In case you like to go to the end first, a quite nice one:
5:53 PM. A mostly spissatus sunset.3:19 PM. Creepin’ Cirrus (spissatus) has creeped overhead.2:07 PM. Creepin’ Cirrus, creepin’ up from the south during the afternoon.
A little whirl in the air overhead and to our south now seems to have spawned some Altocumulus castellanus (Ac with vertical spires), according to nighttime sat imagery. Could be a very nice sunrise this morning, and because they’re going to be cold (colder than 0 F), likely to be some virga around, something that would really enhance the sunrise color.
It now appears the skies will clear completely later in the day as it passes by.
“In other news….” the tremendously cold air foretold in the models, supported by spaghetti, to ravage the East maybe ten days ago is now beginning to arrive. They’ll be some whining from back East (as in the next segment). Perhaps some folks in the East will now throw in the towel and finally decide to move to Arizona. Pretty sure some will.
A whiny, Seattle note: one of the HARDEST things to take when I lived there and biked to work for about 25 years, was the very pattern we have now with Seattle sitting under a HUGE, high amplitude bubble of warm air known as a ridge. The jet stream and storms are about as far away as possible in January from Seattle, and its nice and toasty along the West Coast IN GENERAL. Here’s a loop of the 500 mb maps (requires a lot of bandwidth). Below, the 5 AM AST map for this morning, illustrating the CLASSIC, “Warm in the West, cold in the East” one:
But not “warm in the West” for Seattle.
Fog forms in Puget Sound under these situations and the sun is too weak in all that clear warm air just a coupla hundred feet above you and often cannot burn off this shallow fog that you can see through a lot of the time!
And even if it does clear up, as it eventually did yesterday afternoon (time lapse there from just about where my Dept lab-office was), its still cold and clammy all day (yesterday it was 38 F in SEA with the sun out in the late afternoon). Sometimes the fog was so thin you feel like you could reach up and touch the warm air you knew, as a weatherman, was just above you.
So, like the last few days in SEA, you get foggy days, and “high” temperatures in the 30s, often with frost and ice on the roads in the mornings, so you can’t even bike to work in this “fair weather” pattern. It was tough to take because you had such a great chance for a sunny day with the storms pushed elsewhere, and it didn’t happen.
End of whine; glad to be in Arizona. I did love my job and my pals there in SEA, still do.
Rain still ahead here for the 28th; varies in amounts from model run to model run. Moisture from that storm now off Baja in the map above (its got lightning in it) will fiddle around out there until some westerlies “swooshes”1 the remains of that system this way late in the week.
Sadly, there appears to be no rain in sight for us after the 28th episode.
A storm from the Pacific passes slowly over Arizona on the 28th bringing desperately needed, soaking rains to almost all ag units, wildllife, desert vegetation, and us. It then plods on across NM and into the Plains States doing the same, eventually exiting across the Ohio Valley, having drenched some of our most drought-ridden regions between the 28th and 30th. These beneficial rains across so much of our country might be worth a trillion in 2013 dollars1, hence, the moniker, “The Trillion Dollar Storm.”
Here are a few IPS MeteoStar panels (I favor their depictions) from yesterday’s 5 AM AST model run because they’re a bit more spectacular than last evening’s 5 PM AST run (remember from spaghetti the storm on the 28th is in the bag for AZ, and that each model run from here on out will be more or LESS spectacular in rain production, so why not take the “best of the best”? A few panels with the most rain in them to put in your model outputs scrapbook? Too, I was afraid you hadn’t seen these, and I just couldn’t let go of them myself, like pictures of an old girlfriend you just can’t throw away but probably should:
Valid for 5 AM AST, January 28th. Been talkin’ about rain on this day lately, and here it comes from the Pacific across both California’s.Valid at 5 PM AST, on the 28th. Soaking rains cover much of the State especially in the central mountains.
Valid at 5 AM January 29th. The storm is slow to depart, and more soaking rain has occurred in the 12 h prior to this map (dark green and blue regions). How much is such a rain worth to our wildlife and vegetation alone?Valid for 5 PM AST, on the 29th. A storm center has intensified in the central Plains States and a tremendous rain, snow to the north, has enveloped it. It moves out slowly with a soaking rain shield to the north and west of the center. It could hardly be better than this given the intensity of drought in this region.
