Cloud-maven – Page 74 – About real clouds, weather, cloud seeding and science autobio life stories by WMO consolation prize-winning meteorologist, Art Rangno

In case you missed it; these clouds and a trace of rain (!)

Once again we were treated to a spectacular sunset, another one in a long series of occasional sunset spectacles, ones that probably go back before the 1900s. We didin’t have color film in the 1800s, so we can’t be for sure if there were spectacular sunsets here except via artist’s renderings, of necessity, of course, analog ones comprised of subjective estimates of sunset colors being seen, not the real ones. I you would like to read about clouds in paintings over the centuries, go here and here. In this second link, you will find that Leonardo da Vinci was quite interested in Cumulonimbus downbursts gave painting them a shot. Its not that great, to be honest.

We meteorologists often sadly ruminate on the career of Leonardo, thinking that had he only turned his attention away from art, sculpting and the like, and instead turned to the problem of weather forecasting, how much farther ahead we would be today. A real shame. Maybe we wouldn’t be relying on spaghetti plots so much.

Also got a trace of rain here in Catalina–you could sure get that smell of rain as soon as you went outside this morning.

SONY DSC — 5:25 PM. Altocumulus opacus under lit by the setting sun. Altostratus clouds were above that layer.

We also had some real interesting mottled-looking skies yesterday due to Altocumulus underneath a layer of Altostratus translucidus. Those underlying Altocumulus clouds were in a layer with a lot of instability (temperature dropped rapidly with height in it) and so there were many little spires (castellanus and floccus varieties). This happens because a little bit of warmth is added to the air when moisture condenses in it, and that bit of warmth was able to drift upward. As that happens the air around those little cells of updrafts settles downward gently to take the place of the rising air creating voids. So, you get clear air spaces between the little cloudlets. I think that’s what happened here.

Let see, what else is going on…. Most of that plume of moisture from the tropics is gone, and so only expect a few Cumulus today. Oh, yeah, big storm about to slam northern Cal and Oregon. Take a look at this map series from the Washington Huskies to get an idea of how its growing in size before hitting the coast.

No rain predicted here in past two model runs (last evening and last night, 06 Z) for the next 15 days, but we are quite sure that’s wrong. Will be looking for that end November early December rain to reappear because I have a subjective hunch it will. If it doesn’t reappear, I will likely pretend I never said anything about it, in keeping with long tradition in public weather forecasting.

BTW, and belaboring the point a bit, here’s an example of how errors in public forecasting SHOULD be handled; “right up front”, in this case, an anonymous Seattle forecaster addresses the terrible temperature forecast he made the previous day following day:

19 19 19_unknown_unknown

(It was a fun time….hope you get a smile out of it)

The End.

Some clouds; excessive excitement over model flip flops (web crawlers: not about shoes or girls wearing them) for late November

Here they are:

Today? More pretty clouds.

The weather way ahead, like on November 29th

Just after I was asserting from this typewriter that the big storm, the Great Wet Hope in late November, was surely bogus, out popped another wet forecast for AZ n the model run crunching global data from 11 AM AST yesterday. Here it is below, first panel. You MAY remember that the nice early rains that we had in November last year were associated with a similar pattern of an upper low center near San Diego.

What to think of this “outlier” forecast, one NOT supported in the ensemble of spaghetti plots (model runs where small errors are deliberately input to see how those runs change from the ones based on the actual data). There very little support for panel 1 in those “perturbed” runs, but there it was again, a big AZ rain!

Well, its still unlikely, but the chance of it actually happening are now much improved. Something out there is causing the model to come up with a good rain in AZ at the end of the month. I did not think I would see any rain again in AZ in any more model runs.

And, sure enough, the model run based on data just 6 h later than the one shown in the first panel, took it away again! See the second map below and look at the astonishing differences over Arizona and the Southwest overall!

