Cumulus clouds – Page 23

Cold slam

That’s your weather forecast for today. There’s nothing you can do about it. Why go on about it?

Next, these from yesterday–was under control, only took 127 photos. Every thousand or so shots I take is NOT of a cloud, and yesterday there were two exceptions, which I will post here as an anomaly; a quirk really:

5:48 PM. Sun broke through the Cumulus and Stratocumulus clouds for this orangy foreground as the white light of the sun is burned orange at low sun angles by passing through a denser portion of the atmosphere. The shorter wavelengths (blueish) are scattered out leaving reddish hues to come shining through. Banner cloud remains in its same crevice on Samaniego Ridge like a trap door spider or a piece of lint in a corner of the room you haven't vacuumed for awhile. — 5:48 PM. Sun broke through the Cumulus and Stratocumulus clouds for this orangy foreground as the white light of the sun is burnished orange at low sun angles due to having passed through a denser portion of the atmosphere and the shorter wavelengths (blueish) are scattered out leaving reddish hues to come shining through. Banner cloud remains in the same crevice as yesterday on Samaniego Ridge like a trap door spider or a piece of lint in a corner of the room you haven’t vacuumed for awhile.

2:55 PM. Horse demonstrating that the appearance of water in a tributary to the Sutherland Wash was real, not an illusion. Thanks, horse. The bit of water in the Sutherland dried up just down from the private land fence opposite the rusty gate. — 2:55 PM. Horse demonstrating that the appearance of water in a tributary to the Sutherland Wash yesterday was real, not an illusion. Thanks, horse. The bit of water in the Sutherland Wash itself dried up just down from the private land fence opposite the rusty gate on the east side. (Horse people know where this is.)

5:56 PM. Gritty view through wires and a telephone pole of the highlight color of yesterday's sunset. Sometimes I think you're here only for the eye candy. — 5:56 PM. Gritty view through wires and a telephone pole of the highlight color in Stratocumulus clouds of yesterday’s sunset. Sometimes I think you’re here only for the eye candy.

Yesterday’s rare ice-forming anomaly

I was hoping you wouldn’t read this far. Something incredible happened, rarely seen here in Arizona. Our slightly supercooled clouds, with top temperatures between -5 and -10 C, formed ice. When I first saw the indication of something falling out of those shallow clouds on the Catalinas, I was beside myself. Here’s what I saw, not taken while driving¹:

11 AM. A shopped photo of the ice fall on the Catalinas to make it look like it was taken from a car, the way you might have seen this. — 11 AM. A shopped photo of the ice-fall from these Stratocumulus clouds on the Catalinas to make it look like it was taken from a car, the way you might have seen this ice fall. Note how I cleverly tilted the image to make it look like it was taken in a hurry before the light changed.

Same image with writing on it. — Same image with writing and an arrow on it to help you out.

I thought it was some kind of fluke since it was indicated just yesterday from this keyboard, based on prior experience in Arizona, that ice rarely forms in our clouds at temperatures above -10 C (14 F). Maybe someone was nefariously cloud seeding I wondered…. Or had flown an ice-producing aircraft through these clouds upwind somewhere. (Its about what cloud seeding would do in marginally supercooled clouds like these, too, not much but something.)

———academic discussion—–

Ice appearance in clouds with tops warmer than -10 C is common in “clean” environments like over the oceans (see the works of Mossop in the Australian Pacific, Borovikov et al in the Atlantic, Hobbs and Rangno in the Washington State coastal waters and the Chukchi Sea offn Barrow, AK, or Rangno and Hobbs in the Marshall Islands) in clouds with warm bases (ones substantially above freezing for the most part) that can be anywhere even in “continental” environments far inland where cloud droplet concentrations are high due to natural and man-produced aerosols (see Koenig in Missouri, Hallett et al in Florida, Rangno in Israel) among many others). We sometimes have those warm-based clouds here in the summer, too.