Pretty much the same thing popped out of the models from last night’s 5 PM AST global crunch, so its great now that we have 4 model runs separated by 12 h each that have substantial AZ rain! Gives confidence that this rain will occur as predicted, as well as that confidence that came from yesterday’s venerable spaghetti plots. I am so pumped! In the depictions above, Catalina gets about an inch of model rain!
Reality, of course, will be something else, but now, in these model outputs, us Catalinians are more into the rain areas predicted than on the edge as was the case a couple of days ago, less “iffy” for a rain to happen. So, I am going for it: one half inch in Catalina on the 28th. You won’t hear your favorite media weather presenter telling you this today because its not really responsible to say an amount this far in advance. But, here on the internet? Anything goes, and I have demonstrated that just now.
Clouds?
I know that if I were to read your weather diary for yesterday it would read something like this;
“CIrrus lurked on the south to through west horizon all day. Didn’t come over Catalina, just kind of stayed down there. I was hoping to see more of it.”
Here is that stagnant Cirrus at sunset that you wrote about yesterday. You DO have a weather diary, don’t you?
5:51 PM. Sunset getting noticeably later now days. Also, its well away from Twin Peaks (left of center), where it set on the December 21st, the winter solstice.
Expect some more patches of Cirrus today. You can see the “moisture front” these clouds were in yesterday here in this water vapor loop from the University of Washington Huskies Weather Department. That whitish area on the southern AZ border is where the Cirrus clouds were yesterday. You will be able to see the “white stuff” (areas with more water vapor) beginning to head this way.
TE
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1In the 1960s we would have termed this upcoming storm a “Million Dollar Storm”, but with today’s economic realities, where we talk about “trillions and trillions” of dollars all the time, a “trillion dollar” this or that seems more appropriate, more “with it.” Its great that dollars are only made out of paper; there will always be more paper for dollars! If they were made of anything else, I am sure we would run out of it.
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. 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.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.2:57 PM, just 12 min later. Its got more writing on it.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 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.
$$
“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, 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” 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).
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.
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 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:
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.
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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!
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 1: 40 AM AST last night.
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.
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.
Valid for 5 PM AST, January 22nd.
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.
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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.
Backdoor rain? Looks like any chance of rain will happen later this afternoon through overnight as mainly mid-level clouds twist around our low from the east. That low is now over Yuma, AZ, and the center will pass to the south of us tonight. We don’t see that happen too often. Here’s a nice loop of the circulation around it, also showing the radar echoes–very handy. (Some cloud shots at the bottom, way down there.)
Right now, our low is looking pretty dry, not much going on in it, or around it right now, and so any rain falling from mid-level cloud bands, like Altocumulus (with virga) and a likely deep band of Altostratus (also with virga), will be pretty light; sprinkles to maybe a hundredth or two. The better part of this is that with mid-level clouds coming from the east, they won’t be much dissipated by the air going downhill from the Catalina Mountains as you would expect with low clouds. However, in Mexico, since it is so cold in the center of this low, there will likely be reports of snow in unusual places, as in the last storm. The U of AZ Beowulf Cluster model, the best around for us, sees only a brief, fairly close call for rain tonight.
Still, while this low passage will be a little disappointing as far as rain goes, the skies will be great today with scattered Altocumulus, likely with a little virga, and scattered Cirrus, with a great sunset. Both of these cloud types can be very “photogenic” on days like this. Likely those mid-level clouds will clear out tomorrow morning, so get’em while you can. If you don’t, of course, this compulsive cloud photographer will.
Full cold ahead
Get ready for some terribly cold days just ahead, likely some snow in Catalina still, though the more moist Canadian model prediction for this storm has dried out overnight–tending to be more in line the with US models which have always had this cold wave as a light precip event. Precip is pretty much guaranteed here, and some snow probable in Catalina, but max and least precip totals from this storm have to be revised downward in view of the latest Canadian results. Minimum amount, 0.10 inches, max, 0.50 inches (was an inch due to how much offshore flow the prior Canadian models had the night before last). So, most likely amount is between those two extremes, or about 0.30 inches with precip beginning during the day on the 11th.