I won’t show it, but the “perturbed with errors” model runs that we look for to discern credibility in the longer term forecasts like these, STILL does not support much of a chance for a rain to be realized on the 29th.

But, that second appearance of an “outlier” in another model run….hmmmmmmm. Will be watching for a return; you start to get a feeling that it might well be seen again.

As I finish this blog blurb, the 11 PM global data should have been crunched by now, and will look to see if there is yet another huge change (well, there are always large changes, but here, I’m talkin’ for us!) Will let you know in about 2 minutes…. Stand by, generating new web window now…..

Oh, my gosh! Its changed again (3rd panel) to a huge West Coast troughy situation, completely different than the run at 5 PM AST last evening with the big ridge over us (bulge to the north). I have to post this latest map, again for late on November 29th. The situation you see in the third panel leads to another big rain forecast in AZ, though a couple of days later, early December! This is so great! Compare the second and third maps.

Now, you can really start to put some credibility in the supposed “outlier” forecast and, as a discerning meteorologist, say to the spaghetti plots with their little deliberate errors, “Go to HELL! You’re missing something big out there with those puny errors you start with.”

Calming down now, well, you can’t cast the thought of warm dry weather (seond panel) for late November out yet, but something IS being missed out there, which makes this an exciting period–just to see what happens. Though an admitted precipofile, at least here in AZ, not so much in SEA, I am putting my mental marbles on the trough in the West depictions now. Just a hunch.

The End.

Computer model calculates substantial AZ rains on the 29th, but is it real?

Let’s check, could be goofy, but its all we’ve got right now for a rain, the map below valid for Thursday, November 29th, 5PM AST. The whole series is here.

Of course, the weather sophisticate would want to see what’s “up top” at the same time; see where the jet stream is (brown areas on the map below). Seeing that the J-Stream is right over us, and also being an Arizona precipophile, he might opine, “I find this quite credible.” It also shows massive cold in the West, Rockies, and northern Plains States.

“Who you gonna call”, to establish credibility? Storm Busters! (Or not) Yeah.

Here is the NCEP “ensemble of spaghetti” for this same time, from the SAME model runs, showing the huge system in the West:

Summary of spaghetti: There is no indication of a major cold trough/storm in the West, as would be indicated by a bunch of blue lines dipping down to AZ. Ain’t there.

In fact, its kind of shocking to me that there isn’t the slightest indication of a major trough in this region. So, the actual model run shown in the first two maps turns out to be an extraordinary outllier; some goofy measurements somewhere out there on our globe, got into the model and produced a spurious huge trough, cold and storm.

Amazing isn’t it, that there can be little tipping points due to slight errors in measurements somewhere that can wreck the whole thing, make giant changes from what really is going to happen? And to detect them, that’s why we do the “ensembles of spaghetti.”

What will happen in the next model runs? That trough on November 29th will almost certainly go away. So, the rain in AZ is “real” in the model run, but not real in life. And as we say here, “dang!”

After viewing this spaghetti plot, our AZ precipofile would now look back at those awesome maps for November 29th, and dejectedly, or even with model rage, and say, “Those maps from last night are full of….oops…. have no credibility whatsoever. What is the matter with this model it could even begin to calculate such a ludicrous pattern. Who’s the goofus out there that reported some bad data?” He would not mention a chance of rain late in the month to his neighbors.

This was meant as a “learn you and me up on spaghetti plots” module.

Yesterday’s clouds

Mostly very thick Altostratus clouds with lots of embedded droplet clouds, ones like layers of Altocumulus clouds inside them. Made for a very dull afternoon. Here are a couple of shots:

DSCN3232 — 3:42 PM. Mostly Altocumulus here, some slight virga.

DSCN3234 — 3:52 PM. Same view, 10 min later. Can you see what’s jetting at you?

The End.

Another big Cirrus streamer from the Equator heading our way!

Well, when there’s no rain in the model predictions for 15 days, you have to get excited about something….

