Whiff


How sad.  A few contours to the south of us, that jet to the south of us, that is,  and we’d have got our tenth or more inch of rain.  But no.  That trough over southern California and northern Baja had to zip out and “up” (that is, to the northeast) like a jet taking off from an aircraft carrier.  Gone now.  All we’ll have is leftover wind and a threatening looking, but too shallow a deck of…….Stratocumulus.   Too warm on the top of this layer this morning for ice formation, and that, as you know here in AZ, means that nothing comes out the bottom because the droplets in the cloud are too small to fall out.

But yesterday afternoon, an ice bonanza!

Alas, those Cumulus and Stratocumulus complexes were too high-based for the considerable ice crystals and snow forming in them to reach the ground as melted drops,  except for “sprinkles-its-not-drizzle” here and there1.  Heck, the drops that made it down around 5 PM AST weren’t even that big.

I wonder if you saw the rapid transition to ice-producing clouds yesterday.   Not much going on up to 1:30 PM.  Then, all of a sudden, it seemed, there was ice almost everywhere in those little clouds.  It was fascinating since they did not appear to be deepening upward to lower temperatures.

Let’s review yesterday with a long cloud harangue, starting from that wonderful sunrise with an Altocumulus lenticularis undulatus (has something like ocean waves or rolls in it to produce this where the air is rising and falling to produce cloud, then clearing), here is yesterday.  Hmmm.  I wonder if you remember where THIS sentence started?

Next, that promising scruff of cloud (I would call it, Stratocumulus) topping Mt. Sara Lemmon.  It was promising because with cloud bases lower than the top of Mt. Sara, there’s a better chance of rain reaching the ground.  But, up they they went as it got warmer, a usual thing.  Has to be a flood of water vapor coming in to overcome the rise of cloud bases with daytime warming.   As boffo as that trough looked over southern California, it couldn’t really “bring the bacon” if bacon was moisture that is.

We did have a lenticular cloud, too, for awhile.  Let’s see that, too.  It will be good for you.  Notice how it is near the same spot as the “undulatus” cloud?  That’s what lenticulars do; they have favorite haunts.  When the flow is from the southwest, this is where they are going to be, over and over again, downwind from Mt. Sara L.

 By mid-day and early afternoon, Cumlus cloud bases were well above Mt. Lemmon, a couple of thousand feet at least.  Here is a mid-day shot of those non-ice producing, Cumulus fractus and humilis clouds next.

 

 

The first Cumulus photo was taken at 1:50 PM, and if you were a real sharpie, you would have seen some tell tale vales, but probably only Mr. Cloud Maven person did, they were that faint.  But here in this second shot of Cumulus humilis and such, you can PLAINLY see that in the center, one of those little guys has converted COMPLETELY to ice.  It was pretty amazing to see that in such small clouds.  Soon the whole sky was filled with clouds “icing out”, becoming nothing but ice crystals and snow flakes.  Here are some more photos of that stage, including a short rainbow demarcating where the snow was melting into drops.

 

 

 

 

 


So what caused all the ice to appear in clouds that didn’t appear to be growing in height?  Well, first of all, by the end of the afternoon, they were certainly colder at cloud top, so that would explain the late afternoon ice everywhere.  Also contributing, was that is was getting colder over us as the day wore on as that trough approached.  So, even if the cloud tops stayed the same height, they would have gotten colder.  Finally, dust has been known to have a role in causing clouds to glaciate at higher temperatures than if there was no dust getting into them.  This is something that we saw happen in Durango, Colorado during a randomized cloud seeding experiment when dust storms hit and “ice nuclei” measurements shot up.  So, dust, too, may have had a role.

The afternoon TUS balloon sounding suggested that the tops were only about -15 C (5 F), maybe -17 C in one that momentarily bulged above the main cloud top level-Cumlus clouds do that.

However, the amount of ice is not commensurate with a temperature that “high” and so I reject the sounding temperature.

