Cloud-maven – Page 69 – About real clouds, weather, cloud seeding and science autobio life stories by WMO consolation prize-winning meteorologist, Art Rangno

Creepin’ Cirrus; pedantry on display

“Storms” at 30,000 feet, single ice crystals falling from various varieties and species of Cirrus clouds. That’s about all we got for “weather” in the next few days as Cirrus creeps up from the tropics into Arizona. But those Cirrus produce great sunrises and sunsets, so have camera ready. And while not much is happening, you should practice logging what you see up there.

Cirrus clouds are the first clouds we see when something is up with the weather, even when it stays up high, but even in these “storms at 30,000 feet”, the moist level tends to decline over time, meaning there might be a chance for mid-level clouds to appear….such as, you guessed it, say, Altocumulus clouds, clouds mainly comprised of droplets, in the near future. That would be pretty exciting; mo’ better sunsets!

Maybe if it was a “cold one”, an Altocumulus cloud with virga hanging out of it, would give you a great opportunity to talk with your neighbors about the Wegner-Bergeron-Findeisen¹ precipitation mechanism (be sure to use all three names to attain the greatest personal stature with them).

——–Warning! Beginning pedantic unit———-

What’s “WBF”, you say?

Hell, you see it all the time! Well, actually only once in awhile here in Arizona. Below, in a pictogram, is a representation of “WBF in action” from a few days into our cold spell just passed so you’ll know when you see ice virga hanging from a droplet cloud you’ll know what the HELL has happened up there. (Dry spells, such as we are in now, make me want to cuss that bit more.)

The background.

Your car has been parked outside all night, and the air was moist. You finally wake up and go outside and you see that dew has formed on your car windows, well, all over. But even though its a bit below freezing, not too much because we’re in Arizona, you also see that in a couple of spots, ice has formed; “horror frost” crystals as we call them here in Arizona because we don’t like frost and cold air of any sort. (The real name is “hoar frost”, and watch out how you use that in a sentence.) The remainder of the drops you see on the car are still in the liquid phase, or have JUST frozen.

But here’s the exciting, magical thing that happens around those “horror frost” ice crystals, demonstrated with a photo through a car window. I’ve added stuff on this jpeg to help explain the magic show going on when the two, liquid and ice, mingle.

And what you see that has happened here is the same thing that happens in clouds when ice and droplets mingle, are co-located so-to-speak. When an ice crystal forms in a droplet cloud, it becomes a vapor hog, water molecule hoarder, because at water saturation, the condition that results in the drops forming in the first place, its SUPERSATURATED with respect to an ice crystal! Amazing, and CRITICAL for life as we know it on this planet because most of the precipitation that falls in mid-latitudes is related to this process. We would have virtually no precip here in Catalina ever without this process.

What does that mean? When the two phases are in proximity as here, the droplets nearest the crystal evaporate, and the ice crystal grows and falls out, usually, as precipitation. Most rain on this planet is due to that process! There are two others that are also important, all ice, all liquid, but today I’m only talkin’ WBF, the “mixed phase” process.

In a cloud, especially a flat one like Altocumulus, this “mixed phase” condition results in ice crystals that grow too heavy to stay in it–its kind of like a “Thanksgiving-for-ice-crystals” inside a mixed phase cloud, and they fall out in those fine strands because they are so fat.

In another way, the ice crystals in a mixed phase cloud are like a low pressure centers, the droplets high pressure centers and the molecules move from high to low pressures.

Mixed phase clouds would go away completely, of course, UNLESS there was some upward motion to keep new droplets forming. But, as in “Ghosts of the Perlucidus” blabbed about here a couple of days ago, sometimes there isn’t enough upward motion to keep the droplets “alive” and only a ghostly remains of the droplet cloud can be seen in a thin patch of ice.

Further detective work re the above jpeg.

Those ice crystals has to have formed when the drops around them were still liquid, probably just as the window reached a freezing temperature or a hair below. If all the dew drops had frozen at once as clear ice, you would not have seen this crystal growth happen because everybody is in the solid phase, no “high or low pressures.” So, while dew drops were forming and growing while the temperature dropped below freezing, there was something quite unique about a particle on the window that caused ice to form when most other places were quite happy to be liquid. We call those special particles that might have triggered an ice crystal, “ice nuclei”, though, too, there may have been a window surface imperfection that did it.

Anyway, ice nuclei are always much rarer in clouds than “cloud condensation nuclei”, particles that the cloud droplets form on. A demonstration of that is in that photo above.

Cirrus clouds, almost never having water, “don’t need no water” because its often supersatured with respect to ice above 30,000 feet without having a droplet cloud. So, even without the water phase, an ice crystal can get fat and fall out in many Cirrus clouds, such as the revered, Cirrus uncinus with its pretty trails. Veil clouds like Cirrostratus? Not so much growth.

———-End of pedantic unit———

Yesterday’s clouds

You may have spotted those creepin’ Cirrus at sunset yesterday. If not here they are, a classic example, ones that kind of drift up to the north out of the tropics into Arizona that from weak circulations down there, even in drought times here, periodically passing overhead, keeping our skies from being boring, particularly for those many of you who out there who are cloud-centric, head-on-a-swivel when outdoors:

5:48 PM. Disant Cirrus, loaded with a few contrails, creeps toward Catalina. Outta be here by now but its dark and I think I can make out something so this is not really a forecast because I kind of cheated by looking at the sky just now. — 5:48 PM. Distant Cirrus, loaded with a few contrails because there’s an airway down there, creeps toward Catalina. Outta be here by now. Its dark and I think I can make out something so this is not really a forecast because I kind of cheated by looking at the sky just now but I WOULD have said that without looking… And if those clouds did get here, there might be nice sunrise for you.

What ahead?

Of course, there’s some rain on the model “horizon” (IPS MeteoStar rendering of WRF-Goofus model), but like that “puddle” on a desert highway on a hot day that you never get to, and I’ve tried, because it moves away as you speed down the road, the “puddle” staying the same distance away, our model rains seem to do the same thing. I’ve used this metaphor before, but I can’t think of a better one. I think its pretty good, too; damn good, really, to cuss a bit more. :} Here are a couple of examples of rain in southern Arizona from last night’s global model run to get your hopes up, most likely to be dashed:

Valid for 5 PM AST, January 28th, Monday. Green areas denote the rain the model thinks has fallen in the prior 12 h. Yeah, right! — Valid for 5 PM AST, January 28th, Monday. Green areas denote the rain the model thinks has fallen in the prior 12 h. Yeah, right.

Valid for 5 PM AST, February 1st, Friday. I would gladly eat my words with whipped cream on them if this happens.

The END, FINALLY!
—————————-

¹They’re not “mostly dead” now, but “all dead”, to crib a line from “The Princess Bride.”

“The Ghost of Perlucidus” (along with some history)

On a movie-sounding title theme again today, or this title could be the title of a bedtime story for kids, one that alludes to the Greek citizen bee keeper, Perlucidus, due to his early work in distributing hives, honey and honeycombs. Some cloud patterns resemble honeycombs, and so when Luke Howard decided to create a Latin system of names for clouds around 1802-03, he wanted to pay homage to Perlucidus¹. Yesterday morning we had Altocumulus perlucidus and those clouds are discussed in detail below the lengthy “historic learning module” below.

