In our last chapter, we saw that photos, perfectly fine ones here on the computer, were ending up corrupted when they arrived at WP for some reason. Unlike many computer problems, re-booting my own computer did not cure it. The next best thing to do, of course, is to wait and see if it just goes away2. And today, waiting has seemed to have cured the problem, since all the test photos up loaded got in OK. Check below.
Looks like our thick mid-level clouds overhead now have enough depth and moist air below them to drop measurable rain over the next 24-36 h. Will be happy if we get 0.10 inches here in Catalina. U of AZ mod total (last night’s 11 PM run) for here is more, 0.10 to 0.25 inches category, even better.
Some January 1st, 2015 snow photos. 3 inches total; 2 inches depth on ground at dawn (due to melting and settling).
OK, one more…. So far so good, suggests file corruption problem, wherever it came from, has been rectified somehow.
The weather way ahead
Ignoring the very light, sprinkly rains1 in the area now, ones that won’t amount to much, and since seeing predicted rain for us in the models is something like a little Valium for you, I thought I would post a couple of recently predicted Catalina rain boppers.
Of course, if we got all the rain forecast in the medium range, 10-15 days, that the models predict, we could grow pineapples and mangoes here without irrigation, so you have to keep that in mind as you look at these maps.
HOWEVER, CM, your own Catalina Cloud Maven person, DOES think that substantial rain from one of these is ahead for us, even if they come and go on the model runs.
Those “Lorenz plots” from the NOAA spaghetti factory. Of course, you knew I would say that, because you would say that, too.
Those plots are indicating a great chance for troughs in the lower flow band of the jet stream to be here in the Southwest in the middle to latter part of January. So, its not certain, but you lean that way. This is something you’ll also want to pass along to your less weatherwise neighbors today. To be wise in weather is to be great in a small way.
PS: 3 F now in Asheville/Fletcher, NC, where bro lives. Man, they got kudzu there, too. How bad is that?
1“Showers” is not the correct terminology for the of rain we have in the area right now. “Showers” of rain are marked by sudden changes in intensity since they are associated with cumuliform clouds that vary greatly in the horizontal, while light rain that changes intensity gradually falls from mostly flat or stratiform clouds that change gradually in the horizontal.
2I think it was Bob Metcalf, the inventor of the ethernet, who said:
Three separate bands of snow in one day? Unforgettable, if not unbelievable, for Catalina, Arizona, made more so because its late February occurrence. Here at the top of Wilds Road we received a total of 5.5 inches from those three bands, with a peak amount of 4 inches on the “ground” (actually it was measured on a hitching post) just as the third and final band ended at 9 PM last night. The totals with each band, measured just about the time the snow was ending1:
Time of band Top of Wilds Road: Sutherland Heights (1 mi NE and 170 feet higher)
11:30 AM to 2:30 PM 2 inches 3 inches
4:30 to 6:00 PM 2.5 inches 2.7 inches (most fell in an hour and a half!)
8-9 PM 1 inch 2 inches (this just in), 6 inches on the ground there in sheltered locations)
Totals: 5.5 inches at the top of Wilds; 7.7 inches in Sutherland Heights. What a day, Mr. and Mrs. Catalina!
Water content in this snow here, 0.49 inches, so far. Waiting for melt down to get last few hundredths still frozen on the sides of the collector of the tipping bucket raingauge. Measured at Sutherland Heights: a fabulous 0.73 inches!
It’ll be gorgeous in the first few hours today after dawn, but with our late February sun, our great local scenes won’t last long. While more cold air is ahead, though with no precip in the few days, a HEAT WAVE has reared up in the models for the beginning of March, 8-10 days out!
Some photos for yesterday’s memorable snows2 (plural here is even amazing), From the beginning…
6:11 PM. Wider angle view of that same scene after the second band dropped 2-3 more inches of snow in just over an hour. Getting pretty dark, camera or photog not doing the greatest job here.
Will be taking more photos of course, early today!
The situation aloft (500 millibars) as S+ snow band 2 hit:
Some Cu-Stratocu, patches of CIrrus and Altocumulus as a another lobe of cold air races SE from the Pac NW today. There’s a chance of snow flurries late tonight into tomorrow morning (can you imagine?) as the core of the trough goes by.
