Altocumulus clouds – Page 22

More Cirrus on tap today

No, Cirrus is NOT a microbrew as you may have thought from the title and if you were visiting this site for the first time. (and to continue being juvenile from yesterday’s “Dusty Parhelia” submission because that’s who I am….)

In fact, Cirrus clouds are the exact opposite of a microbrew. Cirrus is a high CLOUD, 15,000 to 45,000 feet above ground level, lower in the Arctic or when its cold, higher in the Tropics or when its warm, like today here in Catallina. They’re composed of ice crystals with some momentary exceptions at the time of formation. To continue a theme, there are no “ice crystals” in beer; beer is also generally found at ground level.

Q. E. D.

BTW, if you’re still interested in beer and clouds, get this book:

Clouds in a Glass of Beer: Simple Experiments in Atmospheric Physics by Professor Craig Bohren. In spite of having an interest in beer or perhaps because of it, he is a Distinguished Professor Emeritus of Meteorology at Penn State University, one of the leading party schools in America. Writes about optics, too, a real atmo optician. Kidding aside, his book is one of the best you can get on how the atmo works.

To sum up, it should be another fun day of Cirrus cloud viewing for you and me. What kind will we see?

Yesterday’s clouds

Man, yesterday was great! Some unanticipated Altocumulus castellanus and floccus, middle-level clouds with little turrets, many having long fall streaks of snow (virga) rolled in during the afternoon underneath the higher Cirrus clouds, keeping the temperature down a bit. Here are some shots of what went overhead, in chronological order, in case you missed the “show.”

The show ended with dessert, another one of our gorgeous sunsets; they are particularly so when two or more cloud layers are present. In those case, you see the residual scattered light that has passed through the lower part of the atmosphere when the sun sets, turning the lower clouds gold or orange (the longer, “redder” wavelengths of light are still making it through) while the higher ones, where the sun’s light is not so scattered in passing through the atmo, are that bit lighter in color, white before this last photo. The greater the height difference in the clouds, the greater the differences in sunset colors between them. When you add shadows and highlights where the sun is striking the clouds, well, it doesn’t get any better than this. OK, I am feeling lazy now about captions; been up since 3 AM something. Can YOU name these clouds? If not, just enjoy.

The End.

Cirrus altocumulus castellano-floccogenitus

We had a rare form of Cirrus yesterday, whose name I have made up in the title as a hint of where they came from, due to the very high altitude and low temperatures of some Altocumulus yesterday. Those Ac morphed to Cirrus, hence the strange, unpronounceable title.

Reminder, weatherscience mavens, its more proper to say “low” temperatures; not “COLD” temperatures, FYI, though you constantly hear it. (“Things”, like coffee, air, chairs in the sun, etc., are hot, warm, cool, tepid, and cold; temperature is not a physical thing, and is high. moderate, or low, etc.))

Still bristling over some unexpected clouds yesterday, so I wanted to complain about something minor, bring some discipline to the field.

Mr. Cloud-maven person was not paying attention, asleep at the wheel, etc., when some Altocumulus castellanus and Cirrus castellanus came a truckin’ over the horizon and floated over Catalina after dawn yesterday, but had not been mentioned in this blog in advance. I am sure, since they had not mentioned from this keyboard, you may have been in some distress yesterday when they showed up and you weren’t sure what was happening. My apologies. It will almost never happen again.

Here are some photos of the interesting clouds that passed overhead yesterday. I was quite excited to see them partly because I had not prepared myself mentally for them. Now, there is something strange in the first caption. But I wrote it that way on purpose because I REALLY want to know if YOU know WHERE the HELL you are, and where the mountains are around here. Next, after that outrage, some interesting banded Cirrus. Then a hint at where those Cirrus came from in the background of the 3rd shot.

SONY DSC — First, this sunrise over the Tortolita Mountains with Cirrostratus nebulosus (vellum-like cloud) and a hint of Cirrocumulus (tiny, brighter, flocculent specs).

DSCN1187 — This banded Cirrus gave some hint as to its origin. Might be termed, Cirrus uncinus, or floccus, or fibratus, its a pretty complicated set.

Caption function not working now for this third shot in WP, so here it is:

3) A nice example of Cirrus uncinus in the foreground, tufted or hooked ice clouds trailing tiny ice crystals. In the background, a clue to the origin of the patchy, banded Cirrus.

4) Another shot of the approaching Altocumulus castellanus (Ac cas) and (Ac floc) floccus clouds as they arrived overhead, some of which have morphed completely into ice (Cirrus) clouds, such as that larger element over the house in the foreground! In the upper left quadrant of this shot are Ac clouds that, to this eyeball, are still liquid.

Droplet clouds have more sharply defined edges because droplet clouds have MUCH higher concentrations of particles in them than ice crystal clouds (which tend to make them “fuzzy”, ghost-like, striated, fibrous, etc.