A further disappointment is that the mods now see this storm as a quickly moving event, and the precip is over by evening on the 12th, so it ends up as just a 24 h period of rain and snow chances, most coming, of course, in the first segment, a line of rain changing to snow with the frontal cloud band and wind shift line on Friday, the 11th. Dang.
What about the second cold blast on the 15th-16th?
Still coming, but this wiggle in the jet stream shooting down at us from the northwest, has a trajectory toward us that is farther east than it was shown in the models earlier, and the farther east and the further away the trajectory is from the coast, the drier these cold pushes will be. So, that second blast of cold air, while still looking very cold, is also looking pretty dry right now; may only get a passing snow flurry, or we’ll just see scattered small Cumulus with some virga.
In these latest model runs the jet stream pattern that has led to our “trough bowl”, the favored location where storms have been collecting in our region for the past month, begins shifting to the east at mid-month, and what’s more, the amplitude of the north-south oscillations in the jet stream fade to a more west to east flow.
This very different than what was depicted just the night before last. Here’s what I mean. Shown below is the first forecast panel, high “amplitude” pattern in the jet stream–always associated with temperature extremes, cold where the jet dips down, like HERE, and warmer than usual where it shoots up from the southwest,for example, there in Alaska.
Valid for the evening of January 15th. An example of “high amplitude jet stream configuration associated with temperature extremes.
This is a very common pattern. You probably remember how warm it was in Alaska during the 1962-63, and the 1976-1977 winters, but how friggin’ cold it was back East when this kind of high amplitude pattern was pretty extreme and persisted for weeks: the jet racing into Alaska from the mid-Pacific, and then shooting south into the US. Really horrible times for the East in those winters.
But look at what the model sees for the end of the 15-day forecast period, shown below! The jet hardly has any amplitude, just shoots in from the Pacific in a west to east flow. That means no temperature anomalies to speak of, and a moist West Coast regime, sometimes with precip getting this far south, too.
Valid the evening of January 22nd, a Tuesday.
What does spaghetti say about all of these changes?
Its pretty clueless, that is, slight changes in the observations make a big difference in what happens, and that’s why its so wild looking in the Pacific and the US (shown below). This means you probably can’t count on the above pattern a lot, except that the amplitudes have gone down, that seems to be a pretty solid expectation. That jet surging into AZ could just as well be intruding into Washington State in a west to east pattern. That would mean that our 30-days of below normal temperatures here in AZ, beginning in mid-December (shown here by the NWS, lower right panel), are about to end after about a week to ten days, and with that, a long dry spell likely to set in.
Yesterday’s clouds
Mostly Altostratus, thinning at times to Cirrus, and late, a few Altocumulus/Cirrocumulus patches. Here are a couple of shots.
7:22 AM. Under lit Altostratus at sunrise. Those little pouches are regions of light snowfall (virga).1:49 PM. Boring, generic Altostratus translucidus, an ice cloud. Sometimes droplet clouds like Altocumulus are embedded in them, but none can be seen here (they would be dark, sharp-edged flecks). The massive clearing that occurred in the late afternoon is visible on the horizon. If you saw that clearing, it would have been a great time to tell your friends that, “Oh, I think it will be sunny in 3 hours.” It would have been quite a magical moment for you.5:36 PM. This beauty of a patch of Cirrocumulus undulatus (tiny granulations in waves) and a lump of Altocumulus (lower left). TUcson sounding indicates they were about 15,000 feet above the ground at -20 C (-4 F). No ice apparent. It happens.
The above, a quote from Douglas Adam’s hypersupercomputer, “Deep Thought”, from the 1980s classic sci-fi radio series, “Hitchhiker’s Guide to the Galaxy”, spoken by DT as he prepares to give the answer to “life and everything.” In the context of the computing grandeur of DT, as one website quotes, “Don’t even mention these”:
The Milliard Gargantubrain
The Googleplex Star Thinker
The Great Hyperlobic Omni-Cognate Neutron Wrangler
The Multicorticoid Perspecutron Titan Muller
The Pondermatic
These still make you laugh from that classic NPR radio series-Eagles theme here).
