With continuous thunder and threatening skies for Catalina, the mammoth Tucson storm that dropped a record 2.83 inches for the wettest day ever in September at the International Airport passed by Catalina early yesterday afternoon. Here’s what a fraction of it looked like (using a bad ISO setting, darn it). Also at the TUS AP it has become the wettest September of record halfway through the month with over FIVE and a half inches!
Of course, we here in Catalina land have been missed by most of those heavy September rains and have had only a crummy 1.17 inches. Still, better than nothin’. And there have been some fabulous sights during these past days. Below are a couple of shots from yesterday. That easily visible roiling motion in that last shot, if you saw that Cumulus congestus-going-to-Cumulonimbus, was a real indicator of how unstable the air was, that is, how easily it could go upward yesterday. This situation us due to the cooler air aloft we have right now, along with mid-80 temperatures at the ground. This is the kind of roiling, churning action you see in those big boys in the Plains States, East, and South when severe weather lurks.
Mods think we have a chance for rain today, too. Maybe it will be our time, we will win the rain lottery today.
Below, thanks to the U of AZ, we have a time lapse movie of part of the storm, anyway, to the right side of the image.
Dreamy weather ahead:
Of particular excitement in the longer range NCEP (“government”) models, although almost certainly wrong as they usually are that far in advance, is that a tropical storm advances toward Arizony in early October. Mark your calendars. Might as well.
It’s great when things are as they are supposed to be. Below, “the usual” kinds of scenes in July in southeast AZ from yesterday, such as Cumulus boiling off Mt Lemmon in the late morning, followed by dense rainshafts in almost every direction in the later afternoon. I love these scenes!
Well, “usual” for SE AZ, except that high reaches of the Canyon del Oro wash watershed were deluged by 2-3 inches of rain (see two of those dumps in progress in the second and third photos below). And Mt. Sara Lemmon had over 2 inches! (Must check washes out this morning to see if any are running around Catalina and environs, and how green it is already starting to get.
Here in Catalina land, after another 0.27 inches yesterday and overnight, we now have had 2.37 inches since the beginning of July!
The very pleasant news ahead is that the numerical forecast model by our friends in Canada, that can be seen here, is now suggesting, based on last evening’s data, that a series of itty bitty disturbances1 in the upper air are going to affect our region from now through July 13th. These little lows/troughs arise from the tropics and their role is to take the underlying humid air and organize it into larger clusters of thunderheads (aka, “Cumulonimbus capillatus incus” clouds; use this name if you want to impress your friends) so that the rains last longer, and might be heavier than on days with no disturbances aloft. How cool is this forecast except for those times when the roads are impassable?
I have not yet checked other model outputs, ones that might be different, because I like this Canadian one the best already and don’t want to know other things that might ruin my current very good mood. Ignorance truly IS bliss! However, I do feel that the “pendulum” has swung back to the wet side here, as it always eventually does in climate, and so there is that pinch of intuition thrown in that wet forecasts are more likely to be correct. Lets hope so.
Finally, even ordinary gray skies are pretty, even dramatic and interesting in weather like this. Check out the last photo, taken in the evening after the first rains in Catalina.
The End.
1 In the perhaps unneeded technical jargon of atmospheric sciences, they might be described as “mesoscale”–namely, ones much smaller than the gigantic highs and lows we see on the usual weather maps for the whole US
Check this out for yesterday at 6:05 and 6:15 PM. First, part of the precursor FULL rainbow to the east of Catalina. (In most locales a rainbow to the east would mean the storm has passed.) The second shot was taken at the height of this magnificent storm. I thought I had seen it rain as hard as it could here, and with as low a visibility as possible last summer. But, no. This topped them all! Golder Ranch Road, only a few hundred yards north is gone, and I could hardly make out our horse, Jake, in his corral, only 50 yards or so away! At this moment, too, the wind raged. Everything was moving violently amid the occasional lightning strike. The wind probably reached 50 kts (60 mph) during one of two of the violent puffs that came through at that time. It was just incredible; unforgettable.