I think, with bases around -10 C yesterday afternoon, that for clouds to produce as much ice as we saw, they would have to be -20 C (-4 F).  I think maybe the strong temperature drop to the northwest from the balloon launch site might have played a role, that the temperature of the balloon instrument was correct, but it was a few degrees colder over Calalina and to the northwest of us.  That “surmision”, a deduction,  you get from, say, the 500 mb map where it was far colder at Flagstaff than here.  Of course, you might think I am lying, and just made that last part up because I am really clueless about what happened.  Due to your doubt, I will now post the 500 millibar map from my home university so that you can see I did not make this up.

As you can see, while TUS is only at -18 C, Flagstaff is -23 C, and San Diego is -28 C!  So going to the NW (a heading of 310 degrees) from the balloon launch site their at Davis-Monthan meant it was a LOT colder in that direction, mile by mile even maybe.   Also, you can see by Flagstaff’s wind, that the jet core at this level had not passed over us, a key to wintertime rain here.  Never did.  Hence, a “whiff” on this storm, to use an old word right before a new word from baseball, as in, “he whiffed on that slider” (struck out). I can’t believe how I am educating you today!

The End.

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1 Sorry, have to carry on this theme about what is drizzle and what’s not.  You should find another TEEVEE weather presenter if he or she calls what happened yesterday for a few minutes, “drizzle.”   Rain and snow mixed is NOT “sleet”, by the way, either, another looming corruption of our weather terminology.

Windy; slight rain foretold overnight

Doubtful to me, but a tiny amount of rain (less than o.10 inches) is foretold by the  massive U of A Weather Department Beowulf Computer Cluster for Catalina overnight.  Check this out.  Would be very nice, even if just a dust settler.  BTW, you should wipe down your rain gauge collector funnel since all the dust from the past few weeks might prevent some drops from rolling from the outer collector into inner magnifying tube.  Hey, maybe some WD-40 on the collector funnel would really get those drops in there!  Hmmmm.   Never done that.

Below, this morning’s Tucson sounding showing a bit of moisture at 550 mb or about 12,000 feet above Catalina (where the two heavy lines pinch together some).  The one on the right is the temperature and the one on the left, the dewpoint temperature.   This suggests their may well be some “flying saucer” clouds, Altocumulus lenticularis today, one that hover in place while often expanding and shrinking in minutes as the incoming air moistens and dries.  There are also indications for clouds at Cirrus levels, above 300 mb or 30,000 feet, and down around the tops of the Catalina Mountains; those would be Cumulus fractus, humilis, then later fattening up to mediocris as afternoon and evening wear on.  They will be marginal for producing ice during the day (which would mean virga), but, if the model is correct, they would deepen upward farther so that ice does form in them (tops colder than -10 C or so) and cluster into groups with appreciable virga and some rain overnight, probably looking more like Stratocumulus, a sky-covering layer  by morning.

You can also perhaps see that the winds are pretty strong over us already.  Not much now, but as the sun heats the air at the ground, and that air rises, compensating downward motions occur as the air above takes the place of the air that is warmer and gets lofted.  So, as we usually see, the wind will be picking up drastically this morning as both that happens, and those stronger winds above us are “mixed downward” in turbulent blobs we see as gusts.   Also, that that Tonopah low pressure center strengthens as it passes by to the north.

You can follow the development of this “Tonopah low” now located, of course, near Tonopah as of 5 AM AST today, here with the University of Washington Huskies’ surface map loop.  This former Husky employee notes that the Washington Huskies had a great basketball and softball weekend.   Oh, also, the loop will update automatically.  Here is the NWS detail on wind and stuff today for Catalina.

 

“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




Dark clouds but no rain yesterday. What happened?

Quick answer:  1) drops too small to coalesce and form ones bigger ones ; 2) no ice in ’em, for the most part.

