6:05 AM. Pretty ripples in Cirrocumulus below some Cirrus. What a fantastic and subtle scene this herring bone pattern was!9:34 AM. Pretty much a whole Cirrocumulus morning, punctuated by a few Cirrus clouds. Why isn’t it Altocumulus? Granulation is too tiny; no shading. BTW, no ice evident though this layer was colder than -20 C (-4 F).10:30 AM. An aircraft has punched this very thin Cirrocumulus layer and left a tell-tale ice trail that looks like natural Cirrus. Same cause for that second, white ice patch farther to the west. Its almost impossible to detect something like this since the ice trail from the aircraft is almost exactly in the form of a Cirrus uncinus. The absence of natural Cirrus is a clue about what happened.10:34 AM. The aircraft-induced Cirrus is passing overhead, and if you look VERY closely you can see that tiny “supercooled” cloudlets of Cirrocumulus are still there around it. The ice crystals fell below the Cc layer and disappeared over the next 15 minutes.2:27 PM. Later that day….widespread natural Cirrus overspread the sky, with a very thin patch of Altocumulus on the right (granulation is a bit to large for Cc).3:44 PM. Those Cirrus clouds thickened and lowered some, trending (as we would say today) toward Altostratus (translucidus–the thin version).
Today’s clouds
Today our passing cold-core trough is overhead and in the middle of it, the moisture is low enough to trigger Cumulus and small Cumulonimbus clouds as the middle and high clouds exit “stage right.” Should be an interesting day since these cumuliform clouds will be so high-based (above the Lemmon summit) and cold that lots of ice will form, producing virga, and in some places, sprinkles. A hundredth or two is possible, but that’s about it. Heck, I guess there could be some lightning here in southern Arizona as well.
This will be the last interesting cloud day for awhile, as you likely know.
Below, your weather map for 5 PM AST when there should be plenty of ice action all around:
Sent to ME just yesterday from an El Niño expert in Monterrey with the NOAA SW Fisheries Center, this update:
“(An El Nino is coming)….faster than you might think: http://www.esrl.noaa.gov/psd/map/clim/sst.shtml Looks to me that we’ll have what I’d consider a ‘full-blown’ El Niño in the tropics by the end of the month, maybe even sooner. And it looks like it’ll be on the big bad side …”
I felt like a recipient of insider trading info! But what do I do with this info? Guess I’ll just pass it along verbatim to you. Maybe you’ll be as happy as I am, hearing this news. El Niños generally lead to wetter conditions throughout the SW, so maybe we’ll get some substantial water next winter, but then if it floods like in Jan ’93 like it did with that El Niño, I am sure we’ll be complaining (almost 17 inches of rain that month at the old Tonto Creek Fish Hatchery/Oak Creek Canyon area). Thirty-eight inches (!) of rain that Jan ’93 month at one southern Cal mountain location, Lytle Creek Ranger Station, I think it was.
—————————Currently————————–
Upper trough trudging across area today, tomorrow and into Sunday, a mostly dry one. However, some Cumulus should form later today, maybe with a couple of Cirrus/Altocumulus/CIrrocumulus at times, too. The air aloft should be cold enough by late today, but especially tomorrow, to spawn large enough Cumulus clouds with tops cold enough to contain ice, viz., small Cumulonimbus clouds of the kind we had a couple of weeks ago with virga and dust eruptions. So there is a chance of a sprinkle or a hundredth or two tomorrow afternoon here. Check here for the great U of AZ model output from 11 PM AST last night–not finished yet at at 4:37 AM. But it will likely have some precip around the Catalina area tomorrow afternoon when the calcs finish.
Its for this coming Tuesday night into Wednesday morning, from our best computer model. As you can see by the caption, its valid, too.
Valid.
If you visit the models day in and day out, you will have noticed by now that this has been a pretty normal rain year in model rain, model rain for Catalina often showing up 10-15 days in advance, but then disappears as the predicted rain day gets a little closer. This situation has gone in the reverse direction where no rain has been foretold in the models anywhere near us until this run from overnight, a nice change from the usual give and then take away aspect.
