Category: Cumulus clouds

Spinning on down from Glasgow to Rocky Point, a low

This is pretty interesting; don’t see this happen too often where a lobe of low breaks off and spins from Montana, back toward the south-southwest to pretty much over Rocky Point, MX, as you will see in this past 48 h water vapor loop.  In a water vapor loop, you pretty much see all that the movement that is taking place in the atmosphere and here you can begin to understand why it takes biggest computers on earth to model it.  Here’s a close up from IPS Meteostar.

Note, too, those white puffs exploding in west Texas as our little low spins thisaway.  Those are massive thunderstorms that our low has and will be triggering in west Texas and eastern New Mexico over the next few days.  This is great to see that happening due to the drought those poor folks have been experiencing over the past couple of years.  This little low, as tiny as it is, will make a huge dent in those conditions in some areas.  It really would be great to be there in some little town, like the well-named town of “Plains”, TX, and see how happy the folks are getting as the rains hit.  It would be like the end of a Hallmark movie where everyone is quite happy about how things have turned out.

Here are two shots showing what its like now in Plains-Floydada, TX, area,  First, you can see that the earth is quite flat there.

Note green along highway. It has been raining off and on in these areas for the past month, so things are perking up. There were occasional bursts of wildflowers, too.
These aren't horses. What are they?

But while Texans are getting happier and happier (and I hope they don’t complain about flooding because that would be just plain WRONG), what’s in it for us?

Well, the quality of moisture is less here toward the center of the low, maybe about 1/3 as much in the air over us as in Texas.  So, what does that mean we will see?  Maybe a few Altocumulus in streaks, maybe finely patterned Cirrocumulus, and then as afternoon comes on, some Cumulus with high bases because its so dang dry.  I better predict some Cirrus cuz I see some now!  Also, I think I will forecast that the low temperature this morning will be about 62 F here in Catalina because that’s what it is now.   Maybe some ice optics, too, now in progress!  Continuing, these clouds, too, mean some great opportunities for sunrise/sunset color and ice optics now that I see one (parhelia).

But with those high bases goes low temperatures, likely well below freezing, and you know what that means.  The tops are likely to be colder than -10 C to -15 C, 14 F- to 5 F), an ice-forming threshold hereabouts for small, high based Cumulus.   With the formation of ice, VIRGA, snowflakes and ice crystals come out the bottom.   You can see this by the hazy look around the clouds where it is evaporating–ice takes longer to evaporate.

In the higher terrain, the virga will melt into rain and reach the ground, and the clouds will likely get tall enough to produce lightning, but not here today, but to the north of us at least early in the afternoon and evening.  Our best chance of rain with thunderstorms in southeast AZ will be tomorrow as the moisture gradually increases over us from the backflow around the north of the low.  The low is forecast to pass to the south of us tomorrow and Thursday.  You can see all this happening in our local U of AZ weather model here.  (Note the local time is in the upper left hand corner.  You will see the precip is only forecast to occur in the afternoon and evenings with this system.

So, finally, some weather excitement in the offing!

Rain and cold foretold for Catalina on Saturday as big, long-foretold storm bops Cal then moves on to AZ

Things are falling into place.  Remember the spaghetti from a week or more ago, in which it was clear, or at least at attempt was made to explain to both readers of this blog,  that a large trough was almost certainly going to be along the Cal coast?  We intuited that from the lack of spread in some contours in that “spaghetti” plot along the West Coast some week or more in advance.

Well, that trough is truly turing out to be a behemoth, a gigantosaurus for April.  The people of California are going to be very excited today and tomorrow about cold, showery weather, mountains of snowfall in the mountains, maybe a funnel cloud or two in the Sac or San Joaquin Valleys.  Here is that trough as shown on today’s 5 AM AST 500 millibar map from the U of WA weather department, the one prophesized with high confidence so long ago:

However, for many days after that, the models did not think the rain in Cal was going to get here.  Of course, still being in the cool season, our rain is nearly all dependent on whether the jet stream in the middle levels (500 millibars or about 18,000 feet above sea level) is able to be over or especially,  south of us here in Catalina.

But lately, in the forecasts, been shifting the jet southward and rain has started to show up in two or more recent model runs, always a good thing.  You may also remember that in our spaghetti plots back a week ago, it was not clear in the models where the Cal trough was going to go after it bashed the West Coast.  Hence, while things were clear for Cal (actually, they were going to be cloudy and rainy), they weren’t so clear for here until lately.

From the U of WA, this for Saturday morning (colored splotches denote where the model thinks precip has fallen in the prior 3 h); below, the jet stream at 500 mb from IPS Meteostar for the same time.