I wanted to distract you with laughter if you are one of those persons who love Arizona or are a snow birdy solely because of its warm, sunny weather in winter. Not gonna happen this month1.
The answers to “weather and everything” below, and you’re not going to like them, unless you’re a skier, and you come to Arizona for great powder skiing!
By the numbers, what’s ahead:
Weather event 1. a little cut off low travels across northern Mexico from southern California bringing some fabulous-looking clouds today (high ones like Cirrus), and a brief shower at anytime tomorrow through Tuesday morning when its closest to us. Nice. But its not too cold yet. That comes later.
Rain in #1? Top pot (-ential): 0.25 inches; bot pot, just a trace. Most likely amounts hereabouts? A few hundredths to a tenth. Hoping for the development of a narrow, odd line of high-based (Altocumulus level) Cumulonimbus clouds that wrap around the upper low center as it goes by to south tomorrow. Wispy storms like this could produce little shower areas not conducive to model resolution at any time since the moisture threads running around it will be very narrow. You’ll have to be watching. Have camera ready for spectacular Ac castellanus (he sez) today and/or tomorrow.
In summary, today you will begin to be clouded over. On to event 2
Event 2, begins January 11th.
Summary: Yikes! Takes a few days to get through this. Check this prog out from Canada from last evening’s global data crunch (especially, the upper left and lower right panels):
Valid for 5 PM AST, Friday January 11th. “Totally awesome!” This new depiction moves this giant trough to offshore of southern Cal-Baja. You know that means. More water streaming north into AZ before the Big Cold hits, molecules of water vapor being sucked out of Pacific. That would be fantastic. One of the best model forecasts I have seen in a LONG time. Congratulations to Enviro Can for coming out with this last night. A real winner.
OK, quite exuberated over this Canadian forecast. For one thing, the dreaded super cold air is delayed, though it still happens after this big trough goes by. But mainly from this prog above, our precip potential is jacked up by twice with an upper level configuration like this, so much of it offshore now.
In the preceding days after Event 1 ends Tuesday morning on the 8th, the temperatures will rebound nicely, too, before the Big Whammy on the 11th-12th.
Rain in Event#2, January 11th (begins later in day)-13th? I think now you have to be thinking the “top pot” here in Catalina is 1.00 inches over a 48-72 h period, bottom pot, 0.30 inches (i.e., less than 10% chance of more; 10% chance of less). Median of these “best extreme guesses”, 0.65 inches. So, we got us another sure-fire substantial rain, even if the minimum is all we get. Go desert wildflowers!
Now, a caveat… US mods don’t have the flow as far offshore in event #2 as the Canadians do, thus, our mods have a much drier depiction for this storm. In these kinds of situations, no model has the complete truth, and so mentally you try to integrate the two. The lower precip bound of just 0.30 inches here is due to a compromise in actual flow patterns that might eventuate.
Quitting for a second to dream about pounding rain on the flimsy Arizona roof we got…the only kind to have if you’re a real CMJ (cloud maven junior); are a precipophiliac, as I am, or just like the sound of what the wildflowers are getting out there in the desert.)
Snow in Catalina in #2? Sure looks like it, toward the end of the precip, overnight 12th-13th. Will expeculate that 1-4 inches will fall between Saturday night into Sunday morning.
Event #3. The storms, though not nearly as moist as #2, troughs just keep “falling down the shoot” as the jet stream zips southward along the West Coast carrying storms to us for the foreseeable future with the timing of #3 on the evening of the 15th-16th (US WRF-GFS mod run from last evening’s data). Here’s what that cold trough and following blast of cold air look like on the evening of the 15th. A little snow is possible toward end of this event in Catalina, too. This goes by really fast, which is bad for precip totals, and “good” for extra cold air arriving here, since its shooting down at us so fast, that cold air can’t be modified much into warmer air as it goes southward.
Vallid for 5 PM AST, Tuesday, January 15th.
Only in the “dying embers” of last night’s model run, one that ends after 15 days, on the 21st, does it appear that there is a break in the pattern of below normal temperatures here. But, as we know, the atmosphere “remembers” for weeks at a time, so it may not be last long.