The rain? 1.01 inches of which most (about 0.9 inches) fell in the first 20 minutes! Lots of erosion apparent today in our modest gravel roads. We’ve now had more that 2 inches of rain in only the first five days since the summer rains started. Fantastic. Even today, after only a few days with rain, there were traces of green at the bottom of otherwise dead looking grasses. And, now some of the washes will start to run for awhile, too.
And, more days with strong storms here and there are ahead. How great is this after our crummy winter?
There may have been some sharp eyed folks that saw a great looking Cumulus congestus in the distance off to the NNE of Catalina yesterday. The shots below were just before 7 PM LST. Perhaps there was a shower or thunderstorm on the Mogollon Rim.
Sadly, even I was fooled for a few microseconds until you notice that there is NOTHING even slightly resembling the size of that cloud anywhere in the sky. Then, it dawns on you that it must be a “pyrocumulus”, the kinds of artificial Cumulus clouds that form atop the highest, and hottest portions of fires when there is a bit of humidity in the air. Once the fire dies down some, then all you see is smoke, the last evidence of the trees and the plant life consumed below. Likely was a new fire, too, dammitall. It was probably 50-75 miles away; also just visible in the satellite imagery. The second shot is an attempt at a close up, marred a bit by some kind of large insect that happened to fly by as I was shooting. Just above the horizon of that second photo, you can JUST make out the telltale smoke below the bottom of the pyrocu. The last photo, from Hornepayne, Ontario, Canada, is an example of a pyrocu up close, just as it was forming. This was due to a prescribed burn by the Canadian government. The cloud droplets are white while the smoke is black. The cloud droplets are about 100 to 1000 times larger than the smoke particles, and reflect (have a higher albedo) more of the sun’s light than do the smoke particles.
Rain update: Still looks like a great onset of the rainy season after a little “hip fake” today and tomorrow, that is, a slight insertion of tropical air ahead of an unusually strong, winter-like storm in northern California. That weak insertion of tropical air should lead to a few weak, high-based showers and thunderstorms on the high terrain. And with high bases, there will be the chance of exceptional winds near showers due to the virga and rain falling into otherwise pretty dry air. After this little episode, the normal summertime anticyclone aloft rears up from the Tropics and after a couple of dry days and plants itself to the north of us. This allows more humid tropical air to arrive pretty much on time, around the 3rd and 4th of July. So, get ready! It will be so great to see all the dust washed off the cacti, the stupendous sunsets, the lightning, the rainshafts, the whole works. I’ve waited a year for this season to roll around again! There won’t be a living thing that is not “happy” by the middle of July I would think, unless there has been too much flooding, always a possibility here.
Seattle’s Curt Cobain might have said something like this if he had lived in the desert. Alluding, of course, here to the SEATTLE teen angst band, Nirvana, and their big hit, “Smells Like Teen Spirit”. BTW, a song covered later by Bill Nye the Science Guy in an educational ditty, “Smells Like Air Pressure”. But why do this, have a title like this? Contrived, ludicrous “cleverness.” The world needs more honesty.
Began as a good rain at 2:40 AM, and by 4:20 AM, was changing to snow, for those detailed oriented folk. Measured 2 inches on two locations here at 3200 feet, top of the car outside and on the “barbie” cover just as the snow was letting up around 6:30 AM. Two minutes later, it would not have been as deep since all of the surfaces are above freezing in temperature and the snow depth lessens by the minute. This was the third or fourth snowfall here in Catalina since we moved here in mid-2008, and was just that bit more than the “record” deepest of 1.5 inches in December 2008.
Here’s the SHARP FROPA, passage of the dramatic cold front “plus”) this morning at 3 AM as seen in the temperature and pressure records (software is a bit immature and won’t allow printing of two parameters on the same chart). Note sharp rise in pressure at “FROPA”, the classic sign of a cold front’s passage.
La Nina-like conditions seem to return over the next couple of weeks, so lay back and enjoy the soil moisture while you can! Some photos, the first something we Arizonans (of late) called an “Arizona Christmas tree”, a snow covered cholla cactus.
Too bad Steven Sondheim wasn’t a meteorologist. He might have written some great weather songs. Instead, he chose to write about “clowns.”
