Category: The weather ahead

“Back door man”, synoptically speaking

Who can forget Jim Morrisey and the Doors, and their raw, lusty,  “Back Door Man“?  Speaking of weather, though, and lows going the wrong way, that is, sneaking in the “back door” as it were, check out this forecast from the Canadian model for the next 24-26 h, an upper level low comes back over us from the EAST!  First, its over Las Cruces, NM (last night at 5 PM AST), and then, as in a shell game, its over there! On top of Nogales, at 5 AM tomorrow morning!

This is great because as the little center retrogrades back over us, with the little water it has in it, we are guaranteed moderate temperatures that will delay the burning out of our wildflower bloom, 2) virtually guaranteed nice sunsets with a few scattered Cumulus clouds around today and tomorrow, 3) will say it again, they should be virgae-ing here and there (snowflakes falling out), 4) Virgae means one or two drops could land on the ground in Catalinaland, perhaps benefitting an ant colony somewhere, 5) but you always hope for a busted forecast in these situations, some errant injection of moisture that will lead to a real shower.  Its not out of the question in these situations, but you’ll have to be watching since I won’t be expecting it.  You’re on your own, especially tomorrow.

The best part of this odd movement?  All the rain that will fall in drought stricken regions like New Mexico and Texas.  Yay!

From the University of Washington Huskies’ Weather Department, this link showing what the moisture pattern looks like over us and the rest of the US.  In this loop you can see how complicated the atmospheric motions are because you are looking not just at the clouds, but also moisture in the air even where the skies are clear.  Enjoy.   And you can also appreciate how darn hard it is for a computer model to get all of this right.   You will see that a moist tongue of air is feeding into our low from the northeast.  By tomorrow, it should have wrapped all the way around, and with luck, a blob of showers somewhere in AZ.  Doesn’t look like it will be here, but rather to the north of us.   Let’s hope this thought is WRONG.   I love being wrong when I think it might be dry!

 The weather ahead model dreamland

The longer term 10-15 day forecasts continue to have a couple of rains here in Catalina.  Rain is indicated on the 17th, 19-20th, and 24th.  This from the Weather Research Forecast model (WRF) -Global Forecast System (GFS) usually pronounced “Werf-Goofus” for those forecasts beyond about a week, which the last few are.  Don’t count on them except in our dreams for now so why did I even mention them?  I like dreaming about what could be.

Yesterday’s clouds

They really wasn’t what was expected yesterday from this viewpoint, scattered small Cumulus, some with virga.  Here’s what we did see, the second photo showing that there actually was one by Flagstaff:

When the jet goes by, the clouds, lower ones, roll in

And that’s pretty much what happened yesterday.   Here are some maps showing what happened as the jet stream in the middle troposphere (500 millibars or about 18,000 feet above sea level) went overhead while deploying to the east and south of us.  The sky change was pretty dramatic as you may have noticed.

First, how the forecast model had it timed, then the sky pictures as it was happening.  These panels, from IPS Meteostar,  are for 2 PM, 5 PM and 8 PM AST (these panels look almost identical, but believe me, that reddish area, indicating the strongest winds, is shifting eastward over southern Arizona!)  By 8 PM AST, the jet is completely past us (third panel).

The last panel, from the University of Washington, is the actual observations and “contour” map for 500 mb at 5 PM AST yesterday, that time when the sounding balloons (“rawinsondes”) went up.   That flag and four and half barbs at Tucson tell us that the wind was over 100 mph at 18000 feet above sea level over us at that time, likely the heart of the jet at 500 mb.  Its pretty unusual to see winds that strong so low.

You can also see in that contour map with satellite images of clouds that the clouds pretty much end south of that wind maximum at Tucson.  At the same time,  you can also see clouds puddled around inside the low in northern Arizona, encircled by a jet stream.  This sight, no clouds or just high and middle clouds, on the outside of the jet core, and low clouds with precipitation, is a common occurrence in the Southwest into the southern Rockies.  Scattered light snow showers were common in northern Arizona yesterday.  It is virtually required before any precip occurs in SW in the wintertime, that you have to be circumscribed (“inside”) the 500 mb jet.   BTW, this “rule” does not hold in coastal regions, such as southern California, or very far east of the front range of the Rockies, or in the summer months,  of course.  But its pretty solid here storm after storm.

