Altocumulus overhead; sunrise photo op coming

An upper level disturbance is going to pass over us today (see map with bend in the winds at 30,000 feet coming toward us here), but the only thing we’ll notice is some nice Altocumulus clouds floating over followed by a clearing later on today. Those clouds are overhead now in the pre-dawn hours, we’ll likely have another one of those gaudy, too-colorful-to-be-believed-like-one-of-those-velvet-art-pieces-sold-on-street-corners-sunrises that we are known for here in AZ. Might even have a little virga with them. Lucky us! So you should have your camera battery charged up in case this one’s really good! You’ll want to add to your collection of 78,000 or so fabulous sunrises and sunsets in Catalina, AZ…like I will.

Note, too, that in this depiction of winds (the wind is flowing along the lines) that where the wind has a “U” shape, there are clouds to the east of those bends for the most part, that is, ahead of where that “U” shape in the winds is headed, and not much to its rearward, or in most cases, immediately to the west of the “U” bends in the winds. We will see the “ahead” portion of a “U” in the winds above us, and the clearing that comes afterward, all today!

The end (for now).

How Cirrus clouds grow up to be “uncinus” ones

What a glorious day yesterday was, if about 20 degrees F below normal! So much new snow on the Catalinas down to such low elevations for almost mid-April. Some sites in the Catalina Mountains reported over an inch of water content in that snow! Yay! Here in Catalina we had a bountiful 0.69 inches, more just to the north and west. Choose April 9th, and “Tucson” in drop down menu on this U of AZCats rain page to see the amounts around here. Truly a remarkable storm for April.

About those Cirrus “uncinus” clouds

How many saw those fabulous Cirrus clouds in the morning? Once in awhile, during the passage of Cirrus clouds you get to see how those long, delicate strands you often see by themselves, get that way, from their initial appearance to the end point; the long strands. Usually you can’t because Cirrus clouds are traveling so rapidly up there at 30,000 feet or so that they have gone over the horizon before much happens. Yesterday, an example of that “life cycle” passed overhead, moving from the W to the E at about 70-80 mph or so. In all of the photos below, the subject Cirrus cloud is in the upper right part of the photo.

Here then is most of the life cycle of a Cirrus cloud as it happened over Catalina. The starting point is that whitist cluster of little cloudlets, upper right. Those strands of Cirrus below that and that appear in rows to the lower left, are old dying cirrus clouds at the end of their life cycle. That top cluster in 1) has just appeared, probably only about 10 min old, and now the larger ice crystals are JUST beginning to leave the origin zone, much like a hiker reeling out rope to a friend stuck on a rock below. Those strands are like that rope having been let go of, then caught by the wind on its way down and stretched to full length while falling through the air. The remaining photos 3)-overhead view and 4)–leaving the scene, show that process continuing as the top cluster fades with longer and longer filaments of ice. In 4), you can see one strand in a side view as it speeds away revealing the lack of wind shear (changes in wind direction and speed) in the layer in which the cloudlets first formed. How do I and you know that? That one tiny filament that is straight up and down pretty much reveals that

You can now see how and why these delicate strands are there. Each long “rope” of ice represents one of the initial tufts that appeared within the cluster; each one has a contribution to make, a “rope” of ice to send downward. Almost always, except in deep storms, the strand of ice encounters drier and drier air and the crystals fall at lower and lower speeds until its negligible. The bottom, or lowest part of these strands then, have the tiniest of ice crystals, and the tail of the strand at this lowest point may appear almost horizontal if you could be up there.

The end.

“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.

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.

“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.