The difference from dry to wet is how the models have been foretelling where the jet stream in the middle of the troposphere will be located–in the SW, rain falls under and on the interior side1. All along they have been forecasting it to be north of Catalina/southern AZ. But now, without even looking yet, just seeing that rain on the map, you can bet that the jet is south of us. Let’s look and see if C-M is talking through his hat; big ranch, no cattle:
Valid at 11 PM AST, the same time as the rain map above. “Rain map”? Could be a movie I think. Sounds familiar.From a recent hike: “Happy Together.” If it rains, we’ll be just as happy.
The End
—————- 1Not so for most of the country. This relationship becomes exactly the opposite by the time you get into the East and southeast US: rain falls BEFORE the jet core in the middle of the troposphere gets to you as you can see on that same rain map above for the areas of the Midwest as humid tropical air streams north ahead of that big low forming in the Texas panhandle. There’ll be some big weather out there in the Plains States and eastward as our powerful trough exits AZ.
Rained, too, between 3:42 PM and 3:47 PM, actually 273 seconds, if you had your stopwatch out. It was great. I ran around trying to get wet, but couldn’t do it.
3:44 PM. Proof that rain drops did fall yesterday afternoon. Don’t forget to recycle stuff and also don’t forget that this kind of rain is NOT “drizzle”1. Drizzle are fine close together drops that almost float in the air. Tough to bicycle in drizzle if you wear glasses, in fact, I would say its impossible even if you’re wearing a baseball cap and helmet on top of it because the drizzle blows underneath the cap and onto your glasses so you can’t see anything right away. Rain drops fall too fast for this to happen. This from personal experience in Seattle. Always wear a helmet when bicycling.10:23 AM. After a completely clear morning, Altocumulus clouds formed rapidly over and downwind of Mt. Lemmon. Before long, most were shedding ice.11:45 AM. Distant Cumulus cloud forms just underneath some Altocumulus clouds. Here’s where you KNOW that the day is going to be pretty good as far as convection and virga go because these clouds were so cold, and its late March when the sun is strong.1:51 PM. Two hours later the sky was full of glaciating Cumulus clouds, and isolated heavy virga trails, ones heavy enough to reach the ground with a few drops. Looking SW over Oro Valley and toward Marana.2:31 PM. Thunder was heard just a minute prior to this photo, The storm was just west of the Tortolita Mountains.3:29 PM. Part of the cloud mass that brought the sprinkles (coded as RW–) to Catalina. Probably measured below that little streamer, dead center. The virga hanging well below solid young cloud bases told you that those bases were far below the freezing level yesterday. How cold? Sounding indicates that the bottoms of the Cumulus clouds were about -12 C (10 F). The higher tops were colder than -30 C (-22 F)6:36 PM. Residual Altocumulus cumulogenitus containing a lot of ice if you look closely..
Today’s clouds
Still enough moisture for very shallow Cu fractus, Cu humilis, hold the ice (tops too warm). Skies will also be overrun with Cirrus, maybe verging on Altostratus, as part of low and trough barging into northern California today.Will get nice and breezy this afternoon, as the low zips on into the Great Basin and makes its presence known here. Instantaneous puffs might reach 40 mph this afternoon. No rain possible with this system, darn.
However, deeper Sc and Cu with ice in them should be visible up toward the NW-NE horizon today since a little rain and snow is expected on the M-Rim today, this from the U of AZ super mod’s 06 Z (11 PM AST) run, here.
The End.
—————————- 1Here’s the interesting story behind getting THREE public service messages in a single caption/photo: I wanted to both better serve my public by getting some public service messages out there while at the SAME time, documenting some weather singularity, in this case, one of the rare rain events in the Catalina winter of 2013-14. Suddenly, in the midst of the rain I was dancing in, I noticed some shiny drops on the lid of the recycle bin, and things just “came together” you might say for a remarkable photo.