And, of course#2, the sophisticated models of today know all about this “rule”, incorporating it in their outputs, and so we weatherfolk don’t really need to look for where the jet max is anymore like we did in the olden days of forecasting.  Still, its simplicity is appealing.

On some occasions, such as yesterday, when only brief virga accompanied those lower clouds, it is a “necessary” condition for rain here, but not always “sufficient.”  It was just too dry, even with this low’s little puddles of lower clouds filling its center.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


 

 

 

The cloud sequence:  1)  1:38 PM:  “nice weather we’re having.”  2) 2:18 PM:  wha’ happened?  Yesterday afternoon’s band of clouds accompanied the jet core passage overhead.  Cool, and it got even cooler.  Was hoping for a sprinkle, but didn’t get it.  There was a brief radar echo north of Catalina about this time.  That was it!

Since we’re still inside this jet/low this morning, there’ll be some lower clouds, Cumulus here and their, likely with a little ice, but too high and too sparse to have rain at the ground.  Most of the dust should be gone now, so a great looking day is ahead!

The weather farther ahead?  Some model fiction below, for March 19th.  Nice scoop jet rises up into southern AZ after scooping water out of the Pacific off California.  Would be a nice rain, if real.

Cirrus and Altostratus ice clouds today; dust and sprinkles ahead

Being a fussy type, I will complain that the sky has not been quite right lately with a continuing, though slight,  smoke layer aloft.  The sky has not been as blue as it should be.  A couple of days ago when it was windy, it was good ole’ Arizona dust made the sky not so blue,most of that brought in from the northwest of us.  Dust as a rule, is not up high in thin layers like smoke can be.  Dust particles are usually too big for that (several to 10 microns or so in size).  They fall out quicker.  The period in this sentence,  font size (12),  is about 100 microns.  Hmmmm.  Wonder if that translates well to your screen?  Probably not.  Oh, well.

Today, however, we will see some interesting Cirrus clouds (it’s dawn now and they’re already here), probably some uncinus types with tufts and long interesting twisty trails hanging down.   Later, before the clearing, these ice clouds will likely be thick enough to call them “Altostratus”, those ice clouds thick enough to produce widespread gray shading.  Only one kind of Cirrus is allowed, in our cloud definitions, to have gray shading and that is the species, “spissatus”, and they can only be patchy clouds that don’t cover a lot of the sky like an Altostratus cloud would.

Here’s where you can see this hook shaped arc of Cirrus coming at us in this 24 h loop from the University of Washington Huskies Weather Department.  Also, you can see it on this map below, also from the Huskies.  Of course, this is a “man’s” (read, adult person’s) weather map, not one of those Mickey Mouse types you see on TEEVEE so much.

What’s the payoff today?  A great sunset as the back side of this blob of ice clouds should be over us by late afternoon.  That will allow the sun to underlight the bottoms of the Cirrus-Altostratus clouds, the latter likely with virga which will add to the effect by having something like stalagmites hanging down in that underlit time.  Well, we are out on a limb here with so much detail, but that’s what I would hope for.

Dust, then sprinkles ahead

In the meantime, the models have been revving up the strength of a trough of cold air headed this way.  Tomorrow it generates the dreaded Tonopah, Nevada, low pressure center, and again, as last week, it will be intense, lots of isobars around it.  Lows like to nest around Tonopah and so that phrase, “Tonopah Low” has been around for decades.   Tomorrow, as the wind picks up in the afternoon, you’ll see the usual coating of dust start to build up on your car, etc.  I wouldn’t wash it until Thursday.

That’s because now, the jet stream at 500 millibars (18,000 feet above sea level or so) will finally get a little to the south of us, and the wind maximum at that level marks lower clouds and precip to the north, and much drier air to the south.

As that jet passes over us tomorrow night, it should mean that by Wednesday morning we have some lower clouds like Stratocumulus and Cumulus a plenty, and with the lower freezing level that comes with troughs, those clouds should be able to produce ice, which in turn means snowflakes that melt on the way down into raindrops.   Well, really stretched that out.  But, then again, I am not a TEEVEE weather presenter who would short change you on technical explanations because they think you are too dumb to take it.  Oops, going over the line here.

