Category Archives: Definitions

“Stuck Inside of Tucson with the Seattle Blues Again”

Paraphrasing Bob Dylan’s song title, one that had the line, “Stuck inside of Mobile with the Memphis blues again”, that great, driving song he did in the 1960s.  See photos of Seattle-like conditions of low-based Nimbostratus below with a temperature of only  37 F (!) right now in Catalina!  Egad.   As you can also see, after 0.39 inches of rain up until about 11:30 AM this morning, there is also some flooding going on.

(Of course, me and most Arizonans really LOVE rain; it’s to be treasured at all times!  In Seattle, where I just spent three weeks, not so much.)

Local weather for Catalina here.

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Some iridescence with your clouds? And a photo comparison of our current droughty conditions compared to last April’s green

Yes, we had some yesterday evening in those Altocumulus lenticularis clouds or just “clouds” for most of you.  This delicate “rainbow” coloring in last evening’s clouds is due to the diffraction of light around really small cloud droplets, ones that have just formed, a few microns to 1o microns or so in diameter.  Because the droplets have to be “really small” to produce this effect, iridescence is almost always located at the upwind edge of clouds that thicken downwind, as these do.  It was more colorful than I could photograph, but here are a couple of shots of that phenomenon we call cloud iridescence, or irisation:

By the way, the winds at cloud level here (around 2o -22 kft above the ground and at -30 C or so) were just about 100 mph (85 knots) at this time as that huge trough over southern California edges closer to us.  Unfortunately, it is “ejected” to the northeast out of southern Cal this morning and that means that this whole upper level system will be moving faster and faster as it moves toward Arizona and then into the Plains States.  That means that the band of rain generated with this system will be moving through at a faster pace and for that reason won’t produce as much rain as it might have if the system was not speeding up.  Still, looks like we should get, here in Catalinaland, around a quarter to half an inch.  Very exciting, since it will do what vegetation we have some good.

Free range grazing land now down to about just dirt, as little of the spring grasses have poked up before being ravaged by hungry cattle and native wildlife.  Kinda depressing after last spring’s bountiful display of grasses and wildflowers.  I have contrasting photos below as well.  You won’t like what you see in this comparison because it brings our droughty winter into sharp focus.   What is nice about our desert is that the mesquite and acacia bushes/ trees don’t seem to care how dry it is and are still are intensely green this time of the year, some consolation for the lack of green elsewhere.

You also may be struck by how tall I am, perhaps I played basketball in college you wonder.   In the first photo illustrating the dry conditions, I am apparently several feet taller than my wife, Judy, who walks ahead of me with Zuma, one of our dogs.  I guess I could have been on stilts, but I am actually on our horse, Jake, and am not that tall FYI.

The end.

 

 

Cirrus uncinus display; the tops of storms made visible

First, some instructional material:  You should be looking for your camera now, as seen in the first shot! Those Cirrus clouds to the SW are moving at you rapidly (95 kts, 115 mph at 30-35 Kft ASL!), and so there’s not much time!  In this first shot you can already detect some Cirrus uncinus, Cirrus clouds with hooked, or tufted tops in the center, with long icy strands trailing to the left. At this point perspective makes them bunch together so that they may not appear that “photogenic.”  However, just wait!  And, it was worth waiting just a few minutes for.

Take a lot at which they looked like passing overhead in the second and third shots, only about 7 minutes later. Just magnificent, some of the best Cirrus uncinus examples I have seen.

What is interesting about these clouds is that you are getting a glimpse of the structure of “stratiform”–that is, steady rain and snow storms that happen every day around the world, except that here in these photos,  you are only seeing examples of the very tops of them. Those widespread rainy/snowy storms are usually packed with thousands of these kinds of clouds in a solid overcast up there, each “cell” shedding tiny ice crystals which then waft their way down, growing, perhaps merging into “aggregates” of ice crystals we call snowflakes, and, that most of the time except in Wisconsin in the winter, melt into raindrops as they fall below the melting level.  Chances are, our little snowstorm of a few days ago had tops just like this.