——historic learning module————

Our Latin cloud naming system follows the tradition of Latin names first established in the hard sciences like botany and biology. After they did their naming thing, we weather folk decided, under leadership of Luke Howard, to “join the club”, to sound like the other scientists of the day when we were talkin’ clouds, that is, pretend to be on as solid a foundation as, say botanists, whom we likely envied, by creating a similar Latin naming system for clouds. That would show them!

Unfortunately, we really didn’t know what clouds had in them in those days, there were no aircraft measurements. Were they ice clouds or liquid droplet clouds, a mixture of both? And so the naming system that was developed came out a little fuzzy; flawed really. I guess “fuzzy” is appropriate for clouds. As the singer said, “I really don’t know clouds at all².”

OK, after that “side lobe”…an example of fuzziness and flaws in our names: while Stratus and Altostratus have virtually the same name, and can look VERY similar on occasion, one (Stratus) is completely composed of droplets, and the other (Altostratus) is almost always completely composed of ice particles and snowflakes (aggregates of ice crystals, bunches locked together). No doubt Howard saw the visual resemblance from the ground, and may have thought they were composed of the same stuff.

Yet, from the name of Altostratus, you would think it is a droplet cloud like Stratus, but just located at a higher level (“alto” meaning “high” in Latin). Even our scientists confuse Altostratus in their peer-reviewed papers with something else because of this naming problem. A better name, since Altostratus is full of ice precipitation (unknown when Howard was making up his names, of course) would have been, “Altonimbostratus”. Nimbostratus, by definition, is a precipitating layer cloud, too.

Another problem in our naming system is that unlike in botany, where a redwood tree does not become a pine tree over time, clouds are always morphing into new forms.

And then we have to come up with silly expressions such as “Altostratus opacus cumulonimbomutatus”, what might pass for the remains of a Cumulonimbus cloud that has lost its base and only the heavy, higher level ice-cloud anvil (Altostratus) remains.

So, as Howard was attempting to follow the Latin scientific naming conventions of the day for clouds, up popped the descriptor, “perlucidus” for clouds patterned like a honeycomb in homage to Perlucidus¹.

Two cloud genera (there are TEN^{3-I really like footnotes. They give a piece a really erudite feel even when its not}), have the descriptor, perlucidus attached to them because they can attain a honeycomb pattern. These are Stratocumulus and Altocumulus, to repeat.

——-End of historic learning module———–

Yesterday we had some very cold Altocumulus perlucidus, some cloud elements shedding ice and disappearing because of it. The TUS morning sounding indicated these were in the range of -25 to -27 C. Here’s what these clouds looked like when they were still mainly composed of liquid droplets:

7:29 AM. Classic Altocumulus perlucidus (honey-combed pattern) with fine veils of ice crystals falling from many of the droplet cloud elements.

9:15 AM. Here, in brighter light, one can see the droplet clouds at left, while there are patchy, hazy regions in between. Those are the ice crystal remains, "ghosts" of the perlucidus cloud elements that have completely changed into ice (glaciated). — 9:15 AM. Here, in brighter light, one can see the droplet clouds at left, while there are patchy, hazy regions in between. Those are the ice crystal remains, “ghosts” of the perlucidus cloud elements that have completely changed into ice (glaciated).

9:24 AM. Ovalized shot of the icy ghosts of perlucidus. There really is no cloud name for this grouping.

Strange Brew yesterday

There were also some very strange looking lower clouds as dry convection, associated with that little warming we had yesterday afternoon during this historic cold wave, bulged upward into a pretty moist laminar stable layer that resisted like heck being pushed up. When it was pushed up by that convection, which with greater moistness you would have seen as small Cumulus, instead you got slivers of clouds on top of where the Cumulus should have been. Those slivers of moist air that just reached the condensation level where droplets form in the air sliding over the top of the “invisible Cumulus.” The result, these odd forms shown below, resembling lenticular clouds with ragged bottoms in some cases:

12:15 PM. This dome shaped oddity. Was only there for a minute or two. Jumped out of car to get it. I hope your happy.

12:38 PM. Then over the Catalinas, these strange forms of lenticularis clouds. — 12:38 PM. Then over the Catalinas, these strange forms of lenticularis clouds likely forced by dry convection rising up from underneath.

The last photo of a band of Stratocumulus with a ton of ice in it is worthy of a comment. A few days ago, the models had this day having significant precip, precip that would have been snow, followed by the same vast clearing we had later yesterday. Imagine last night and this morning’s cooling air augmented by a snow cover! Yikes. Woulda been 5 degree colder than what is already a pipe bustin’ cold morning. Wouldn’t have had so much afternoon melting because the ground has been chilled for several days now.

Wishing you happy pipes this morning. They’re freezing up here, temperature now 22.x here.

BTW, the list of Arizona low record temperatures will grow substantially today, as if you didn’t know it.

The weather ahead? Warmer. Can it be otherwise?

Also at 12:38 PM, looking farther down the Catalinas. Strange indeed.

The End

——-

¹Shockingly, this part has been completely made up.

²She also said, “Ice cream castles in the air”, followed by, “Feathery canyons everywhere.” And finally, “Clouds got in my way.” (BTW, “Clouds got in my way”, too, as if you couldn’t tell!)

³The the ten are: Cumulus, Stratocumulus, Nimbostratus, Altostratus, Altocumulus, Stratus, Cirrus, Cirrostratus, Cirrocumulus, and the mighty most of the time, Cumulonimbus.

“The Seeds of Uncinus”; a review

Starring Justin Bieber as Harry Potter in the upcoming 12th Harry Potter movie, the musical….

(There, that should grab some attention. But then people would be disappointed, maybe mad, but still they might see something here about Cirrus uncinus clouds that they didn’t know before.)

Had some great Cirrus uncinus clouds yesterday! I was not thinking about uncinus at all yesterday, but rather amorphous blobs of Cirrus, but there they were. Maybe you saw those “Ci unc” with their great tails hanging down, streaking across the sky. And there was something “wrong”, too.

What was it? Its rare when it happens.

The tails were going the “wrong” way, evident later in the day. As streamers of crystals from the “head” of Ci unc trail out, the wind nearly always decreases going downward, and the tails fall back behind the head TOWARD the west, or toward whichever way the wind is blowing FROM. Yesterday, the tails went in front of the head, a real odditity telling you the wind was a little stronger below the head. Hope some of you logged that anomaly. Its hard to get your CMJ T-shirt without having noticed that.

Some photos, too many, no doubt, but that’s what I do, and I’m quite good at it:

9:07. "Angel's hair" passes to the south of Catalina. Cirrus uncinus and Cirrus fibratus, maybe a thin layer of Cirrostratus above it. — 9:07. “Angel’s hair” passes to the south of Catalina. Cirrus uncinus and Cirrus fibratus, maybe a thin layer of Cirrostratus above it. Note the long tails streaming away from Catalina (center).

