Category Archives: Lenticular clouds

Boffo storm bops Burbank before belting Benson

…and the rest of Arizona tomorrow.    Actually, at this hour, 5 AM, the storm coming here has not yet gotten to Burbank.   Its only close.   But, people get excited when you say things like that in the title, and that’s what we’re about here, weather excitement, not accuracy excitement.

Weather excitement?

Take a look at the NWS site here.  They are beside themselves with excitement, issuing what appears to be hundreds of warnings for the entire State of Arizona, and not one drop of rain/snow has fallen yet!  Imagine how excited they will be at the NWS when something actually happens!  (hahaha, just kidding; you’re doing a great job down their guys and gals.)   They just want to WARN us about this well-predicted, STRONG storm, one having the unusual characteristic of being well-predicted in the models more than a week in advance.  Hardly ever happens.

So, with the NWS all worked up about winds and rain and snow and cold and stuff like that in our IMMEDIATE Catalina future (next few days), here at this keyboard we will try to fill in a cloud appearance niche, or try to.

Examining the AZ station and cloud plot here posted by our friends at the University of Arizona Wildcats Weather Department, this nice map.  
You can see a sheath of clouds (whitish area) extending southward from southern NV and UT down past Yuma AZ.   There is no radar echo with it now, or will there be.  Your interpretation:  must be Cirrus and Altostratus (thick ice clouds), maybe with some Altocumulus at the bottom toward the back (west side).  You’ll notice, too, that it is COMPLETELY separate from the main frontal band that has not yet (5 AM AST) gotten to Burbank, CA.

Note cloud empty area or slot behind (to the west) this sheath of middle and high ice clouds over the Colorado River Valley.  A very common sequence in the Southwest interior in late winter and spring is to have a completely separate slice of high clouds, even thickening up to look quite gray, maybe with some virga, give a false impression that the storm is imminent, much closer than it really is, followed by a spectacular clearing from western horizon. Often, this sequence, as is possible today, leads to astonishingly colorful sunsets here if the timing is right. You won’t read about possible colorful sunsets at the NWS today! This why I am here, to warn you about a nice sunset while they warn you about winds and stuff.

However, at the current rate of movement, this band of high clouds will pass overhead in the middle of the day.  Drat.

What next?

After the high clouds go by, there is enough moisture around for middle clouds, though not decks of them.  So in the hours after the ice shield goes by, that is this afternoon and evening, we should see some Altocumulus and patches of Cirrocumulus.   As the winds increase over us, almond shaped clouds (flying saucers) are likely.

Update at 6:13 Am AST:  “Lenticulated sunrise” in progress now!  Check toward Mt. Sara L.  Here it is, in case you missed it.  Gorgeous.

Continuing….   Those kinds of clouds are good harbingers of storms.    Some small Cumulus are likely to start showing up in the afternoon as well I think, but will be high based and too shallow to produce precip.

It will be, I think, one of our most photogenic days so get yer cameras ready for some interesting, and finely granulated Cc, or Ac lenses.

The main slug of low based clouds, rain/snow, cold air, windshift to the NW, graupel, lightning, etc., comes in after mid-night with the front.  Temperatures are likely to drop 10-20 degrees as the front goes by tonight and the rain begins.  Check it out here from the great weather calculator at the University of Arizona.  And here for even more detail!  Even the Great Beowulf Weather Calculator at the U of AZ is excited about this storm, predicting more than 3 inches of water-equivalent snow on the upper regions of the Catalina Mountains, which is clearly too much!

But how great it would be if it was correct!

Hang on.  Breezes already at 6:37 AM, and you know what that means:  one heckuva windy day this afternoon and evening, dusty, too.

I think I need to rest now, maybe lie down for awhile, let the weather excitement dissipate.

The End.





Yesterday’s clouds, dust, and smoke; virga ahead

It was zero visibility in Parhrump, Nevada, yesterday afternoon with wind gusts to 85 mph, as the cold front was about to crash on by.   I guess we were lucky to only have 40-50 mph puffs of wind here in Catalinaland overnight, and not so much dust (yet).  A sharp, but dry cold front is bearing down on us, but the low center that was so intense yesterday over Nevada, then moved across Utah, has faded trying to move through the Rockies.  This means that the winds will be much less than yesterday.

Does that mean no dust around Catalina today?  Nope.  Those strong winds in Nevada and western Arizona yesterday raised a lot of fine (as in tiny) dust particles that are likely to be suspended for a day or two, and so we’ll likely see dusty skies today, without so much wind anyway.