Sometimes, clouds like these, and returns from vertically-pointed radars that can detect clouds like these, are referred to as “generating cells”, for obvious reasons.  The trails you see here are clearly visible on very sensitive “cloud sensing” radars–they are not visible on “First Alert” Doppler style radars and such used by the NWS because the ice crystals are too small at this point to produce a return on “normal” radars.  These cells form in a relatively shallow layer that usually lacks wind shear, likely mixed out by the little up and downdrafts in it.  Its only after the crystals fallout that they encounter wind shear and end up being stretched out into “tails” as here.

Falling from heights of 30,000 feet takes a long time, for an ice crystal falling at only around 0.5 meters per second or around 1.5  ft a second or even less.  It will take  LONG time for anything to reach the ground, perhaps 2-3 hours to reach the melting level.  So the little generating cell that produced a ice crystals at the top of major storms that grow and merge into snowflakes is likely over Alamosa, CO, and points northeastward by the time that flake landed on you at the ground with upper level winds such as we had yesterday.

I think its kind of interesting, but I may be the only one!

The end.

Exit right (or to the east)

Here’s what happened on top of us yesterday, that gorgeous snow day with so many wonderful sights to see. These maps below,  courtesy of San Francisco State University , for 500 millibar pressure level, about 18,000 feet above sea level, for 5 AM LST as the snow band moved through Catalina, and then 5PM LST,  a little before sunset:

 

 

A visual on what the clouds did as this happened yesterday is below. Interpretative cloud statements on the following gallery: shallow, deeper (precip begins in distance), deepest (small, soft hail falls here and there from miniature cumulonimbus clouds), less deep (barely-able-to-precip stage again), shallow, nil. Pics 1,2, 3, 4, 5, and 6, respectively.  If you want all the visual glory of yesterday, go to the U of A time lapse movie here.  However, you’d better hurry, these wonderful films are overwritten each day.  You can really see the clouds flatten out after about 3 PM LST here, and there are some spectacular snow showers going by on the Catalinas.

The end.

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“Smells like desert snow”

Seattle’s Curt Cobain might have said something like this if he had lived in the desert.   Alluding, of course, here to the SEATTLE teen angst band, Nirvana, and their big hit, “Smells Like Teen Spirit”. BTW, a song covered later by Bill Nye the Science Guy in an educational ditty,  “Smells Like Air Pressure”.  But why do this, have a title like this?  Contrived, ludicrous “cleverness.”  The world needs more honesty.

Began as a good rain at 2:40 AM, and by 4:20 AM, was changing to snow, for those detailed oriented folk.  Measured 2 inches on two locations here at 3200 feet, top of the car outside and on the “barbie” cover just as the snow was letting up around 6:30 AM.   Two minutes later, it would not have been as deep since all of the surfaces are above freezing in temperature and the snow depth lessens by the minute.  This was the third or fourth snowfall here in Catalina since we moved here in mid-2008, and was just that bit more than the “record” deepest of 1.5 inches in December 2008.

Here’s the SHARP FROPA, passage of the dramatic cold front “plus”) this morning at 3 AM as seen in the temperature and pressure records (software is a bit immature and won’t allow printing of two parameters on the same chart).  Note sharp rise in pressure at “FROPA”, the classic sign of a cold front’s passage.

La Nina-like conditions seem to return over the next couple of weeks, so lay back and enjoy the soil moisture while you can!  Some photos, the first something we Arizonans (of late)  called an “Arizona Christmas tree”, a snow covered cholla cactus.

 

 

 

“Send in the clouds”….then the wind, the rain, the cold front, the snow

Too bad Steven Sondheim wasn’t a meteorologist.  He might have written some great weather songs.  Instead, he chose to write about “clowns.”

Hmmmm.  Perhaps he WAS thinking about some weatherman in those days when he used the word “clowns.”  Who can forget that the LA Times  headline about weather forecasting in 1981;  the headline that declared that weather forecasting in the media consisted of,  “Clowns and Computers.”   Personally, I think humor has no role whatsoever when talking about weather….   Oh, well, I digress.