——-end of academic interlude——–but not really——

These fuzzy very light snowshowers soon ended and the day went on as foretold, no ice in the clouds.While out on Old Jake, shown above, I was taking photos of particularly dark based clouds and was going to tell the story about why they looked so black, and yet did not precip–to warm and cloud top, and drop sizes near the top, too small for ice initiation. Just about every case in which aircraft measurements have been made in such clouds that form ice at top temperatures above -10 C (14 F), inside them are cloud droplets larger than 30 microns AND a few drizzle drops (liquid drops between 100 and 500 microns in diameter, or rain drops. Droplets larger than 30 microns and substantial concentrations lead to collisions where the drops that collide can coalesce into a single drop. Let us not forget Hocking or, later, Jonas and Hocking and the 38-40 micron drop size limits they found for this to happen from lab experiments. Below that 30-40 micron diameter size, the little cloud droplets act like marbles; too much surface tension.

OK, there’s that little discussion preparing you for what comes next. Continuing with the story…was there one? Well, anyway, Mr. Cloud Maven person, riding on his own forecast made that early morning for no ice in the clouds (meaning no rain), decides to also ride on his old horse, Jake, who needs some more of that exercise.

Confidently, though dark Cumulus clouds underlying a broken to overcast deck of Stratocumulus, looked even exceptionally dark in places, Mr. Cloud Maven person smiled at this darkness of the cloud bottoms, knowing that the darkness in the bases of shallow Cumulus only spoke to how high (and small) the cloud droplets were in those clouds; they had to be highly “continentalized”clouds, ones with tremendous droplet concentrations in them and because of that, all of the droplets in them have to be tiny, being so great in number. And, in being a Cumulus cloud with an appreciable updraft, even more droplets are activated in “continental” air than are at the bottom of a layer cloud like Altocumulus.

When the drops are tiny, more sunlight is reflected off the top of the cloud and the darker they get on the bottom, and the more removed they are from producing a drizzle drop, or are in having the precursor droplets to drizzle drop formation, cloud drops larger than 30 microns.

This is what a Cloud Maven person thinks before he gets on a horse….

So, as I am riding along near the Sutherland Wash, these patches of dark bases form nearly upwind…. I watch them for awhile, quite unconcerned, and smiled again, thinking about the other horseback riders, people on bikes out there that likely turned back in fear of a terrific downpour, not really having the knowledge they need about clouds.

Then suddenly I noticed ice streamers coming down NW of Catalina only a couple of miles away! It was falling from the downwind part of these darker clouds, where after a period of time, ice, if it was going to form would be. But, how could this happen?!!!! Before long, the thicker regions of the cloud began to emit stranded precip, a sure sign of graupel up top in the cloud. Graupel in clouds with supercooled droplets only 23-25 microns in size, much smaller than those required for coalescence, and the present of those droplets leads to ice splinters when they are banged by a graupel particle. A coupla graupel (soft hail) and after awhile, (10-30 minutes) a cloud can have a lot of ice, 10 per liter or more in concentration, plenty enough for precip beside the graupel-melting to rain stranded part. Here is a shot of the further, SHOCKING development:

3:06 PM. First graupel strands emit from base of Cumulus congestus. More ice aloft can be seen on the right. Horse's ears show that he, too, is surprised by this sight. — 3:06 PM. First graupel strands emit from base of Cumulus congestus. More ice aloft can be seen on the right. Horse, too, noting precipitation in the distance, is surprised by this sight. “It’s OK, Jake, its over there and moving away from us.”

3:18 PM. I smiled, a sardonic one, as the drops began to fall (see smudge, lower center). A dark-looking complex of Cumulus topped by Stratocumulus had formed ice upwind of me, and now, me and horse were going to get wet. — 3:18 PM. I smiled, a sardonic one, as the drops began to fall (see smudge, lower center). A dark-looking complex of Cumulus topped by Stratocumulus had formed ice upwind of us (see upper right), and now, me and horse were going to get wet.

I had to laugh at myself on the way back, the rain drops wetting us down, when I thought about being quite confident yesterday morning about no ice would form in our clouds. When you have an occupation that tends toward error, its good to have a sense of humor. There’s nothing worse than a humorless meteorologist at a party, one whose likely obsessing over his error-filled life.

So, why ice? The TUS sounding at 5 PM AST did not suggest tops colder than -10 C Z(moisture top was about -5 C is all), but where the moisture ended, the air was incredibly dry, reported as “1 percent” relative humidity. Here is that 5 PM TUS sounding:

Arrows point to main top height, and where the highest Cumulus tops might have gotten to as they momentarily, due to inertia, mounded above the main moisture level. Normally, they plop back down because they get chilled, and the tops are cold relative to the surrounding air.