BTW, we are joined in cold air by our planetary neighbors in China, who are experiencing one of the coldest winters in 20-40 years. In a preliminary newsy item from China, they have attributed the cold winter to warming….and melting ice caps. Hmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmm.
In an aside, should we see some really cold air, as is likely, the argument that “its colder because its warmer” may show up here. Its out there and I think it showed up after our February 2011 record freeze. Remember, I am a cloud-maven, not a climate-maven, but some statements do seem silly. Severe weather happens; always has, always will.
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1Its great, though, to see all those out-of-state license plates these days (Ohio, Ilinois, MN, PA, Iowa, ID, AK, Ontario, Can, seen just yesterday), knowing there are so many people who want to be where I am all the time, a permanent resident. I am sure all of us Arizona “barnacles” feel the same way!
Was going to rest brain today, not blog-blab, but then went to mods; brain rest over.
“Holy Smokes!”, “Good Grief!”, my modest brain erupted with when perusing the 00 Z1 (5 PM AST) WRF-GFS model run this early AM. If the predicted features verfify over the next 15 days, what appears to happen beyond that, this could be one of the most severe January’s in the Southwest in decades. Yikes. And our “test the effects of flapping butterfly wings on the model run” (figuratively) “spaghetti” plots from NOAA, those slightly perturbed/disturbed model runs, seem to support last night’s ACTUAL run, at least into the first two events described below2. “Hence”, as they used to say, the excitement this morning from this keyboard, but maybe some dread, too.
Quickie overview for Catalina
(taking the current model run (00 Z) at face value:
Jan 7th into the 8th: Some rain, maybe a tenth or two.
Jan 11th-12th: rain changing to snow, total precip maybe half an inch, with an inch or two of snow. Post event, temperatures dropping into the 20s at night, lower in washes and such.
Jan 16th. Another chance of snow, doesn’t look like as much precip as the prior event, but colder yet afterward. Temperatures lower yet, could get into the lower 20s, teens in the washes.
Furthermore, the pattern doesn’t appear to break after this last storm on the 16th. It remains cold here through the end of the model run on January 20th. As you likely know by now, once the jet stream gets into a pattern, it likes to keep it going. No one knows why, or when it will break. If we did, our longer term forecasting would be better.
Some more discussion below of this forecasted pattern, one that could lead to one of the more severe Januarys in the West in some decades. While precip is always dicey here until the last moment, the exceptional cold seems very probable. Be ready!
Here’s what the model (as usual, rendered here by IPS MeteoStar) has churned out for us in the way of rain/snow events for us,with the storm formerly mentioned here as arriving on the 8th, now arriving on the 7th. (Heck, for awhile it was GONE!) This series of three trough/storm events shown below might be thought of as cool, colder, coldest. Not so good as a series if you’re visiting here to enjoy warm weather.
Valid for middle of the day, January 7th. Not a bad storm, but not a great one, either, but good in the sense it keeps the stream of storms up after a week’s break. Maybe a tenth or two of rain.
Here’s the next one, valid for the evening of the 11th, and this one starts to get your attention, as in “Yikes! If that materializes, its snowing here!”:
Valid for 11 PM January 11th: Summary; yikes! So cold, rain turning to snow in Catalina, maybe a couple of inches. The thing to notice is the central contour number here, “12” lower than the “ordinary” storm shown above. The lower these numbers (contours where the height of the 500 millibar pressure is reached, the colder the air must be underneath it. The denser the air is, the faster the pressure changes as you go up. So a “540” contour represents really cold air in the Southwest moving into Arizona. I would not want to be a grapefruit in the few days after this goes by.
Finally, this, a brutally cold trough over us again, with the jet stream running a straight shot just down the interior of the West Coast from pretty much the place where Santa Claus lives, Barrow, AK. Below, valid for the morning of January 16th:
Valid for 5 AM AST, January 16th. Egad! While precip might not be as much in the prior trough passage, this one looks colder after it goes by. Part of the contribution will be that the prior storm would have laid snow down over a vast area interior of the West, and that will help to keep the cold air blasting southward here colder here than it otherwise would be.