You can see it highlighted in red on forecast maps here from the Huskies, the Washington ones. Have cameras ready for various forms of Cirrus and Altocumulus clouds, the latter later.
U of AZ Wildcats local model thinking just pretty Cumulus tomorrow as central region of low up there passes overhead. Some with virga, maybe reaching small Cumulonimbus size, with some wisps of precip on top of Ms. Lemmon; a little measurable rain is even foretold for east central and northeast Arizona tomorrow! Nice.
In the meantime, a nice poppy photo for your enjoyment from a hike just a coupla days ago .
Logged on March 22nd1. Someone’s inside it.
The End.
__________________
1Its not a “poppy”, for Pete’s Sake, but rather a Calochortus leichtlinii. Wanted to see if you were paying attention and know ANYTHING at all about the fabulous wildflowers we have here. A quote from the Flower Essence Society about this flower: “The nurturing qualities of Mariposa Lily draw the soul (and apparently, the worm in the photo above) into a deep interior space like the chalice of the flower itself.”
Looky here, valid in only about 9 days, that is, just off the forecast confidence horizon, predicted rain for SE AZ! Valid for April Fool’s Day, at 5 PM AST. We hope its not another model cruel joke, since time is running out on the chances of cool season (Oct-Apr) rains.
SInce I know you love spaghetti, here’s some for about that same time, the evening before the map above, and it has a strong indication of a strong trough moving into the SW from the Pacific. Count on it. At the least, it will get real windy when this happens, count on it, and with a little more luck, there will be enough amplitude in the jet stream, that rain WILL occur.
Valid at 5 PM, the day before the predicted map, that is, 5 PM on March 31st.
The last batch of spaghetti was disappointing, that shown here about two weeks ago. Sure, there’s been a “trough bowl” in the SW as was predicted way back then; that’s what was producing the pretty clouds we’ve been seeing, the passages of weak troughs aloft over us, ones that have been also keeping the temperatures reasonable.
But, that predicted “trough bowl” so far back did not have the amplitude necessary to bring rain as was thought could happen back then. “Trough bowl” turned out to be more of a “plate”, than a “bowl.”
Here’s what I mean, below, from the first panel of spaghetti from last evening: see the little dent toward the south in the contour lines passing over Arizona? That represents a trough where clouds like to form, such as yesterday’s Cirrus clouds..
Map for last night as model runs begin.
But we need the big polar jet stream over us to get rain in the cool season, not a wispy jet up at Cirrus levels as we have been having. You may have noticed how fast the Cirrus clouds were jetting along up there. Well, for the past couple of days, they were zooming along at over a hundred miles an hour.
What we need are deep, cold troughs where the red height contours (5700 meters in the above map) are way south of us. Here’s why rain is predicted in the first map, as an example. Below is the configuration of the jet stream for that day that rain is predicted, showing that the 5700 meter contour and the core of the jet stream is over central Baja California. Now THAT is a rain map for AZ!
Let us begin by breaking up the weather talk monotony with a photo of a bee evaluating a thistle1, this from a hike yesterday to some weather petros2, to resume the weather talk.
10:31 AM. “Sentient Bee-ing and Thistle” $1800. (See link to Sci Am article below if you don’t think bees think about stuff.)8:46 AM. Crossing strands in CIrrus fibratus. Indicates that they have formed at different heights in layers of air with vastly different wind shear (change of direction with height). Rarely do you see this because at Cirrus levels (here around 30-35 kft above ground level, the wind direction usually does not change much. The strands running from left to right across the photo is the higher Cirrus cloud.
9:14 AM. Several species of CIrrus here; fibratus, uncinus, and spissatus (lower right).
9:35 AM. After the delicate Cirrus forms passed, lower blobs of dense Cirrus spissatus with some castellanus *turreted” versions) followed.
9:45 AM. Cirrus fibratus radiatus–last of the delicate Cirrus clouds left a memorable scene as they disappeared past the Catalina Mountains. However, the look of radiating fibers may be due to perpspective, not sure.