So, an overshooting top COULD have gotten to -10 C, and certainly, with that incredibly dry air just topside, those drops in those evaporating turrets would have chilled a couple of more degrees C. So, maybe that’s it, in fact, the overshooting moderate Cumulus tops DID reach to, or below, the -10 C normal ice-forming temperature here.

However, the concentrations that developed in these clouds HAD to be due to other processes beyond just the run of the mill ice nuclei since there are so few of them at -10 C, and that where drops larger than 23 microns come into play. Without those, there would never have been showers yesterday, only a very isolated drop or two. Those larger than 23 micron size drops lead to “ice multiplication” where just a couple of initial ice particles can “multiply” like rabbits in clouds because of ice splinters shed when hit by graupel. However, as we speak, the full understanding of how ice forms in clouds with these “high” temperatures has not been pinned down. Some researchers, the present one included, believe that ice splintering alone is not sufficient to explain the rapidity in the appearance the high concentrations (10s to 100s per liter) that develop in clouds like we had yesterday. You probably don’t care about what I think, but rather go with the majority opinion… Oh, well, it always safer that way.

As a test of even deeper knowledge that an aspiring cloud maven junior might have, this question:

What kind of ice crystals and other frozen particles would have been in those clouds yesterday?

Quiz music here No help from the audience, that other person who reads this blog.

No cheating; don’t get out your Magono and Lee (1966) translated-from-a-Hokkaido-University monograph on ice crystals and the temperatures and humidities that control their shape.

Answer1: What is a (hollow) sheath?

Answer2: What is a needle?

Answer3: What is a graupel (more a lump around a pristine ice crystal or frozen drop than just an ice crystal?

Answer4: What is an amorphous ice fragment?

Congratulations and adulation! You are now officially a cloud maven junior. Don’t forget to order that CMJ Tee.

Below, examples from the “ice crystal bible”, Magono and Lee 1966:

Needles, followed by sheaths, followed by “lump” graupel, and then some ice fragments in the last two panels.

——————–

Only a crazy person would take photos while driving, like that crazy woman I once knew whose hobby was taking photos of dust devils while driving! Oh, my.

Jan 25th-26th storm creates billions in beneficial rains

Oh, yeah, billions and billions of tons of rain dropped out of the skies over AZ, and much of the SW over the past two days. It, too, might have saved billions in dollars by deterring crop losses, vegetation and critter stress, and own our stress over the drought, “Will it get worse?” That watery relief was so great. Could hardly stay indoors yesterday. 267 photos of clouds and rain, which I think says something about neurotic-compulsive behavior.

(BTW, too many clouds shots “is” WAY down at the bottom after too many rain tables–this is really a horrible blog today.) Continuing….

Totals?

The 24 h rainfall records that were set are here.

Amounts in Catalina “proper” ranged from 1.03 inches at Our Garden garden, 0.80 inches in Black Horse Ranch, 0.71 inches at the bridge over the CDO wash at Golder Ranch Dr, to 0.72 inches here on “Upper Wilds Rd.”

Check the happy totals from the Pima County ALERT network for the 24 h ending at 4 AM today. Since its a “rollling archive” you’d better look at it when it partitions the best 24 h storm total or you’ll miss it. Hence, this pdf:

The great Jan 26th storm total pdf

The U of AZ rainlog network totals are here, but to get the full 24 h storm amount you’ll have to go to the upper right hand corner and select “date range”, then put the 25th to the 26th in that window (the U of AZ assigns the 7 AM total recorded today to the previous day on these maps. So, that early morning rain before 7 AM yesterday was assigned to the 25th. That’s why you have to appear to be lumping two days together to get a 24 h storm total. Sorry its so complicated.

A national organization that has different gauges in some cases is “CoCoRahs”. Their statewide totals for 7 AM can be found here. Again, like the U of AZ, you’d have to lump two dates together to get the 24 h total, in this case, the 26th and 27th since CoCoRahs records the rain on the date of the measurment, does not assign it to the day before as Rainlog does. Confused yet? The CoCoRahs method corresponds to the NWS methodology. Confused yet? The rainlog method works great for summer when the 7 AM measurements almost always correspond to rains the REALLY did fall on the prior day. Confused yet?

Mind is worn out now, will rest for a minute…. There….moving ahead again.