Read below if you want a LONG discussion about yesterday; dull photos way below

Let’s talk about it, though probably more than you want to.  You’re probably a little down because it didn’t rain yesterday, hour and hour though it looked like it should, except for a couple of “sprinkles-its-not-drizzle” drops.    You probably had to use your headlights in the middle of the day like people in Seattle do.    It began to clear up some, gradually, in the afternoon. Here are a few of scenes below, beginning with the morning overcast, with the last two shots between 4 and 5 PM AST as the clearing was underway.

So, what kind of clouds are they?  Well, Stratocumulus in the first shot, in the second shot a higher layer of Altocumulus or water-topped Altostratus1 is underlain by Stratocumulus and Cumulus clouds  (when the bases are more isolated, we call them “Cumulus”;  when they are more connected together, we hedge the name toward “Stratocumulus”.)

The third shot, showing Stratocumulus looks particularly ominous, probably the darkest part of the daytime was here around noon AST.  A shot toward the mountains next shows the underlying Stratocumulus and Cumlus below the higher layer of Altocumulus/Altostratus.  These clouds can’t be “nimbo” this or “nimbo” that because there is no rain to speak of falling from them.  (“Nimbus” means rain in Latin.)  Note the good visibility under all of the clouds; no precip there.

Finally, with the breakup of the overcast, shown in the last two shots, we can get an idea of the thickness of the lower clouds, at least at that point, about 2,000 to 3,000 feet at most.  Also in those last shots you will notice that the higher layer has moved away or dissipated, and with a bit more heating, the clouds are tending more toward Cumulus rather than Stratocumulus.

The higher layer, located at Altocumulus level, about 12,000 feet above ground level, was actually the cloud layer producing the sprinkles, and was a key player in how dark it was; two layers, naturally, stacked on top of each other, will make it darker looking than just one, especially, in this case, when they are both pretty shallow.   And with a top at about -18 C, you can almost be assured that the top was composed of mostly droplets, not ice crystals.   A droplet cloud reflects much more sunlight back into space than ice crystal clouds like Cirrus and Cirrostratus.

Anyone still reading?  I’m doing my best here…

That last photo demonstrates that in spite of having a little rain overnight, and even during the day, there was a lot of haze/smog in the air.  It wasn’t washed out by rain.  And, the more clouds get bunged up with aerosol particles on which drops can form on,   the higher the concentrations of cloud droplets are in them, and the smaller they are as a result.   Smaller drops cause more sunlight to be reflected back into space, and when that happens, the bases look darker.  In Seattle, in our airborne studies, it was usually the case to have darker based clouds downwind of the city, and light gray clouds near the coast and offshore, even when both cloud layers were about the same depth.  However, there are natural sources, like volcanoes that can also affect clouds this way.   For example, “VOG” (volcanic smog) in Hawaii darkens clouds there because VOG has particles that can form drops in clouds.  I seen it myself and I know a dark, polluted cloud when I see one!

What happens when you get smaller drops in clouds, as smog produces in them?  It makes it harder for something to fall out the bottom in two ways.

First, in smog filled shallow clouds, drops don’t get big enough to collide and stick together to form larger drops (something that happens when they get to 30-40 microns in diameter (about a third of a human hair in width).  But, even in the event that could have happened yesterday, drops got that large, the result would have been only TRUE DRIZZLE, fine, close-together drops that go under your umbrella if there is a breeze of any kind.  Very tough on people who bicycle and wear glasses.

The more important key to not raining clouds, was that the clouds did not have, IN GENERAL, cold enough tops to form ice crystals.  The lower ones seem to have topped out around -5 to -7 C (23-20 F),  temperatures at which smoggy clouds with itty bitty drops cannot produce ice.  

The higher layer, seen in the second and fourth shots, was just cold enough, about -18 or so at top from the morning TUS sounding, to form a few ice crystals.  Also, being higher, it was probably not impacted as much by smog.

Quitting here, brain exhausted.  Hope this is somewhat comprehensible.