We had some nice Altocumulus/Cirrocumulus lenticular clouds in the afternoon yesterday.  I wonder if you saw them?   They weren’t around for long.  Here’s what they looked like.

The last shot is of a cigar-shaped flying saucer with multicolored lights, OR, a Cirrocumulus lenticularis showing some slight iridescence (which are those rainbow colors near the edges of the cloud due to diffraction).    You have to look very hard to detect coloration in this cloud shot, but its there.  Diffraction is the bending of sun’s white light as it passes around the tiny (micron-sized) drops in the cloud and that leads to a separation of the white light into its components of reddish, greenish, blueish colors.

Take yer choice on what was photographed, but it is true that clouds such as lenticulars have been reported as flying saucers that “hover” then disappear.  This cloud was completely gone in one to two minutes after this photo AND was stationary, as lenticulars are in the face of strong winds aloft and at the ground, which also influences the observer’s reports of unexplained “hovering.”  This little cloud had been much larger ten minutes before reaching this size.

You can probably understand why such reporting might happen when you look at how smooth this little lenticular was.  And sometimes, when nearer the sun’s position, the colors caused by diffraction are quite vivid. 

Wildfire smoke

Also, in the late afternoon some smoke from the Nogales wildfire headed our way. It gave a great example of what young smoke looks like, that is, smoke recently emitted from a fire nearby. Its always got lots of gradations of the smoke in it because it hasn’t been around long enough for turbulence to mix out the smoke into a homogenous layer.   This happens when smoke has been around for days and days and has traveled thousands of miles, and so its one way of telling that a smoke layer has come from a long distance.

Sometimes high, smooth, long-range transport smoke layers can be mistaken for Cirrostratus, hold yer hat, “nebulosus”, a completely smooth ice cloud without much internal detail.  Below, the smoke from the Nogales area as it headed northward toward Catalina.

Rain possible?

It seems as dry as this system is, about all we can hope for is a trace.

It does appear that there will be enough moisture by tonight and for a couple of days as this cold air over us hangs around that we will see high-based (that is, probably based at or above the top of Mt. Lemmon) Cumulus and Stratocumulus clouds, and with the low temperatures aloft, ice should be able to form in them–which as you know, means virga, snow falling out and melting on the way down.

However, it would appear that only sprinkles are possible at ground level here in Catalina.

What to do?

You won’t want to miss entering the fact that a sprinkle occurred in your weather journal, one that might only last a minute or two, and so its best if you keep, say, your car parked outside where a layer of dust can accumulate, and then, when the rain drops fall, they will leave impressions in the dust.

The full moon of last evening, FYI.

Factoid:  it is thought that the moon was originally part of the earth, the result of a gigantic (!!!) impact that sent part of the earth out into space which then became our moon.  This theory would explain the synchronization of the moon’s face with the earth, that is, having the same face toward the earth.  Hmmm.  Hope we don’t have another one of those soon.  Two moons would be mind boggling.


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.


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.





Near miss on rain; pretty clouds and a nice sunset

Here are a couple of scenes from pretty yesterday, a day that the phony numerical models had rain predicted for us one to two weeks in advance, and then dried that system out as far as we here in Catalina are concerned as the days got closer.  This happens all the time in the models, so you would think I would develop a tough skin to these repeated disappointments, but I haven’t.  Oh, photos.  Here they are-the middle panel having a nice pancake-like stack of Altocumulus lenticularis clouds northeast of Charouleau Gap:








So what was the missing ingredient? Well, the core of the jet stream at around 18,000 feet above sea level, what we call the 500 millibar pressure level as well, stayed just to the north of us. If you have read this blog, you know that the core at 500 mb has to be over or to the south of us and that didn’t happen. Its a necessary condition in the cool season here, but not always sufficient. Shown below is last evening’s 500 mb map, courtesy of the University of Washington with station plots and infrared satellite imagery. Those two flags and a wind barb for our Flagstaff balloon site (“rawinsonde” site) shows that the core of the jet stream was just about right over Flagstaff at that time, and the wind was over 120 mph (105 knots)! Note that the wind at the same pressure height on this map is “only” 65 knots over Tucson.  By this morning, that core had settled a little more southward to between Albuquerquequeque and El Paso, and along with that the precip shifted a bit south as well.  Darn, had this happened 12 h earlier we likely would have gotten a small amount of rain.

If you look at a loop of the radar echoes during the late afternoon and overnight from IPS Meteostar, you will see that the precip is confined to near that jet stream location and northward.