Why this visual difference, which I want you to learn, to see for yourself and impress your friends?

There are more cloud droplet condensation nuclei than there are ice crystal nuclei. For example, liquid Altocumulus clouds might have 100,000 to 500,ooo drops per liter in them, while ice crystal clouds may have only tens to a few thousand per liter (and then only in newly formed elements) of ice crystals. In general, there are more cloud condensation nuclei than ice nuclei, too.

Today

While “Joe” is spinning up into his little hurricane-like self in some kind of weather tantrum off the California coast today before heading to Oregon, our skies over Catalina will be marked by various forms of Cirrus clouds, ice clouds well above 25,000 feet above the ground, and not much else. BTW, you can follow Joe’s progress here from the U of WA, if interested.

If you’re interested, instead, of following our Cirrus clouds as they approach and go overhead today, go here, also from the U of WA. You see the Cirrus clouds pealing off the main frontal band in the Pac NW and then fading as they head this way. (I would increase the speed of the loop for maxium excitement.)

The End.

The lenticular that came for breakfast and stayed for dinner

Some of you already know that there is a favored position for a lenticular cloud downwind from the Santa Catalina Mountains. Yesterday, a little fluff of Altocumulus lenticularis kept reappearing all day! It didn’t have the “classic” look of a lenticularis early on, but that’s what it was, hovering over the same spot, changing size some, disappearing then reforming over the same spot. That rough bottom early on suggests turbulence. You don’t want to fly there. Often, flying IN lenticular clouds is, as the smoothness suggests, completely lacking in turbulence. Its when you come out the downwind end of those clouds that you can experience some nauseating bumps.

Why was the lenticular cloud there all day?

Because there is a standing wave, or hump in the airflow downstream of the mountain that raises a moist layer to its saturation level where a cloud must appear, and not much changed in wind direction and moisture all day up there. The morning and evening sounding for Tucson were almost the same. Also, while that lenticular cloud was nearly always there, it was often “buried”; obscured inside that sometimes thick layer of Altostratus with its virga that moved in during the afternoon hours.

Some photos. (BTW, since I started adding captions, WYSIWYG has gone bonkers in the Word Press edit page. So excuse the strange organization and text in odd places–still learning here.)

Below, photos of some of the other clouds of yesterday. I have to say if there was a disappointment, it was that there wasn’t as much Altocumulus as I thought, and virga trails were not as long as I expected, either. They were barely hanging down from that Altostratus layer, an indicating of smallish snowflakes in the Altostratus layer as well as very dry air below it.

DSCN1173 — "Altostratus over horse arena".

Lastly, a sunset shot, indicating the back edge of these high and middle cloud layers was over the horizon to the west.

Arriving in local skies today: clouds, high and middle ones

Now that your camera battery is fully charged, you will be ready for the panoply of high and some mid-level clouds that will be arriving overhead today. Should make for some great sunrise and sunset shots, but also daytime shots due to the interesting twists and turns in the Cirrus (ice) clouds that will float by. Maybe later today, Cirrocumulus and Altocumulus clouds will show up adding that extra dimension to sunset color. Typically, in these situations, the first clouds on the scene are Cirrus at the highest levels (30,000 to 500,000 thousand feet above ground level (hahaha-just checking to see if you are reading this)–OK, 30,000 to FORTY,000 feet above the ground here on a warm day in Catalina-Tucson like today.

Next, with the moisture layer thickening downward from those high CIrrus levels as the day goes by, there might well be some Cirrocumulus (Cc) cloud patches, ones between about 15,000 and 25,000 feet above ground level. Some times they evolve to Cirrus clouds within minutes after they form when they’re colder than -30 C (-22 F). Cirrocumulus are short-lived clouds usually in thin, isolated patches. They can have no shading by definition and they can display the most delicate granulations imaginable.

But those patterns change in seconds to a few minutes, and you have to have your camera by your side to get the best shots of that sort of thing, like other nature photographers who shoot birds and stuff like that. Did you realize that by shooting clouds that you were becoming a “nature photographer”? Often these patches can be higher level lenticular clouds (thin sliver clouds) that have smooth portions on the upwind side and then break into tiny elements downstream.

Finally, as the day comes to a close, some Altocumulus clouds might arrive on the scene; if not today, then by tomorrow at daybreak. They may also be in the form of sliver clouds, lenticulars that hover downwind of mountains–look to the northeast of Mt. Sara Lemmon today. But, given the high temperatures aloft, indicating that the Altocumulus clouds will have more water in them than on a cold day, look for some sprouts and little turrets. That extra warmth, say at 15,000 feet, results in an enhance updraft when clouds form at those levels because condensation releases a small amount heat to the atmosphere inside the clouds. That bit of extra heat is likely to lead to those itty bitty turrets (castellanus species of Ac)

Here is an example of the delicate Cirrocumulus (Cc) clouds we may see today and tomorrow.

