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.
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.
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.
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.
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.
What a nice day yesterday was, ending with this fabulous, but run-of-the mill sunsets we get to see here in the Catalina area on a regular basis. Yesterday was interesting because we had two graupel (soft hail) showers, the first about noon, and the second with a blast of thunder (1) at 1605 PM. If you weren’t lucky enough to get any, measure it and report it to the National Bureau of Standards, or the NWS, here’s what it looked like on our old chaise lounge a couple of minutes after it fell (see below). Some of it was “conical graupel”, pointed on one side, though that is not visible here. Graupel, soft hail form when there aren’t many ice crystals in the cloud and the cloud is chock full of droplets at below freezing temperatures. Those droplets freeze instantly onto the ice crystal as it makes it way down to the ground, eventually losing all of its identity as it become a little snowball. Usually, where this happens in the cloud is in a very limited region, and, it usually doesn’t last for a long time. So, consider yourself especially “lucky” to see graupel/soft hail, hail. I do. If you want to relive yesterday’s clouds, as seen from the U of A, go here. “Above Catalina” is at the left, beyond Pusch Ridge.
What’s exciting now is that something akin to an atmospheric iceberg is barreling down on us (SE AZ) from the north. This “cold low” center, representing a column of extraordinarily cold air in this case, goes from the ground all the way up through the “troposphere.” IN this case, the troposphere is squashed down to less than 20,000 feet over Wy0ming right now. The stratosphere is above that, and above “cold lows”, the stratosphere dips down over them. Usually its twice that height at our latitude.
Here’s what I am talking about, shown in this morning’s 500 millibar pressure map (about 18,000 feet above the ground) or usually half way up through the troposphere (map courtesy San Francisco State U.) The winds flow along the green lines, ones that bend gently toward the west over the Great Basin. That bend in the wind represents an area where a small low center amid this giant river of wind will form in the next 24 h and that little center of circulation should pass right over us!
Now, not a single model output that I saw from last night’s runs had enough moisture in this forming upper center to have snow even fall on Mt. Sara Lemmon (e.g., the U of AZ regional model from last night).
A few days ago, the Canadian model was suggesting a signficant storm here from this center. I really believe it. Well, that’s “bye-bye” since the center is not well to the west of us as that Enviro Can model indicated it would be, but rather will end up right over us (which means much drier). The U of WA model run from this morning’s data says that a little “L” will be right over my house on Thursday morning (see reddish map below) ! Man, it will be cold over me! Might lose some plants in this one before its over.
However, I am going to stick my neck out and expect (hope) there will be just enough moisture for flurries around here (Catalina area) anyway tomorrow into tomorrow evening.
BTW, the U of A has just issued a special weather discussion here. You’ll want to check this out!
The computer models are diverging significantly on the “tail of the scorpion” on this incoming front and the two troughs that pass over us in the next few days. First, a Pacific front blows through on Monday with its upper air accompaniment racing to the northeast. But then this monumentally strong wave disturbance barges in from Canada over the Rockies and actually deploys toward the SSW while intensifying and curling into an upper center, this center trailed by a gigantic mass of cold air that oozes over most of the US. High pressure levels in the cold air, 1060-1065 millibars initially, may set some records here and there in the northern Rockies.
The “best/worst” full display of this predicted sequence is here from our friends at Environment Canada, and the output from last night, of which one panel is shown below.
This panel at left, from that Canadian model run, is the most exciting panel of future weather I have seen this winter!
Now, if you’re a bit jingoistic about models and want to know about our US model results for this situation, I have to tell you, sadly, that they do not have this “good” a configuration over the SW as far as precip goes.
There is no upper vortex, Virginia, over western AZ in the US models, as in shown in the upper left panel here.
And that makes all the difference in whether AZ will get much precip out of this second of a two part event. In the US models, such an upper low does not form over AZ but rather just a bitterly cold slug of air, mainly dry, intrudes on us and that second strong upper trough just trucks on by.
So, its a dicey situation, but, because my dad was Canadian (from Winnipeg) and I really want to see some precipitation here after a rainless January, I am going to say that this Canadian model is the correct one, jingoism aside.
Furthermore, in order to have precipitation, which I believe will be rain changing to SNOW here at about 3200 feet on Wednesday, there will first have to be clouds (silly, haha), the latter my specialty at the University of Washington.
I love clouds and the way they present themselves in this gorgeous Sonoran Desert environment that we are so lucky to live in. So, there oughta be some interesting clouds beginning today as the cirrus zipping on by begin to announce this monumental change from our mundane, but glorious weather of late. And, of course with that fast moving river of air called the jet stream settles over us, there’ll be some windy periods, too.
The worst part of this scenario is the bitter cold that will likely get here after this mammoth upper low center goes by, and if the US models are correct, it will only get here that bit sooner.
Below, this morning’s cirrus, full of portent, over Mt. Sara Lemmon.
Those of us awaking this morning were literally a-palled by the amount of smoke around. Not even Twin Peaks was visible, some 10 miles to the SW. See examples of smog in the photos below.
Where did it come from? Back trajectories, ones that end in Tucson as of this morning at 5 AM shown below, suggest the smog came from the SE of us (red and blue lines. The green line for air around 12,000 feet, represents where the air came from that air came from the off the California coast ; it was too high to be involved in our smog episode. Best guess, could be smog from El Paso and/or from burning in northern Mexico, that in the presence of light winds, has kind of muddled around and drifted N into Tucson.
Note the pooling of smoke in the low valley ahead in the Golder Ranch area in the first photo. Probably the result of wood-burning stoves used in the small housing development back there. What it shows you is the persistent nighttime inversion that forms in that bowl, the flat top of the smoke indicating a temperature inversion. You then see a “clear slot” of little smog and then the overall deeper smog layer above that, also very laminar in appearance. With the sun’s rise over the mountain, that kind of structure/separation is soon removed as bubbles of warmer surface air float upward and are replaced by downward moving blobs, mixing all the structure you see in the first photo out. In the last photo, a few tiny cumulus fractus clouds composed of droplets have formed over the Catalina Mountains. The droplets in those clouds are probably 10 microns in diameter (about 1/10 the size of a human hair). These droplets are about 100-1000 times bigger than the aerosol particles making up the smog. This makes the clouds to tell from transparent haze blobs because the smog particles are too small to scatter much light while the cloud particles even in small clouds, prevent you from seeing through them. Well something like that.
Hang on to your hat tomorrow; windy, thinking momentary gusts here in “Catalina Heights” will hit 30-50 mph by late afternoon and overnight before a very strong cold front rolls through around dawn tomorrow. This is an unusually strong upper level AND lower level system with a deep low expected to form over southern Nevada during the day tomorrow. Looks like the rain could change to snow above 3,000 feet after the front goes through, too. That would be terrific! The clearing after the front goes by will probably be late in the day with passing light showers possible until early Friday morning. The ones later in the day and overnight, are likely to be snow flurries above 3,000 feet . Don’t expect the temperature to do much tomorrow. And, the amounts of precip are likely to be substantial putting us at or above normal for the month. Yay! Well, this what it looks like to me; check the NWS for the official forecast!