Enjoy 1) the sunset. 2) the dust tomorrow afternoon and evening–really, there’s nothing you can do about it; 3) some “glaciating” clouds on Wednesday, maybe with enough stuff coming out to produce a few hundredths even.  Fingers crossed.

“The answer”, as well as a lot of other things, will be “blowing in the wind” tomorrow

What did that mean, anyway, the “answer” is blowing in the wind”?  What a crazy thing to say!   What “answer”?  I never heard it.  Me?   I liked, “Everyone Knows Its Windy”,  by The Association.   Now there’s a song…and “everyone” will know its “windy” tomorrow afternoon just like they said back then.  Very accessible song.  But first this diversion/tirade.

So much for the “plethora” of storms foretold by our models some nine days ago.   It even appeared that Catalina could have a snow day yesterday or today.  Poof!  The Catalina snow day was moved to Boise, Idaho.  Imagine a week before the Tucson Rodeo, it was announced that it had been moved to Midland, Texas!  Well, the models need to shape up!  They’re just awful beyond a week or so, always indicating, it seems, a big storm here.  What have our weather scientists been doing all this time with all that government money they get year after year????  (hahahaha, sort of).  ((Just kidding guys, now that I don’t get any government money to study weather and clouds at the big university where we all know its hobby work and we’d do it for nothing but don’t tell anyone….))

OK, one of the many “storms” foretold in the model will pass over us tomorrow.  It won’t rain.  The jet stream in the middle of the atmosphere will be a hair too far north, and the lower moisture  needed for precip and circumscribed by it will be so close that we will likely see some Stratocumulus off to the NW-N shedding some virga or snow and maybe some small Cumulus here (Cumulus humilis).    Probably most interesting tomorrow, if there is enough moisture in the mid-levels, say around 2o,ooo feet or so, is for a couple of Altocumulus lenticularis clouds to form, those almond like clouds.  Those can be pretty cool, and sometimes cause people to call in about seeing a flying saucer.  Really, its happened.  But we’re smarter.  We know “a” Altocumulus lenticularis when we see one!  In case you forgot, here’s one near Ashland, Oregon:

The low pressure center with this system is going to be pretty intense as it deepens over southern Nevada and then scoots on across Utah tomorrow.  “Intense” means it will have a lot of isobars around its center, and lot of isobars means wind because the pressure on the outside of the low is so much different (higher) than at its center.  I guess that is something; it will feel like a storm is coming, and the relative humidity will go up after the front passes.

 

The End.

 

 

 

 

The Great Divide…

in models.   Could be called,  “delta models.”  Below, nice pleasant weather, nothing much going on or threatening or an imminent storm, whichever you like from last night’s crunching of global data from two great computer models.  The first from our own US output , and the second from  Canada for the same time and day, this coming Sunday afternoon at 5PM AST, February 26th!

Trough along the West Coast(1)?  Or not (2)  Look at the giant trough protruding southward in that Canadian model!  I really don’t know which one will verify, and so I think I will go look at some flowers until this goes conundrum goes away.

As we all know, “the truth is out there.”  But where?  Fingers crossed for Canadian “solution.”

The End




Plethora of storms ahead; Catalina snow day still being foretold for Feb. 25th which is only nine days away now!

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.

The End.

“Hello I must be going”

This trough about to cruise over Catalinaland is going too fast for much precip, “hence”, to use an old word, the title.   (A quote from a Marx Brothers movie of yore.)  We have about 12 h of rain potential in the form of brief passing showers from this morning to this evening.   So, we will be lucky to get a 0.25 inches or thereabouts from this one today.  BTW, if you look up between 5 PM and 8 PM you will see this trough go by at 20,000 feet above us or so.  Better, deeper  clouds before this time, flattening clouds after this time.   Here is the several day loop, as produced by the University of Washington’s Weather Department’s model from last night’s data, and the “panel of passage” from that below, showing the trough (curved belt of winds) right over us.

The purple blob is not a sports related thing because this is from the Husky (purple and gold) Weather Department, but rather shows another puddle of even colder air than today’s trough is predicted to be over southwest Washington, violently spinning as it wobbles on down into the Southwest and gets stuck there for a day or so.