9:21 AM. Cirrus fibratus (no hook/tuft visible at top because you can't see it here) and Cirrus spissatus eject toward Catalina. Just thought this was pretty, nothing to do with today's discussion. — 9:21 AM. Cirrus fibratus (no hook/tuft visible at top because you can’t see it here) and Cirrus spissatus eject toward Catalina. Just thought this was pretty, nothing to do with today’s discussion.

12:38 PM. Arrows all over in this mainly batch of Ci unc shows seed cloud specks that lead to them much later.

12:15 PM. The heavier Cirrus forms have departed and these delicate ones were to dominate the rest of the day. So pretty. The hooky ones are Ci unc.

But how do these long-tailed Cirrus get that way? How do they start?

With seed clouds, cloud specks with tiny quasi-spherical ice crystals in them, sometimes the ice called “germs” because they’re so small, maybe 10-20 microns in size; tiny dots.

Next is a sequence showing the fleck seed cloud stage to the tail growing stage of Cirrus uncinus, in which the larger ice crystals start to fall out. Unfortunately, by the time the tail is as long as those seen in these shots, those original Cirrus fleck clouds might be a 100 miles away.

Now, is any of this information useful for everyday life? Of course, not! But, let’s say you get on Jeopardy, the TEEVEE program and you have chosen, “Clouds” as your category and the hose (oops, “host”, damn autospeller!) asks you, “This kind of ice crystal is found below the tops of CIrrus clouds.”

You’re answer from today’s “lesson”:

“What is a bullet rosette?” Some kind of prize happens when you say that, and you’re happy for the first time that you read all this.

2:45 PM. As the end of the Cirrus approached, as often happens, you get to see how they looked when they first formed, and here's a shot of that. — 2:45 PM. As the end of the Cirrus approached, as often happens, you get to see how they looked when they first formed, and here’s a shot of that.

2:57 PM. Its got writing on it. — 2:57 PM, just 12 min later. Its got more writing on it.

3:07 PM, ten more minutes go by. I was watching, standing there in a lot of cold air so I could get this sequence. What were you doing? Watching the Seahawks lose to Atlanta? — 3:07 PM, ten more minutes go by, trails lengthen further. I was watching, standing there in a lot of cold air so I could get this sequence. What were you doing? Watching the Seahawks lose to Atlanta in the last 30 s of the game after they just had gone ahead? How could that happen? Its OK, I understand. Clouds don’t always come first for you.

3:19 PM. Last one, was getting too far away.

4:07 PM. The afternoon finished out in an undercutting-the=Cirrus Cirrocumulus clouds, maybe Altocumulus lenticularis in the distance due to having shading. Had some great, delicate patterns as well.

4:10 PM. Cirrocumulus. These are droplet clouds and did not form ice at any time. They were lower and warmer than the Cirrus fleck clouds. Shows how similar the formation process is of Cc and Ci, flecky, dotty, tiny updrafts, maybe 0.1 meters per second. — 4:10 PM. Cirrocumulus. These are droplet clouds and did not form ice at any time. They were lower and warmer than the Cirrus fleck clouds. Shows how similar the formation process is of Cc and Ci, flecky, dotty, tiny updrafts, maybe 0.1 meters per second or less updraft forms them.

Today’s clouds?

COLD, cold trough going over us again today and this evening. Air should moisten up some in the lower levels as this happens allowing for some Cumulus to form, ones likely to develop a little ice in them, which means a little virga here and there is likely. There are also likely to be a couple of Altocumulus or higher based Stratocumulus patches, too, during the day. U of A has predicted soundings over TUS here.

The weather ahead

Temperature extremes pattern still ahead in just a few days now; warm in the West, darn cold in the East. Rain has shown up here on the afternoon of the 27th in last evening’s 5 PM AST global data model run.

Speaking of extremes

A number of low temperature (not “cold” temperature) records have been broken in AZ. Here are a few, as reported by the NWS. Some of these records that were broken go back 100 years, such as the 7 F at Wilcox, set two days ago, breaking the 8 F in 1913, the same time as when the TUS low temperature record was set. The two patterns must have been similar, 1913 and now. Makes you feel special, doesn’t it?

SXUS75 KFGZ 140119
RERFGZ
RECORD EVENT REPORT
NATIONAL WEATHER SERVICE FLAGSTAFF, AZ
600 PM MST SUN JAN 13 2013
...RECORD LOW HIGH TEMPERATURES FOR NORTHERN ARIZONA ON JAN 13 2013...
CITY (PERIOD OF RECORD)          NEW LOW HIGH    PREVIOUS RECORD/YEAR
GRAND CANYON NP N RIM (1926 - 2013)    11          16         IN  2007
PAYSON (1949 - 2013)                   33          35         IN  1960
...RECORD LOW TEMPERATURES FOR NORTHERN ARIZONA ON JAN 13 2013...
CITY (PERIOD OF RECORD)            NEW LOW       PREVIOUS RECORD/YEAR
FLAGSTAFF (1899 - 2013)                -7          -6         IN  1963
GRAND CANYON NP N RIM (1926 - 2013)   -12          -5         IN  1926
THESE RECORDS ARE PRELIMINARY PENDING OFFICIAL REPORTS.
$$

SXUS75 KFGZ 132320
RERFGZ
RECORD EVENT REPORT
NATIONAL WEATHER SERVICE FLAGSTAFF, AZ
1000 AM MST SUN JAN 13 2013
...RECORD LOW HIGH TEMPERATURES FOR NORTHERN ARIZONA ON JAN 12 2013...
CITY (PERIOD OF RECORD)          NEW LOW HIGH    PREVIOUS RECORD/YEAR
FORT VALLEY (1909 - 2013)              20          23         IN  1963
MCNARY 2N (1921 - 2013)                22          27         IN  1964
SUNSET CRATER NM (1970 - 2013)         21          25         IN  1985
...RECORD LOW TEMPERATURES FOR NORTHERN ARIZONA ON JAN 13 2013...
CITY (PERIOD OF RECORD)            NEW LOW       PREVIOUS RECORD/YEAR
FLAGSTAFF (1899 - 2013)                -7          -6         IN  1963
THESE RECORDS ARE PRELIMINARY PENDING OFFICIAL REPORTS.
$$

SXUS75 KTWC 131605 CCA
RERTWC
RECORD EVENT REPORT
NATIONAL WEATHER SERVICE TUCSON AZ
841 AM MST SUN JAN 13 2013 
...RECORD LOW TEMPERATURES SET FOR JAN 13...
LOCATION                  RECORD  OLD RECORD
BISBEE-DOUGLAS AIRPORT      07    15/1975 
FORT THOMAS                 11    12/1962 
SIERRA VISTA                16    18/1916
WILLCOX                     07    08/1913
$$

SXUS75 KTWC 131542
RERTWC
RECORD EVENT REPORT
NATIONAL WEATHER SERVICE TUCSON AZ
841 AM MST SUN JAN 13 2013 
...RECORD LOW TEMPERATURES SET FOR JAN 13...
LOCATION                  RECORD  OLD RECORD
BISBEE-DOUGLAS AIRPORT      07    15/1975 
...RECORD LOW TEMPERATURES SET FOR JAN 12...
LOCATION                  RECORD  OLD RECORD
FORT THOMAS                 11    11/1962 
KITT PEAK                   12    19/1989 
$$

SXUS75 KTWC 131458
RERTWC
RECORD EVENT REPORT 
NATIONAL WEATHER SERVICE TUCSON AZ
0746 AM MST SUN JAN 13 2013
...RECORD LOW TEMPERATURE SET AT DOUGLAS AZ...
 A RECORD LOW TEMPERATURE OF 7 DEGREES WAS SET AT DOUGLAS AZ TODAY. 
THIS BREAKS THE OLD RECORD OF 15 SET IN 1975.
$$

Well hung, that virga yesterday…

“Hanging virga” materialized yesterday, starting from a cluster of late morning modest, but very cold, Cumulus clouds that transitioned to soft and small Cumulonimbus clouds as they approached the northern parts of Catalina, Charoleau Gap and Oracle yesterday.

