Cloud-maven – Page 70 – About real clouds, weather, cloud seeding and science autobio life stories by WMO consolation prize-winning meteorologist, Art Rangno

Upper low passing to south; clouds to wrap around overhead from the southeast and east this evening

Backdoor rain? Looks like any chance of rain will happen later this afternoon through overnight as mainly mid-level clouds twist around our low from the east. That low is now over Yuma, AZ, and the center will pass to the south of us tonight. We don’t see that happen too often. Here’s a nice loop of the circulation around it, also showing the radar echoes–very handy. (Some cloud shots at the bottom, way down there.)

Right now, our low is looking pretty dry, not much going on in it, or around it right now, and so any rain falling from mid-level cloud bands, like Altocumulus (with virga) and a likely deep band of Altostratus (also with virga), will be pretty light; sprinkles to maybe a hundredth or two. The better part of this is that with mid-level clouds coming from the east, they won’t be much dissipated by the air going downhill from the Catalina Mountains as you would expect with low clouds. However, in Mexico, since it is so cold in the center of this low, there will likely be reports of snow in unusual places, as in the last storm. The U of AZ Beowulf Cluster model, the best around for us, sees only a brief, fairly close call for rain tonight.

Still, while this low passage will be a little disappointing as far as rain goes, the skies will be great today with scattered Altocumulus, likely with a little virga, and scattered Cirrus, with a great sunset. Both of these cloud types can be very “photogenic” on days like this. Likely those mid-level clouds will clear out tomorrow morning, so get’em while you can. If you don’t, of course, this compulsive cloud photographer will.

Full cold ahead

Get ready for some terribly cold days just ahead, likely some snow in Catalina still, though the more moist Canadian model prediction for this storm has dried out overnight–tending to be more in line the with US models which have always had this cold wave as a light precip event. Precip is pretty much guaranteed here, and some snow probable in Catalina, but max and least precip totals from this storm have to be revised downward in view of the latest Canadian results. Minimum amount, 0.10 inches, max, 0.50 inches (was an inch due to how much offshore flow the prior Canadian models had the night before last). So, most likely amount is between those two extremes, or about 0.30 inches with precip beginning during the day on the 11th.

A further disappointment is that the mods now see this storm as a quickly moving event, and the precip is over by evening on the 12th, so it ends up as just a 24 h period of rain and snow chances, most coming, of course, in the first segment, a line of rain changing to snow with the frontal cloud band and wind shift line on Friday, the 11th. Dang.

What about the second cold blast on the 15th-16th?

Still coming, but this wiggle in the jet stream shooting down at us from the northwest, has a trajectory toward us that is farther east than it was shown in the models earlier, and the farther east and the further away the trajectory is from the coast, the drier these cold pushes will be. So, that second blast of cold air, while still looking very cold, is also looking pretty dry right now; may only get a passing snow flurry, or we’ll just see scattered small Cumulus with some virga.

In these latest model runs the jet stream pattern that has led to our “trough bowl”, the favored location where storms have been collecting in our region for the past month, begins shifting to the east at mid-month, and what’s more, the amplitude of the north-south oscillations in the jet stream fade to a more west to east flow.

This very different than what was depicted just the night before last. Here’s what I mean. Shown below is the first forecast panel, high “amplitude” pattern in the jet stream–always associated with temperature extremes, cold where the jet dips down, like HERE, and warmer than usual where it shoots up from the southwest,for example, there in Alaska.

Valid for the evening of January 15th. An example of "high amplitude jet stream configuration associated with temperature extremes. — Valid for the evening of January 15th. An example of “high amplitude jet stream configuration associated with temperature extremes.

This is a very common pattern. You probably remember how warm it was in Alaska during the 1962-63, and the 1976-1977 winters, but how friggin’ cold it was back East when this kind of high amplitude pattern was pretty extreme and persisted for weeks: the jet racing into Alaska from the mid-Pacific, and then shooting south into the US. Really horrible times for the East in those winters.

But look at what the model sees for the end of the 15-day forecast period, shown below! The jet hardly has any amplitude, just shoots in from the Pacific in a west to east flow. That means no temperature anomalies to speak of, and a moist West Coast regime, sometimes with precip getting this far south, too.

Valid the evening of January 22nd, a Tuesday.

What does spaghetti say about all of these changes?

Its pretty clueless, that is, slight changes in the observations make a big difference in what happens, and that’s why its so wild looking in the Pacific and the US (shown below). This means you probably can’t count on the above pattern a lot, except that the amplitudes have gone down, that seems to be a pretty solid expectation. That jet surging into AZ could just as well be intruding into Washington State in a west to east pattern. That would mean that our 30-days of below normal temperatures here in AZ, beginning in mid-December (shown here by the NWS, lower right panel), are about to end after about a week to ten days, and with that, a long dry spell likely to set in.