Shown on the Washington Huskies loop is another powerful storm about to strike the West Coast.  THIS one WILL bring the jet stream core south of us as it passes over on Monday night-Tuesday morning, the 23rd-24th, and circumscribed inside that jet stream core will be moisture and clouds low enough to produce at least scattered showers, and may a nice rain band of a few hours duration.  So, maybe the rest of January won’t end up as rainless after all.

The best thing about this next trough is that it gets stuck as a cut off over west Texas and causes quite a bit of rain there in that drought stricken region for a couple of days.  Might have to drive over there and see how happy the people of west and central Texas are when the rains begin.

Don’t want to end this session without a long distance model teaser, “big storm” from IPS METEOSTAR as shown here valid on February 3rd at 5 PM AST.  Note how it resembles once again our early winter pattern of the isolated cut off upper low.  Hmmmm.   Maybe there will be something to this one because of this winter’s theme song of cut offs.


The End.

Twice as nice; 0.53 inches in Catalina (0.58 inches as of 6:39 AM AST)

What a superb rain that was last night.   It just kept coming until finally we piled up an astounding-to-me 0.53 inches by 4 AM this morning.  The regional rain reports from around Tucson can be found here.  As you will see, the upper regions of the Catalina Mountains got around an inch (1.22 inches at CDO wash at Coronado Camp now).  Mt. Lemmon probably got a little more, but the record says “0.00” due to snow at that elevation.  This is a substantial boost for our emerging spring desert vegetation after our four week drought.  This is so much better than that near rainless January of last year!  Looking at some of the statewide precip reports, it looks like the Catalina area and the Cat Mountains got more than anywhere else.  Lucky us.

If you would like to relive yesterday, at least in clouds, go here to the U of AZ time lapse.  One of the things you will see later in the day are Altocumulus lenticularis clouds over the Catalinas.  You will see their upwind edges spurt upwind (seem to go the “wrong way”, against the wind) as the lifted air got more moist, one of the tricks that these clouds can pull.  You will see quite a panoply of clouds in this movie, from Stratocumulus, Altocumulus, Altostratus (dead gray and smooth higher layer), Nimbostratus (when the rains come) along with some mammatus formations.  Hmmmph.   There’s that “m-word” again, the one I used so many times yesterday.  Wonder what’s going on?

“But wait, there’s more!”  

If you call now (well, actually if you continue reading) you’ll find that a few more hundredths of rain are possible this morning before about 8 AM AST, AND, (We interrupt this blog for an important message: “hey”, just started raining again now at 5:03 AM!  Yay!)

all of the model runs are indicating rain again on the 22-23rd timeframe; even the “pernicious” 00 Z run from the 5 PM AST global data.   (I have questioned that output of late, rationally or irrationally,  because it kept drying the State of Arizona out whilst the model runs before and after that time, foresaw precip in spades in the State.

Here is a sample of the IPS Meteostar renderings of what happens in our rain window of the 22-23rd according to our latest model run, one from 11 PM AST data.  Note green areas of precip in the 6 h ending at 5 AM AST, Jan 23rd.  This is pretty satisfying since another good rain will keep us on track for a great spring bloom.

On other fronts…

While I could go on to talk about all sorts of things due to the ambiguity of the subtitle phrasing above, I will actually only talk about weather fronts, not this or that. 

The coming floods in northern Cal-Oregon still on track.  Storms break through from the Pacific “under” the Bering Sea “blocking” high, one that diverts the potent Asian jet stream that comes into the Pacific into two branches, one of which is forced southeastward in the central Pacific where water temperatures are warm.  (Just heard some rain on the roof again.  What a nice sound that is!)  The other branch goes deep into the Arctic and merges with the southern branch in the eastern Pacific after it turns southward over AK.

Those warmer storms, heavy with semi-tropical rain clouds, race to the West Coast once the southern jet breaks through the weakening southern part of the blocking high.  And once that jet stream has broken through, its days before things change, so the duration of rain adds to the colossal totals certain to occur now. In a ten day span, beginning tomorrow, the peak totals in this event will likely exceed 30 inches of rain.

Here is the current weather map (5 AM AST today) from the University of Washington that illustrates the odd flow pattern developing now from the central Pacific to the western US.  The block  is developing from a ridge in the eastern Pacific now (evidenced by the lack of green contours in it) that extends from the tropics all the way to the Bering Sea!  It will fracture in its southern portion tomorrow.  It has overextended its “reach”,  in a manner of speaking, at this point, and will fail just like a dam break and all those clouds to the west of it will flood eastward.  Its a pretty exciting thing for us precipophiles.



