing down out of clouds. A sequence of the big northwest Tucson storm early in the afternoon that moved off toward Marana is included as part of the middle. That shaft really fell out fast, and how you could detect the icey tops BEFORE the shaft appeared. I try to point out how you might have been able to do that in this sequence, and thus, and quite importantly, impress your friends and gain status and some kind of weather sage.
Just looked at the latest AZ mod output, as you can here (forgot to past link until now, 8:08 AM). Colored splotches are where it is supposed to have rained that HOUR. That model has a much less active day today, but much more active tomorrow. Cumulonimbus clouds in sight today? Oh, yeah! But, none are SUPPOSED to get us today. But these mods are always slightly inaccurate, so keep watching this afternoon. Should be another photogenic day, if nothing else.