These particular depictions, especially the latter ones with rain and snow in them for us will be flopping around like a just-caught trout in a boat in the model runs ahead. The main thing that seems “in the bag” for Arizona as a whole, is COLD air. Cold to write home about.
Snow? Of course, its less certain as the troughs wiggle around in the models, and to get that snow the apex of the troughs pretty much have to go over us and those little wiggles could take them to a bit to the east of us, making the coldest spells just dry ones. That would be too bad, because if you’re going to have to endure cold, there might as well be some snow on the ground to play around in.
Now in a personal disclosure, one of the faults I have as a weather discussant, is to get TOO excited about extreme events that are forecast, rationality diminished, hence the “newsy” logo here:
“Right or wrong, you heard it here first!!!!”
It WILL be so much “fun-dread” day by day, to see if these things come to pass, how the models change these depictions above as new data are processed. To repeat, though, be ready!
The End.
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1Or, “CUT”, Coordinated UNIVERSAL time, as it is called today. I hope those people on the edge of the universe are aware of our time convention. Used to be known as GMT, Greenich Mean Time, starts at the 0th Meridian over “jolly old England.” “Jolly”? Huh. Are they referring to Monty Python? Rowan Atkinson? .
2Don’t forget to order your “I ‘heart’ spaghetti!”, tee shirt that shows you’re one of the scientific literati because “spaghetti” gives us insights into whether a model run is a bunch of crap (oops, “model excrement”. New! Now available in down jackets….
First of all, Happy New Year to both readers! Thanks for hanging in there.
The weather ahead…
before a long diatribe about drizzle, followed by some pretty pictures with explanations:
Some picaresque Cirrus later today. Looks like next chance for rain is around the 10th-11th of Jan.
A rare drizzle occurrence
Cloud maven juniors were probably excited beyond description when they went out yesterday morning between 9 and 11 AM and intercepted a rare occurrences of brief drizzle here in Arizona falling from that low-hanging Stratocumulus overcast. This happened after several very light RAIN (not drizzle) showers dropped another 0.02 inches, raising our storm total here in Catalina to a respectable 0.30 inches.
Drizzle is composed of drops barely large enough to cause a disturbance in a puddle of water1, as though a large particle of dust had landed in it. Drizzle drops nearly float in the air (should not be falling at more than about 3-4 feet a second), and in many cases of very light drizzle, the drops can float around like “desert broom” seeds. Visibility is usually lowered, things look fuzzy in the distance. Drizzle precip is so light it can’t produce even 0.01 inches except over periods of an hour or more. Drizzle drops are also more uniform in size than the drops in rain, and are usually very close together.
While drizzle is common along the west coasts of continents in coastal Stratus and Stratocumulus clouds, its much rarer at inland locations such as here in Arizona, thus, the excitement over seeing it yesterday.
The reason why its rare in AZ?
Shallow clouds that drizzle must be what we would term, “clean” clouds; they don’t contain many cloud condensation nuclei and so droplet concentrations are low, maybe 50-200 per cubic centimeter (might not sound low, but for a cloud, it is). Clean evironments are found over the oceans and for awhile, in air coming inland along the west coasts of continents in onshore flow before it gets contaminated with natural and anthropogenic aerosols (smog). Man, we are getting into a real learning module here! Wonder if any readers are left? Probably talkin’ to myself now. Oh, well, plodding on. Nice photos below…far below.
Drizzle occurrences tell you a lot about the clouds overhead. Not only are they low-based as is obvious (they have to be or the drizzle can’t reach the ground), but they are relatively shallow clouds no matter how dark they look. Furthermore, and more subtle, they have larger cloud droplets (ones to small to fall out as precip) in them that must be larger than about 30 microns in diameter (smaller than half a typical human hair diameter). When this larger size is reached in clouds, and those drops are pretty numerous, say 1000 per liter, they begin sticking together when they collide in the normal turbulence in clouds. Those collisions with coalescence result in drops that fall much faster, bump into more drops, growing larger and larger until they fall out the bottom.
In a shallow cloud, those drops can’t get larger than drizzle drops, and that’s one of the ways you KNOW that they are shallow no matter how friggin’ dark they look.