Yesterday’s clouds

Mostly Altostratus, thinning at times to Cirrus, and late, a few Altocumulus/Cirrocumulus patches. Here are a couple of shots.

7:22 AM. Under lit Altostratus at sunrise. Those little pouches are regions of light snowfall (virga).

SONY DSC — 1:49 PM. Boring, generic Altostratus translucidus, an ice cloud. Sometimes droplet clouds like Altocumulus are embedded in them, but none can be seen here (they would be dark, sharp-edged flecks). The massive clearing that occurred in the late afternoon is visible on the horizon. If you saw that clearing, it would have been a great time to tell your friends that, “Oh, I think it will be sunny in 3 hours.” It would have been quite a magical moment for you.

5:36 PM. This beauty of a patch of Cirrocumulus (tiny granulation) and a lump of Altocumulus. — 5:36 PM. This beauty of a patch of Cirrocumulus undulatus (tiny granulations in waves) and a lump of Altocumulus (lower left). TUcson sounding indicates they were about 15,000 feet above the ground at -20 C (-4 F). No ice apparent. It happens.

“You’re really not going to like it”

The above, a quote from Douglas Adam’s hypersupercomputer, “Deep Thought”, from the 1980s classic sci-fi radio series, “Hitchhiker’s Guide to the Galaxy”, spoken by DT as he prepares to give the answer to “life and everything.” In the context of the computing grandeur of DT, as one website quotes, “Don’t even mention these”:

The Milliard Gargantubrain
The Googleplex Star Thinker
The Great Hyperlobic Omni-Cognate Neutron Wrangler
The Multicorticoid Perspecutron Titan Muller
The Pondermatic

These still make you laugh from that classic NPR radio series-Eagles theme here).

I wanted to distract you with laughter if you are one of those persons who love Arizona or are a snow birdy solely because of its warm, sunny weather in winter. Not gonna happen this month¹.

The answers to “weather and everything” below, and you’re not going to like them, unless you’re a skier, and you come to Arizona for great powder skiing!

By the numbers, what’s ahead:

Weather event 1. a little cut off low travels across northern Mexico from southern California bringing some fabulous-looking clouds today (high ones like Cirrus), and a brief shower at anytime tomorrow through Tuesday morning when its closest to us. Nice. But its not too cold yet. That comes later.

Rain in #1? Top pot (-ential): 0.25 inches; bot pot, just a trace. Most likely amounts hereabouts? A few hundredths to a tenth. Hoping for the development of a narrow, odd line of high-based (Altocumulus level) Cumulonimbus clouds that wrap around the upper low center as it goes by to south tomorrow. Wispy storms like this could produce little shower areas not conducive to model resolution at any time since the moisture threads running around it will be very narrow. You’ll have to be watching. Have camera ready for spectacular Ac castellanus (he sez) today and/or tomorrow.

In summary, today you will begin to be clouded over. On to event 2

Event 2, begins January 11th.

Summary: Yikes! Takes a few days to get through this. Check this prog out from Canada from last evening’s global data crunch (especially, the upper left and lower right panels):

annotated 2012011200_054_G1_north@america@zoomout_I_4PAN_CLASSIC@012_144 — Valid for 5 PM AST, Friday January 11th. “Totally awesome!” This new depiction moves this giant trough to offshore of southern Cal-Baja. You know that means. More water streaming north into AZ before the Big Cold hits, molecules of water vapor being sucked out of Pacific. That would be fantastic. One of the best model forecasts I have seen in a LONG time. Congratulations to Enviro Can for coming out with this last night. A real winner.

OK, quite exuberated over this Canadian forecast. For one thing, the dreaded super cold air is delayed, though it still happens after this big trough goes by. But mainly from this prog above, our precip potential is jacked up by twice with an upper level configuration like this, so much of it offshore now.

In the preceding days after Event 1 ends Tuesday morning on the 8th, the temperatures will rebound nicely, too, before the Big Whammy on the 11th-12th.

Rain in Event#2, January 11th (begins later in day)-13th? I think now you have to be thinking the “top pot” here in Catalina is 1.00 inches over a 48-72 h period, bottom pot, 0.30 inches (i.e., less than 10% chance of more; 10% chance of less). Median of these “best extreme guesses”, 0.65 inches. So, we got us another sure-fire substantial rain, even if the minimum is all we get. Go desert wildflowers!