11:32 AM. Strands of Cirrus fibratus mimic the branches of a mesquite tree, both seemingly reaching out. A blob of the rarely seen Cirrus castellanus is on the horizon, lower left.
The cloud day pretty much ended with a brief appearance of Cirrocumulus overhead, enhanced by iridescence:
2Below, an early weather forecasting icon petroglyph indicating that the forecaster was anticipating a sunny day except for some Cirrostratus clouds, ones expected to produce a halo. Pretty sophisticated I thought.
10:17 AM. One of several weather forecasting petroglyph icons.
Here’s the ENTIRE message I got just last night from an El Niño expert:
“For your entertainment, see below… and in other news, looks to me like an El Niño is coming on fast – maybe you and I will get plenty of rain in winter 2014.”
My friend, with insider El Niño “trading” info, lives in Monterrey, California, and is referring to the 2014-15 winter as a whole. Pretty exciting I thought since we can put the current winter pretty much in the trash can and move on…
BTW, the first part of his message referred to a sci lecture at the U of AZ on Monday about global warming impacts (now repackaged as “climate change”, since its not really been warming anymore for some time, well, since your teenaged son was born, for some reason). I think you should go there and hear it.
But, in the meantime, let us look at the ocean temperature anomalies (way below) and see what this expert is talkin’ about when it comes to an upcoming El Nino.
Some Niño background
First of all, let us remember there are two kinds of El Ninos, “Classic El Niño” (aka, “Classic Niño”) and “The New El Niño” (aka, “The New Niño”). Below, we’ll use the short versions.
“Classic Niño” is the one we talked about for hundreds of years, well, maybe not you and me, but the one Peruvian fisherfolk got real worked up over when, suddenly, the ocean water along the extreme northern coast of Chile and all of Peru warmed up and changed what fish were out there it got so warm.
Not only that, it began to rain like HELL in areas that were total deserts because the warm water brought tropical air with huge Cumulonimbus clouds that rained like HELL, to repeat and emphasize a point, and also to add some colorful language to what might otherwise be a dull discourse.
And that rain and warm water extended westward all the way to the Galapagos Islands where the people who lived there, if any, also got worked up over sudden. gushing rains. Well, who knows if anyone lived there, but certainly the totals (haha, I thought I was typing, “turtles” and it came out “totals”–how funny izzat?) got worked up; whole bio communities could get almost wiped out by those sudden, punishing rains.
Before the big Cu moved in, all they had in the Galapagos was Stratocumulus and small Cumulus (boring!) Sometimes those kinds of clouds could drizzle a little, or produce light rainshowers, and that’s about it. Those shallow clouds were topped by a temperature reversal with increasing height, so they could never grow up to be Cbs. The relatively cool waters normally along the Equator in the eastern Pacific were responsible.
When Niños occur, they extended even farther westward than just the Galapagos along the Equator, as the unusually warm water propagated into the mid-Pacific Ocean. Other islands out there, like the Galapagos, and normally very, very dry, would be ambushed by heavy rains from huge clouds they hadn’t seen in years when normally, they only saw “cup cake” Cumulus” with passing occasional very light showers, like Johnston Island way out there somewhere south of Hawaii.
But, the “Classic Niño”, wasn’t really good enough for scientists. So they made up a new formulation of Nino and introduced “The New Niño”, sometime in the 1990s or, as they called it, to be more technical with greater obfuscation for scientific purposes, “Region 3.4”1 which is really a patch of the equatorial waters WAY offshore along the Equator from where “Classic Niño” occurs (120 to 170 degrees W longitude). You can read about it, get more details, here.
Why did scientists do this?
Because “The New Niño”, or “Region 3.4”, to return to jargon) did a better job with something we call “teleconnections.” “Teleconnections” is not a new service by Verizon, but rather how weather in one locale is related to the weather in another region, usually thousands of miles away. It was something that was noticed in the middle of the last century, how, say, stormy weather in one area was associated with stormy weather in another. Often, severe winters in the eastern US are associated with severe winters in Europe, as an example, though it did not happen this winter.