Hmmmm. Perhaps he WAS thinking about some weatherman in those days when he used the word “clowns.” Who can forget that the LA Times headline about weather forecasting in 1981; the headline that declared that weather forecasting in the media consisted of, “Clowns and Computers.” Personally, I think humor has no role whatsoever when talking about weather…. Oh, well, I digress.
Today will be really exciting for us weather buffs (buffoons?) We WILL be excited as mom Nature gives us a reprieve from the steady diet of glorious days, sunrises, and sunsets (this morning’s at left), paradise really, with a blast of wind and then cold, likely to inflect more damage on our probably dead palms here in Tucson-Catalina-Saddlebroke. Also this will be punctuated by a really exciting cold front passage, one where the temperature is likely to drop at least 10 degrees Fahrenheit within minutes as the wind shifts to the W then NW after those bruising S-SW winds. Probably here on the knob, we’ll see 40 mph or more in momentary gusts. Good-bye dead palm fronds.
When will the rain/front hit?
Well, lets say you don’t have a supercomptuer, a Cray, a Fujitsu, or access to thousands of PCs for parallel computing purposes to solve all the euqations in your 57-layer nested grid model using GFS-WRF outer boundary conditions, etc., for your subdomain. What the HECK would you do, besides peruse the internet for answers, which can take a LOT of time? Besides, we know that the internet is loaded with bad information…
Here’s what I do in this “bind.” You get out a little piece of paper or Hollerith card (2nd photo), and you use the technique of “extrapolation.” You got to the internet and check out the recent movement of the cloud band feature upwind of you by marking where the leading edge was, say, 4-6 hrs ago, then where it is currently, and move the two marks forward so that the back one (the old edge) is at the front of the feature and look at where that 4-6 hrs of past movement puts it 4-6 hrs from its present position. Presently, the middle of this mass of Altostratus clouds (last photo) we have over us, will be around Noon to 1 PM using that technique. However, there is no precip in that fat band of clouds, though one would think they would be thickening up as they approach us due to the Cat Mountains and overall effect of the Mogollon Rim. So, maybe there will be some sprinkles around. Our best models suggest the main rain band and front will not arrive until well after dark., and “extrapolating”, using the past 13 h, suggests the front won’t hit until dawn tomorrow! So, it”ll be a long time comin’, but “a change gonna come, yes it is.”
In the meantime, the biggest conundrum in today’s forecast is is what are these Altostratus layer clouds going to do (last photo), the ones at presently zooming above us in winds of nearly 100 mph, bases at 20-22, 000 feet? There are no radar echoes in Arizona to the west of us here in Catalina, yet as you can see they are drooping precipitation down at us in the form of virga. As the air moistens below these clouds, as it should given the approaching system, that virga will tend to hang down lower and lower. I would guess with this scenario that some very light rain or sprinkles will start reaching the ground this afternoon into this evening in Catalina ahead of the main rain area, the one due in well after dark. Our best model for this area is, of course, at the U of A, right here, and you can see the precip creep in then. I think I would use them (U of A and NWS since the last time I used the “extrapolation” technique described above was in 1989 I think. However, you’d be surprised, when timing fronts coming in off the Pacific (where I was forecasting then), how well this simple, simple technique worked.)
Don’t be surprised if a bit of a clearing comes up toward later this afternoon to sunset. Its not unusual to have a vast amount of quasi-threatenbing cloud go overhead all day, maybe with a few sprinkles, and then have a thin slot or brief clearing before the heavy clouds and rain move in later in the evening. That appears to be suggested in the satellite imagery today. We shall see! What an interesting two days ahead!
Still looks like a little snow in Catalina Sunday morning. U of A mod indicates that the total amount of precip will be around half an inch.
BTW, while you’re digesting all of the above, here is where the weather records that were set for yesterday are. You can see that a LOT of records were set yesterday! Generally low temperatures and record snowfalls for the day in the northern half of the US beginning in the Mid-West and “thence” westward to the Pacific Coast.
But first, “storm” 3 of six as foretold many days ago by our wonderful numerical models having “billions and billions and billions” of calculations (to use a numeric phrase made popular by the late Carl Sagan) is going to pass over today. Hoping for a sprinkle late in the day, but virga seems likely in the Altocumulus clouds that will develop/move in today.