How cold were those clouds?

Bases were at 10,000 feet, just above Mt. Sara Lemmon, at about -15 C (4 F), a real bottom temperature rarity for southern Arizona Cumulus clouds. The highest tops, probably only reached 15,000-16,000 feet above sea level and would have been close to -30 C (-27 F), also exceptionally cold for such a low top height. So, the clouds, for the most part, were less than 2 km (6,600 feet) thick. At times, they appeared to be miniature summer clouds with all the glaciation and “shafting” going on. Here are some shots:

10:25 AM. Small Cumulus begin clustering NW of Catalina. No ice evident.

10:41 AM. Same cluster, drifting east toward Charoleau Gap-Oracle. Ice plume now seen streaming to the east from one of the taller clouds. — 10:41 AM. Same cluster, but deeper, drifting east toward Charoleau Gap-Oracle. An ice plume can now be seen streaming to the east from one of the taller clouds. When clouds are this cold, and small, only a few of the “lucky” largest ice crystals may fall directly out below the base, while most float off to the side as here. If you were a skier up there, you’d call it “powder snow”; lots of single crystals rather than flakes.

Remarkably as cold as the bases were (-15 C), nature abhors starting an ice crystal until a liquid cloud drop has formed. So, the sequence goes like this; liquid droplet cloud forms (as in our smallest Cumulus yesterday, “humilis”), but then they must develop further to produce ice. There is a temperature AND drop size threshold requirement for ice formation, even in clouds this cold. As the clouds fatten upward, the drops in them get a little larger, and at the same time the temperature drops, too, and, voila, the ice-forming criteria for that day are met, and out pop the ice crystals. Those depth/cloud top temperature criteria change some from day to day.

And, as you likely noticed and wrote in your weather diary, those cold, but shallowest clouds yesterday did not produce ice, while ones that got a bit colder and fatter did. Most of the time, low-based clouds that reach just -10 C to -12 C begin to produce ice, and even at higher cloud top temperatures in the summer on occasion, the latter, a LOT of ice at cloud top temperatures warmer than -10 C.

There’s the enigma. How’s come yesterday’s tiniest clouds, with bases at -15 C, did not produce ice immediately? What is it about those itty bitty first formed drops that makes them so resistant to freeze? Surface tension? This kind of result for small cold clouds was found repeatedly in our aircraft studies at the U of WA.

11:29 AM. I looked to the sky for answers about ice formation, but it didn’t seem to know either.

11:04 AM. The same cluster continues to expand and deepen with lots of "hanging virga". — 11:04 AM. The same cluster continues to expand and deepen with lots of “hanging virga” just beyond CG, and in the distance.

Before the vast mid-afternoon clearing (associated with that passing trough /wind shift line above us), there was another complex of glaciating modest Cumulus and Cumulonimbus clouds with significant virga that went over the same area as shown in these photos. No doubt, someone got a flake or two, or more likely, a tiny ball of graupel (soft hail).

SONY DSC — 1:56 PM. Tiny non-ice producing Cumulus looking toward the SW. Notice the lean of the tops of these little guys toward the left, or toward the SE. They show that the winds have veered from westerly to northwesterly since the morning hours, this veering associated with the passage of the trough over us. When you see that lean in that direction, its pretty much over (the chances of precip).

By mid-afternoon, it was “all over” as the Cumulus dwindled to tiny versions, with no ice, and ultimately disappeared within two hours.

And with the clearing skies late in the day, the plummeting temperature. Was 31.x F by 7 PM, but just after that, the “sliders” started, as they usually do here on a little hillside, and the temperature pretty much leveled out and has briefly hit 28 F. In the meantime, just down the road, its 21 F in the Black Horse subdivision! The CDO wash would be even colder if we had a measurement there.

You can see our regional temperatures here from the U of AZ, and the more local ones here from Weather Underground, now owned by The Weather Channel and they better not screw it up any more than they already have re radar depictions (they don’t work as good.)

The weather just ahead?

More little troughs like yesterday, such as one passing over us today, and later tomorrow, likely to again to be ones, especially tomorrow, bringing a few small Cumulus over us in the afternoon, some of them shedding ice. We already have some ice clouds, low Cirrus, today, and along with those, maybe a flake or two of Altocumulus. It’ll be pretty scenic again.

Then The Warming, a vast and an amazingly quick change in the flow pattern that warms us up during the middle of the coming week. And, no rain indicated in mods for next 15 days, though as always, there is hope in the final few days that it will be wrong. More on that way down toward the bottom.

Some newsworthy weather is farther ahead…

There is something that will happen that you’ll read about, extreme cold in the East, 8-12 days out. This happens as a gigantic storm-blocking ridge piles up along the West Coast, all the way into Alaska. In these situations, Pacific storms are diverted to Alaska where the folks up there think its comfy with all that marine air blasting into them from the ocean, but then, that air turns cold over the continent and streams down into the US akin liquid nitrogen rolling down the side of Mt. Lemmon.

Why even talk about this when its so far out in the models, since they are often a joke that far out?

You do it, stick your neck out, because of how POTENT the “signal” is in the NOAA “ensembles of spaghetti” for this to happen. Besides, you might be getting a “scoop” as well, if the other forecasters aren’t on their toes.

A pattern of extreme temperatures over ALL of North America is just about certain. Check this out below. I’ve added some text on to help you know what to think when you see it. That’s what I try to do here; tell people what to think. Its great!

Valid 216 h from last night, or the evening of January 21st, AST.

The red arrow is up the shaft of a gigantic ridge, the one foreseen in the models lately. Note how special we are along the West Coast in this plot; there are no other protrusions of ridges anywhere in the whole northern hemisphere like this ours!

What is a ridge composed of? Deep WARM, comfy air. So a huge blob of warm air IS going to arise along the West Coast in 8 days. That translates to much warmer than normal temperatures practically from Alaska to here, probably a heat wave in southern Cal around this time.

At the same time, when the flow is disturbed like this, and has so much “amplitude” (goes north and south so much) like it shows here, that is, goes WAY to the north on one side of the ridge and then WAY to the south on the other, you get temperature extremes as you could EASILY guess. Extra warm over “there” somewhere means extra cold over “yonder” (in this case, the eastern half of the US.

Why do these coming temperature extremes have so much credibility?

Its because of the remarkably (to me) tight bunching of the lines (500 millibar contours), the way they are in the above graphic. This means the signal, the factors putting this pattern together are powerful, and have not been disturbed by the “noise” of the many small errors DELIBERATELY put into the model at the beginning of the run to get these differing plots. For 8-10 days out, these are about the “tightest bunching of lines” I have seen, meaning the forecast is robust; namely, is going to happen.