No rain seen in models for two weeks now, but remember the wild chaos of the predictions beyond six days now, as indicated in “spaghetti plots.” That means rain for southern AZ may well show up again soon, along with that horrific early April cold spell.

The End.

Rain today, clouds yesterday

Yep, that’s right, rain IS imminent! In case you forgot what they looked like, there’ll be a display of “hydrometeors” before 7 AM here in Catalina. Should last the whole morning at least. If you don’t believe me and think I just made this up, go here.

BTW, “hydrometeors”; what real meteorologists, well, maybe pretentious ones, call rain drops; remember, we’re METEORologists, we like to see things falling out of the sky.

Not raining now at 4:38 AM, but its on the radar here for the Catalina area from a great weather provider, Weather Underground. Amounts here likely to be around an inch in the next 48 hours. Still looking for a drop in temperature enough to bring our current (5: 1o AM) mid-fifties temperatures into the upper 30s in the rain as the cold front goes by, maybe tomorrow morning as well as a second little pulse of clouds and precip keeps things going for a second day. That temperature drop should lead to a little snow in the heavier periods of rain.

Second pulse?

Racing from the north central Pacific is a little blob of clouds down the “backside” of our humongus trough. Here, from the University of Washington Huskies, still playing basketball in the NIT tournament, is a 500 millibar map. The blob of clouds that will extend our rainy spell is located, on this map, a few hundred miles west of San Francisco. It is CRITICAL to us to get that second day of showers after the current front goes by with its strong rainband today.

The green lines on this map are contours along which the wind blows. Here you can see a HUGE fetch from the north central Pacific to Oracle Road, Catalina. To demonstrate this more clearly, click on the map below to get the full version, and place a finger on one of the green lines in the north central Pacific, say, just south of the Aleutians. You might want to pick the one labeled, “5580”. Then with your finger on that line, follow it southeastward (“down” toward the lower right), maintaining contact with the montior screen, until you exit the right hand side of the map. I hope you haven’t had a peanut butter and jelly sandwich before doing this.

If this map pattern was stationary, that’s where the wind would go, forever, “down” and then “up”. Where your finger reached the point farthest to the south on this map, and where the wind makes a sharp turn around San Diego, is what we call a “trough”. And, if you were to see a map at a LEVEL in the atmosphere, there would be a long extension of lower pressure from the Pacific Northwest to San Diego at the time of this map. But no, we meteorologists complicate things by using constant pressure surfaces which go up and down in height all over the map instead of constant level surfaces instead of an easy to understand constant level map with highs and lows on it. Oh, well.

This “second pulse” of clouds and precip is moving so fast, it will get to the “bottom” (south end where the wind curves to the north) of the trough before it has a chance to exit Arizona. That will add a whole second day of showers and rain with a very low freezing level tomorrow. Its a bit rare to see something like that catch up so fast to the main trough and, in a sense, delay its passage.

Yesterday’s clouds

Okay, you had yer flying saucer clouds here and there during the day, that is, in proper cloudspeak, Cirrocumulus (Cc) lenticularis (first photo), Altocumulus lenticularis (second photo, is lower, has shading, compared to Cc–that short flat cloud below the Altostratus layer), you had yer Altostratus band (3), followed by yer clear slot, beginning at 4 PM -hope you planned a picnic around it, or trip to the beach (4), then quickly followed by heavy, dense Altostratus layer, (see second shot with saucer cloud).

No sunset color due to the solid cloud banks to the west. Should be enough breaks in “post frontal” low clouds for sunset color today, however.

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.

Cloud quiz

While waiting for the rain, here are some of yesterday’s clouds. What were they?

Answers printed upside down at the bottom except that WordPress wouldn’t let me do that. It would be great if you turned your monitor upside down before you looked at the answers. One is a trick “question” because I took a picture of a cloud behind what appears to be an inanimate plant, focusing on the dead plant and so the cloud shown in the background is a little fuzzy to make it more difficult.

1. Cirrus spissatus, the only type of Cirrus allowed to have gray shading in the daytime. Note mammatus like feature in the center.

2. Contrail, unusually turreted one (hmmm, perhaps a part of some government conspiracy–hey, I am kidding the “chem-trail” people). There’s also a patch of Altocumulus floccus (or Altocumulus perlucidus would be OK, too) lower part of photo.

3. Cirrus castellanus-turreted Cirrus, don’t see that species too often because it is rarely so unstable at that height. “Unstable”-the temperature dropped a LOT as you went higher up there, more than usual.

4. Altocumulus floccus, horizon, upper right, Cirrus fibratus (pretty much delicate, straight fibers) middle.

5. Ocotillo (hahaha, its not a cloud!) ((Another example of the juvenile humor that the writer seems to be afflicted with). OK, it looks like mostly Cirrus castellanus in the distance.