The jet stream is powerful over us from the southwest, and when you have these weaker disturbances with marginal moisture, you can get some glorious, fine granulations in the clouds (Cirrocumulus to be exact) as we saw two days ago. See photo below. So, I am expecting to see the following types of clouds today: Altocumulus with virga, some clusters large enough to produce a sprinkle even at the ground (see second photo from two days ago with “mammatus”-see footnote below and virga), Cirrocumulus, and some cirrus. Could be a fabulous sunset with these kinds of clouds around.
OK, so “storm” 3 today may be just a few clouds without any precip. Oh, well.
Cold and unusual snow occurrences ahead for the West and for Cat Land, too
The low pressure center and accompanying Arctic blast now developing in the Pacific Northwest will be historic. What I mean is the that climate record books will be altered for things like late snow occurrences, one of the lastest snow occurrences (as in Seattle), latest lowest temperatures, all time February low temperatures, and unusual flurries and brief snow accumulations at anytime in places in California. This is a whopper of an atmospheric ice berg from the ground all the way up through the troposphere in the West as it progresses down the West Coast. Snowfall at SEA LEVEL is likely all the way down to….Los Angeles suburbs.
Then after shuttling down the coast, this “ice berg” takes a sharp right turn (as seen from the weather maps), that is, toward the east and to Arizona! Egad. Not only will it be unusually cold again, though nowwhere near the “historic” cold wave early this February when all kinds of low temperature records and pipes were busted, though another hard freeze does seem in the cards after the rain/snow/wind pass by. Monday and Tuesday mornings look awful darn cold right now.
Did I mention wind? Along with this situation will be an unusually strong low pressure center that will give us the kind of blustery day this Saturday as we had last Saturday with gust to 50 mph here on the Catalina Rise just west of the Cat Mountains. So, if you’ve got dried out, stiff palm fronds you’ll probably lose a few more in this one.
Did I mention snow? Its now looking like a greater chance for a small accumulation of snow as low as 3,000 feet here on the west side of the Catalinas on Sunday morning. I’m not buying skis just yet, but this is a real interesting situation.
And, finally, it looks like an appreciable rain, too, with this, maybe more than half an inch between later Saturday and Sunday night. Man, will this be welcomed around here!
Since I am overly excited about this interesting weather pattern that is on our doorstep, it should be noted that objectivity is in decline… At the Unviersity of Washington we had a forecaster who loved snowstorms. And so, when he saw a snowstorm coming and forecast an amount, say 10 inches, you had to divide that forecast by 100 to get the most snow that could possibly fall from that storm.
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Footnote: On the fifth floor of the Atmospherics Science Building at the University of Washington, there was a line of large cloud photos on the wall, one of which was a “Cumulonimbus mammatus” that strongly resembled the “mammatus” in the second photo below. The photo caption to that effect was vandalized, and we suspect by a female meteorologist/grad student who might have taken exception to this traditional, formal descriptor established decades ago. The word “mammatus” was crossed out and replaced by “testicularis.” It was horrible thing to see.
You’re probably smiling now remember singing this little ditty as a kid, maybe singing it with your friends on the bus, whenever you saw “Altocumulus floccus virgae” clouds such as are pictured in the first photo. Wasn’t it great when you saw these kinds of clouds while on a vacation trip and mom and dad had to stop somewhere to get you some pie after you sang that song? Well, I nostalgiate here.