In the the case of El Niños overall, research in the area of teleconnections fournd that “New Niño” was better associated with GLOBAL telenconnections than was the “Classic Niño.” So, most of us have moved on and scrutinize “Region 3.4” water temperature anomalies. To explain, in what has become a lecture (is anyone left? Elvis certainly would have “left the building” by now) I use arrows in the sea surface temperatures below to point out where Classic Niño occurs and where the “The New Niño” one does. They usually, though not every time, occur at the same time.
El Niños, as you likely know, are associated with greater chances of rain in the whole Southwest, along the southern Gulf Coast, and even folks in Saudi Arabia have some evidence that more rain even falls there in the winter when a Niño occurs! However, its best, for these teleconnections to work out, to have a big Niño, like the ones in 1982-832, or 1997-98.
Map of the latest sea surface temperature departures from normal, this from just yesterday!
I don’t see much going on as yet, but my friend has access to stuff I don’t, like water temperatures lurking just below the surface that are about to rise to the top if the winds along the Equator all the way to Australia and beyond cooperate. Note its cold as HELL in the “Classic Niño” area right now, but has warmed up some over the winter in the “New Niño” patch which is a good sign.
Been derelict in cloud photos lately, got relatives visiting. But as weak troughs move toward us, they will keep the supply of Cirrus, Cirrostratus, and maybe some Altocumulus streaming by overhead for the occasional spectacular sunrises and sunsets for the next several days.
The End.
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1You wonder if the “New Coke” would have done better if it had been called, “Coke 3.4”? Sounds more like an solid advance in coke formulations, something I might want to drink, with numbers attached like that.
2Had about 30 inches of rain here in Catalina during the 1982-83 water year! Dream about that one if you weren’t here to see all the water flowing in just about every wash imaginable in those days. However, there have been some Niño duds here, too, like 2004-05, or 1976-77, ones that were associated with below normal totals here during the water year.
Cloud tops in those deeper Cu reached -30 C (-22 F) yesterday, plenty cold enough for lots of ice, with a few scattered very light showers reaching the ground, even a few drops here in Sutherland Heights a little before 5 PM, qualifying for a day with a trace of rain. Imagine! Rain! What izzat?
Here is that day below (if you want the short version, go to the U of AZ time lapse film department, online here).
Day Summary: Sunny with Altocumulus castellanus/floccus virgae in the early morning, then in the late morning, Cumulus humilis and mediocris, the latter with virga; Cu grew into shallow, but very cold Cumulonimbus capillatus (lots of “hair”-ice), with virga and RWU (rain showers of unknown intensity) in a couple of spots. Sunny again in mid-afternoon, but Cumulus re-developed in mid-late afternoon with more virga and some Cu reaching the shallow Cb stage with sprinkles here and there.
That’s it, in kind of a jumbled form. Hope you logged all these clouds and changes yesterday.
9:55 AM. Altocumulus castellanus/floccus virgae11:06 AM. Cu developed rapidly over and downwind of the Catalinas. Lots of ice at far left, indicating how cold those clouds were, likely around -20 C (-4 F) at cloud top by this time. Bases, too, below freezing by this time.11:10 AM. A classic, gorgeous example of Ac castellanus and floccus (the latter has no base, just a turret). No ice visible here.2:07 PM. Cold Cumulus and Stratocumulus filled in as trough apex was about to pass overhead (wind shift line, one you can see in the movie linked to above).2:08 PM. Rain showers reach the ground toward Marana whose city limit is pretty much everything you see in this photo I think…2:36 PM. Snow on The Lemmon!4:00 PM. Clearing developed for awhile in the mid-afternoon, but then Cu were quickly reforming. Lots of ice again in this one at left, the oldest portion of the cloud where droplets are evaporating, but the ice becomes visible because it doesn’t evaporate as fast as the droplets do. BTW, air flows THROUGH the cloud, youngest portions on the upwind side, oldest portions downwind. You want to know that if you’re flying around with a research aircraft because if you’re only targeting the young portions, you’re not going to find the “correct” amount of ice that developed in that cloud. Some researchers apparently did this and reported in journals anomalously low ice particle concentrations for the cloud top temperatures that they sampled. For the sake of courtesy, I will not mention their names. But this is why at Washington, we always found a LOT of ice because C-M /we knew where to go!14:31 PM. This was probably the deepest cloud of the day, and there is some suggestion of soft hail (“graupel”) falling out as would be an indicator of some higher liquid water contents before it converted completely to ice. Graupel comes from ice crystals or snowflakes that have bumped into a lot of supercooled cloud droplets that then freeze instantly on the crystal, helping it fall faster and collide with more droplets on the way down, a process called “”riming.” Pilots know full well about riming.6:24 PM. Nice sunset color in clouds and on the mountains.