USGS statewide totals, the greatest in this list, 2.78 inches at Salt River below Steward Dam. Since this is a rolling archive like the Pima County ALERT system, I’ve made a couple of jpegs of the list for the time of the most precip in 24 h, so you’ll get a better idea of how ridiculous it is to have to go to so many sites to get a comprehensive view of rainfall in ALL of Arizona, all available data. Kind of remarkable that being concerned with drought and climate change that one has to go to SO MUCH “darn” TROUBLE to get a comprehensive view of rainfall! (End of rant)

NWS reports as of 5 PM AST, also in jpeg format so that they can be easily read. These include the regional and statewide reports for the 18 h ending at 5 PM. (I have no idea at present why these amounts are for the 18 h instead of 24 h):

Finally, those totals from folks who report to Weather Underground can be found here.

The rain data at WU default to a 24 h midnight to midnight rain day and so to get the storm totals, you’ll have to select yesterday’s date (also, since you’re likely to display weather stations showing just the temperature and wind direction data, you have to go the “weather station” dark blue button and open that window up and select “precipitation.” Is anybody still out there reading this? I doubt it. Well, now I just found that it only displays the hourly values for the date I chose! Forget it.

The vortex that passed just about over Catalina, the very heart of this generous storm is made visible here in the water vapor imagery from the U of WA. Watch how a vortex develops from the buckle point over central Baja, and as it approaches, spawns the heavy, heavy rainband that suddenly moved over Oro Valley and Catalina between 10 and 11 AM. Pretty cool, huh? There was some thunder in it, but it you didn’t hear it then, you had another chance beginning after 3:10 PM as a thunderstorm develops over the north end of the Oro Valley and tracked across Saddlebrooke.

Some clouds to go with those numbers:

8:06 AM. First rainband has moved through producing 0.40 inches. Looking SW at Stratocumulus during slight break in rain.

8:47 AM. Skies remain dark, low hanging and dramatic, then evidence of cells, Cumulonimbus towers probably five to ten times higher than the Stratocumulus clouds emerge to the SW. — 8:47 AM. Skies remained dark, low hanging and dramatic, then evidence of cells, Cumulonimbus towers probably having tops five to ten times higher than the Stratocumulus clouds emerge to the SW. It was going to be a rest of the good day.

9:48 AM. During a momentary sunbreak, this trapped cloud below the Samaniego ridge. The wind is blowing from right to left, but the cloud is recirculating in the lee of this ridge. On a mountain peak, such a cloud in the lee of the peak is termed a "banner cloud." — 9:48 AM. During a momentary sunbreak, this trapped cloud was seen below the Samaniego ridge (just above the Los Cerros Water Co tank that needs repainting badly; looks kind of shabby though the water company itself is pretty good). The wind is blowing from right to left, but the cloud is recirculating in the lee of this ridge. On a mountain peak, such a cloud in the lee of the peak is termed a “banner cloud.” It was neat to see it here.

9:59 AM. Here comes that wild, torrential rainband, just having been spawned by the little vortex whose center passed so close to us yesterday. This was so great to see because the rain totals were going to be jacked up significantly. 0.31 inches fell as it went by Upper WIlds Road", but places nearby got twice that! Some thunder occurred here--showed up on the LTG network. Clouds? Line of Cumulonimbus. — 9:59 AM. Here comes that wild, torrential rainband, just having been spawned by the little vortex whose center passed so close to us yesterday. This was so great to see because the rain totals were going to be jacked up significantly. 0.31 inches fell as it went by Upper WIlds Road”, but places nearby got twice that! Some thunder occurred here–showed up on the LTG network. Clouds? Line of Cumulonimbus.

10:12 AM. The rain pouring out of that Cumulonimbus iine shoved the air out of the way and this arcus cloud raced ahead of the line, akin to our summer storms. The wind shift and gustiness flowing out from the storms are a little ahead of the cloud's position. — 10:12 AM. The rain pouring out of that Cumulonimbus iine shoved the air out of the way and this arcus cloud raced ahead of the line, akin to our summer storms. The wind shift and gustiness flowing out from the storms are a little ahead of the cloud’s position.

11:19 AM. Post-rainband evidence of a substantial amount.