For us it means a further extension of droughty, but warm days that follow soon on the heels of our cold spell, into the 20-25th of January.

Beyond that?

As robust as the forecast is for 8-10 days out shown above, the models are pretty much clueless about how this pattern falls apart (not too surprisingly). To experience model cluelessness hereabouts, check this plot out below for 15 days away from the same computer run and notice the “out of phase” pattern being indicated. The gray lines show a trough in our region (maybe storms and cool), and the yellow lines, from a model run just 12 h later, last evening, shows a ridge over the West (warm, sunny weather indicated here). A forecaster, looking at this, and covering all the bases might say:

“Continued cool with variable clouds and showers today, otherwise mostly sunny and warm.”

That’s about what you get out of this last plot. Not much confidence.

The End.

Valid for the evening of January 27th AST.

Hanging virga on tap (its not a beer)

Cloud patches and upper level trough approaching this morning. They’ve got some precip in’em, but its a little dry underneath those cloud patches coming toward us so that only a few ice crystals/flakes will make it to the ground from the isolated, hanging virga we’ll see in the later morning hours. Should be kind of pretty though, big, long trails of snow coming down from really cold Altocumulus, Stratocumulus, and small Cumulus (coldest tops likely to be below -25 C, -13 F).

Trough apex and wind shift aloft goes over us at mid-day (seen here from the U of WA), and you know what that means. Those morning clouds will move off, leaving only small, COLD-like-us, Cumulus clouds since the atmosphere is mainly moving downhill behind the upper level trough wind shift line, and that means a clearing.

Here are the temperatures around this morning; “milder” on hillsides, colder in low spots hereabouts, as you know from experience. Cold air drains like water off hillsides, is replaced by warmer air just above that is not in contact with the cooling ground surface. The air then cools at the surface, slides down hill and fills up washes and lower elevations in general. (Right now, 6:43 AM update, holding steady at 29 F, but down the road and down the hill, in Black Horse Ranch, its 23 F. See map here.)

Happens over and over again, and so if you have a temperature trace to watch, and you live on a hillside, you will see blobs of warmer and colder air passing by soon after dark, usually just at one or two miles per hour. Even the smallest little creek beds have little, slow downhill moving streams of cold air. If you live in a bit of a low spot on the side of a hill, you’ll know this from, say, walking the dog along a road along the hillside.

Check this nice graphic below from the U of AZ of regional temperatures with the infrared satellite image overlain on them. Tucson was 26 F at that time while here in the little hills above Catalina it was 29 F at 4 AM). HUGE difference… Well, its something.

Note -14 F at the Grand Canyon, -15 F at Bryce Canyon, UT. Only 7 F at Big Bear Lake, CA (L35 on map), 33 F right on the coast of southern Cal at NFG¹, by San Diego. It’ll get colder yet at most of these stations in the hours before sunrise.

You can also see in this graphic the cloud patches that are heading our way in SE Cal and western AZ.

Other than today, precip chances have been diminishing after a model “feint” indicating some snow on the 14th. Its gone now, like so many model-indicated precip days. It now is looking more likely that January will end as another dry month, even if it rains some near the end of the month (beyond the current dry-for-15 days model predictions).

Some scenes and clouds from yesterday.

First this nice shot of the Catalina Mountains… OK, I really didn’t get a picture of them yesterday, and so this will have to do. Its what the Catalina Mountains WOULD look like if they were 11 inches high and it had snowed on them, and it was windy when it was snowing. Here’s another one of the effect of wet snow on our dried out from summer grasses. I thought it was kind of pretty how the snow stuck on stems.

Now some scenes of those great, if chilly-looking blue skies dotted with small Cumulus clouds yesterday; no ice detected falling from them by these eyeballs. Should see similar sights today, except ice/snow should be hanging down (he sez).

8:45 AM. Pretty Stratocumulus hovers over Oro Valley.

1:28 PM Cumulus humilis forms over Oro Vally. No ice haze visible though cloud tops were, from the TUS afternoon sounding data, -11 to -13 C, below the usual ice-forming temperature here of about -10 C. — 1:28 PM Cumulus humilis clouds form in a line over Oro Vally. No ice haze visible though cloud tops, from the TUS afternoon sounding data, were -11 to -13 C, below the usual ice-forming temperature here of about -10 C. A second factor in ice-formation is drop sizes in the clouds. The smaller the drop size (as in small clouds like these, or in lenticular clouds) the lower the temperature required to initiate ice (from U of WA studies).

———

¹Oceanside Camp Pendleton Marine Corps Air Station

FROPA! (plus some corrections in red….)

2:26 AM, Catalina: S- (light snow), 33.9 F, 0.01 inches so far. Precip not registering on Wunderground map site for some reason.

3:20 AM: S– (very light snow), 34.8 F. Temperature beginning to recover following precip, snow almost over, just a “skiff”, 0.3 inches.

6:20 AM: Total now a measly 0.02 inches, less than expected, but in keeping with jet “rule of thumb”; nil precip until 500 mb core goes by¹, and its just getting here now–120 mph wind now at just around 18,000 feet over TUS, an extremely exceptional event for winds that strong to be that low!

Correction on storm total: Mr. Cloud Maven person forgot that when it snows, the small orifice into which the rain water usually flows without hesitation is clogged by that SNOW and the tipping bucket does NOT tip until the snow melts. It began melting in mid-morning, and by the time it was done melting, there was a total of 0.10 inches, 0.14 inches at the Sutherland Heights gage. This is a lot better than 0.02 inches.

County ALERT gage totals disappointing, too, just a few hundredths to a tenth of an inch; most with zeroes. Mountains reports missing since it fell as snow. (As with my own gage, the snow is melting into the buckets in the ALERT gages and they are now showing precip! )

(Here, the snow has melted and dribbled into the gage–NO it hadn’t!!!!) ((Shoulda looked inside the funnel before writing that!))

Only expecting small Cumulus today, but its cold enough that they could have some ice in them. It would be something for you to watch for.

Here’s the temperature and pressure traces for this dramatic cold front passage (FROPA) here in Catalina last night around midnight with the chart below beginning around 7 PM, this from a pitiful jpeg of computer monitor since the software I use will not print two parameters on the same graph (please fix this, Lightsoft Weather Centre, UK!):

You can’t read it, but the temperature dropped from 50.x F to 33.x F in about an hour, with period of very light snow, no accumulation at the end of that hour. And you can see what we meteorologists call a “pressure check” when a cold front goes by; starts rising immediately.

Yesterday’s clouds

Lots of lenticular formations around, beginning with this rosy specimen just downstream of the Catalinas at dawn:

7:17 AM. Altocumulus lenticularis downstream of the Catalinas.

Lenticular clouds downwind of the Catalinas persisted for hours yesterday. Its sometimes hard to tell that they are not over the mountains, but you can see that in the U of AZ time lapse for yesterday.

BTW, if you want to know how the UFO thing got started, legend has it that it was due to a hovering Altocumulus lenticularis cloud downstream of Mt. Rainier in the 1940s.