1Measuring snowfall and snow on the ground, is one of the biggest bugaboos we have in meteorology. If there is any wind at all, forget about getting an accurate total, too much blows over the collector can. So, the precip amount reported for this storm is going to be on the low side. And, as the snow piled up yesterday, it was also disappearing at the same time on the bottom due to melting. Finally, as it piles up, it sinks down due to weight. So, the depths reported above are conservative, since if all the snow landed on a below freezing metal plate, we would only be dealing with one of those problems, settling, as with snowpacks in the high mountains.
2Hardly any of which was forecast from this keyboard. Wish there was a font smaller than ” 1 point” and this is it, in case you’ve never seen it. You don’t want to rub it people’s faces that maybe you were a little asleep at the wheel; too preoccuppied with the amount of precip which you forecast was going to be MORE than the models were predicting, and which happened, not the phase (solid or liquid) of the precip. But then, what REALLY matters to the vegies out there? The amount, of course, well, OK I guess vegies like it if more if the water sits there in a form that melts and has a lot of time to soak in.
2:26 AM, Catalina: S- (light snow), 33.9 F, 0.01 inches so far. Precip not registering on Wunderground map site for some reason.
3:20 AM: S– (very light snow), 34.8 F. Temperature beginning to recover following precip, snow almost over, just a “skiff”, 0.3 inches.
6:20 AM: Total now a measly 0.02 inches, less than expected, but in keeping with jet “rule of thumb”; nil precip until 500 mb core goes by1, and its just getting here now–120 mph wind now at just around 18,000 feet over TUS, an extremely exceptional event for winds that strong to be that low!
Correction on storm total: Mr. Cloud Maven person forgot that when it snows, the small orifice into which the rain water usually flows without hesitation is clogged by that SNOW and the tipping bucket does NOT tip until the snow melts. It began melting in mid-morning, and by the time it was done melting, there was a total of 0.10 inches, 0.14 inches at the Sutherland Heights gage. This is a lot better than 0.02 inches.
County ALERT gage totals disappointing, too, just a few hundredths to a tenth of an inch; most with zeroes. Mountains reports missing since it fell as snow. (As with my own gage, the snow is melting into the buckets in the ALERT gages and they are now showing precip! )
(Here, the snow has melted and dribbled into the gage–NO it hadn’t!!!!) ((Shoulda looked inside the funnel before writing that!))
Only expecting small Cumulus today, but its cold enough that they could have some ice in them. It would be something for you to watch for.
Here’s the temperature and pressure traces for this dramatic cold front passage (FROPA) here in Catalina last night around midnight with the chart below beginning around 7 PM, this from a pitiful jpeg of computer monitor since the software I use will not print two parameters on the same graph (please fix this, Lightsoft Weather Centre, UK!):
You can’t read it, but the temperature dropped from 50.x F to 33.x F in about an hour, with period of very light snow, no accumulation at the end of that hour. And you can see what we meteorologists call a “pressure check” when a cold front goes by; starts rising immediately.
Lots of lenticular formations around, beginning with this rosy specimen just downstream of the Catalinas at dawn:
Lenticular clouds downwind of the Catalinas persisted for hours yesterday. Its sometimes hard to tell that they are not over the mountains, but you can see that in the U of AZ time lapse for yesterday.
BTW, if you want to know how the UFO thing got started, legend has it that it was due to a hovering Altocumulus lenticularis cloud downstream of Mt. Rainier in the 1940s.
Viewing this U of AZ time lapse movie will tell you why lenticulars have sometimes been reported as UFOs. It really does look like a hovering “vehicle” in the morning hours in the movie, and a “hovering”, which is what we know alien spacecraft do; hover. In the face of the strong winds up there yesterday, hovering is, for most folks, unexpected, suspicious behavior. Check it out.
Finally, after the heavy mid-level overcast in the mid-late afternoon, a brief sunset bloom due to a distant clear slot beyond the horizon (way down at the bottom).
What’s out there beyond the present cold spell and the warming after that?