Yesterday’s clouds

In case you missed them….   Cumulus and Stratocumulus, punctuated with a splash of Cirrus fibratus undulatus (Cirrus with rolls, showing something akin to swells in the ocean in the atmosphere).  The wind at Cirrus level in that shot is blowing from left to right.   No ice falling out in Cu and Sc; too warm at cloud top.  Only about -5 C (23 F) or warmer.

The End.

April precip climo; yesterday’s cloud

Well, no surprises here.  The chance of rain continues to diminish overall in April, with an especially dry period in the current 35 year record in the middle of April.  It has not rained on the 9th and 19th in all those years!  Odd.

Since rain at this time of year has to be associated with cold troughs (like the Joe T of yesterday), these frequencies also tell you when a passing trough is more likely.   We had one go by yesterday evening, and its still nearby, fitting the pattern above of an enhanced chance of rain day or trough passage in the first few days of April.

BTW, most of these data are from the folks at Our Garden in Catalina, who happen to be very weathercentric, thank heavens.  You should really go there and buy everything they have as a “thank you.”  (hahahah, sort of.)

Today’s upper level configuration from the U of WA is shown below.  You can see that “Joe” is still around; in fact, he’s in the process of forming a closed center just over the horizon in New Mexico.   This will eventually be a great rain producer, as mentioned yesterday, for portions of the southern Plains States.  It would be great to be there during those downpours.  Anyone for a road trip to OK?  (hahahahah, sort of#2).

Yesterday’s cloud and its shadow

Here it is, in case you missed it.  Well, OK, there was more than ONE, but not too many more.   And, disappointingly, they faded before sunset!  What were those clouds?  Cumulus fractus, maybe as “large” a one that it could be termed a Cumulus humilis, but that was it.  No ice, of course, not cold enough, only about 32 F at top; just droplet clouds.

 The weather ahead?  Dry now

That mid-April chance of rain has disappeared on the models, now seeming to fit the 35-year climatology of it being VERY hard to get measurable rain here in mid-April.  Dang.  Nothing in sight now for the next two weeks in the latest model calcs.

Whence graupel?

What a fantastically gorgeous, if uncomfortable day yesterday was!  Such skies!  Such odd temperatures for March 19th.  And another day with ice falling from the sky, mostly “graupel”, but also some snowflakes (aggregates of dendritic crystals) at one point, too, when “stratiform clouds” came by (flat, layered ones) about mid-day.  The total water equivalent, 0.08 inches, 0.75 inches for both days combined.   With a high of only 50 F, it was also the fourteenth lowest high temperature ever at Tucson in March.

It was great, too, that “sample” day yesterday of the Last Glacial Maximum, imagining what it was like thousands and thousands and thousands of years ago when humans and dinosaurs co-existed on this cold planet.  I could almost see the dinosaurs coming down out of the snowy Catalina Mountains, being chased by hunters, or vice versa.  I have to say I haven’t researched this, but I have seen some movies about it.

What is graupel, you ask?  A form of German wrestling?  “Die zwei Männer  graupeling sich auf der Strasse”?

Well, no my friend, it is what we weatherfolk call a tiny snowball that falls from a cloud.  You can also call it “soft hail”, because we call it that, as well.  You can easily mash it between your fingers because unlike hail, it has a LOT of air in it.  We had a LOT of that “graupel”-soft hail off and on yesterday, once, around 7:38:36 AM AST with a roll of thunder.

Here’s what they looked like, up close, along with a raingauge measuring stick for size (its one inch between labels).  You may have also noticed some, many at times, looked like little pieces of space debris, having a definite conical appearance.  This is called “conical” graupel.  Its quite common actually. The third shot shows, and this was somewhat miraculous, an element of conical graupel on the way down.   I was stupefied that I had gotten such a shot by accident!

On the right side of this third photo you will actually SEE a conical graupel in flight, on its way down, and how it falls, wide end first because that is the heavy end.  Also note the heavy shaft of snow/soft hail up against the Catalinas downwind.   The graupel that fell in the photo came from the back side of that Cumulonimbus cloud.  The second cloud shot shows the bottom of the cloud from which the graupel was falling.  Many of you know that I specialize in these kinds of photographs, the bottoms of clouds, hoping to have a show someday.

But, what do you see in the cloud base photo?  Not much.  The best eyes will detect that slight, slight striated look due to falling graupel.  Falls in strands reflecting the complex nature of the organization of liquid water and updrafts, wake capture in clouds.  The first precipitation falls out through the heaviest concentrations of liquid water (at well below freezing temperatures), and that’s what graupel does.   This the same as when the largest and heaviest raindrops in summer fall out from a cloud base with not much else going on.  And, like our graupel, they are spread around, sparse compared with the heavy rain that likely will soon follow.  So, graupel is the first thing that falls out of large Cumulus clouds, ones growing up to be Cumulonimbus ones.