12:12 PM. Some of the prettiest cloud shots come right after a rain. Here, in the tops of Cumulus over the Catalinas shearing toward the right, the apparent curvature in the whole scene including the low Stratus fractus along the mountains, hints at the curvature seen in the eye of a hurricane. — 12:12 PM. Some of the prettiest cloud shots come right after a rain. Here, in the tops of Cumulus over the Catalinas shearing toward the right, the apparent curvature in the whole scene including the low Stratus fractus along the mountains, hints at the curvature seen in the eye of a hurricane, and may well have reflected that little vortex that went by yesterday.

2:21 PM. Dramatic skies develop again(!). These clouds developed strong showers that marched across Oro Valley. — 2:21 PM. Dramatic skies develop again(!). These clouds developed strong showers that marched across Oro Valley and across Saddlebrooke.

2:30 PM. Same clouds just 9 min later. Just like summer, ice forms up top, out the bottom comes the precip!

3:17 PM. Even more like summer, this thundery shaft. Four in-cloud discharges occurred. — 3:17 PM. Even more like summer, this thundery shaft.
Four unusual-for-January in-cloud discharges occurred.

4:55 PM. So appropriate for near the end of such a fine rain day, a rainbow.

Clouds today?

Some great scenes of wash fog, such as in the CDO just now. But after that scattered to broken moderate Cumulus, probably grouping into clumps more like Stratocumulus, filling the sky some this afternoon.

While the U of AZ model has showers developing today, cloud tops now, and in the model forecast appear to be to warm for ice development. So, for today, it seems that only clouds and not showers are going to happen.

We’re on the edge of precip when the cold blast hits tomorrow just after dawn. It seems that the range for that would be a miss (0) to a tenth of an inch at tops is about all we can must of that event early tomorrow morning.

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.

Yesterday: a rare drizzle occurrence in the morning and later, gorgeous Cumulus-filled skies

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.

—————-
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.
—————–

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:

Flatlined

The recording raingauge, that is. A coupla drops is all that fell here in Catalina after some indications of cores around us later yesterday afternoon that were producing measurable rain. You can go to the U of AZ rainlog site to see some local amounts–the Pima County ALERT site is down right now. They’ll have some reports in the mountains and elsewhere, providing it wasn’t snow. The most I’ve seen so far is 0.05 inches, lucky dogs.

Some nice cloud sights on a day of dramatic, icy development. I wonder if you say the first Cumulus/Stratocumulus blob glaciating far to the WSW, beyond Twin Peaks? I thought it would happen first toward the NW-N because the air got colder if you headed in those directions. Yesterday’s cloud highlights, once again pioneering here the “novella-sized”, explanatory caption:

: 3:58 PM. By this time it looked very promising for a few hundredths of rain.

The weather ahead: measurable rain!?

I am sure, that due to our fine array of weather practitioners on TEEVEE (ones that make an incredible amount of money, mind-boggling really, and ones that have the same kind of fun doing weather forecasting as I do) that rain is in the offing for Catalina in the days ahead. So why bludgeon the topic here? Well, let’s guess a range of amounts that could occur, bottom and top, based on SOP-eyeball of weather patterns and goofy, variable progs:

Last night’s Canadian run, has a near miss now, rain partitioned to the SE of us. Booo! But, then rain with a follow up system on Jan. 1st, maybe with some snow in it here. So between the first threat and the second, both happening between the evening of December 30th and the evening of the 1st, the range has to be wild, maybe not useful. At the bottom, we could be completely bypassed in measurable rain from two strong troughs (we’re still in a “trough bowl” BTW), but I guess if you’re in a drought, you only get misses. But, being the optimist, AND with our own USA! model indicating measurable rain as of last night’s run, the range of amounts over the four days of chances, has to be from a trace to 0.50 inches at most. So, a range with all the factors at play is not too useful.

The average of those two, 0.25 inches, often works out as the closest estimate. Let’s see what the U of AZ has this morning… Oops, no update, budget cuts strike some more!

The End.

Nice day, OK clouds

Here they are, left column:

The weather ahead

A huge buckle in the jet stream is forecast to form right off the West Coast in about a week, and its a pretty spectacular interruption in the pattern of a jet stream whizzing by far to the north of us that we have had now for sometime. Below is an example of ‘now” in the jet stream winds, and below that, a forecast panel (from IPS Meteostar) showing this striking change a week from now. There’s a big (“high amplitude”) trough in the eastern Pacific, a high amplitude ridge (hump in the jet stream toward the Pole) in the West and another big trough in the East.