Today will be really exciting for us weather buffs (buffoons?)  We WILL be excited as mom Nature gives us a reprieve from the steady diet of glorious days, sunrises, and sunsets (this morning’s at left), paradise really,  with a blast of wind and then cold, likely to inflect more damage on our probably dead palms here in Tucson-Catalina-Saddlebroke.  Also this will be punctuated by a really exciting cold front passage, one where the temperature is likely to drop at least 10 degrees Fahrenheit within minutes as the wind shifts to the W  then NW after those bruising S-SW winds.  Probably here on the knob, we’ll see 40 mph or more in momentary gusts. Good-bye dead palm fronds.

When will the rain/front hit?

Well, lets say you don’t have a supercomptuer, a Cray, a Fujitsu, or access to thousands of PCs for parallel computing purposes to solve all the euqations in your 57-layer nested grid model using GFS-WRF outer boundary conditions, etc.,  for your subdomain.  What the HECK would you do, besides peruse the internet for answers, which can take a LOT of time?  Besides, we know that the internet is loaded with bad information…

Here’s what I do in this “bind.”   You get out a little piece of paper or Hollerith card (2nd photo), and you use the technique of “extrapolation.”  You got to the internet and check out the recent movement of the cloud band feature upwind of you by marking where the leading edge was, say, 4-6 hrs ago, then where it is currently, and move the two marks forward so that the back one (the old edge) is at the front of the feature and look at where that 4-6 hrs of past movement puts it  4-6 hrs from its present position.  Presently, the middle of this mass of Altostratus clouds (last photo) we have over us, will be around Noon to 1 PM using that technique.   However, there is no precip in that fat band of clouds, though one would think they would be thickening up as they approach us due to the Cat Mountains and overall effect of the Mogollon Rim.  So, maybe there will be some sprinkles around.  Our best models suggest the main rain band and front will not arrive until well after dark., and “extrapolating”, using the past 13 h,  suggests the front won’t hit until dawn tomorrow!  So, it”ll be a long time comin’, but “a change gonna come, yes it is.”

In the meantime, the biggest conundrum in today’s forecast is is what are these Altostratus layer clouds going to do (last photo), the ones at presently  zooming above us in winds of nearly 100 mph, bases at 20-22, 000 feet?  There are no radar echoes in Arizona to the west of us here in Catalina, yet as you can see they are drooping precipitation down at us in the form of virga.  As the air moistens below these clouds, as it should given the approaching system, that virga will tend to hang down lower and lower.  I would guess with this scenario that some very light rain or sprinkles will start reaching the ground this afternoon into this evening in Catalina ahead of the main rain area, the one due in well after dark. Our best model for this area is, of course, at the U of A, right here, and you can see the precip creep in then.  I think I would use them (U of A and NWS since the last time I used the “extrapolation” technique described above was in 1989 I think.  However,  you’d be surprised, when timing fronts coming in off the Pacific (where I was forecasting then), how well this simple, simple technique worked.)

Don’t be surprised if a bit of a clearing comes up toward later this afternoon to sunset.  Its not unusual to have a vast amount of quasi-threatenbing cloud go overhead all day, maybe with a few sprinkles, and then have a thin slot or brief clearing before the heavy clouds and rain move in later in the evening.  That appears to be suggested in the satellite imagery today.  We shall see! What an interesting two days ahead!

Still looks like a little snow in Catalina Sunday morning.  U of A mod indicates that the total amount of precip will be around half an inch.

 

BTW, while you’re digesting all of the above, here is where the weather records that were set for yesterday are.   You can see that a LOT of records were set yesterday!  Generally low temperatures and record snowfalls for the day in the northern half of the US beginning in the Mid-West and “thence” westward to the Pacific Coast.

 

OK, enough rambling!

 

 

 

Virga anyone?