Viewing this U of AZ time lapse movie will tell you why lenticulars have sometimes been reported as UFOs. It really does look like a hovering “vehicle” in the morning hours in the movie, and a “hovering”, which is what we know alien spacecraft do; hover. In the face of the strong winds up there yesterday, hovering is, for most folks, unexpected, suspicious behavior. Check it out.

Finally, after the heavy mid-level overcast in the mid-late afternoon, a brief sunset bloom due to a distant clear slot beyond the horizon (way down at the bottom).

12:28 PM. Here's comin' at you; Cirrostratus way up top, below, Altocumulus lenticulars, and Cirrus spissatus (thick ice clouds) — 12:28 PM. Here’s comin’ at you, looking to the west; Cirrostratus way up top, below, Altocumulus lenticulars, and Cirrus spissatus (thick ice clouds possibly evolved from glaciating lenticular patches. Very complex scene. Thought about omitting it because what I couldn’t name and explain things?)

1:02 PM. Altocumulus opacus invaded sky rapidly from the west. Bottom looks pretty much like a lenticular, but it was scooting along, something true lenticular clouds don't do. Hmmmm. Maybe I should omit this one, too. — 1:02 PM. Altocumulus opacus invaded sky rapidly from the west. Bottom part looks pretty much like a lenticular, but it was scooting along, something true lenticular clouds don’t do. Hmmmm. Maybe I should omit this one, too.

1:27 PM. ACSL is back again downwind of the Catalinas! (Altocumulus Standing Lenticular)

5:46 PM. A heavy layering of Altocumulus (opacus) is under lit by the sun for just a few moments. Like me, you may have initially given up on a "bloom", by, by golly, it happened! BTW, as often happens, these heavy looking clouds were a lot higher than you might think, about 17,000 feet above Catalina (from the TUS sounding.) — 5:46 PM. A heavy layering of Altocumulus (opacus) is under lit by the sun for just a few moments. Like me, you may have initially given up on a “bloom”, but, by golly, it happened! BTW, as often happens, these heavy looking clouds were a lot higher than you might think, about 17,000 feet above Catalina (from the TUS sounding.)

What’s out there beyond the present cold spell and the warming after that?

This is kind of intriguing to me even though its kind of a waste of time, too. We’ll be reel cold for awhile, then it will suddenly warm up to seasonal temperatures for a few days. We know that. But then what?

Our models have been churning out wildly different forecasts toward the end of the month, and with those, wildly differing weather occurs here, naturally. These model forecasts are like a 5-foot wide puddle of water on a pot-holed street like the ones we have here in Catalina that they only repair in the most rudimentary way, throw some asphalt crumble in the hole, that its pretty much what they call a “repair.” Maybe its because we’re considered “po’ folk.” Let’s see, where was I? Oh, yeah, that puddle could be an inch deep or three feet deep. You just don’t know for sure.

One way to “dip stick” that “puddle” is in our NOAA spaghetti plots. At the end of this is the latest one from last night’s global data. You can see how wild (humorous) the forecasts are in the yellow and gray lines, indicating exactly opposite conditions in the West at the end of the month for those model runs at 00 Z (5 PM AST) and 12 Z (5 AM AST yesterday). Pretty bad.

The spag plot below from last night’s data suggest the warm ridge has the edge at this point (note clustering of blues lines to the northern US; red lines still confused). With a ridge holding forth, it would be a comfy time in AZ late in the month, not cold and blustery.

Still, its not the final word, remembering that the atmosphere remembers. It will be interesting if it remembers enough to bust our venerable spag plots. That’s what makes it so darn interesting!

The End.

——————

¹Its interesting that such an old style methodology, of the type used by forecasters before the rise of weather computing models, would seem to have equaled our best models in 2012.

Into the cold

Today, as everyone knows, will be the last pleasant day for quite awhile, so we’d better get out and enjoy it if you can, maybe call in sick. Likely to be a couple of AZ low temperature records set over the next week.

The skies will be great today, as they always are with some clouds present, and for a few days afterwards in the cold air with those deep blue skies along with passing Cumulus clouds, that at times and even though they are shallow, will send some virga down as the colder parts of the troughs go by. Should provide for some nice late afternoon and evening photo ops in the days ahead.

Today the satelllite imagery plus looking out the window, shows lots of Cirrus clouds today, probably devolving into dense, shady Altostratus at times. And a scenic, Altocumulus lenticularis cloud¹ downstream from the Cat Mountains is pretty much a lock.

Also, in the progression of clouds today, we will probably see that clear slot that so often separates the middle and high clouds from the low, frontal clouds go by. If the timing of that clear slot is right, could be an extra special sunset.

Some Cirrus from yesterday, another one of those rarer days with virtually no contrails in the Cirrus, followed by a nice Catalina sunset:

2:36 PM. Cirrus fibratus (pretty straight fibers) looking NW. Note lack of contrails.

5:45 PM. Cirrostratus with embedded Cirrus of some kind (upper right). — 5:45 PM. Cirrostratus fibratus (has streaks) with what looks to be a lower Cirrus uncinus (upper right and in the distance).

Rain, from the U of AZ mod run at 11 PM AST, has the rain beginning tonight after 10 PM AST and lasting but a couple of hours. Amounts here in Catalina, between 0.10 and about 0.40 inches, average of 0.25 inches, virtually no change from what was predicted 24 h ago.

Just about everything mentioned yesterday is the same today in the model, marginal cloud top temperatures for precip at the TUS site for most of the time the front goes by (in the model), but cloud tops will be colder over us and more likely to precip.

Seems temperatures will be marginal for ice-in-rain drops at the ground here since the much colder air will not arrive with the front’s very narrow rain band but encroach as it departs.

Also of some interest, the jet core at 500 mb is shown to become bifurcated with one branch overhead S as the rain moves in (another branch over NW AZ). This would be compatible with a rule of thumb about the rain and the jet at 500 mb. Rain, with extremely rare exceptions (<5% of the time), does not fall here on the southeast side of a jet stream racing to towards the NE, as we will have over us today. Will be curious to see if this “rule” holds up this time.

Tomorrow will be one of those cold days with spectacular small Cumulus clouds contrasted against the deep, dark blue of the winter sky. Should be some great scenes of light and shadows on the Catalina Mountains.

Snow ahead?

Snow falls here later in this cold, almost week-long episode, as a series of troughs plunge southward along the West Coast to AZ. Most likely day for some snowfall in Catalina, is now on the 14th². Here’s the map for that, valid for 11 AM AST, Monday, from IPS MeteoStar:

Monday the 14th 2013011000_CON_GFS_SFC_SLP_THK_PRECIP_WINDS_114 — Green areas denote those regions where the model has foreseen precip in the previous 6 h.

The weather way ahead–Dr. Jeckyl or Mr. Hyde?

Check out these bowl of rubber bands from “flapping butterfly wings” (slight perturbations put into the initial data ingested into the WRF-GFS model after which its re-run a number of times to see what slight differences do). The first one below is for the evening of January 20th, a real laugher considering its only 10-11 days away now and the mods are still clueless.