Don’t see any weather ahead that I like, and so not talkin’ about that today.
—————————————- 1One of the many pioneering innovations here at “cloud-maven” is the novella-sized figure caption.
Virga here and there, chance of sprinkles through early afternoon, then blammo, clearing as wind shift aloft makes it way across Oro Valley/Catalina. CLouds will consist of Cumulus mediocris virgae, small Cumulonimbus capillatus virgae. Cloud bases will be below freezing and higher than Ms. Mt. Lemmon, so will be tough to get rain down to the lower elevations, though a virga trail may hit The Lemmon. Tops of Cu, -15 C to -25 C, i.e., cold enough for ice formation, of course. Crystals will be mostly stellars and dendrites with some clustering into aggregates we would normally call “snowflakes.” Some of the very coldest tops will contain some solid columns, maybe some prisms and hexagonal plates.
If you’re having trouble here because you’ve forgotten a few things, you might well want to get your Magono and Lee (1996) ice crystal “bible” and review crystals types and the temperatures they form at. Heck, maybe I’ll just put the first couple pages here for you…Magono and Lee (1966). Everybody had one back then. Very important to have that with you. As a further challenge, I have not rotated two pages to the upright position to make it too easy for you.
I suppose, too, that you COULD hire an small aircraft to go up there and check on these predicted types using the old “black glove” technique of the early 1960s, where a scientist would stick out a black-gloved hand from the passenger side of the aircraft and then report/log the ice crystals he found. Not making this up.
Yesterday’s clouds (something’s “wrong”)
Day started out dusty; ended up dusty.
8:16 AM. Dirt roads ‘n’ dust; that’s who we are. Got some Altocumulus, but they are so high and cold (-30 C) that they transformed into patches of Cirrus (ice) clouds almost immediately. Pretty normal, even at temperatures that low, for a liquid drop to form first, followed by freezing. Weird.
8:23 AM. Here, a real bird, not a fake one, begins to notice something extraordinary; the virga trails from the parent cloud are going the “wrong way”, toward the northeast!8:35 AM. “What’s going on here?”, the photo asks. Well, the virga trail is going FASTER and leading the head or “generating cell” from which it issued, meaning the wind increases with velocity going down, not UP, as usual! Incredible, really! Hardly ever see this. Is it due to global warming/climate change, the polar vortex has maybe turned upside down? I think so. Has annotations on it.
12:07 PM. Then I saw this, a cloud with no name above the Catalinas. Could be the silhouette of a polar bear, eyes and head at lower left looking downard, asking what have we done to it? Its white, too. Can’t be Cu fractus, though a thermal has pushed a damp layer up here, causing the concave shape. You don’t want to fly that small plane in or below this cloud, looking for ice. It would be real bumpy.
Above, through the dust, for some perspective of our ghost “bear.” Pretty cool, huh? I hope there are some left by the time I get done with this blog! Maybe I should check….let’s see what the Canadians (well, one Canadian at U of Victoria) has to say about this dire sitiuation, get informed about stuff. Here’s a link provided by the climate provocateur, and former WA State Climatologist, Mark Albright, who forwarded it to me for my own illumination. I found that post interesting, unexpected…maybe you will, too.