Like a solar flare, there has been another massive ejection of high clouds from the equatorial region and its heading toward Catalina, AZ. Here, from the Washington Huskies Weather Department¹, is a 24 h loop of the event. Hope our cell phones still work. Here’s the latest still image:

annotated 201211141030 — Satellite image for 3:30 AM AST supplemented with various interesting annotations, some of which are correct.

What are the ramifications of ejected Cirrus coming all the way from the Equator to Catalina? Pretty skies, sunsets and sunrises, which is quite important to us humans. Also, when it starts arriving today, we’ll have milder nighttime temperatures. Yes, even Cirrus clouds cut down the outgoing longwave radiation leaving the earth’s surface at night, and of course, moderates the incoming visible (shortwave) radiation (sometimes called “sunlight”). We don’t want to dumb this down too much.

After 9-11, when all the aircraft stopped flying for a week some guys at a small university, one so small I don’t think it even had a football team, found that the daytime and nightime temperatures were affected by the lack of contrails. Daytime temperatures were a spec higher and nighttime temperatures a tiny bit lower, suggesting that even CONTRAILS have an effect on the weather and climate. It was an important finding. Of course, without a football team I am clueless, as are you are, concerning what university those findings came from.

You know what gets a lot of us scientists about that contrail study after 9-11, is that something simple and important was done that I (we) could have done had only we thought of it. We’re kind of bitter about it. Might have got a raise, too, got the name out there. Citation index fluffed up some. We’re dealing with a lot of loss here. Heck, you probably could have done this, too, it was that easy.

The study of contrails is a pretty big topic these days, though the effects are deemed small for the present. Here’s a short article for you. Here’s an unrelated one, one about smog’s effects on clouds, but one you should read, anyway. Might be true. Reading the second one is like doing an extra pushup. Its good for you. And me since one of the authors of the second article (Danny Rosenfeld) criticized me (and Pete Hobbs) royally in print in the late 90s only because we said his work was invalid. Show’s I’m magnanimous, following the ideals of science meaning that as scientists we have no personal feelings about our detractors.

Yeah right. Check the climate blogs and those ones who refuse to allow other scientists to even comment on their work! Its a hideous situation out there now, far from the ideals of science where one WELCOMES criticism. But, I diverge….getting worked up when I should be concentrating on clouds.

BTW, that little blob of clouds north of the ice cloud mass coming at us, is due to a little disturbance that will hit the coast of Cal in a few days. With it, the clouds here will get pretty thick, probably as will happen later today or tomorrow with the ice clouds, causing the optical depth to exceed 4.00000000000 (4).

What does an optical depth of four mean?

That means that the sun’s position is not discernable. (Also, can’t be a Cirrus cloud, BTW, but rather Altostratus if its an all ice cloud). Optical depth is usually something used by the smog folks. A really clean sky has an optical depth of 0.05 or even less. Smog laden skies, such is the coastal areas of southern California, or back East on humid days in the summer, have optical depths of 0.2-0.5 at times, horizontal visibility might only be a mile or three; the leaves are gray and the sky is brown, as the song says. Aren’t we happy we don’t have that kind of smog?

Looking way out, just now, I saw this in the ensemble of spaghetti, thought you should see it, too.

While no weather beyond warm breezes and high clouds is portended here, where would you really like to be in the West in two weeks or so for some really heavy rains? Can you tell? What’s a place I mention too many times when comes to Cal rains? Yes, the King Range around Shelter Cove, between Frisco and Eureka. This plot gives high confidence to major flooding in northern California in the 10-15 day window. Why? Because so many of the blue lines (564 dm height contours) dip down toward the tropics in the eastern Pacific in support of the actual forecast from last night (represented by the yellow lines). Remember that the blue lines result from small errors put into the model runs at the beginning to see how robust a forecast is. The wilder the spread of the lines, the less reliable a forecast is. The more they group together, the more robust, more reliable a forecast is. They look fairly bunched up in the eastern Pacific, and this is the reason for having this plot here today. I suspect we’ll be reading about heavy rains in Cal during that 10-15 day window. It will be fun to see if we can make such a call so far in advance!