If the map below looks familiar its because it is the modis operandi for this winter where isolated spinning cyclones roll down the West Coast toward Arizona, ending up cut out of the main flow.   And here’s another one with cold, and maybe rainy portent,  for Catalina in a couple of days.  Pretty remarkable how this pattern has recurred this whole winter beginning in early November, and after the long “sunny malaise” of several weeks, has returned.  Awesome.

But wait, there’s more! (I am screaming here as in proper advertising) 

This pattern doesn’t end with this current greyhound of a trough, but rolls along with one COLD trough after another, some dry, some with precip over the foreseeable future (still screaming)!  The West and Southwest are going to answer the Euro cold of the past two weeks with some of our own that may garner headlines!  February 25th, still looks like it might be a snow day in Catalina, rain changing to snow on that day!  Can you imagine? Hang on.

A quote from Mark Albright, U of Washington research meteorologist and former WA State Climatologist before he was fired for saying that the Cascade Mountains of Washington and Oregon still get a lot of snow in spite of GW:

“Yeah, better prepare for snow on 25 Feb according to the new 14 Feb 00 UTC gfs run.”

So, there you have it.

Some cloud shots from yesterday’s gorgeous if cool day.

First Cumulus “pancake-us” (humilis), and second, the “supercooled” Altocumulus layer that announced the approach of today’s trough.

Sprinkles! (coded as “RW- -” if you are keeping a weather diary!) (Its not drizzle!)

Pretty excited up there, as usual.

The Cumulus and Stratocumulus clouds began filling in yesterday, and some shed ice/snow virga in the late afternoon.  With that a few drops of rain (melted snow, of course) plopped down on Catalina.  In case you missed those drops, here they are.

Also, here are a few shots of those clouds, ones based about 7,000 feet above us, judging from their height above Mt. Sara Lemmon.

Note the trails of virga dropping out of Stratocumulus clouds near and over the Cat Mountains in shots 3 and 4.  That was the “worst” of our “storm”  right then when the clouds got their deepest, which wasn’t all that deep, maybe 3,000 feet or 1 km.

By now, too, you will know instantly that the top temperatures of those clouds, to be able to produce ice, were lower than -10 C (14 F).  This kind of knowledge about local clouds and ice, is also a great “ice breaker” at parties and barbecues.  In fact, the TUS sounding suggests that the general top was about -12 to -13 C, with likely momentary tops protruding to -15 C or so.  This would suggest marginal ice formation in clouds with bases as cold as ours were, about -7 to -8 C (about 18 F).  (Strangely Believe It:  warmer cloud bases with the same top temperatures as we had yesterday, leads to more ice formation, and precip.)

Below the photos is the mid-level weather map for the time the sprinkles occurred from the University of Washington.  Since the wind follows the green contours on this map, you can see two things.  The wind maximum at this level (500 millibars) is south of us over northern Mexico, and that the wind was on the verge of shifting to the WNW above us at map time (5 PM AST yesterday).   That wind shift line is referred to as a trough, and at, and ahead of the wind shift line, clouds and precip are stimulated, while behind it, the air gets drier and clouds are mashed down or disappear.  You could even see that happening to the west of us yesterday afternoon while the clouds were heavy and precipitating over the Catalinas.  Those clouds over the mountains, too began to whither, and the virga ended, not JUST because it was heading toward evening and getting cooler, but also because of that trough was passing to the east at that time and the drier, descending air was moving in over us.

In this map, you will also see the much stronger trough over northern California, one that is racing toward us and will bring rain as early as tomorrow morning!  Yay!  However, the U of AZ massive Beowulf Weather Calculating Computer Cluster foretells only about a tenth of an inch from this next storm (here).  Boo!   I will suggest that might be a little on the light side, but that’s because I am biased and strongly want more rain than a tenth from this new storm; I’ll venture 0.25 inches or so here in Catalinaland by Wednesday morning.

More storms after this next one?  Oh, yeah!

The End

Snow day February 25th; “webby” Cirrus

Remember, whether it happens or not, you heard about it FIRST here!  Tell your friends.

Was pretty excited to see this 500 millibar map (about 15,000 to 20,000 feet above sea level) for the morning of February 25th below from our friends at IPS Meteostar.  Pretty cool, eh?  This from the model run based on global data taken at 5 PM AST yesterday.