Note the yellow lines, a “control” run from last night’s 5 PM global data, and see how they BULGE toward the north over the western half of the US. Then look at the hard-to-see gray lines representing a “control” run from just 12 h earlier, that from yesterday’s 5 AM AST global data. They BULGE southward, the opposite way the yellow lines do.

The yellow lines indicate a huge ridge over the West, with little precip and seasonal temperatures in the SW US. On the other hand, the 5 AM control run shows a continuation of our present storm pattern and continued injections of cold air down the West Coast. Check out that gray line over northern Cal, for example.

So, from one model run to the next lately, our weather toward the end of the month in Catalina has gone from “yawn” to “yikes” (the latter blurted out yesterday when I saw that 5 AM output and all the storms it had). But blurted out a “yawn” when viewing the output from last evening. No precip after the cold week.

However, in deciding which of those two outcomes is most likely you have to dwell on the predominance of those blue lines that also bulge northward and are mainly located in southern Canada. Those strongly indicate that the “highs” , the bulges to the north over the western US, will prevail on the 20th, not the storms and cold weather with them.

: Arrow points in the general direction of Arizona.

But how about after the 20th, at the very end of last night’s model run 15 days out? Now you see BOTH the yellow and the gray lines are bulging to the south (creating a trough bowl), AND, more importantly, those blue lines are not constrained to southern Canada, but are all over the West as well. Remembering that the atmosphere remembers suggests that the models are remembering, too, trying to regenerate the kind of flow pattern we’ve already been experiencing after a significant, quite pleasant, really, break from the cold week.

While this last panel is also a real laugher in many ways, due to all that uncertainty that’s indicated, the wildness in all those lines, you might want to hop off the fence in a longer term forecast toward the end of the month by thinking that what we’ve been having will return, a sort of “Back to the Future.”

Re-inforcing this view is how the red lines (570 dm height contours), usually on the periphery of the jet stream, become more compacted in the LATER, second plot compared with the first! This is a little remarkable since that would suggest the models have a better handle on the circulation pattern at 15 days over 11 days. Odd. Note, too, that those lines at 15 days are FAR to the south of AZ, supporting the idea of a cold trough in the SW.

———————————

¹These are the almond shaped clouds composed of droplets with smooth, sharp edges that hover over the same spot, expanding and shrinking, sometimes for hours at a time, as the grade of moisture changes in the air being lifted behind the mountains.

²Personal aside: Have friend, former WA State Climatologist who also worked at the U of WA as I did, arriving here with his wife on the 12th for a vacation from the dark days of wintertime Seattle. They will be here for the whole cold week and possible snow as it turns out, and then go back. Having looked at the progs, he now wants to take a “vacation from his vacation”, maybe head off to Costa Rica after arriving in AZ!

FROPA, cold just ahead

Summary: Wildcat mod has the front with a rain-turning-to-maybe a bit of snow-in-rain (its NOT SLEET!) between 10 PM AST on the 10th and 2 AM on the 11th.

Duration of precip?

Just three hours or so, quite awful; too short for any significant accumulation of snow in the cold air behind the front. This forecast cribbed from the U of AZ Weather Dept model outputs found here from the 11 PM AST data of last night¹. Here is a map of the predicted amounts just after the precip ends here at 2 AM:

Its interesting that on this website we have been talking about not chances of rain, but rather amounts of 0.10 inches as the least amount likely and 0.50 inches at the top amount, and then yesterday, due to fast movement, lowering the top amount possible to 0.40 inches, with a median amounts of 0.30 inches or so and this is what the Beowulf Cluster has come up with last night, the first of these runs I have looked at for this storm! It seems like if I guess something, then it just seems to come true, except on all those other days…

Now for a discussion of some vexatious, tedious details about our rain prospects in the coming FROPA:

Here is the jet configuration as the rain is about to begin on the evening of the 10th, from IPS:
As you can see, this model run (from IPS), from the global data taken at 5 PM AST, has the jet core at this level (500 mb) close to right over us, but a bit to the north if you look closely. Precip is almost always partitioned in a black and white manner by where the core is at 500 mb in the SW US in the cooler half of the year (Nov-Apr).

So, its of some concern that the jet has not gone past us here at 5 AM AST the morning of the 11th after precip has been predicted by the models! That jet core is nowhere near us when the Wildcat Beowulf Cluster has rain here at 11 PM AST on the 10th; its still upwind over western AZ.

So, of some interest to see whether the rule of thumb about the jet core and precip holds up in this situation. If it does, we could have a real disappointing FROPA, just sprinkles maybe. Because the deeper colder, moist air is on the left hand side looking downwind, it implies shallower moist air arrives here, shallower clouds, or separated layering during the FROPA band. On the right hand side looking downwind, is usually far drier air with clouds limited to shallow Cu-Sc, mid-level clouds, often Altocumulus lenticularis, and Cirrus. I just now checked with Beowulf predicted soundings, sometimes forgetting that there are model predictions of moisture layers above us, and they check out with the above assessment during the day tomorrow when the jet is far away from us.

Now looking at the Tucson soundings from our Beowulf model during the time of the precip, 10 PM to 2 AM on the 10th to 11th, it IS true that the clouds WILL be pretty shallow! In fact, the projected temperatures in the moist surge accompanying the rain band in that model run are only a little below our ice-forming temperature of -10 C (14 F). If the model is off by a couple of degrees (too cold) we could get nothing, or traces, just harmless Stratocu.

Gee, this is so interesting for a Cloud Maven person now! You, too, I am sure!

Here’s an additional thought. Those Beowulf soundings are literally for over the mountain in Tucson. Every mile to the north, because we are near the jet core, means everything will be that bit colder, cloud tops that bit higher. Furthermore, with the southwest to west flow, they’ll bank up the best they can against our side of the Catalinas.If Beowulf looked that the vertical layering of air right over Catalina tomorrow night, it likely would see lower cloud top temperatures than those shown for Tucson, and greater chances for rain here compared with there. Get it?

So, we’re really left with a more marginal rain situation than would appear to be the case looking at the Beowulf rain amounts in the first panel above. Dang. Seeing what really happens will be a joy in a sense because of all these factors.

After the front….

Waves of cold air, one after another. Beginning on the 11th, it will be one of the coldest 7 or so days in years here. Hope you don’t live in wash, where temps in the teens are likely at some point. The NWS of course, is all over this. Its been well predicted for more than a week in advance.

After the cold

One of the more astonishing forecast series has come out concerning the flow patterns after our week-long spell of severe cold with a powerful jet stream shooting down at us from Canada. All of the jet stream activity in the ENTIRE US is forecast to recede north into Canada! That kind of pattern means the whole US has been “milded”, as that happens, to continue a language innovation theme here. Take a look at this flow pattern over the US and compare it to the one in the second panel. Its an amazing change, almost a summer-looking pattern when the jet stream recedes to Canada.

Not much going on here. January thaw over the whole US? Looks like it except for the extreme NE.

But this is NOT quite at the end of the model run. What’s to happen next? What would you guess? No hints here on this map, that’s for sure. Remember what to fall back on, the past. Predict the future from the past as a first guess. If you did, not seeing anything going on here, you would see in the last few panels, another powerful, cold trough beginning to head in our direction. Of course, it may go away, but you have the past on your side; the atmosphere remembers what its been doing, and maybe it has not yet forgotten our cold spells after the mild one ahead that finishes out the month.