Now, a caveat… US mods don’t have the flow as far offshore in event #2 as the Canadians do, thus, our mods have a much drier depiction for this storm. In these kinds of situations, no model has the complete truth, and so mentally you try to integrate the two. The lower precip bound of just 0.30 inches here is due to a compromise in actual flow patterns that might eventuate.

Quitting for a second to dream about pounding rain on the flimsy Arizona roof we got…the only kind to have if you’re a real CMJ (cloud maven junior); are a precipophiliac, as I am, or just like the sound of what the wildflowers are getting out there in the desert.)

Snow in Catalina in #2? Sure looks like it, toward the end of the precip, overnight 12th-13th. Will expeculate that 1-4 inches will fall between Saturday night into Sunday morning.

Event #3. The storms, though not nearly as moist as #2, troughs just keep “falling down the shoot” as the jet stream zips southward along the West Coast carrying storms to us for the foreseeable future with the timing of #3 on the evening of the 15th-16th (US WRF-GFS mod run from last evening’s data). Here’s what that cold trough and following blast of cold air look like on the evening of the 15th. A little snow is possible toward end of this event in Catalina, too. This goes by really fast, which is bad for precip totals, and “good” for extra cold air arriving here, since its shooting down at us so fast, that cold air can’t be modified much into warmer air as it goes southward.

Eve Jan 15th2013010600_CON_GFS_500_HGT_WINDS_240 — Vallid for 5 PM AST, Tuesday, January 15th.

Only in the “dying embers” of last night’s model run, one that ends after 15 days, on the 21st, does it appear that there is a break in the pattern of below normal temperatures here. But, as we know, the atmosphere “remembers” for weeks at a time, so it may not be last long.

BTW, we are joined in cold air by our planetary neighbors in China, who are experiencing one of the coldest winters in 20-40 years. In a preliminary newsy item from China, they have attributed the cold winter to warming….and melting ice caps. Hmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmm.

In an aside, should we see some really cold air, as is likely, the argument that “its colder because its warmer” may show up here. Its out there and I think it showed up after our February 2011 record freeze. Remember, I am a cloud-maven, not a climate-maven, but some statements do seem silly. Severe weather happens; always has, always will.

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¹Its great, though, to see all those out-of-state license plates these days (Ohio, Ilinois, MN, PA, Iowa, ID, AK, Ontario, Can, seen just yesterday), knowing there are so many people who want to be where I am all the time, a permanent resident. I am sure all of us Arizona “barnacles” feel the same way!

Rain, snow (s), extreme cold ahead in mod run (pretty worked up today)

Was going to rest brain today, not blog-blab, but then went to mods; brain rest over.

“Holy Smokes!”, “Good Grief!”, my modest brain erupted with when perusing the 00 Z¹ (5 PM AST) WRF-GFS model run this early AM. If the predicted features verfify over the next 15 days, what appears to happen beyond that, this could be one of the most severe January’s in the Southwest in decades. Yikes. And our “test the effects of flapping butterfly wings on the model run” (figuratively) “spaghetti” plots from NOAA, those slightly perturbed/disturbed model runs, seem to support last night’s ACTUAL run, at least into the first two events described below². “Hence”, as they used to say, the excitement this morning from this keyboard, but maybe some dread, too.

Quickie overview for Catalina

(taking the current model run (00 Z) at face value:

Jan 7th into the 8th: Some rain, maybe a tenth or two.

Jan 11th-12th: rain changing to snow, total precip maybe half an inch, with an inch or two of snow. Post event, temperatures dropping into the 20s at night, lower in washes and such.

Jan 16th. Another chance of snow, doesn’t look like as much precip as the prior event, but colder yet afterward. Temperatures lower yet, could get into the lower 20s, teens in the washes.

Furthermore, the pattern doesn’t appear to break after this last storm on the 16th. It remains cold here through the end of the model run on January 20th. As you likely know by now, once the jet stream gets into a pattern, it likes to keep it going. No one knows why, or when it will break. If we did, our longer term forecasting would be better.

Some more discussion below of this forecasted pattern, one that could lead to one of the more severe Januarys in the West in some decades. While precip is always dicey here until the last moment, the exceptional cold seems very probable. Be ready!

Here’s what the model (as usual, rendered here by IPS MeteoStar) has churned out for us in the way of rain/snow events for us,with the storm formerly mentioned here as arriving on the 8th, now arriving on the 7th. (Heck, for awhile it was GONE!) This series of three trough/storm events shown below might be thought of as cool, colder, coldest. Not so good as a series if you’re visiting here to enjoy warm weather.

Jan 7th 2013010500_CON_GFS_500_HGT_WINDS_066 — Valid for middle of the day, January 7th. Not a bad storm, but not a great one, either, but good in the sense it keeps the stream of storms up after a week’s break. Maybe a tenth or two of rain.