To the right of the dead yucca stalk, Altocumulus tufts are shedding snow. The opacity of the virga is a give away that its snow, and not rain. In some of these little tufts, the water droplet cloud that preceeded the formation of ice has disappeared, and all that is left is falling snow. How much snow is it? Just a flurry, if you were up there, even though it looks pretty thick. Once in awhile in our research on ice in clouds at the University of Washington, we got to sample these from top to bottom. Because the ice crystal concentrations are usually pretty low in clouds like the ones shown, a few per liter and often less than 1 per liter, those delicate ice crystals don’t bump into each other much and break up, and you find gorgeous images of star-like crystals in these fall out streaks, the kind you see on Christmas cards (examples here). How do I know what from ten miles away and 16,000 feet or so below them. Its a funny thing, but ice crystals are differently shaped depending mostly on temperature. To get the temperature of these clouds you can get a pilot report (unlikely) or examine the humidity profile of the Tucson sounding for “00 Z” (5 PM LST yesterday afternoon and make an educated guess. The highest relative humidity on that sounding was at 525 mb ) about 15-16, 000 feet above the ground) with a temperature of -16 C (about 3 F), namely, darn cold. Continuing, we in this field have a well known chart by Magono and Lee (1966) that shows the temperature at which certain forms of crystals grow. At the temperature I am guessing those clouds were at, those crystals would have grown as stellars and dendrites, which grow between about -12 C and -18 C. Sometime I will show you some of these crystals, but for brevity will quit here on this topic.
The second and third photos show what one of these tufts looks like before the crystals have grown and fallen out. Top center, the largest raggedy tuft (Altocumulus floccus) show no fallout of ice. In the last photo, twenty-nine minutes later, there is a fine veil of ice crystals below it (upper right hand corner). Only now, with virga, are they “Altocumulus floccus virgae”! I’m singing right now! And, if you look really carefully you’ll see that most of those little guys have a little ice fall underneath them. Certainly, in those clouds you would find PERFECT crystal specimens!
I’ll end here on an exciting note. The Enviro Can model CONTINUES to show a very strong system moving into our area on Saturday afternoon, likely accompanied by winds as strong or stronger than we saw last Saturday, before the rain and cold air hits on Sunday. Snow levels are going to be really low and we might see some ice in the rain on Sunday here in Cat (alina) Land. Amounts are looking substantial at this point. Man, do we need it!
In the meantime, an upper trough off Baja passes over tomorrow. It has enough moisture with it to provide more “clouds for pies” (Altocumulus floccus virga, and, of course, Altocumulus castellanus virgae, which also qualifies as well for a pie). And, some cirrus will be around, too. However, I am going to stick my neck out and say there will be sprinkles tomorrow. Mods really don’t have a thing, so you’ll have to keep that in mind.
Be sure to keep you’re camera ready for sunsets like last night (see below)!
This is one of the best days in my life! The NOAA NCEP computer model has looked at the new data that came in overnight from around the world and now, in calculating the new maps from that data, it thinks we are going to have quite the series of storms here in SE AZ! Our spring grasses and wildflowers might yet get help in time to save the blooms!
Take a look at these images from last night’s NCEP model run reproduced by IPS Meteostar here (0ne of the best weather providers on the web in my opinion). Below are highlights from IPS Meteostar model reproductions, namely those half dozen “future maps” having rain in them for around here. BTW, a weather convention is that precip is colored green.
There are no less than six storms predicted to occur over the next two weeks! It doesn’t get any better than this in you live in a desert!
Of course, if you’re a real weather forecaster, you know that it is likely that none of the below will be accurate. But the excitement is in that it MIGHT happen just as the computers are predicting. It’s something like a Fantasy Baseball team you have assembled prior to the season and in your players you see all their potential maximized. In essence, it is just like this with last night’s model run, every rainstorm you see here, together as a unit of six, is like a fantasy team combining to win the pennant. It probably won’t happen quite. But, the excitement is in the air, until those models break your heart by taking all the rain away in the next few runs, as they sometimes do.
Here are some maps from last night’s wonderful run with brief notes:
1) Valid this Thursday, most likely just a close call. Note tiny green area just north of Tucson.
2) Below, valid Saturday, the 19th. Rain moves up northward from a band in northern Mexico and on this map, has already passed over Tucson.
3) Below, valid Sunday the 20th. Major southern California storm eases into southern Arizona!
4) Below, valid Wednesday the 23rd, another rain!
5) Below, valid Friday, the 25th of Feb, a real dump Mr. Model thinks.
6) Finally, valid on February 28th, still more! And man do we need it!