12:39 PM. Iridescence in Cirrocumulus patch. Very pretty for a minute or two, then gone.
3:24 PM. Day ended up cloudy and dusty with some areas looking like sprinkles could have fallen out and reached the ground, but nothing here, and echoes on radar were awful weak when present.
Rain continues to show up on the forecast horizon, which is about 8 days
Best chance of rain, 21st-23rd, mods fuzzy on which day has the best chance. If you love spaghetti, you’ll love this one below. The vast change in the pattern, indicated for almost two weeks now, is just about here. Some mod runs have rain as this “trough bowl” develops, and a strong trough passes through from the west. Seems more likely than not from here that rain will fall as that happens.
Valid for 5 PM AST March 22nd.
The End. (Nice sunrise, lots of Ac cas, Sc, virga around!)
..will be playing your favorite western tunes in the inimitable style of Johnny Cash at the Whistling Cactus Bar and Hitching Post this Friday and Saturday… :} (Hahahaha; “inimitable style of Johnny Cash”; that means Cash’s style can’t be imitated!)1
6:37 AM: I see now that there’s a lot more dust than last evening! Wow. Dusty Sunrise!
4:13 PM. Cumulus fractus. Dust is visible if you look hard on the horizon. The back scattering of sun light from dust aerosols makes them hard to detect looking away from the sun. But looking toward the sun, the sky has a whitish, gritty look as we had yesterday. When smoke aerosols are present, the sun can appear very orange or reddish, not white in the mid-day-afternoon hours. See the photo below, taken in the forward scattering direction, that whitish look near the sun. For those who want to go deeper, this. Images here.4:12 PM. Whitish, gritty dust exits Tucson and envelopes Mark Albright’s house in Marana/Continental Ranch, carried on a SE blast of wind from Texas and NM.
6:11 PM. Same view as above but most of the sun’s white light has been scattered out leaving the longer yellow and orange wavelengths to carry on.6:20 PM. Classic appearance of a dusty sunset.
Satellite image of aerosol content as seen from above (:}. Green area is the dust plume that appeared to originate in SW Texas and southern NM, then blew into Tucson town yesterday afternoon. Looks like its still here this morning. Go here to see more jpegs of aerosols.
Today’s mix of clouds and dust
Cloud action today, likely some small Cu and Ac later today as a weak upper level trough approaches and passes over us. Should be enough clouds around to pose a sprinkle threat. Imagine.
Should be an especially interesting day for cloud watchers since the dust aerosol should get into the small Cu. Sometimes that can lead to much larger cloud droplets in them because the dust particles are so much larger than the usual aerosol stuff that gets into our clouds.
What does that mean?
Will help those lower Cumulus clouds to form raindrops, since the larger the cloud droplet, the higher the temperatures at which ice forms. Sometimes, even drizzle drops, formed from just droplet collisions can result in Cu mediocris clouds with large dust particles in them (no ice involved). Would sure like to have an instrumented aircraft in the clouds of today!
Normally, ice would be expected to form at temperatures below about -10 to -12 C here in AZ. Today, it might be higher with virga falling from shallower clouds than usual.
The weather ahead
Found some rain for ya… March 21st. See those green areas in SE AZ? Been quiet on rain lately. Don’t like to talk about rain when there’s none indicated for two weeks at a time. The rain shown for us on the map above has been coming and going around this date in the model runs, mostly going, actually, but scored one here based on yesterday’s 5 PM AST global data and that has allowed me to take the rain muzzle off.
So….in sum, we can look forward to another chance of rain in March, one just ahead, and, of course, more of “Dusty Sunset” in the meantime leading up to this chance.
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1Saw a vinyl record album with those EXACT words on it in the Durango Market on Main Street, Durango, back in the ’70s when I lived there. Pretty funny, because you KNEW that imitating Johnny Cash was exactly what that singer was going to do!