Note on that map, we are encircled by the jet stream, indicated by the brownish orange regions at the outskirts of this behemoth of a trough, a requirement for winter precip here.  How “be-a- moth-ian” is it?

Check out how abnormal this pattern is in the panel below this one, marked by the dark blue bulls-eye here in Arizona!  So, its really an unusual pattern that is being calculated by the computer.

An aside:  Oddly, we use contours of the height above the ground of a pressure surface for our upper level maps1, and the LOWER that height is (such as over AZ in the top panel), the COLDER the air must be overall below that height.  Low sea level pressure also adds to this height “deficit”, but mainly its the density of the cold air that does it.  The more dense the air is, the more rapidly you reach above you any particular pressure level.  (It really would be so much better to have pressure maps with highs and lows at a constant level above us than having to divert attention for this explanation.)

So, in the panel below, its the LOW HEIGHT of at which the 500 millibar pressure was reached (i. e., 5340 meters) that tells you this is a cold, cold, cold, cold system.  (They say that redundancy is the key to remembering things.  Remember, “534” (decameters) is COLD).

What DOES that the huge anomaly from normal in the bottom panel tell us weatherfolk?

The forecast map for February 25th is a real outlier model forecast, and so we shouldn’t be proclaiming a snow day or anything like that here 15 days in advance because it is such an extreme prediction and likely to go wrong.  So, that’s what I have not done here.

HOWEVER, this outlier prediction shown below, is a part of a jet stream pattern that is developing RIGHT NOW in which low pressure systems and cold fronts will come zooming down into the Southwest from the northwest, one that is likely to go on for  a couple of weeks or more.  I would guess there might well be a hard freeze at some point, though not in the immediate future.  Be ready!

This developing pattern also means more chances for rain here in Catalina over the next few weeks, and with the cool air ahead, holding our late winter vegetation together better even if there is not much precip because it won’t get burned out.  So, overall, good news unless you came to AZ for consistently warm days.  Ain’t gonna happen so enjoy the warmth we have now!

 Webby Cirrus clouds

Yesterday, moving rapidly out of the north, were some “webby” looking Cirrus clouds.  These are always seen only right after they have formed, maybe 10-20 minutes or so after that.   They start out as tiny flecks (which for a moment might be termed, Cirrocumulus clouds), and, possibly, for the briefest moment, may be comprised of liquid.  They then convert to ice and as the individual crystals grow and fall out,  or are dispersed by turbulence,  the tiny flecks become larger and larger and some of the ice falls out in strands.

After about a half an hour to an hour, they are usually just masses of tangled looking Cirrus without much cellular structure.  Here’s what they looked like yesterday in that younger formative stage.  At most upwind end (lower part of photo), the newest flecks have formed, while the older Cirrus elements are broadening and becoming “webby” looking.  The likely ice crystals in these older Cirrus, for some additional annoying trivia, “bullet rosettes”, spikey-looking crystals having columns jutting out from the original “germ” ice particle.  Nice images of bullet rosettes here at the beginning of a long article…

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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1In the olden days, weatherfolk liked to look at “isentropic surfaces” which helped them figure out where the air was sliding upward and likely to form clouds and precipitation before there were computer models. These areas were well represented on constant pressure maps where the cold and warm air was being pushed around.

Catalina Fifteen day forecast updated, “rain possible days” days only shown

5 PM AST data, last evening            11 AM AST data

8 Feb                                                         9 Feb

Th, Feb 9      🙁

F, Feb 10       🙁

Sa, Feb 11     🙁

Su, Feb 12     🙁

M, Feb 13     🙁

T, Feb 14     🙂                                             🙂

W, Feb 15     🙂                                           🙂

Th, Feb 16     🙁                                           🙂

F, Feb 17      🙁

Sa, Feb 18     🙁

Su, Feb 19     🙁                                           🙂

M, Feb 20     🙁

T, Feb 21     🙁

W, Feb 22     🙁

Th, Feb 23     🙁

 

Symbolia:   🙁 = sunny, no chance of rain;  🙂 = rain possible

Forecasts based on WRF-GFS model run from 00 GMT, 9 Feb data.

The End