Here’s the next one, valid for the evening of the 11th, and this one starts to get your attention, as in “Yikes! If that materializes, its snowing here!”:

January 11 11 PM 2013010500_CON_GFS_500_HGT_WINDS_174 — Valid for 11 PM January 11th: Summary; yikes! So cold, rain turning to snow in Catalina, maybe a couple of inches. The thing to notice is the central contour number here, “12” lower than the “ordinary” storm shown above. The lower these numbers (contours where the height of the 500 millibar pressure is reached, the colder the air must be underneath it. The denser the air is, the faster the pressure changes as you go up. So a “540” contour represents really cold air in the Southwest moving into Arizona. I would not want to be a grapefruit in the few days after this goes by.

Finally, this, a brutally cold trough over us again, with the jet stream running a straight shot just down the interior of the West Coast from pretty much the place where Santa Claus lives, Barrow, AK. Below, valid for the morning of January 16th:

Jan 16th 5 AM 2013010500_CON_GFS_500_HGT_WINDS_276 — Valid for 5 AM AST, January 16th. Egad! While precip might not be as much in the prior trough passage, this one looks colder after it goes by. Part of the contribution will be that the prior storm would have laid snow down over a vast area interior of the West, and that will help to keep the cold air blasting southward here colder here than it otherwise would be.

These particular depictions, especially the latter ones with rain and snow in them for us will be flopping around like a just-caught trout in a boat in the model runs ahead. The main thing that seems “in the bag” for Arizona as a whole, is COLD air. Cold to write home about.

Snow? Of course, its less certain as the troughs wiggle around in the models, and to get that snow the apex of the troughs pretty much have to go over us and those little wiggles could take them to a bit to the east of us, making the coldest spells just dry ones. That would be too bad, because if you’re going to have to endure cold, there might as well be some snow on the ground to play around in.

Now in a personal disclosure, one of the faults I have as a weather discussant, is to get TOO excited about extreme events that are forecast, rationality diminished, hence the “newsy” logo here:

“Right or wrong, you heard it here first!!!!”

It WILL be so much “fun-dread” day by day, to see if these things come to pass, how the models change these depictions above as new data are processed. To repeat, though, be ready!

The End.

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¹Or, “CUT”, Coordinated UNIVERSAL time, as it is called today. I hope those people on the edge of the universe are aware of our time convention. Used to be known as GMT, Greenich Mean Time, starts at the 0th Meridian over “jolly old England.” “Jolly”? Huh. Are they referring to Monty Python? Rowan Atkinson? .

²Don’t forget to order your “I ‘heart’ spaghetti!”, tee shirt that shows you’re one of the scientific literati because “spaghetti” gives us insights into whether a model run is a bunch of crap (oops, “model excrement”. New! Now available in down jackets….

Looking back, looking ahead: some climo info and a prospect for rain on the 8th

First, let’s look back and think of all the things we could have done better. Its always great to mope around about things you did, but can’t change, but then, after a good mope, jettison those thoughts, push ahead and vow to do better in the coming year, maybe fill in your weather diaries more completely, not miss that Altocumulus lenticularis in the lee of the Catalinas this year, learn a new language, thoughts that lift our spirits, for a time, anyway.

What could our weather have done better in 2012?

Rain more.

Check this annual chart out, kind of depressing except for July, August, and December (green bars are the observed totals):

OK, got that said, now let’s look at January, a month that is not beginning on a rainfull note. Here is the daily occurrences of measurable rain over the past 36 years, the first 32 from Our Garden’s garden near Columbus and Stallion here in Catalina; and the years after that, a bit to the SE close to the water tank up at Swan and Wilds. There will be slight differences between the two locations as a rule, and once in a great while, large ones, as this past July when the Garden got clobbered with over 6 inches that month!

There’s some SLIGHT indication, after 36 years of data, that the chances of rain might increase after the 15th, but, like the early peaks in the first week, they might just be “noise”, statistical flukes that disappear with time, a lot more time.

What are the chances of a wetter than normal January, and even a wetter than normal first few months of the year (into May)? Not that bad, surprisingly. We had a dessicating January through May last year, and climate/weather doesn’t repeat those kinds of things very often on a year to year basis in the Southwest. End of reasoning.