The End.

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1Nobody knows your university by its scientific accomplishments, but only by its athletic accomplishments. Its been written up. I certainly wouldn’t. If online universities could have football teams, it might be the end of “brick and mortar” universities.

In case you were wondering where those high clouds came from…

From down there, as seen here.

More of those high clouds, and we hope with some Altocumulus, will be dropping by from the deep tropics over the next week or so.

Camera alert: Sunsets and sunrises will be spectacular at times over this period and with more than one layer, there is more than one dominant color.

The saddest headline ever read re the coming winter? From the Climate Prediction Center here:

“El Nino watch discontinued”

They’d been talkin’ up an El Nino this winter and spring for months! And, as you know, El Nino occurrences tend to cause wetter winters here. Doesn’t mean we still can’t have some good storms, but the odds are lower.

Yesterday’s clouds

Next rain in 9-10 days?

The NCEP model, using last evening’s global data, produced some green pixelation in Arizona (light rain areas are green in the model run output) for Monday night into Tuesday, November 19th-20th. However, look below at the NOAA ensemble of spaghetti plot for that day. I don’t see any rain here. Do you?

Cloud-maven juniors would be so scoffing at the thought of rain in Arizona in a computer prediction that is associated with a spaghetti plot like this for that same day! For confidence in rain that far ahead here in Catalinaland, we would need a plot that shows something like you see over Japan (upper left); the lines all squeezed together. But you don’t see them here, do you? They’re a mess, indicating the model is generally clueless about what will happen here in 9-10 days. So, while it could still happen, it has to be considered a very long shot.

MOnday Nov 20 spag_f216_nhbg — Forecast map for Monday, 5 PM AST.

Here’s the WRF-GFS model output, rendered by IPS Meteostar that shows rain in AZ, a model run in that had this green pixelation (areas where rain is forecast to fall in the preceding 12 h) for overnight Monday into Tuesday morning, the 19th-20th. Nice, but wrong. The entire model run, is rendered here in case you think I am lying about this.

I’ve added an arrow to help locate Arizona for you.

So, in view of the ensemble of spaghetti, can’t count on green pixelation remaining in Arizona in future model runs. Not starting out as a good day today.

Yesterday’s clouds and skies overall, how nice.

First, the “stratiform” clouds that were still “sprinkling-its not drizzle” as daybreak came. Then the blue skies dotted with Cu.

Raining hard here at 4:08 AM

Little cell going by (aka, weak Cumulonimbus). I hope you’re up to enjoy the sounds of a good cellular rain on the roof. I feel like another song coming on. Ooops, same one, but its a good one because it not only has rain and thunder in it, but also pathos¹. (I thought the thunder in this song gave it a lot of dramatic impact, and we had some thunder NE of Saddlebrooke yesterday afternoon around 2:45 PM.)

Cell has added 0.03 inches to our 0.13 inches and this morning’s total is now a quite nice 0.16 inches on top of the 0.30 we got yesterday. Raining harder now after it let up! Oh, that didn’t last long. Dang.

Total here at 6:55 AM: 0.18 inches! Two day total here, 0.48 inches.

This is so great since this second part of this two part storm was “marginal” as a rain producer, might have only produced 0.05 inches as the bottom estimate for rain, made a few months ago (just kidding), with a top possible amount of 0. 40 inches. So, we’re getting close to the middle of the prediction range made so long ago, 0.225 inches, a prediction you may remember, one that was based on spaghetti.

This rain is associated with the strong cold front that passed through Catalinaland about 2 AM, just after those strong gusts occurred, 30-40 mph last night. Here’s what the nighttime temperature did, drop 14 degrees!