The End

1The smoothness of that higher layer is due to ice crystals falling out the bottom, obscuring an Altocumulus-like cloud from which they are originating.  Sometimes this has been called the “upside down” storm because the top is liquid like Altocumulus clouds where it is COLDEST, but underneath is all the ice, where the temperatures are higher.  (Man, this is getting way too complicated to comprehend!)

0.03 inches! Not as much as expected!

Want to keep the excitement level up…after all, it is raining somewhere near by…  Besides, if you’re excited, it will sound like more happened than really did.  (Another ploy is to report large amounts of rain somewhere else:   “An Avra Valley location got 0.39 inches late yesterday and last night.”  Really did.)

http://159.233.69.3/temp/pptreport.txt

Well, at least this rambling low “below” us in Mexico is not a total “gutter ball.”  It was looking at little grim for rain last evening with all the stars out.   Here is a loop of that low’s drift, with obs and satellite imagery on a 500 millibar map from my former “home” Department at the University of Washington:

http://www.atmos.washington.edu/~ovens/loops/wxloop.cgi?sat_500_full+9

You will see here that a blob of deep clouds is sneaking around in “back” of us and will likely deliver an odd fall of rain from the northeast as the low scoots off to Texas.   The models, in all their wisdom,  think the rain in those sneaky clouds can get over the Cat Mountains but to the east of us here in Catalina.  Don’t expect a lot, then, maybe just a hundredth or two if we are lucky this morning before those clouds starting thinning and moving off.  Still, it would be something.  Rain and snow threats are still in the model outputs (last night’s 5 PM AST one) in the days ahead for us, but have diminished  in magnitude; become more marginal in later runs, dammitall.  Hence,  this font size to reflect that.

Cloud report

Yesterday was one of the great days of clouds we have here so often, so pretty with all that snow coming down out of such little wispy clouds.  Here are some scenes, beginning with the momentary underlighting of  Altocumulus clouds shedding long virga trails.  In the second shot, I will no doubt have to admonish people again that to see what I saw, you must hold your computer monitor over your head. This was a long fiber of virga (snow), like those shown in the first photo, but was overhead.  So nice!

Cloud tops of these little clouds, those flat flakes at the top of the virga (sometimes called, “generating cells”, source regions for all that ice, by my reading of yesterday’s Tucson sounding,  were about -25 C (-13 F) at about 15,000 feet above the ground here.  These are low temperatures for us at that level, BTW.

The rest of the day was generally a joy, too, with terrific examples of glaciating (turning completely to ice) Altocumulus castellanus clouds (next shot).  Those whitish turrets in the foreground above the bush have glaciated, while the others are still mostly liquid water clouds, on their way to becoming icy, and cirrus-like.  This glaciation has just happened and you can infer that because the snow has not yet fallen from the bottoms of those clouds above the bush.  If you really look hard you can see the telltale filaments, fibers, stranding in those clouds, too.

A really nice example of “Ac cas”, turreted middle-level clouds, are those whitish clouds in the distance toward Kit Peak.  That next shot is of an Altocumulus turret long after it has glaciated with only a ghost of its former height shown protruding above a long, fibrous, icy trail.  There may have been other smaller turrets as well.

What was happening here is that the air just below these Altocumulus clouds, was only moist for a short distance, and then became extremely dry.  So, initiatlly, the ice that fell out of these clouds may have grown in size, but then when they starting falling into the dry layer, began evaporating rapidly.  As they did, the fallspeeds of the crystals went down to practically nothing and so, being something like diamond dust snow, seemed to float horizontally in the air.  And as they do this at these small crystals sizes, they lose the stranding become something akin to a fog of ice crystals that gradually disperse from the parent clouds.   Sometimes layers of Cirrostratus clouds, or large patches of thick Cirrus (spissatus variety) form in this way.  An example of ice clouds having formed like that yesterday in shown in the next shot.

Finally, just some shots of some pretty clouds, the next (supercooled) Altocumulus perlucidus (tending toward castellanus) and NOT showing any ice, and then just more shots of those little snowstorms in the sky.

The End, finally!

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.

0.34 inches! And a surprise snow job!