If you want something official, and not satisfied with my statement, here’s the Climate Prediction Center’s three month outlook for January, Febuary, and March of this year. Remember, they also told us an El Nino was coming, then said it wasn’t…

The weather ahead

While the US WRF-GFS model run from last night (00Z run, 5 PM AST) still has us rainless for the next FIFTEEN days, the superlative Canadian Environment Canada model, while looking at the very same upper low center in the US model that passes to the south of us on the afternoon of the 8th, says it will have rain in it for us! US mod says it stays dry here as it goes by over northern Mexico. Here are the forecast panels from our Canadian friends for 5 PM January 8th:

Spaghetti maps guarantee a substantial upper level low/trough will affect us on the 7th-9th, too. Not sure why its so DRY in the US model as it goes by on the 8th-9th. I am guessing that will change over the next few model runs.

The End.

Mostly in absentia yesterday: contrails

Yesterday was as remarkable in its way as the day before in its generic beauty. Delicate Strands and fibrous blobs of Cirrus in interesting shapes floated by overhead with nary a contrail to contaminate those scenes. While our little part of the sky above Catalina, Arizona, is a low contrail impacted zone of the sky, yesterday seemed exceptional. It mgiht have been because, and since I am guessing here, will not check it out, those wonderful clouds and that moist layer they were embedded in was LOWER or HIGHER than usual, and the flight levels that the jets were flying in remained very dry so that they don’t persist. Its the ambient humidity up there that makes them various lengths. If its too dry, there is only that bit right behind the jet–recall Appleman (1951) and the Appleman diagram.

Also, the wind direction at flight levels helped; due west generally keeps those contrails packing airways just to the north of us and to the south streaming along beside us, not over us. That always helps.

But, I didn’t really see much off to the north, where there are usually a half dozen or so on any “Cirrus-ee” day.

Was it because it was New Year’s Day and air traffic is unusually low because no one wants to travel because they wouldn’t be able to watch the Rose Parade and various football bowl games? Don’t know, but maybe.

I have given you a LOT of things to think about, and while you’re doing that, I will post some evidence, contrail-less Cirrus skies. You won’t find this kind of day we had yesterday along the Atlantic Seaboard on any day with Cirrus with all the jet activity.

The weather ahead?

There isn’t any. Well, any worth mentioning right now. Gotta get through this week or two dry spell somehow…

Will dredge up some January climo tomorrow or the next day.

The End.

Yesterday: a rare drizzle occurrence in the morning and later, gorgeous Cumulus-filled skies

First of all, Happy New Year to both readers! Thanks for hanging in there.

The weather ahead…

before a long diatribe about drizzle, followed by some pretty pictures with explanations:

Some picaresque Cirrus later today. Looks like next chance for rain is around the 10th-11th of Jan.

A rare drizzle occurrence

Cloud maven juniors were probably excited beyond description when they went out yesterday morning between 9 and 11 AM and intercepted a rare occurrences of brief drizzle here in Arizona falling from that low-hanging Stratocumulus overcast. This happened after several very light RAIN (not drizzle) showers dropped another 0.02 inches, raising our storm total here in Catalina to a respectable 0.30 inches.

Drizzle is composed of drops barely large enough to cause a disturbance in a puddle of water¹, as though a large particle of dust had landed in it. Drizzle drops nearly float in the air (should not be falling at more than about 3-4 feet a second), and in many cases of very light drizzle, the drops can float around like “desert broom” seeds. Visibility is usually lowered, things look fuzzy in the distance. Drizzle precip is so light it can’t produce even 0.01 inches except over periods of an hour or more. Drizzle drops are also more uniform in size than the drops in rain, and are usually very close together.

While drizzle is common along the west coasts of continents in coastal Stratus and Stratocumulus clouds, its much rarer at inland locations such as here in Arizona, thus, the excitement over seeing it yesterday.

The reason why its rare in AZ?

Shallow clouds that drizzle must be what we would term, “clean” clouds; they don’t contain many cloud condensation nuclei and so droplet concentrations are low, maybe 50-200 per cubic centimeter (might not sound low, but for a cloud, it is). Clean evironments are found over the oceans and for awhile, in air coming inland along the west coasts of continents in onshore flow before it gets contaminated with natural and anthropogenic aerosols (smog). Man, we are getting into a real learning module here! Wonder if any readers are left? Probably talkin’ to myself now. Oh, well, plodding on. Nice photos below…far below.

Drizzle occurrences tell you a lot about the clouds overhead. Not only are they low-based as is obvious (they have to be or the drizzle can’t reach the ground), but they are relatively shallow clouds no matter how dark they look. Furthermore, and more subtle, they have larger cloud droplets (ones to small to fall out as precip) in them that must be larger than about 30 microns in diameter (smaller than half a typical human hair diameter). When this larger size is reached in clouds, and those drops are pretty numerous, say 1000 per liter, they begin sticking together when they collide in the normal turbulence in clouds. Those collisions with coalescence result in drops that fall much faster, bump into more drops, growing larger and larger until they fall out the bottom.