This is kind of intriguing to me even though its kind of a waste of time, too. We’ll be reel cold for awhile, then it will suddenly warm up to seasonal temperatures for a few days. We know that. But then what?
Our models have been churning out wildly different forecasts toward the end of the month, and with those, wildly differing weather occurs here, naturally. These model forecasts are like a 5-foot wide puddle of water on a pot-holed street like the ones we have here in Catalina that they only repair in the most rudimentary way, throw some asphalt crumble in the hole, that its pretty much what they call a “repair.” Maybe its because we’re considered “po’ folk.” Let’s see, where was I? Oh, yeah, that puddle could be an inch deep or three feet deep. You just don’t know for sure.
One way to “dip stick” that “puddle” is in our NOAA spaghetti plots. At the end of this is the latest one from last night’s global data. You can see how wild (humorous) the forecasts are in the yellow and gray lines, indicating exactly opposite conditions in the West at the end of the month for those model runs at 00 Z (5 PM AST) and 12 Z (5 AM AST yesterday). Pretty bad.
The spag plot below from last night’s data suggest the warm ridge has the edge at this point (note clustering of blues lines to the northern US; red lines still confused). With a ridge holding forth, it would be a comfy time in AZ late in the month, not cold and blustery.
Still, its not the final word, remembering that the atmosphere remembers. It will be interesting if it remembers enough to bust our venerable spag plots. That’s what makes it so darn interesting!
1Its interesting that such an old style methodology, of the type used by forecasters before the rise of weather computing models, would seem to have equaled our best models in 2012.
To help understand that odd word, “plethora” in the title in case you are befuddled by it, I have added a YouTube teaching module to help you out: “What is a ‘plethora’?”
Well, one of the great model runs of our time has come out once again last night after yesterday’s great model run of our time based on the that morning’s data. SEVERAL rain days foretold in the next couple of weeks! One of these is actually a snow day, Feb, 25th, first predicted by the models about a week ago. This would be the “real deal” here in Catalina, not some “diabatic” (a weather term opposite of “adiabatic”) fluke as was our inch or so of snow two days ago, one that happened due to extremely heavy precip in the clouds above us, thus drawing the freezing level downward.
The first rain day is today, likely beginning after 5 PM AST, and then continuing into tomorrow for a second day. Here are some rainy/snowy snapshots from our friends in Canada at the EnviroCan weather service where they use a modified version of the ECMWF (European) forecast model here. The first panel is valid for 5 PM today just before the rain is supposed to begin. (If you don’t click on the panels below, you’ll need binoculars to see what I am talking about.)
Does this pattern look familiar in that first panel?
Yep. “SOSO” as we have been seeing all winter when storms strike. In the lower left panel you will see all that moisture streaming (colored regions) into our today’s cut off vortex from the south from the Mexican Pacific and linking up with a moist plume from the Gulf. Interesting to see that. Also, as it gets cut off, and great for us, it begins to dawdle while edging eastward along the US-Mexican Border, allowing those moist plumes to “filler up”, just like at a gas station. So, the rainy areas with this low should be expanding/appearing as clouds are enhanced; deepen up and begin to precip. Very exciting.
What’s been great is seeing the amount of precip predicted in Catalina from this low increase gradually over time as the models were seeing that it was not going as far south as they thought earlier. Here is another panel for this storm, valid for tomorrow afternoon at 5 PM AST. While the low has gone by to the south during the day tomorrow, this model suggests that it likely will have rained on and off during the day. This is because so much moisture arrived in this low that it has developed a “wrap around” band of rain to its north and west, good for us, kind of like a sucker punch. You should be able to see that happening today and tonight in this great IPS sat and radar link, as well as clouds “appearing” over the deserts to the west and south of us, and then developing echoes as they deepen.
Our local U of AZ Wildcat Weather Department has this great depiction of this “wrap around” development from their own model run here. Nice!
Here are the additional days ahead with more rain, and also, low snow levels. Mt Lemmoner’s rejoice! Below, the next panel, Sunday afternoon into Monday morning, this next trough.