Mr. Cloudmaven person foretold certain cloud types would occur yesterday in conjunction with “storm” 3 yesterday (which was really only the passage of an upper level trough over us–see map for 5PM yesterday).  Let’s see how he did, that is, whether he is an actual “cloudmaven”:

(0=not observed, 1 observed, -1, cloud observed, not predicted:

Cirrocumulus,  0

Altocumulus floccus virgae,  0

Cirrus,  1

Cumulus fractus, -1

Cumulus humilis, -1

Cumulus mediocris, -1

Stratocumulus, -1

Stratocumulus virgae, -1

Cloud score:  -4  =s bad cloudmaven; credentials suspect.

Here are some of the cloud sights from yesterday in case you miseed them and want to fill in some entries in your cloud diary:   1) 4:42 PM, 2) 5:26 PM, 3) 5:53 PM, has band of cirrus with trough passage, and 4) 6:12 PM, with some virga/ice fallout showing (darkish veils below clouds).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

However, I did opine that there might be a sprinkle with this trough (see map again for example of yesterday’s “trough.”  (Sounds like the stockmarket in ’09.)  Having been specially trained to recognize virga and precipitation when a forecast of precipitation is on the line, I found it easy to recognize just how close I came to getting that sprinkle as evidenced by some virga trailing down from some of the patches of Stratocumulus clouds.  See above hills in photo at left.

You now know, if you have been reading this blog and thinking about it all day,  that ice formed in these clouds because they had crossed a temperature threshold, had gotten cold enough to form ice.  That “virga” was, if you flew through it, snow flurries.   Where it melted into raindrops closer to the ground is not visible.  However, it is unlikely that virga of this magnitude reached the ground.

You might now even guess the temperature which the tops of the clouds reached.  My guesstimate from the TUS sounding at 5 PM yesterday is somewhere between -15 to -20 C, a threshold for ice (precip) formation in shallow clouds such as these.  Estimated depth of the thicker clouds seen here? About 2000 feet or so is all.

BTW, if you noticed these very subtle virga/ice in these Stratocumulus clouds that began to show up late in the afternoon, you are a cloud observer supreme!

Yesterday’s weather map:

The end.

Bloggin’ cold, maybe snow here in Catalina

But first, “storm” 3 of six as foretold many days ago by our wonderful numerical models having “billions and billions and billions” of calculations (to use a numeric phrase made popular by the late Carl Sagan)  is going to pass over today.  Hoping for a sprinkle late in the day, but virga seems likely in the Altocumulus clouds that will develop/move in today.

The jet stream is powerful over us from the southwest, and when you have these weaker disturbances with marginal moisture, you can get some glorious, fine granulations in the clouds (Cirrocumulus to be exact) as we saw two days ago.  See photo below.  So, I am expecting to see the following types of clouds today:  Altocumulus with virga, some clusters large enough to produce a sprinkle even at the ground (see second photo from two days ago with “mammatus”-see footnote below and virga), Cirrocumulus, and some cirrus.  Could be a fabulous sunset with these kinds of clouds around.

OK, so “storm” 3 today may be just a few clouds without any precip.  Oh, well.


Cold and unusual snow occurrences ahead for the West and for Cat Land, too

The low pressure center and accompanying Arctic blast now developing in the Pacific Northwest will be historic.  What I mean is the that climate record books will be altered for things like late snow occurrences, one of the lastest snow occurrences (as in Seattle), latest lowest temperatures, all time February low temperatures, and unusual flurries and brief snow accumulations at anytime in places in California.  This is a whopper of an atmospheric ice berg from the ground all the way up through the troposphere in the West as it progresses down the West Coast.  Snowfall at SEA LEVEL is likely all the way down to….Los Angeles suburbs.

Then after shuttling down the coast, this “ice berg” takes a sharp right turn (as seen from the weather maps), that is, toward the east and to Arizona!  Egad.   Not only will it be unusually cold again, though nowwhere near the “historic” cold wave early this February when all kinds of low temperature records and pipes were busted, though another hard freeze does seem in the cards after the rain/snow/wind pass by.  Monday and Tuesday mornings look awful darn cold right now.