Also you may have noticed that the graupel almost always was associated with a Cumulus clouds yesterday, localized clouds in lines with dark bases over you.  Cumulus clouds are loaded with liquid water, at least in the rising portions.  In those rising portions, a few ice crystals, or cloud drops might freeze.  Thereafter, they begin collecting drops that freeze on them when they contact the ice.

Cumulus clouds at below freezing temperatures are avoided by aircraft because this is where cloud drops can hit the airframe, freeze instantly, and weigh down the plane, as happened with our little graupel.  In Cumulus such as we had yesterday, a half an inch of icing can build up on the leading edges of airframes in just a few minutes while flying in their upper portions.  Near cloud base, the drops are too small to build up much ice.

With some of the graupel up there in those clouds, at some point early on, the freezing of drops on it as it collided with them produced a side that was slightly heavier than the rest of it.   That heavier side began falling downward, collecting more drops to make it more lopsided, conical.  You can then assume that graupel that are not conical, collected drops pretty symmetrically, something that would happen only if they were spinning on the way down.

Associated with the formation of graupel, as on this day, is a sudden burst of ice formation in the entire cloud leading to “glaciation”.  The liquid drops at below freezing temperatures are completely annihilated during this process in the turret initially spawning the graupel, and along with the remaining graupel, a dense shaft of precip drops out of the bottom. consisting of graupel and large snowflakes (aggregates of single ice crystals, sometimes hundreds of individual crystals in them).  So, on the back of this Cumulonimbus cloud raking the Catalinas, graupel, on the forward side where glaciation has taken out the liquid water, aggregates, probably huge ones.

Gads, I want to go on, but this is getting to be a little LONG!  However, here are a few more shots from that beautiful day. Some dessert after the heavy meal.

The End I think.


Re-living the Last Glacial Maximum–well for a day, anyway

After yesterday’s re-acquaintance with winter, a brief period of snow falling here in Catalina for a few minutes, and a whopping 0.67 inches of rain, we have another deep winter day ahead.

Here’s the National Weather Service’s forecast for Catalina, at least elevations of about 3200 feet.

“Today: Snow showers likely before 2pm, then rain and snow showers likely. Partly sunny, with a high near 46. West southwest wind between 8 and 16 mph. Chance of precipitation is 60%. Total daytime snow accumulation of 2 to 4 inches possible.”

A glimpse of a Catalina paleoclimate

A day like this, with snow expected and daytime temperatures reaching only the mid-forties let’s us experience what Arizona was like in the springtime 15,000 years ago or so during the Last Glacial Maximum (sometimes called the Wisconsin Maximum, referring to the area around the Great Lakes where ice was really piled up–no wonder we get visitors from Wisconsin; they remember.)

But, let us not overlook the other areas of the country during that Last Glacial Maximum.  Ice was piled up more than a kilometer deep in Seattle!  I am not kidding.  Here is a shot of what the Space Needle might have looked like in those days of the Last Glacial Maximum when snow and ice were building up.  Its pretty impressive since the Space Needle is a few hundred feet high.  Hard to imagine, but there REALLY was ice deemed to have been 1 km deep in Seattle 15,000 years ago!

A huge amount of global warming took place, of course, after the Last Glacial Maximum, people started going back to Wisconsin and other northern climes.   The warm era that followed the end of the Last Glacial Maximum, and the one we are now in is called the “Holocene”, BTW.

However, our current era also has a rather dark moniker,  also being termed an “Interglacial” period, as were all those periods between ice ages in the Pleistocene when it was nice and comfy.  “Interglacial” sounds kind of temporary, and they were back then, only about 10, 000 to 20,000 years long, and we are about 12,000 years into the “Holocene.”  However the duration of interglacials is not pinned down real well and “orbital” forcing of ice ages (Milankovitch cycles, Wiki) puts the next one around 50,000 years from now.

Maybe it would be good to go look at some petroglyphs today and think about what the weather was like back then for those folks who made them.

Oops/Correction:  Actually, in researching “petroglyphs” they seem to have appeared AFTER the Last Glacial Maximum, about 7,000-9,000 years ago.   Hmmmph.  That petroglyphs would appear then is understandable.  People were happy it was warmer and took their happiness out on the rocks which were no longer so cold, thus explaining the world-wide burst of rock work.  I work hard to provide you with information like this, information you can’t get elsewhere.

Today’s clouds

Its so cold up top today!  Its -11 C at just around the top of Mt. Sara Lemmon.  Since the tops of the clouds over us, even shallow ones,  will be -15 c, and the deeper ones to -30 C today, lots of snow will form in them, and that means virga and rain/snow showers, graupel (soft hail likely).  The upper level trigger for most of this will begin affecting us this morning, and with a LITTLE heating, cumuliform clouds should begin enhancing the Stratocumulus deck we now have.