Brrrrr, another cold blustery day Sunday, but notice this one is NOT a cut off and so will move through rapidly. Then, 4th panel, a dollop on Tuesday, just a minor trough passes by, and then, after a break, the Arctic iceberg on the 25th. Check this trough out in the last panel. Awesomely cold!
With luck, and a little verification of these predictions, maybe the washes will run later this spring!
The Cloud Report part of blog
Had some complicated, but nicely detailed Cirrus clouds float over in the early afternoon, a part of our invading storm’s circulation. This was followed by a large clearing and then encroaching Altocumulus patches trailing virga (ice crystals) in gorgeous, fine strands that wiggled this way and that in the setting sun’s light as that falling snow responded to slight changes in the wind below those little flakes of Altocumulus cloud. Enjoy.
Mr. Cloud-maven person hasn’t said much about clouds lately, which is kind of ironic since he deems himself a “cloud maven” and not much more. Rather, he has been obsessing about POSSIBLE storms in AZ 15 days away which is kind of futile anyway.
So, as an excuse to show more cloud photos from that gorgeous day of snow and cloud shadows on the Catalinas yesterday, will go into a cloud lecture, a post-mortem so to speak. Here are some cloud shots from yesterday, most below the one at left. Note, not one cloud shows any virga yesterday, and some of them got, at least moderately humped up. A promiscuous cloud maven person might have called one or two of the cumulus clouds, a “Cumulus congestus” (though they would be WRONG). Well, maybe not that wrong–see the 1987 World Meteorological Organization International Cloud Atlas that I can’t stand because they goofed up on their cloud designations as you will see if you could only find one of those yourself. Still kind of bummed out by that atlas, but one member of that cloud selecting panel told me they were too busy in their Paris meeting going to the Eiffel Tower and such rather than paying attention to getting the cloud photos they had properly named. Now, where was I?
Right, I was talking about yesterday’s clouds…. Well, here are some cloud shots, ones that I was going to post 15 minutes ago before getting upset again over the 1987 WMO cloud atlas. (Really, I could have done a better job than the WMO all by myself; it was a real boondoggle, that meeting of “cloud experts”, yeah right.) OK, photos!
Now looking at ALL of these, you see no fibrous material falling out, even though some of the clouds look pretty dark in these perty scenes. I was so happy to be alive and live here yesterday, feeling very, very lucky. So, remembering the University that Bullwinkle Moose went to play football as the “Frostbite Flash”, “Whatsamatta U.”, we might say the same thing to these clouds, “Whatsamatta U?” How’s come there no precip falling out, and those who read this silly site will answer immediately, “Them clouds ain’t got no ice in’em”, which would be correct.
But why? It was awfully cold yesterday, and even Mr. Cloud-maven person, who does not even have the Master’s Degree, was wondering. So, off to the TUS “99 Luftballoons” sounding data for yesterday afternoon, posted by our great U of A Weather Department below (where the lines come together are where the clouds were located). Didn’t seem possible to me, but those cloud tops were hardly as cold as -5 C (23 F). Ice does not form in clouds, even though they are below freezing, at this temperature in the natural state except in very special circumstances. Ice formation in clouds, still not WELL understood, is known to be a function of drop sizes AND temperatures. Over the oceans where cloud drop sizes are large, it happens. Usually, someone can get a whole scientific paper out of a cloud that formed natural ice when the top has never been colder than -4 C!
Here in Arizona, what we would call a continental cloud forming environment. Cloud drops “is” smaller because there are so many more particles for the drops to condense on, and so the concentration of drops is higher, meaning the drops have to be smaller to condense out the same amount of water as over the oceans where the air has fewer particles for clouds to form on. In a nice cumulus off the Washington coast of the sizes we had here yesterday, the cloud drops would be as large as half the diameter of a human hair (“wow”, huge, he sez, 30-50 microns in diameter, for the sake of a number) here in AZ in those clouds yesterday would be lucky to have drops in them as big as 20-25 microns, too small to activate ice forming processes, known to be related to drop sizes. Oddly, the bigger the cloud drops, the HIGHER the temperature at which ice forms, especially if drizzle drops have formed. The drops in our clouds yesterday were too small to have an appreciable fall speed, so they don’t fall out either.