In a shallow cloud, those drops can’t get larger than drizzle drops, and that’s one of the ways you KNOW that they are shallow no matter how friggin’ dark they look.

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Aside about rain not due to the ice process:
The largest drop ever measured, 1 cm in diameter, was observed in a Hawaiian Cumulus cloud that did not reach up to the freezing level! Unfortunately, the authors of this finding did not publish their results and so did not get a Guinness record like me and Pete Hobbs did when we reported a smaller 0.86 centimeter diameter drop in Geo. Res. Lett., 2004–found them in Brazil, and again in the Marshall Islands–hit the pilot’s window like little water balloons. Instead of being in a book with other famous people, like ones who can eat 47 hot dogs in 12 minutes, those researchers who encountered that larger drop in Hawaii sat on their finding! Unbelievable.

Strangely believe it, from lab experiments, drops bigger than 0.5 cm are not supposed to exist, but rather break up around 0.5 centimeters in diameter. (hahahahaha, lab people). End of aside.
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¹Officially, 200-500 microns in diameter, equivalent to a couple or three of human hairs, maybe ONE or two horse’s tail hairs, to add a western flavor to the description.)

Yesterday’s gorgeous skies!:

Took more than 100 photos yesterday. Was out of control, euphoric, thinking how great this earth is, maybe leaning toward thoughts of higher being and creativity therein, thus explaining the “creative” punctuation above. Here are a few shots of those magnificent clouds and our magnificent, snow-covered Catalina Mountains. First, those drizzle-producing clouds:

Not a bad storm, but not a good one, either

0.28 inches here in this part of Catalina, 0.31 inches at the bridge and Golder Ranch Dr., half mile away, 0.29 inches at Sutherland Heights. Coulda been more. Pima County ALERT gage reports here FYI. Most there, 0.47 inches, Catalina foothills, compatible with the southerly flow; clouds bank up more on that side of the Cat Mountains when the flow is mostly southerly. U of AZ rain network, here.

OK, I shouldn’t be the storm grinch… It was great to get something when the models were often oscillating between zeroes and rain out a week or so from yesterday.

December is a benchmark for us: now with 2.11 inches of rain, its the first month of this calendar year with above normal rain outside of July and August. All of this has fallen since we fell into the “trough bowl” in mid-December.

Point, models!

The onset of rain here, that is the first drops, did not fall until about 6 PM, EXACTLY as the U of AZ Beowulf Cluster model run said! It doesn’t get better than that. The amount, too, was exactly that predicted, in the range of 0.10 to 0.50. Think I’ll quit. Yesterday at this time, me, myself and I were anticipating around half an inch, with a 0.20 inches as lower limit, one we just climbed over; 0.80 inches upper limit . Also, thought the first drops to fall, in our little attempt to “Beat the Model” would occur before 5 PM AST.

The transitioning sky yesterday afternoon

Not much seemed to be happened yesterday as the Altostratus clouds thickened and thinned with the sun occasionally popping out strongly enough to produce shadows.

But, as a cloud-centric person, the only variety of human reading this blog, you may have noticed, even been awestruck by the drastic change that occurred between about 2:30 PM and 3:30 PM. Started getting hopeful about some drops getting down in Catalina before 5 PM. Here’s what happened, all due to a surge of moist air that started to come in below the height of the Altostratus in mid-afternoon, and that surge being associated with the approaching upper level trough. First, two “before” pictures of a “stagnant” sky:

DSCN3494 — 1:59 PM. Yawn. Sun bright, no sign of the drastic change hoped for. Clouds are Altostratus translucidus; too much shading overall to be called Cirrus, though a higher, separate layer of Cirrus was sometimes seen.

DSCN3503 — 2:32 PM. Sky changing rapidly. Distant lower layer on horizon. Small Cu popping up around the Catalinas! Here we go!

DSCN3515 — 3:03 PM. Sky changing fast! Looks a little threatening already. Stratocumulus forming under Altostratus opacus and translucidus. Altocumulus also present.
Photo title: Horse under a lowering sky.

The weather ahead

Grim, in a word now. “Trough Bowl” exiting right (east) for an extended period of time, so we’re more or less away from the storm track for awhile. Gradual warming trend, of course, along with that.

HOWEVER, a fantasy storm has shown up, if you’re a fantasy weather forecasting league person, this one will get you a LOT of points. Check this forecast out from the WRF-GFS 00 Z (5 PM AST) global data (rendered by IPS MeteoStar). Summary? Juicy.