Did I mention wind?  Along with this situation will be an unusually strong low pressure center that will give us the kind of blustery day this Saturday as we had last Saturday with gust to 50 mph here on the Catalina Rise just west of the Cat Mountains.  So, if you’ve got dried out, stiff palm fronds you’ll probably lose a few more in this one.

Did I mention snow?  Its now looking like a greater chance for a small accumulation of snow as low as 3,000 feet here on the west side of the Catalinas on Sunday morning.  I’m not buying skis just yet, but this is a real interesting situation.

And, finally, it looks like an appreciable rain, too, with this, maybe more than half an inch between later Saturday and Sunday night.   Man, will this be welcomed around here!

Since I am overly excited about this interesting weather pattern that is on our doorstep, it should be noted that objectivity is in decline…  At the Unviersity of Washington we had a forecaster who loved snowstorms.  And so, when he saw a snowstorm coming and forecast an amount, say 10 inches, you had to divide that forecast by 100 to get the most snow that could possibly fall from that storm.

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Footnote:  On the fifth floor of the Atmospherics Science Building at the University of Washington, there was a line of large cloud photos on the wall, one of which was a “Cumulonimbus mammatus” that strongly resembled the “mammatus” in the second photo below.  The photo caption to that effect was vandalized, and we suspect by a female meteorologist/grad student who might have taken exception to this traditional, formal descriptor established decades ago.  The word “mammatus” was crossed out and replaced by “testicularis.”   It was horrible thing to see.

“Little snowstorms in the sky, I think I’d like to have some pie”

You’re probably smiling now remember singing this little ditty as a kid, maybe singing it with your friends on the bus, whenever you saw “Altocumulus floccus virgae” clouds such as are pictured in the first photo.   Wasn’t it great when you saw these kinds of clouds while on a vacation trip and mom and dad had to stop somewhere to get you some pie after you sang that song?   Well, I nostalgiate here.

To the right of the dead yucca stalk, Altocumulus tufts are shedding snow.  The opacity of the virga is a give away that its snow, and not rain.  In some of these little tufts, the water droplet cloud that preceeded the formation of ice has disappeared, and all that is left is falling snow.  How much snow is it?  Just a flurry, if you were up there, even though it looks pretty thick.  Once in awhile in our research on ice in clouds at the University of Washington, we got to sample these from top to bottom.  Because the ice crystal concentrations are usually pretty low in clouds like the ones shown, a few per liter and often less than 1 per liter, those delicate ice crystals don’t bump into each other much and break up,  and you find gorgeous images of star-like crystals in these fall out streaks, the kind you see on Christmas cards (examples here).   How do I know what from ten miles away and 16,000 feet or so below them.   Its a funny thing, but ice crystals are differently shaped depending mostly on temperature.  To get the temperature of these clouds you can get a pilot report (unlikely) or examine the humidity profile of the Tucson sounding for “00 Z” (5 PM LST yesterday afternoon and make an educated guess.   The highest relative humidity on that sounding was at 525 mb ) about 15-16, 000 feet above the ground) with a temperature of -16 C (about 3 F), namely, darn cold.  Continuing, we in this field have a well known chart by Magono and Lee (1966)  that shows the temperature at which certain forms of crystals grow.   At the temperature I am guessing those clouds were at, those crystals would have grown as stellars and dendrites, which grow between about -12 C and -18 C.  Sometime I will show you some of these crystals, but for brevity will quit here on this topic.

The second and third photos show what one of these tufts looks like before the crystals have grown and fallen out.  Top center, the largest raggedy tuft (Altocumulus floccus) show no fallout of ice.  In the last photo, twenty-nine  minutes later, there is a fine veil of ice crystals below it (upper right hand corner).  Only now, with virga, are they “Altocumulus floccus virgae”!   I’m singing right now!  And, if you look really carefully you’ll see that most of those little guys have a little ice fall underneath them.  Certainly, in those clouds you would find PERFECT crystal specimens!

I’ll end here on an exciting note.  The Enviro Can model CONTINUES to show a very strong system moving into our area on Saturday afternoon, likely accompanied by winds as strong or stronger than we saw last Saturday,  before the rain and cold air hits on Sunday.  Snow levels are going to be really low and we might see some ice in the rain on Sunday here in Cat (alina) Land.  Amounts are looking substantial at this point.  Man, do we need it!