And, as you no doubt know, the atmosphere pressure goes up instantly as the cold front goes by and the colder heavier air piles on top of you. (Time hacks don’t match on these charts for some reason–have not noticed that before….)

annotated 2012101009_Cat temp drop — Arrow points to passage of cold front at Catalina, AZ.

annotated pressure 2012111012 — Atmospheric pressure on top of you here in Catalina, AZ. Arrow denotes cold front and rise. With this denser air, you may notice that you’re having difficulty getting up, moving around as you push more “molecules” of air around for any given movement compared with yesterday when the air was not so dense. It also might be because you have more clothes on today…. Hahahaha

Here’s a really nice link to radar happenings locally from The Weather “Underground” (nothing to do, BTW, with “The Weathermen” of the 1960s-70s even though it sounds like it).

Learning module….skip if bored already.

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One of the things that is happening right now at 5:01 AM LST, is that cells are appearing on the radar or intensifying as they move toward Catalina. This happens a lot when the air at cloud height is moving toward the Catalinas and upslope toward Oracle and Mammoth, getting squeezed between the Tortolita Mountains and the Catalinas. That lifting makes the tops go up to higher colder levels, and when the tops to the west and southwest are too warm for ice formation, say above -10 C (14 F), then just a bit of lifting triggers ice formation making a cloud “visible” on radar as the ice grows in size into snowflakes, maybe collides, too, with some itty bitty cloud droplets (too small to be seen by radar) growing even larger and falling faster. This is maybe the biggest reason why Catalina has so much more rain than upwind areas (17 inches annual rain) compared with about 11-12 inches upwind. Most of that difference comes in the wintertime in situations like this, and so some extent, like yesterday’s more general rains.

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What’s ahead for today?

Back edge of this rain band, more or less solid clouds dotted with deeper ones producing rain, is on the doorstep.

Here it is as of 4:45 AM from the U of AZ Weather Department Satellite Facility, with a CONSIDERABLE amount of arrows and writing on it:

So, according to this “diagram” the back edge of this band on the sat image should be here by no later than 10 AM today, that is, chance of additional rain up until around 10 AM in a brief shower, but only a hundredth or two likely. After that, just clouds, probably a lofted Stratocumulus layer, then a widespread clearing with scattered to occasionally broken Cumulus.

Since it is so cold aloft now with the freezing level around 5,500 feet (snow shower now (7:29 AM) on Samaniego Ridge), ice will like form even in modest Cumulus clouds this afternoon, that means virga or maybe an ISOLATED light rain shower possible through around dusk.

Yesterday’s clouds

Here are some of the best cloud photos from yesterday, such a pretty day here in Catalina, where Cumulonimbus clouds stayed just to the north of us off and on all day.

The End, at last!

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¹Actually, I made it sound like I wrote this song in yesterday’s blog, but in fact, I did not, though I WOULD have if I had thought of it. Note that the person who uploaded this song to You Tube, did not know how to spell, “Cascades.” No wonder we’re falling behind.

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Hel-lo-ooooo, its 3 AM and raining, and you’re not up

That’r right, real cloud maven juniors get up in the night to experience all the raindrops they can after a droughty period. Been up since a little after 3 AM; its now 4:07 AM with an accumulation of 0.16 inches, a Dust-B-Gone amount, of which I have experienced exactly 100% of it as an audible event on a thin Arizona room roof. Its great to have a thin roof so you can listen to the rhythm of the falling rain. I feel like writing a song…

Quite nice, too, to hear this after SO MANY weeks of nothing except litho and bio meteors, i. e., dust and spores, Burrow weed and desert broom seeds floating in the air, and other untoward aerosols and particles that are best left on the ground.

Listening to rain on a roof can be used for meditation purposes, letting life’s questions resolve themselves without really trying, like, what are those ants going to do NOW with their wonderful little symmetric cones? Did they know it was going to rain and close the hole up in time? Note tire tracks and resiliency of ants… Says something about bouncing back after a disaster.