Brain, such as it is, exhausted, quitting here.

The End

Not quite: Just peaked at the 11 PM AST US model run now at 7:50 AM, and the “past” comes back in a hurry in this latest run. There is no substantial mild period to the end of the month. Its MUCH shorter, maybe a week before things cave in again in the last week of Jan. Hang on.

———————————

¹If you do peak, you might also send some $$$ their way. They are in dire straights these days. Mr. Cloud-maven person has.

Jenny’s post

Clouds go round and round with a sprinkle-rain landing close by last night

One of the things I like to do when I am wrong, yesterday having predicted a trace to a few hundredths of rain last night from that disturbance going by to the south, is to spend a LOT of time talking about how close I was.

Its true the zuperkomputer, the Beowulf Cluster, at our U of AZ Weather Department, did NOT predict rain here at all, but it did not have the sprinkles as close as they came to us, either! Exulting here that bit. Going to look on “trace detector” (car parked in dust and sun outside) now, just in case there is a drop image somewhere. Will report back on that later. Stand by.

Also, you should be looking around for drop images in the dust on stuff, too. If you’re going to be a “trace king”, you have to look hard in AZ so you don’t miss anything. A lot of reported traces shows that you are indeed a true CMJ! A trace of rain is incredibly important to microbes; a drop is like the ocean to them. Think about it the next time it sprinkles on you.

Below, the evidence of how close we came to one drop of sprinkle-rain last night (remember, it would NOT have been “drizzle” had it occurred; drizzle falls from LOW-based clouds that hug mountains, not from Altostratus clouds such as we had):

Sprinkle from Altostratus deck just to SE of Catalina at 2: 40 AM AST today. Will be looking on car parked outside (trace detector) just in case a drop fell here. — Sprinkle from Altostratus deck just to SE of Catalina at 1: 40 AM AST last night.

Arrow added into the same image above in case you did not see how close that sprinkle came to us the first time. — Arrow added into the SAME image as the first one in case you did not see how close that sprinkle came to us when you first looked at it. I really want you to know. I feel its quite important.

Loop of clouds and sprinkle rain going round and round here.

As a CMJ (Cloud Maven Junior), you would have seen and logged the low hanging virga extruding downward in one spot from that thick layer of Altostratus at sunset, that As band that also had something that looked a bit like an anvil extruding from it. Here is the “documentation” for these claims:

5:16 PM. Heavy Altostratus with scary anvil-like feature and VIRGA just to SW of Catalina about 50 miles.

Finally, this sunset shot of the same band 30 minutes later, making the same points as above again to better imprint them on you:

5:36 PM. Same band of Altostratus with anvil-like feature and virga (to right) at sunset.

The above has been, in effect, a burst of altruism. Let’s say I am hiking on the trails, I’ve missed a forecast, and you’re heading in my direction. At about 100 yards you will want to exit right or left and bushwhack it for awhile until I have passed to avoid an extended “in hindsight…”, hike-delaying conversation in which you have no real interest. Its gonna happen. It would be kinda like this blog-blab right now….

Now, feeling better, some REALLY pretty Cirrus uncinus from last evening:

5:17 PM. Pretty Cirrus uncinus along with some other varieties/species.

Now that I have gotten yesterday’s burr-under-my-saddle dispensed with, can ahead now, not stuck anymore, clouds moving away, can have new thoughts…

Will look at model outputs and see which one has the most rain/snow in it for us on the 11th-12-13th, with that Arctic blast, and think about the onset of that new “zonal” pattern after that, that pattern that will mild us¹ quite a bit after the Arctic blast. Beginning look at mods now….

WHAT?!!! Its back! That “trough bowl” collecting area for storms in AZ and the Southwest, after only short respite from cold storms. What happened to theThis is remarkable, check this prog for January 22nd at 5 PM AST. If it looks familiar, its almost the same as the map for yesterday afternoon, the 7th, but 15 days later! I repeat myself in the gif for emphasis now that I see I have repeated myself.

What’s the gut check here? “Spaghetti”, which seems appropriate for a “gut check.” Yesterday we saw that the NOAA spaghetti plots varied wildly 15 days out, making ANY model forecast that popped beyond about a week out pretty unreliable.

But what aspect of the atmosphere do we know about that makes a prog 14 days out that looks like weather we had yesterday look that bit more credible: the mantra, “the atmosphere remembers.”

Persistence, a forecast based on weather you’ve already had for the past week or three, and projecting it into the future is one of our more reliable forecasting techniques. Sounds silly, but its true. The pattern eventually changes, but its hard to catch that tipping point when it does. Yesterday, the mods had that pattern change and it was some support for that in the NOAA spaghetti plots. That support has weakened, though not gone, seen here if you dare.

——————Module on conversational meteorology——–making the past the future

Imagine, that on January 1st last, a neighbor asked you, knowing that you were a cloud maven junior, maybe have Asberger’s Syndrome, and in your case, focus on itty-bitty weather details and data:

“What kind of weather do you think we’ll have in January?” Without divulging details of your forecasting methodology, hindsight, and then trying to remember, if you could, what the weather had been like in the two weeks leading your neighbor’s question, i.e., the time when the new flow pattern began here, you could have furrowed your brow and said, with at least feigned authority:

“I see below normal temperatures, perhaps much below, with a good chance of above normal precip. “‘Hey'”, and then going a bit too far, you might have ventured into, “…and I think there’s a good chance of a real snow here in Catalina this month with all that cold air we’ll have.”

Today, with a severe cold spell ahead, you would be the forecasting guru of the block, icon of the next block party, and all you had to do was remember, which can be hard sometimes.

In weather, it really is true: the past is often the future.

—————-End of conversational meteorology module———————————————————–

So what to think?

Its not a bad idea to hedge your forecast longer term forecast with “persistence”; continuing below normal temperatures, maybe not as severely cold as what’s immediately ahead on the 12-14th, precip on the 11th. Amounts, due to the speed of this thing, still 0.10 inches at the bottom, but I’d reduce the max potential to 0.40 from 0.50 inches, median then 0.30, about the same as the last prediction. The flow pattern with this will be like the last front on the 31st, and so we’ll do better than most of areas around us in amount because the clouds will bank up against our side of the Catalinas more than elsewhere. Still expecting rain to change to snow at the end of the FROPA on Friday morning, the 11th, but amounts likely to be an inch or less now. Dang, again.

Because it will be so cold aloft, and here, and there are minor disturbances that blow on through for the two days after the 11th, a passing flurry is likely (that from, as you KNOW, from “heavily glaciated clouds”, at least at times.

A bit much today, so will gift you by quitting here.

The end.

———————–

¹Using “mild” as a verb here; might be first time ever such use–William Safire, language-maven, where are you now that we need you? Remember when we made fun of Alexander Haig, the Nixon admin Chief of Staff, about the way he used nouns as verbs, i.e., “gifted him.” Now he can be considered a language pioneer since we hear that usage all the time. Don’t forget to use “mild” as a verb today at least once: “the weather pattern is going to mild us for awhile before the big freeze hits.” That would be great! Thanks.