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Aside about rain not due to the ice process:
The largest drop ever measured, 1 cm in diameter, was observed in a Hawaiian Cumulus cloud that did not reach up to the freezing level! Unfortunately, the authors of this finding did not publish their results and so did not get a Guinness record like me and Pete Hobbs did when we reported a smaller 0.86 centimeter diameter drop in Geo. Res. Lett., 2004–found them in Brazil, and again in the Marshall Islands–hit the pilot’s window like little water balloons. Instead of being in a book with other famous people, like ones who can eat 47 hot dogs in 12 minutes, those researchers who encountered that larger drop in Hawaii sat on their finding! Unbelievable.
Strangely believe it, from lab experiments, drops bigger than 0.5 cm are not supposed to exist, but rather break up around 0.5 centimeters in diameter. (hahahahaha, lab people). End of aside.
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1Officially, 200-500 microns in diameter, equivalent to a couple or three of human hairs, maybe ONE or two horse’s tail hairs, to add a western flavor to the description.)
Yesterday’s gorgeous skies!:
Took more than 100 photos yesterday. Was out of control, euphoric, thinking how great this earth is, maybe leaning toward thoughts of higher being and creativity therein, thus explaining the “creative” punctuation above. Here are a few shots of those magnificent clouds and our magnificent, snow-covered Catalina Mountains. First, those drizzle-producing clouds:
10:12 AM. Last of the drizzling Stratocumulus overcast. Patchy area of drizzle to west on the Tortolita Mountains here. The Stratocu gradually broke up after this time.
11:54 AM. Stratocumulus clouds still in charge, but lift here for a peak at the new snow on the Catalinas.12:13 PM. First snow showers appear to the north-northwest as the stratocu deck begins evolving into Cumulus congestus and small Cumulonimbus clouds with large breaks.12:35 PM. Snow showers from relatively shallow Cumulus race along the Catalina Mountains. These kinds of snow showers occurred right up until late afternoon.12:37 PM. Snow and light rainshowers from shallow Cumulonimbus clouds also begin moving into Oro Valley before striking the Catalinas. Look at how similar these smaller clouds with their rain/snow shafts appear to our summer giants.12:59 PM. Shower over the Oro Valley moves onto the Catalinas. Arrow points to a filament/strand coming out that is almost certainly composed of graupel (soft hail), something that was common yesterday from these clouds.2:38 PM. HOWEVER, graupel often falls out of Cumulus congestus clouds on their way to being a Cumulonimbus without any sign of precip overhead, as here. This is because you are getting the result of the very first ice to form and fallout, usually those first ice particles are pretty rare in many of the shallow clouds as we had yesterday, and, because the updrafts are weak, they fall out as isolated little snowballs, too few to produce evidence of a shaft. But hang on, a shaft often, in the deeper clouds, imminent.Also at 2:38 PM, looking northwest. A view of smaller Cumulus with the deep blue of the winter sky we love.3:07 PM. “Congestus on the Catalinas.” You might ask, “where’s the ice?”, since yesterday all clouds reaching this size produced ice/snow/rain. Well, its on the other side (due to wind shear that carried the ice off toward the east. I think that’s the real reason why “the bear went over the mountain”, as we used to sing.
3:11 PM. Example of the medium Cumulus clouds (mediocris) that developed ice in them yesterday because it was so cold aloft, tops here colder than -12 C. (estimated). Arrows point to ice, necessary for measurable precip here.3:50 PM. Another modest Cumulus with plenty of ice (probably 10s per liter if you were guessing). Lowest top temperature likely lower than -15 C.
4:08 PM. I have no idea. This patch of ice cloud is left over, a “ghost” really, of a medium Cumulus cloud whose droplets evaporated. But what would it be called now? Altostratus translucidus cumulomediocristransmutatus? Cirrus spissatus cumulomediocristransmutatus? Silly, but I know of no name for such a patch of ice/virga4:49 PM. You knew that on this cold day you would be treated to some of our finest scenes in winter, golden scenes of cloud-capped, snowy mountains, and later, those rosy under lit remaining small Cumulus and patches of Stratocumulus. What a fine day it was!