In the meantime, an upper trough off Baja passes over tomorrow.  It has enough moisture with it to provide more “clouds for pies” (Altocumulus floccus virga, and, of course, Altocumulus castellanus virgae, which also qualifies as well for a pie).   And, some cirrus will be around, too.  However, I am going to stick my neck out and say there will be sprinkles tomorrow.  Mods really don’t have a thing, so you’ll have to keep that in mind.

Be sure to keep you’re camera ready for sunsets like last night (see below)!

0.07 inches

It was beginning to seem like measurable rain could not fall again here!  But then those Stratocumulus clouds because closing in in the afternoon, then soon after that some snow virga began to trail down from them here and there, and the next thing, large regions of the sky were suddenly shedding virga and rain at the ground.  Also, as with the day before anmd at the same time, a windshift line moved across the Tortolita mountains and into Oro Valley helping to augment those Stratocu.  Here’s the pictorial record:

Your thoughts at this time: "Look, the clouds are quite thin, and the sun is going to be out soon! It will be a nice day after all." Background: the morning overcast of low clouds has dissipated and you are responding to new conditions.
The lower clouds gradually fatten up on solar calories, and because there is a disturbance aloft approaching that you can't see, the clouds begin grouping into darker regions that cover ever larger portions of the sky. The upper air disturbance is the "conductor" of the cloud "orchestra" and its getting closer to passing overhead at the time of the 2nd photo. However, you may still not be too concerned, but after all, there is no precip drooping down from all these clouds that you now see. BTW, I went into the Tortolitas to get this 2nd panaramic shot looking downwind toward Oracle and the Oro Valley for you (hahaha-just kidding).

 

Quickfire quiz:  Why isn’t there virga trailing down from those clouds in the 2nd photo, except in the very far away clouds where you can see just a tad????

(Answer, printed upside down if I could):  “They are not cold enough yet to have ice form in them, and ice in clouds is necessary for rain at the ground, as a rule in AZ.”

So those Stratocumulus and some of them are starting to look more like Cumulus clouds at about this time (2nd photo), have to get colder by deepening upward some, and/or colder air must move in aloft to chill them down.

Weird factoid about ice in clouds:   A cloud will form MORE ice for the same top temperature as its bottom gets warmer!  That could be a whole 100 page discussion.  Now, if you’re really pedantic, you can go here to read about all the mysteries that we (those who make a living studying clouds) are going to try to solve in a project in the Virgin Islands this summer, called “ICE-T” here.

In the 3rd and last photo, the nose of the windshift coming across Oro Valley is marked by that highlighted shred cloud in the center of the photo.  It was moving from R to L, undercutting the  higher based clouds that were still moving from the SW.   As you can see by the obscured bases all around, there is widespread areas of rain at this time, augmented by taller clouds with thicker, darker shafts of rain, probably leaning toward a “weak” Cumulonimbus classification if you could see the whole thing.  Note how the distant hills and mountains are obscured in rain.  Yay!

It was after this shot that Catalina got its little amount.

 

Next “storm” this being 2 of the model foretold six days of rain some time ago?  Wednesday.   However, the mods are unimpressed with the moisture in this and none that I have seen have a drop as this upper air disturbance goes over us.   At the LEAST, we should have some nice Cirrus, and probably Altocumulus clouds.   And you know what that means now….   The possiblity of a trick sunset due to a parhelia (aka, sun dog, mock sun).

Also, I really like the the Canadian model run today that calculated where the highs and lows are going to be for the next several days based on last evening’s weather measurements around the globe.   I really, really like it because it shows  a huge storm here and in the SW six days out.   My preference has nothing to do with objective science.  The models have been fluctuating on how this next storm is going to be, minimal or gigantic, sometimes that’s just the way the models are when there is a lot of uncertainty about things upwind of us. Its one of those that is accompanied by an Arctic blast down the West Coast.  Can’t wait!

The end.