There have been a coupla comments on that aircraft effect in clouds blog of a coupla weeks ago and so I thought I would follow up with this sequence from the Atmos Sci Building rooftop at the University of Washington where I spent most of my time instead of at my desk.1
Here is a rarely photographed sequence of the effect of an aircraft on a supercooled cloud. The first photo, right after a contrail-like feature was seen in these Altocumulus clouds.
Look at what seems to be a dark contrail-like line in the middel of the photo. The Altocumulus (perlucidus) cloud layer, mostly comprised of supercooled liquid drops, is probably around -20 C, though I did not get a PIREP on this day for some reason.
In the minutes after this first photo, the aircraft trail seems to disappear as it widens and the shadow lessens. This stage is not shown because I didn’t realize what was going to happen until minutes later. This second stage is almost impossible to pick up visually because there are no ice trails yet, nor is the cloud opening up at this time. This “invisible” stage might last 5 minutes before you see the hair-like signs of a fallout of ice crystals.
This second photo is about ten minutes after the line in the first photo. Now it is clear that ice has formed, the crystals are growing and falling out as "virga", and a clearing is starting to open up.
Ice grows rapidly in the presence of the supercooled drops. Ice represents something of a low pressure center in the middle of all those droplets and that attracts the vapor from them, causing them to evaporate. That vapor deposits as ice on the newly present ice “germs”/crystals created by the aircraft. Since the drops are disappearing, before long, you get a hole or ice canal in the cloud where the droplet cloud used to be.
In this third photo, there is no longer any doubt about what's is going on. The hole is there, and its only a question of how much larger it will get.
The ice crystals shown above are clearly falling out (ever-so gradually because they are so small still, perhaps a few hundred microns in width). Becasue they are so small, they usually evaporate well before any precip reaches the ground. However, recently it has been shown that in deeper clouds and more moist conditions, that an aircraft can actually produce a bit of rain/snow at the ground due to this effect.
Here is last photo I took that day.
The ice crystal induced hole in the Altocumulus layer has gotten closer to exiting the liquid cloud (has moved to the edge of it) as well as expanding some. This suggests that the ice cloud was moving faster than the droplet cloud, something that happens when waves in the atmosphere are producing the droplet cloud. It was also getting closer to the observer, however.
Sometimes, if the cloud layer is lifting enough, the original Altocumulus clouds will gradually fill back in because all of the ice has settled below the liquid cloud layer.
For history buffs, holes in clouds with ice in the center, or ice canals were seen in the 1930 and 1940s, but as you can see, unless the observer saw the original trail (which they usually didn’t) no one knew what caused them. Eventually an ice canal was was photographed in 1946 that was so convoluted it was realized that ONLY an aircraft could have done it.
Furthermore, that report in 1946 preceded the discovery of modern cloud seeding with dry ice by Vincent Schaefer in 1947 who performed his most convincing, and could be seen as ironic, demonstration of seeding with a similar convoluted ice canal as was seen in 1946 in a supercooled Altocumulus cloud layer Its interesting in retrospect, as so many things are, that Schaefer did not have to drop dry ice on his clouds that day in 1947 in which he made history, but rather only had to fly his prop aircraft through them and likely would have gotten the same effect!
BTW, there is a lot of new interest in this topic, a new article recently appearing in Science mag.
I mention this cloud seeding benchmark since these aircraft events represent inadvertent cloud seeding, and in a sense they demonstrate that you CAN get something in the way of precip to fall out of a previously non-precipitating or barely precipitating cloud by seeding. When clouds are already naturally precipitating, what happens when you do cloud seeding is subject to question; the science domain in this murky world is highly polarized.
The “Story of APIPs”–Aircraft-produced Ice Particles) is told (in the usual “style” you will often find here) in the gigantic powerpoint “show” on this website under Sci Talks toward the middle of the show, around slide #472 (hahaha).
This ppt “show”, BTW, is WAY overdone, but, what the HECK! Why tell only “the whole 9 yards” when you can tell 12 or 14?
1Hahaha, sort of. Sometimes, looking at those several thousand film shots from the rooftop of the Atmos Sci Building, I do wonder about that. But then again, since I used 1/100 of a second exposures with my film cameras, these photos would only PROVE that I had been on the roof, maybe 30 seconds in 30 years there at the UW.