What do these kinds of clouds tell us?

The atmosphere is moist, but only patchy moist, a frequent occurrence in desert areas because “patchy moist” at middle and high levels in the atmosphere is most often all you get on the southern periphery of the major storms to the north of Catalina in the cool part of the year.

The atmosphere over us, too, is only in ascent at an overall rate of maybe an inch or two a minute; a bit more inside the clouds, less outside the clouds. One way to KNOW how slight the air is rising, even in the clouds, is to observe that snow is falling out of some of them, tiny ice crystals, typically in the low hundreds of microns in maximum dimension (width of a few typical human hairs, which are about 100 microns in width.) Such tiny ice crystals have fallspeeds less than 0.3 meters per second, and so they wouldn’t be able to fallout with higher overall “slab” lifting, the rate of that the whole upper air is lifting at these cloud levels. Q. E. D.

What caused the lifting? When you see clouds scattered over such a vast area, they have to be due to a disturbance in the wind field, a trough is likely nearby, normally upstream.

I have not looked at maps lately, but will NOW to see if there is a bend in the winds (indicating a trough) at these heights (mostly Cirrus level). I don’t see one on the 300 millibar map (30,000 foot map) and so I am not going to show it. But anyway, I am right, I am sure. Now, I will begin a serious investigation to prove I am right. The models will know if there is lifting going on.

Yes! I have been saved in my assertion by my former employer, the University of Washington‘s MM5 model, and this was the first thing I looked at! Look at the predicted high “clouds” (those above 20,000 feet) over Arizona for yesterday at 2 PM AST! They can’t be there in the model unless it thinks the air is going up some. OK, past the exultation stage now. Moving on. Actually, the model predictions of Cirrus-ee clouds aren’t really that great, so it was quite a surprise to see this.

The End.

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)

When the jet goes by, the clouds, lower ones, roll in

And that’s pretty much what happened yesterday. Here are some maps showing what happened as the jet stream in the middle troposphere (500 millibars or about 18,000 feet above sea level) went overhead while deploying to the east and south of us. The sky change was pretty dramatic as you may have noticed.

First, how the forecast model had it timed, then the sky pictures as it was happening. These panels, from IPS Meteostar, are for 2 PM, 5 PM and 8 PM AST (these panels look almost identical, but believe me, that reddish area, indicating the strongest winds, is shifting eastward over southern Arizona!) By 8 PM AST, the jet is completely past us (third panel).

The last panel, from the University of Washington, is the actual observations and “contour” map for 500 mb at 5 PM AST yesterday, that time when the sounding balloons (“rawinsondes”) went up. That flag and four and half barbs at Tucson tell us that the wind was over 100 mph at 18000 feet above sea level over us at that time, likely the heart of the jet at 500 mb. Its pretty unusual to see winds that strong so low.

You can also see in that contour map with satellite images of clouds that the clouds pretty much end south of that wind maximum at Tucson. At the same time, you can also see clouds puddled around inside the low in northern Arizona, encircled by a jet stream. This sight, no clouds or just high and middle clouds, on the outside of the jet core, and low clouds with precipitation, is a common occurrence in the Southwest into the southern Rockies. Scattered light snow showers were common in northern Arizona yesterday. It is virtually required before any precip occurs in SW in the wintertime, that you have to be circumscribed (“inside”) the 500 mb jet. BTW, this “rule” does not hold in coastal regions, such as southern California, or very far east of the front range of the Rockies, or in the summer months, of course. But its pretty solid here storm after storm.

And, of course#2, the sophisticated models of today know all about this “rule”, incorporating it in their outputs, and so we weatherfolk don’t really need to look for where the jet max is anymore like we did in the olden days of forecasting. Still, its simplicity is appealing.

On some occasions, such as yesterday, when only brief virga accompanied those lower clouds, it is a “necessary” condition for rain here, but not always “sufficient.” It was just too dry, even with this low’s little puddles of lower clouds filling its center.

The cloud sequence: 1) 1:38 PM: “nice weather we’re having.” 2) 2:18 PM: wha’ happened? Yesterday afternoon’s band of clouds accompanied the jet core passage overhead. Cool, and it got even cooler. Was hoping for a sprinkle, but didn’t get it. There was a brief radar echo north of Catalina about this time. That was it!

Since we’re still inside this jet/low this morning, there’ll be some lower clouds, Cumulus here and their, likely with a little ice, but too high and too sparse to have rain at the ground. Most of the dust should be gone now, so a great looking day is ahead!

The weather farther ahead? Some model fiction below, for March 19th. Nice scoop jet rises up into southern AZ after scooping water out of the Pacific off California. Would be a nice rain, if real.

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.