Why is it raining? Got us a little stream of tropical air in the mid-levels of the atmosphere that had been meandering off Baja. Mods saw this coming, maven was skeptical, but what’s great NOW is that we here in Catalina seem to be getting the most out of this little plume of moist air. Here’s a sat loop:

First, this just in: 0.22 inches at 4:22 AM! I am beside myself with joy!

This just in (again): 0.30 inches TOTAL by 6 AM. Fabulous.)

Here is the sat-radar loop from IPS Meteostar and below, these sat and weather map images from the U of WA Huskies Weather Department showing the little blob of clouds “that could” (get here and rain on us). You can see how that Big Trough (over Pac NW) swept it toward us, kicked it in the butt. There is some writing on these images to help you understand them; point things out for you. I really went out of my way here.

annotated 201211090900_300mb — Today, at 3 AM as the rain begins.

Notice the big gap between the little cloud patch over us in the 2nd map for 2 AM this morning and the band coming across California. Means there’ll be a break in the rain here until late tongiht or early tomorrow morning when the Big Cold Front with the Big Trough arrives here. Until then, just the gusty winds and some pretty clouds, filling in from time to time, maybe some rain visible to the north of Catalina.

Yesterday’s clouds

Below are a couple of photos of those nice Altocumulus castellanus with virga that came in rolling in across the sky suddenly yesterday afternoon. Actually, when they grow into real shower preoducing clouds, they’re also transitioning in name to Cumulonimbus (Cbs) clouds, though they are weak ones, not like our summer variety.

If you really looked, you could see that the bases of the Altocu/Cbs were well above the freezing level by noticing all the snow virga dropping below the bases. The TUS sounding suggests that the bases were at 14,000 feet above sea level (around 11,000 feet above the ground) and at -5 C (23 F).

Too dry underneath for much of the precip to get to the ground.

The rain before the storm

Our models have been showing a batch of scattered showers on Thursday for some time, a precursor to the Big Change day on Saturday. Skepticism prevailed at this keyboard since there didn’t seem to be much going on off’n Baja where this moisture was supposed to come from. Here is an upper level chart demonstrating that assertion: don’t see any contour circles out there do you? Just a wandering, single contour off Baja, not much going on compared to that behemoth trough blasting the Pac NW.

But, by golly, there IS a patch of clouds and moist air in that weak circulation off Baja that is going to be swept out of the eastern Pacific by the “broom” of the flow around that giant upper trough that moves toward us from the Pacific Northwest into the Great Basin area on Friday and Saturday, generating a powerful low center at the ground as it does. Some Cumulonimbus clouds have even formed off Baja in this weak tropical circulation, and here, that should mean some nice Altocumulus castellanus clouds tomorrow, likely with virga. Cirrus will also be around for a real visual treat. As we remind reader (s), get your cameras ready. Could be some spectacular scenes; sunrises and sunsets.

Here is a link to what is going on out there (from the Huskies, of course, the Washington ones.) Those white specs that appear and disappear off’n Baja are little Cumulonimbus clouds, showing that the middle levels of the air out there is very unstable. (Those are a type of Cumulonimbus that sit on top of boring Stratocumulus clouds, FYI)

What could be tremendous for us is that the Wildcat model (here), has off and on showers from this tropical surge for no less than 24 h! Amazing. I just now saw this from last night’s run.

Could it happen?

Well, this model is smarter than you and me, and so you figure there is going to be a lot of mid-level clouds and castellanus (spire-clouds) the size of small Cumulonimbus clouds as we see offshore now in the sat images. And with that, the likelihood of some thunder here and there. This preliminary action is getting to be so much greater than I possibly could have imagined; rain in the immediate offing, not waiting until Saturday!