2012123100_CON_GFS_SFC_SLP_THK_PRECIP_WINDS_312 — Valid 5 PM AST, January 12th. Colored areas denote where the model believes precipitation has fallen over the prior 12 h. Blue regions denote especially heavy precip.

annnoated valild 5 PM 12 Jan s012 2012123100_CON_GFS_500_HGT_WINDS_312 — Valid for the same time as the map above showing where the 500 mb trough is with all that rain (over LAX).

But, of course, we know when to laugh at progs like this. Go to the ensembles of spaghetti and see if there is ANY veracity to a big trough in the upper levels, one that would HAVE to accompany a rain map like this. “These are their stories”, to quote a TEEVEE line:

annotated valid 12 Jan 5 PM spag_f312_nhbg — Valid for the same time as the 500 millibar (mb) map above. Not REAL hopeful, though there is some chance of verification as indicated by several of the red lines running across Baja. Look for this storm to come and go in the model runs in the days ahead. Overall though, the big northward bulge in the red and blue lines suggest a storm-blocking ridge along the West Coast is the most likely outcome of this mess, with a trough over northern Mexico and the Rockies, the latter too far east to do us much good but keep the temperatures down.

Umbrella, galoshes, windbreaker at the ready

Low forming in AZ. Jet stream (at 500 millibars) goes by/strengthens to the SE during day; therefore, expect rain to begin before 5 PM, but not before 11 AM. It should continue off and on for about 24 h afterwards (in case you don’t watch TEEVEE where YOUR weatherman/gal will be telling you much of what is below. But to make it that much more interesting for you, this: (Cloud pics way at bottom in case you want to skip all this.)

Let’s play, “Beat the Model!”

Kind of a “fun” day for us amateur and highly paid media forecasters since rain will develop where there is none upstream of us; clouds will thicken downward from the Cirrostratus/Altostratus with Altocumulus as the day progresses, with light rain beginning from that process, heavy layer clouds with virga that eventually reaches the ground as the atmosphere moistens up. For example, at this hour (4:50 AM AST) there are NO radar echoes from precip in all of Arizona, somewhat surprisingly.

As part of the “game”, and AFTER laying this out this rain onset timing (rain beginning after 11 AM and before 5 PM in Catalina, that is, best guess, first drops in mid-afternoon), its then fun to see what the very latest super Beowulf Cluster model of the U of AZ says, the best of the best. Its a test of how well you and me are “learning the territory”; “don’t need no model” if you truly understand our SE AZ patterns (when rain occurs relative to air flows aloft like jet streams), know the local and upwind terrain effects because you’ve lived here long enough, can read satellite imagery, etc.

Of course, you can’t really do this except when the weather is at hand. The models are just too good when it comes to beyond a day or so.

Rain amounts?

Here’s how to make an educated guess from “patterns and such”:

First, determine the outliers, those least and greatest amounts “possible”: bottom of precip amount (if things really go bad) here now looks like 0.20 inches (estimated 10% chance of less), top amount (if things really go well) up to 0.80 inches, (estimated only 10% chance of more than that, i. e., everything appears to be falling into place for a substantial desert rain here. The best guess, now that you’ve figured out the top and bottom amounts in kind of a mental “ensemble”, the average of those two outlier forecasts, 0.50 inches by mid-day tomorrow. That’s it.

Since I have busybeelabored these weather points for some time now for the two of you that read this blog, we should all be making the same interpretations today sans model outputs; just eyeballing stuff, doing our own thing, getting a handle on this storm by really THINKING about it, not just soaking in some model output quite yet. Don’t peak yet! This is better than Sudoku, Angry Birds, bajan, facebook, etc.

NOW let’s peak at the U of AZ model from 11 PM AST to get the latest, best prediction for Catalina and see how it matches up with our own forecast based on perusal of a few simple model charts, sat imagery, dewpoints, etc.

Here are the U of AZ Beowulf Cluster outputs, run from 11 PM AST data. The rain arrival in Catalina is shown in the panel below and its between 5 and 6 PM AST, moved up from 10 PM on the run 24 h ago, but a few hours later than our SOP (Seat of the Pants) forecast above.

This is so great! I love this competition! Its weather sports! Its great to tweak the model’s nose, the model with its billions of calculations when maybe you’re own grades in calculus weren’t so great! I am pumped about rain before 5-6 PM!

Now for a comparison of our amounts….

Beowulf predicted amount: between 0.10 and 0.50 inches from this map below by noon tomorrow (when most of it should be over), which shows the heavier rains to the SE of us, ones up to 0.7 inches.