Canadian behemoth

One particularly bruising storm, one the size of Asia practically, with “tentacles” from the Aleutian Islands to Minnesota, was shown to develop in this series of storms battering the West Coast in the European model run by Environment Canada based on last night’s data.

I show this output below because you RARELY see a low whose circulation is this big, at least one of the biggest I have ever seen, portrayed on a weather map (upper right panel).  The map below showing this colossal low is valid for the evening of Jan. 21st.  The entire West Coast would be battered by this bruiser.

The End.



Low spin cycle continuing off Baja; water being added

That enfante terrible now dawdles over the coastal waters of California and northern Baja today, adding some water to its central system as seen here from IPS Meteostar.  Note, too, a scruff of Stratocumulus clouds racing northwestward in the Gulf of Baja abouit the latitude of the border between north and south Baja.  This is good.  Still, this is a marginal storm as it trucks through on Sunday evening and I will be happy if we get a quarter of an inch.  Mods don’t think rain will get here until the upper center is upon us later Sunday.   Here is the whole map forecast sequence showing temperatures and winds aloft at 500 mb from the U of Washington unranked Huskies who play #12 Baylor in the Alamo Bowl –what a horrible bowl game that is for Baylor–on Dec 29th.  Still, as a spin off myself here into the SW like all of our lows this year, but from the U of WA, I will be rooting, of course,  for the “company team” along with my friends and former grad students with whom I worked.  BTW, these are pretty maps with lots of color as you will see.

You will also notice in this 4 day series of forecast maps for 500 mb that yet ANOTHER low drops into the Yuma area replacing the current one that begins to move toward us later today.  That new low develops via the back door from Colorado and nests over Yuma as a cut off at the end of the forecast cycle above.  That ‘s an unusual trajectory for a low! However, mods think its too dry to produce any rain as you might imagine.   But with another low center aloft ending up in the SW, it demonstrates again our characteristic pattern for this early half of the winter, having become something of a low magnet.  It certainly has been strange to see so many cut off lows.

BTW, the longer term picture after our little rain is a dry one for the next two weeks;  it may well mark the end of our cut off low fantasia.  Hope not.

Today’s clouds…

The marginal amount of moisture circulating around the periphery of this Baja low, I think will spin out some spectacular middle and high cloud streaks and patches over us such as Cirrus, Cirrocumulus with its tiny granulations, and Altocumulus lenticularis here and there, ones that often break up into small and interesting cloudlets downstream.  Get yer cameras ready!  Some of this began to happen yesterday afternoon.  Sometimes you see the most amazing tiny delicate patterns, very photogenic.

Here are a few shots from yesterday, beginning with that sunrise patch of Altocumulus and ending with a sunset shot.

Great weather map day

Check this map out below from the University of Washington Huskies Weather Department.  The whole 24 h series of sea level pressure maps is here and watch how things change in the SW and western Arizona just in that time.  You rarely see lows of this magnitude in our area as we have right now, and this much change in just 24 h in a sea level pressure map.  As you can see from the low center  centered over Ajo, AZ, (below) the air is going in counterclockwise circles in our State.  Well, of course, friction caused by cactus and mountains turns the air toward that low center, trying to get rid of it.  But, the forces producing it so far are stronger so far and so it has a very low pressure (less than 1004 millibars) for this time of year over AZ.

Note, too, that all the clouds and precip (shown here) and by those white areas on the map below, are to the west and north of the center.  But that will change as the upper air low center (second map) spins back to the southwest a bit and the air over us changes in direction from the southwest, as it is now on this upper level map, to a more southerly direction in the hours ahead.

In the meantime, Pacific air should be gaining a presence over the interior of Baja and begin circulating from there up toward us.   Clouds should literally start appearing out of the clear skies to the southwest of us in satellite imagery today (such as here) and then those clouds will work their way up this way, likely increasing in depth and coverage as they do.

Another exciting prospect is that this same process, clouds appearing out of the blue, will likely start happening over us as the day progresses, and maybe, in view of the strong winds aloft, some nice “flying saucer” clouds, namely, Altocumulus lenticularis, flat, lens shaped clouds that hover over mountains will show up over the Catalinas.

These are great days ahead for weather folk, and I hope in spite of any inconveniences caused by quite wonderful inclement weather, you will enjoy this dynamo of a weather day.  Of course, you wanna go here, to the NWS, for all the great details.