Since I have published a lot of critical work on cloud seeding, one might ask if these clouds could have been made to snow by artificial means? Even as a long time critic, the answer is an unambiguous “yes.” With a small plane, and a little dry ice, you could have made a little snow fall out of these clouds because the tops were cold enough for that. Dry ice, the substance you would have used, has a temperature of -78 C, and when pellets falling, they leave a jillion ice crystals in their path as they cool the air momentarily to -40 C and below, the spontaneous nucleation temperature. And, with ice in these clouds, the drops would be evaporating and the water molecules depositing themselves on the ice crystals. Ice crystals in clouds of water drops are like little low pressure centers; the water molecules leave the drops and goes to ice, and ice crystal gets big enough to fall out. Our natural precip here is like this most of the time.
So, summing up this little cloud-ice lesson, our clouds did not get cold enough, and at the temperature the tops DID get to, the drops weren’t big enough to trigger natural freezing. Tell your friends.
As Muhammad Ali might say, referring to the Climate Prediction Center’s three month outlook that was for dry conditions in Arizona from November to January. So, the first round, November into early December, has delivered quite a punch against drought with another 0.40 inches here in Catalina last night. Our December total is already 0.82 inches! Rains have been bountiful, too, during this period in some parts of NM and Texas, horribly stricken with drought, so its been great run of drought smashing weather. Check the latest 30 day US precip totals here (does not include the heavy rains of yesterday in TX, however). And from WSI Intellicast, this 7 day total precip map. Excellent. In Catalina we now have had 2.63 inches since the beginning of November.
Below, the CPC forecast for November through January for the US issued last October 20th. These predictions are weighted by the “moderate” La Nina event now going on in the central and eastern Pacific. A La Nina leads to greater chances of dry conditions throughout most of the southern US. Hence, this forecast. However, the correlations between a La Nina and the map shown below leave plenty of wiggle room, especially early in the winter. Later in the winter is when the great southern US storm deflecting property of a La Nina has its greatest power, so it’s really good that we’re getting slammed early by decent rains; it might be a very dry late winter and spring.
Remember 1971-72? And how wet it was in November and December in the SW, and then poof, almost nothing in the way of precip after January 1st? It was awful. (I was weather forecasting in Durango, CO, then. ((Hay! Not for TEEVEE, but for a randomized cloud seeding experiment!))
Had some pretty Cumulus clouds yesterday before the gray Nimbostratus layer moved in. Here are a couple of shots around the Catalina area. Always nice to see snow on the Catalina Mountains.
The last one is from today showing the gorgeous scenes, changing by the minute as the cloud shadows roll by, of the low level on the snow on the Catalinas. Even here at just under 3200 feet elevation, last night’s rain ended with light snow for a few minutes.
Mods (from U of AZ Wildcats) don’t see precip from this next cold trough, one that lands on us tomorrow. Darn.
Suddenly, it occurred to me that I want you to look at these forecast maps from IPS Meteostar for the next 15 days. Just changed this to the intermediate model run, updated at 06 Z, 11 PM LST. Much more “interesting”–means this writer saw MUCH more precip in AZ on the updated model run just now. Check out the massive trough 12-15 days out and cross fingers. Man, this is an exciting new change!
Well, maybe there were about 27, but anyway….not very many; still, those drops were to be treasured after not seeing a single “hydrometeor” display in SE AZ in so–ooooo LONG A TIME!
PG-13 advisory; DRIZZLE is discussed
I have to warn you at this point. That rain event yesterday WAS NOT DRIZZLE!!!!!!!!!!!!!!!!!!!!!!!!!!! I will be ROYALLY PO-ed if I hear someone in my social network or a TEEVEE weather presenter say that it “drizzled” yesterday!
Why make a BIG THING out of the correct type of precipitation?
I have to tell you a true story (well, I don’t have to, but I am going to anyway) about the importance of drizzle (i. e., fine, close together drops that appear to FLOAT in the air). This event happened during my cloud seeding “vigilante” adventures (see Publications for samples). A well-known professor of cloud seeding in a foreign country asked me to leave his office and never come back after I told him it had been “drizzling” outside, “10s per liter” in the air.