These Beowulf model amounts are often on the HIGH side, and so this is of some concern for us and our prediction, since this model foretells a tenth to a quarter inch or so by 1 PM AST tomorrow when the precip is over except for spotty light passing showers. If that is an amount pushed to the high side, egad!

So, we’re (I’ve roped you into this) a bit on the high side of a model prediction that is known to push rainfall amounts already toward higher than observed. Hmmmmm.

Those lower predicted amounts in the model are probably due to all the low dewpoints we have to overcome with a nice Gulf of Cal/subtorpical influx, and that influx, the model thinks, will end up arriving to the southeast of us. Uh oh. Too late to back off rain amount guess, will ride out the storm; Riders of the Storm Amount, you might say to break up the boredom here a bit.

Now, if you were going on TEEVEE with a forecast after all this investigating, you might, after your educated guess, tweak our own forecast some; somewhere between the original one, which was pretty original, and these model ones. Works out for the best that way. We used to call this, the “man-machine mix”. We still do it.

What can we learn from this exercise?

If those green areas (those having more than 0.50 inches) are farther to the west and over us, we might be detecting a slight eastward bias in the model in these kinds of situations when the moisture roars out of the south-southwest as it will today. No doubt about it, we will be on the edge of the major rains! Fingers crosssed.

I have to admit that due to an internal pro rain bias, I am often on the high side of rain amount predicting.

Wouldn’t it be great if newspaper stories about political events had bylines like, Joe Blow, Democrat, “disclosures” so we might read between the lines some, etc?

Yesterday’s clouds

In a word, phenomenal. So many gorgeous patterns up there in those Cirrus and Cirrocumulus clouds yesterday afternoon, I could hardly take enough photos of them. Like etched glass, this beauty:

I think you should see this….

http://www.atmo.arizona.edu/products/models/wrf_d01_0/wrf_precip_tot.html

and this:

http://www.atmo.arizona.edu/products/models/wrf_d02_0/wrf_precip_tot.html

from our venerable U of AZ Department of Atmospheric Meteorology. They’re both quite good outputs with substantial Catalina rains in them.

Yep, MEASURABLE rain is in the bag! Virtually certain!

Amounts? Mod examined above says we’re in the 0.25 to 0.50 inches, with more, of course, on Ms. Mt. Lemmon and Cat Mountains. Begins tomorrow evening after dark. Watch out for a slightly earlier onset of rain here than the 10 PM AST in the second model, IMO.

Should have some nice looking Cirrus today, and maybe a couple of Altocumulus flakes, too. Don’t forget to log them in your weather diary.

Out of town relatives here today, so quitting before blabbing too much. “Yay”, you say…

The End.

Flatlined

The recording raingauge, that is. A coupla drops is all that fell here in Catalina after some indications of cores around us later yesterday afternoon that were producing measurable rain. You can go to the U of AZ rainlog site to see some local amounts–the Pima County ALERT site is down right now. They’ll have some reports in the mountains and elsewhere, providing it wasn’t snow. The most I’ve seen so far is 0.05 inches, lucky dogs.

Some nice cloud sights on a day of dramatic, icy development. I wonder if you say the first Cumulus/Stratocumulus blob glaciating far to the WSW, beyond Twin Peaks? I thought it would happen first toward the NW-N because the air got colder if you headed in those directions. Yesterday’s cloud highlights, once again pioneering here the “novella-sized”, explanatory caption:

: 3:58 PM. By this time it looked very promising for a few hundredths of rain.

The weather ahead: measurable rain!?

I am sure, that due to our fine array of weather practitioners on TEEVEE (ones that make an incredible amount of money, mind-boggling really, and ones that have the same kind of fun doing weather forecasting as I do) that rain is in the offing for Catalina in the days ahead. So why bludgeon the topic here? Well, let’s guess a range of amounts that could occur, bottom and top, based on SOP-eyeball of weather patterns and goofy, variable progs:

Last night’s Canadian run, has a near miss now, rain partitioned to the SE of us. Booo! But, then rain with a follow up system on Jan. 1st, maybe with some snow in it here. So between the first threat and the second, both happening between the evening of December 30th and the evening of the 1st, the range has to be wild, maybe not useful. At the bottom, we could be completely bypassed in measurable rain from two strong troughs (we’re still in a “trough bowl” BTW), but I guess if you’re in a drought, you only get misses. But, being the optimist, AND with our own USA! model indicating measurable rain as of last night’s run, the range of amounts over the four days of chances, has to be from a trace to 0.50 inches at most. So, a range with all the factors at play is not too useful.

The average of those two, 0.25 inches, often works out as the closest estimate. Let’s see what the U of AZ has this morning… Oops, no update, budget cuts strike some more!

The End.