Rain?  Supposed to begin in these parts between around 4 PM and 6 PM today (you can see this here from the U of WA model).   Interestingly, this model has a rather thin band of precip sitting over us for more than 12 h.   Good grief!  Too good to be true I suppose, since we might get well over half an inch, and would certainly, if it happens, push our wildflower prospects for this spring up in view of our 1.83 inches here in Catalina in November.

Also this;  a nice satellite view of the US where you can see the night lights of the cities, if you’re up early enough and haven’t seen it before.

The End for now.

“Oh so pretty….”

You know the rest of the words to this song, the punch line,  “…pretty ugly.”  Yes, who can forget Johnny Rotten….?

Gorgeous clouds yesterday, but no rain is going to follow them (the “ugly” part)!  I had really hoped for a splotch of glaciating Stratocumulus clouds this morning after the great display of….the tongue twister, Altocumulus (Ac) perlucidus undulatus, a mid-level cloud with a honey-comb of elements (“perlucidus”), and those elements also aligned in rows (“undulatus”).  If you looked off toward Twin Peaks, you saw that the the back edge to these clouds was very smooth looking and did not advance toward us.  That was an Ac lenticularis cloud that started the whole shebang.  That lenticular cloud, as often happens, devolved into little cloudlets and rows;  its smooth lenticular form devolving into cloudlets that trailed downwind over us here in Catalina.    See pretty pictures below. One has the crescent moon in it.


Now it looks “pretty ugly” here for rain since there are no clouds this AM!   “Dang”, as a friend would say.

Why get excited about the chance of a sprinkle, or at least some pretty virga this morning because of the two layers of clouds yesterday afternoon?   No model indicated any rain.  First, it doesn’t happen often, but to HELL with models, they can be WRONG.  Don’t bet against them too often, though.  You will lose everything.

So, if you were just eye-balling the movement of those two cloud layers later yesterday afternoon and using the crescent moon as your fix, you saw that those mid-level Ac clouds were jetting along at a tremendous speed as they passed it.

How fast?

The NWS balloon sounding indicated that at the height of those pretty Ac clouds, about 20,000 feet above ground level, they were blowing along at no less than 80-90 mph (70-75 knots)!   This is a really strong jet for May!  And it indicated that the jet stream must be right over us, or darn close, and it was blowing from the SW.  If you no doubt know,  Buys-Ballots Law, in the northern hemisphere means that a low or trough is to the west of you, and in this case;  above you, not at ground level since you’re looking at higher clouds.

Also, the small Cumulus were beginning to cluster into Stratocumulus over the Catalina Mountains.  Getting pumped because there movement was showing more southerly now; the wind was more southerly at that level than it had been in the morning, also suggesting the influence of the trough to the west.   Here they are.  If you really want to relive yesterday’s clouds, particular in the afternoon and evening, our friends at the U of Arizona Wildcat Department of Atmospheric Meteorology have captured them

here.  For the really sharpies who DO go here, you’ll see that these cloudlets were further devolving in this time lapse to “ghosts” of their former droplet selves in the form of barely visible, icy little veils as they exit the area.  So, can you guess the temperature of those clouds?  Piece a cake:  probably -20 C or less (-4 F or less).  Sounding indicates -20 C, BTW.

Perhaps, I mused yesterday afternoon in a bout of wishful thinking,  that in the core of that trough heading for us, there’ll be a smidgeon of Pacific moisture left within its interior, enough for some thicker lower clouds than now, and those clouds will be cold enough, too, so that they will form ice inside them and we’ll see some virga (trails of snow fall out of them) or get a sprinkle (in spite of what the models were saying)!  Many of you will remember that according to Willis and Rangno (1971–Final Report to the Bureau of Reclamation by EG&G, Inc) that rain can only fall in the wintertime here when you are in the interior of a trough.  I’m sure many of you have this report, and can look it up jf you don’t remember.

Well, we should still see a few isolated Cumulus around, small ones, maybe as big as “mediocris” stage (1 km thick or so, 3300 feet).  And, with the coldest air over us this afternoon and evening, I am going to stick with an expectation of some ice in those clouds!  And you will here about it tomorrow if there is one crystal up there!

Finally, for cloud technicians, how cold will it have to get at cloud top to have ice in those small clouds around here in Arizona today?  Well, between about -10  and -15 C (14 to 5 F)–this is somewhat higher than for those mid-level clouds.  So we will check that out tomorrow, too!


“The end”, unless I think of something else later.


Footnote:  It now appears that last night’s model run of the “Beowulf Cluster” at the U of A has some precip on the Catalinas, between 3-4 PM LST today.  Interesting that after I had this thought based on a crude conceptual model, that the “Cluster” would now have that thought as well….  Hmmmm.