Drizzle is a profound indicator of cloud structure overhead, and the presence of drizzle falling from the clouds in that professor’s region’s meant his numerous reports of how clouds were, ripe for cloud seeding, were in substantial error. So you can understand why a report of true “drizzle” would naturally be upsetting to that professor. Man, am I digressing here! Yikes. My apologies. (BTW, those reports WERE in error, confirmed by aircraft years later! (Spiking football now, with a proper amount of decorum, of course!)
OK, back on task….
With the sky full of low (“boundary layer”) clouds by mid-day (f you’ve forgotten, that was yesterday, May 10th, 2011) and with RW— in the air (“triple minus”, extremely light rain showers) by 1:30 PM, with gusty winds, temperatures in the mid-60s, it turned out to be quite a “storm.” It just as well could have been but a mostly sunny day with just a scattered Cumulus clouds here and there the way some models were “telling it.”
Here’s a pictorial on how it went, from a Catalina, AZ, perspective:
2) 12:03 PM, larger Cumulus growing up into Cumulus “mediocris” beyond Tortolita Mountains on the horizon,
3) 12:29 PM, virga and rain visible to the NW horizon! Now I am getting apoplectic since the best models in the world did not have this precipitation over thataway! But there it is, bigger than watermelons. The models have to be really red-faced about this! Not everything in the world is predetermined by numerical models; you can say things that might be right and those models are WRONG! Just like in the 1970s when a lot people thought global cooling was underway and that’s where we were headed! But they were WRONG! Who were those clowns anyway?! (hahaha, sort of).
4) 1:25 PM. Now where was I before all that excitement? Oh, yeah. Here’s some ice for you. See the frizzy top parts of this cloud in the center of this photo above the dead tree that the birds like to sit in? Well, them’s ice crystals, and likely snowflakes that have formed in that medium-sized Cumulus cloud (above the dead tree) and its in the upwind direction. Behind that is more ice and precip falling from a wide area of a Cumulus-Stratocumulus complex.
Quiz. How cold does the top of THAT cloud have to be to look like that (have that much ice in it, probably a few per liter to maybe 10 or so, not a tremendous amount but significant)? Well, with bases as cold as they were, near freezing by this time of day at around 7, 000 feet above the ground or 10, 000 feet above sea level, around -15 C (or about 5 F). Amaze your friends with cloud trivia like this! Well, maybe not.
5) 1:25 PM. Here it is, a band of precipitating clouds overhead. Now the ONLY question remaining, as you gaze upwind at Twin Peaks clearly visible through the precip and virga is, how much will there be? None? Or as much as a “trace”? Measurable is out of the question, looking at this scene below the clouds. Most of the visibility degradation is due to dusty air, not precip. Darn. (Amaze your friends with skills like this! Well, maybe not.)
6) 3:03 PM. The End is Near
7) 7:06 PM. Nice sunset with traces of Cirrus and Ac len on the horizon, driblets from a storm striking the Pac NW. Isn’t there always a storm striking the Pac NW? I digress again.
Man, I could go on about the weather maps of yesterday, but will quit here.
If you REALLY want to see how it went, take a look at the U of A time lapse video here.
Here’s what happened on top of us yesterday, that gorgeous snow day with so many wonderful sights to see. These maps below, courtesy of San Francisco State University , for 500 millibar pressure level, about 18,000 feet above sea level, for 5 AM LST as the snow band moved through Catalina, and then 5PM LST, a little before sunset:
A visual on what the clouds did as this happened yesterday is below. Interpretative cloud statements on the following gallery: shallow, deeper (precip begins in distance), deepest (small, soft hail falls here and there from miniature cumulonimbus clouds), less deep (barely-able-to-precip stage again), shallow, nil. Pics 1,2, 3, 4, 5, and 6, respectively. If you want all the visual glory of yesterday, go to the U of A time lapse movie here. However, you’d better hurry, these wonderful films are overwritten each day. You can really see the clouds flatten out after about 3 PM LST here, and there are some spectacular snow showers going by on the Catalinas.
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.
OK, enough rambling!
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