Lower clouds with lots of ice in them look like yesterday afternoon’s clouds, shown in the photo below.  That smooth texture on the left side of the photo is due to ice falling out, but the snowflakes and ice crystals are too small to reach the ground, except only the very largest.  The shaft in the distance is due to a much deeper cloud in which the snowflakes and graupel (soft hail) were able to grow far larger than in the other cloud regions nearby. That’s because it had much higher cloud top, forced by stronger updrafts.  The stronger the shafts, the the higher  topabove it is a pretty good rule.

Gee, starting to “graupel” right now at 6:31 AM AST!  Exciting.

So, look for a lot of smooth looking clouds today like those in this photo.

 

 

 

Backspin ending; upper low moving off to east as big trough barges into West Coast

You can see all the action described above here and here:  first the water vapor loop from the Huskies’ Weather Deparment that lets you see ALL the action, dry and moist air moving around, and then from this IPS Meteostar loop, you can drill down and see the clouds with the itty bitty radar echoes they produced over eastern AZ and NM as the clouds spin around that backspining low.   Stopped moving this way, as you will see, early this morning as a big trough with its broad band of westerly winds moves into the West Coast pushing our low away.

Unfortunately, that “big trough” will only bring rain as far south as SFO in the days ahead while we warm up for a few days.  I would look for a string of nice sunsets as Cirrus clouds on the periphery of the rainy systems to the north are drug this way , however, as the week begins.  I guess that’s not so bad.

Here’s a nice weather map for you (more from the Huskies!), one for the 300 millibar level, 30,000 feet or so above sea level.  You can see our spinner over the AZ-NM border, and the “big trough” which is about to brutalize the Pac NW and northern California:

 

Since a couple of those radar echoes last night are in our Catalina domain (a 100 mile radius, and rain was falling at Safford (3 AM AST), an old mining town NE of us), I now recommend that all readers of this blog check their dusty cars for sprinkles-its-not-drizzle on their dusty cars for a possible drop images in the dust, and a journal entry of a rain occurrence.   And, yes, we had plenty of dust yesterday as the lower level winds came scooting from the east-southeast  at 20-40 mph over much of SE AZ yesterday.  The Catalina mountains protect the town and environs around Catalina from these events, so we only get to imbibe dust, not actually experience it being raised up around us as was the case in the city yesterday.  You can notice this blocking effect nicely by driving south on Oracle on days like yesterday until you get to Pusch Ridge, Magee Road or so on Oracle, and then hang on to your hat.  There’s a similar low level wind situation today, and so you could do that today, drive south on Oracle, and experience it for yourself, maybe log the event in your weather journal as well.  I think readers in the years ahead would find it of interest that you did that.  I did it yesterday, and it was pretty exciting to see that east wind roaring though the palms, etc., just as you passed Pusch Ridge!

Yesterday’s clouds

What would a cloud maven’s post be without clouds?  First, take a look at yesterday’s time lapse from the U of A’s Weather Department.  During this one day, you can see the Cirrus clouds first coming from the northeast (they take awhile to appear), and then by the end of the day, they are almost coming from the west as that upper level low center spun back toward Arizona from New Mexico.  This is really cool, something you won’t see very often at high levels, this amount of turning of the wind in one day at that level.  Also, you will see lots of Cirrus forming in dense tufts and then dispersing once ice has formed.  That, too, is cool!

Here are some shots from yesterday:  1) Cirrus, 2) scruff of Cumulus humilis to the north, and 3), a dusty, Cirrus-ee sunset shot.

In the first shot, you may notice that these Cirrus clouds more resemble Altocumulus with its little flocculent masses.  Since Altocumulus clouds are all, or mostly comprised of liquid drops, you have to be able to see that these little cloudlets are ice, not water, thus betraying the greater height of these clouds compared with the Altocumulus (Ac) clouds they resemble.  There is a slight possibility, that for a second, these clouds had a liquid drop, such as upper center in the first photo.  Those look suspiciously like little tufts that may have been liquid drops.  However, while nearly all Ac REMAINS mostly liquid, even when trails of ice fall out, these clouds do not.  One of the mysteries in our science is about the formation of ice.  Some liquid drops in Cirrus clouds have been detected by researchers at the University of Utah1 at -44 C!  These are NOT the same researchers that were associated with “cold fusion” reports, BTW, ones that came out around the same time as this one.

 

 

 

 

 

 

 

The weather ahead

Latest model run, from 11 PM last night, has, after having several days ahead with rain, dwindled them to just two, the 19th and 20th of March.   These are indicated to be, in totality, a good rain.  Hope they “maintain” in the progs!

The End.

——————————
1Sassen (1986, Science)

“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:

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.

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!)

“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.