One of the things that will happen tomorrow, too, with this little slug of moisture and clouds, is that the lower level humidity will be increased some as well; it won’t be just middle and high level clouds that increase. That will help juice up the air before the Big Trough gets to us, maybe helping that Saturday rain out just a bit. Ironically, this little thing ahead of the BT might well produce more rain in a thunderstorm than the BT with all of its drama, the strong SW winds on Friday, frontal passage and wind shift to the NW overnight or early in the morning, and such.

With BT, strong winds are guaranteed on Friday, it will really seem like the season has truly changed which is kind of cool. Rain still looks marginal from BT; could be just a few hundredths, though the “window” is still there for more than a quarter of an inch if everything is optimized (storm hangs on longer, jet stream is a little farther S than predicted, etc.)

The weather ahead

It does appear that we’re headed for a new wet regime after our long, warm dry spell since mid-September with persistent high pressure over us and the West Coast. Last night’s global data, crunched by our super model WRF-GFS, had rain on SEVERAL days after these two chances go by tomorrow and Saturday due to the passage of more troughs plunging in from the Pacific. The pattern we’ve had, warm in the West, cold in the East is fairly common one because the jet stream seems to like to do that, sometimes, as we have seen, for weeks at a time.

But now that pattern is disappearing and a new jet stream pattern is taking shape, one that will likely mean normal or above normal rains here over the next month or so as this new pattern gets locked in for awhile. With those once-in-a-while rains will be below normal temperatures.

A pattern like this, “cold in the West”, almost always means warm in the East, and so the really cold air those unfortunate folks affected by Sandy have been experiencing will soon be gone, a good thing.

Here’s an example of a trough predicted to be over us from last night’s global data on November 15th:

Nice, huh?

The End.

Precision forecasting of the next Catalina rain (an experiment)

After looking at last night’s model run, and the many model outputs before last night, here’s the “skinny” as this forecaster sees it (“as I see it”, means this is an experimental forecast to see how close it can be called. Its gaming the weather. Here goes:

There is a 100 % chance of rain in Catalinaland on Saturday, November 10th (sometimes referred to as “football day” this time of year). The rain will begin between 5 AM and 11 AM that day. It should last a couple of hours or maybe a bit more.

It will be horribly cold. You don’t want to be out on Saturday, November 10th.

The amounts?

In a “mental ensemble” of the best and worst outcomes for this rain situation, I see a bottom (only a 10% chance of LESS) in this rain event as a puny 0.05 inches and the top (10% chance of MORE), 0.40 inches (nice!). To get the best estimate of what will actually fall, take the average of these two, 0.225 inches. So, that’s my forecast, 0.225 inches on Saturday here in Catalina. Get your micrometers out! hahahaha.

Here is the model depiction (WRF-GFS from NCEP rendered by IPS Meteostar) of the air flow at around 18,000 feet above sea level. Recall that rain is pretty much impossible here until the maximum wind at that level goes by. Below is a snapshot of the air flow and its speed for Saturday, November 10th at 10 AM. As you can see below, the red core of the highest winds at 18,000 feet (aka, 500 mb level) is passing overhead then. So, expect it to be raining by then around here. The whole loop for this level is here.

I think you can do this today, cut it so finely, and so far in advance of the event, because the model runs have been SO consistent and in the NCEP’s (Nat’l Centers for Environmental Prediction’s¹), “ensemble of spaghetti” outputs, have been indicating a strong signal, high reliability for this event for a good ten days. So, count on it, though obviously the timing may be off a few hours, but that’s about it. Everything else is pretty much a “done deal”, and you don’t often get to say that this far out (six days). Below this jet map is a snapshot of the high reliability of this forecast as seen in spaghetti. Packing together of the blue and red lines indicates where the forecast is extremely reliable, and that’s what you see throughout the West from last evening’s plot.

Since this is the cloud-maven blog and not the forecasting-maven blog, I’ve added a pretty cloud picture at the very bottom.

The End.

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¹formerly, and more simply, the US Weather Bureau)