What a great storm, giving all it had to Catalina, 0.34 inches, when it looked like it might be considerably less.  I really liked that storm, and will always remember it.

In case you missed the snow with flakes as big as pie plates (2-3 inches in diameter, small pies) because you work in an office with no windows, these photos below.  They were equal to the biggest flakes1 I’ve ever seen, including that December 1990 Seattle snow and blizzard with all the lightning.  The greatest momentary depth was about an inch on the rise above Catalina town.  Within minutes it was down to half an inch it seemed.

 

 

 

 

 

 

 

The temperature fell no less than 10 degrees as rain began to fall and the cold front slammed Catalina about 11 AM, from 52 F to 42 F. It looked like the temperature might be recovering, the rain had pretty much quit (read, clouds tops lowered in height as well), when this second part of that band (deeper clouds again) showed up with something resembling the earlier arcus cloud that had earlier crossed the Oro Valley and rammed up the slopes of the Catalinas.  You can see under the dark line that the visibility drops tremendously.  Don’t need to look at the radar to see that something is upon you at this point.

I thought it was going to be just heavier rain after the first rain spell that dropped a few hundredths, but after the rain started, there was some ice in it immediately, and then the big flakes began to come down, drawing the snow level down with them.  Yes, that’s right, when the clouds are loaded with snow as yesterday’s were, a heavy load of snow drops the freezing level.  It takes so much heat for the atmosphere to try and melt that boatload of snow coming down that it can’t keep up.  Recall from physics that when melting ice, it stays at the same temperature 0 C (32 F) until it has completely melted.  This phenomenon is due the “latent heat of fusion”, in this case, taking heat out of the air to melt the snow, which causes the snow level to fall.   I think it was discovered by Stanley Pons and Martin Fleischmann, at the University of Utah some years ago.  Both of whom went on to become quite famous for their work, I might add.  So, if the freezing level in light, itty-bitty snowflakes is 4,ooo feet, it might stay there, and with them, you sometimes even get a thin layer of 0 C (32 F) air (an “isothermal” layer) where the flakes are melting.

Now drop massive 1-3 inch flakes out the bottom of the clouds.  Well, its easy to imagine how the freezing level would have to drop as the air being drained of heat as it tries to melt those massive flakes, ones staying at 0 C until they are completely melted.  You may have noticed that during that heavy, heavy snowfall yesterday that the temperature dropped another whopping 9 degrees from the first cold plunge from 42 F  to 33 F in response to that heavy precip.

That really heavy precip was not anticipated, and was the reason why I was caught off guard by the snow here at 2500 to 3000 feet elevation.  Had we (spreading the blame around with “we”) been thinking a snow rate of around 1-3 inches an hour, we would have been thinking of sharply lowered snow levels and snow (!) in Catalina.  And, as you would guess, once the heavy snow ended, the temperature was quickly on the rebound into the 40s in the afternoon.

But that thought of heavy precip never crossed my mind, nor did the thought early yesterday that a really strong rain band, the one that caused it,  would erupt to the west of us out of the blue practically as it did yesterday morning before rolling into Catalina.  In retrospect, it was like a fastball down the middle of the plate with a 2-0 count, but you didn’t take a swing.  It coulda been such a great forecast day if brain fully intact!  This is why you remember storms!

Below, next to the shot of the major rainband as it came in, is the more dramatic appearing arcus cloud (that undercutting shelf cloud below the main Cumulus and Stratocumulus clouds) that announced the approach of the cold front and wind shift line about 10:30 AM yesterday morning.  Man, that was a great sight!  SO dramatic as that colder air swept across Oro Valley and the Tortolita Mountains, giving a boost to the overall cloud updrafts above it.  Enjoy.

 

 

 

 

 

 

 

More Catalina precip in the near future.  Details when it gets here Thursday night.

The End.

The End.

———————-

1Weatherfolk call flakes, “aggregates”,  because they are made up of dozens of individual ice crystals that are locked together.

“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