Patterns like this are usually associated with extremes in temperatures; warmth in the West; cold in the East. It is certain when this pattern materializes in about a week, some high temperature records will fall somewhere in the West and some low temperature records will fall in the East. In the West, warm air is drawn far northward, aided by low pressure centers spinning around in the eastern Pacific, while in the East, cold air zooms down with high pressure centers from northern Canada.

Why bother talking about a forecast a week in advance?

Because it has a lot of “credibility” in our ensemble (spaghetti) plots. Here is last night’s “ensembles of spaghetti” plot produced by NOAA for one week in advance. Look below at these “ensemble members” the different blue lines, ones that are loaded with slight errors at the beginning of the model run, to see how strong the forecast a week ahead is.

Those bunched blue lines in the eastern Pacific (see arrow) inspired this whole spiel about the coming change because its a nice example of when the plots show something reliable in the way of a longer term forecast, and in this case, a forecast that also shows a big change in the weather patterns over thousands and thousands of miles, from eastern Pacific to the western Atlantic.

If you’re looking around this whole plot, you’ll see the lines are also very bunched in the extreme western Pacific and westward across Asia. Those blue lines are always bunched over there because there is little variance in the flow in that region; its locked into a pattern by the geography, unlike in the central and eastern Pacific and into the US where the jet stream is MUCH more variable. A simile: imagine a fire hose turned on at the hydrant, the part of the hose at the hydrant stays in place while the end of the hose flops wildly around. Its something like that; western Pacific to eastern Pacific.

Our weather?

Well, after all that gibberish, not much change will occur here; its everywhere but here! Seems we’re doomed to another dry seven to 10 days ahead with occasional periods of high clouds and great sunsets as weak disturbances from the sub-tropics pass by, ones that can only produce Cirrus clouds.

Future weather has a lot of AZ rain, but its more uncertain using US models

Here’s is the latest model run from our USA WRF-GFS (aka, “goofus”, as the Europeans might call it, looking down their noses at our inferior weather predicting model compared with their “ECMWF” model as described (here) in the November 9th issue of Science.

It was an upsetting read, BTW. Seems the Euros use bigger, faster computers than we do, ones that they were able to afford by charging a lot of money to see the results. Very bad.

In case you want the meat of that Science article: “From the BEGINNING (this writer’s emphasis) ECMWF has been the world champ in medium range forecasting. Today ECMWF forecasts remain useful into the next week, out to 8.5 days. That leaves the rest of the forecasting world, inculding the U. S. National Weather Service with its less powerful computer, in the dust by a day or more.”

What have our guys (includes women) been doing all these years? (Just kidding, maybe.)

OK, onward with what we have to work with…..

This WRF-GFS run is just from last nights 11 PM global data crunch, the VERY latest as of this writing. I picked it out from earlier runs to show because this run latest has a lot of rain in Arizona. Namely, it was a subjective call to display a few snapshots from it. Displaying the results of this run has nothing to do with scientific objectivity. Enjoy; it might not be real rain that falls to the ground, only real in the model’s calculations. Still, its great to see and think about.

Instead of showing the full size of these model outputs as I normally would do, I thought I would size them in proportion to their credibility based on the Science article. We can’t see the better ECMWF-British model results unless we pay a lot of money, so this will have to do. Unless you click on these below, you’ll have to use a microscope…

0001xz — Valid for November 29th, 11 PM AST, only 264 hours away!

0001MY — Valid for 11 AM AST, November 30th, 12 h later

0001QK — Valid for 11 PM AST, November 30th–off and on rains now for TWENTY-FOUR hours!

0001yK — Valid for 11 AM AST, December 1st. Still raining around here.

0001LI — Valid for 11 PM AST, December 1st. Rain still falling in the 12 h ending at this time.

So, once again, our late November-early December storm has returned to the model fold. Its been coming and going. For example, the 5 PM AST global model run had NO RAIN in AZ, so I didn’t want to show those results.

But just ahead….this

In the nearer future….. Seems the Environment Canada computer model, built around the SUPERIOR ECMWF model, has rain here in about 48 h from now resulting from a tiny, weak low that ejects from the deep tropics right over us. Cool, though the air itself would be warmer and more moist than we usually see at this time of year in a rain situation (higher dewpoints). Must regard this as a serious rain threat now. Here’s a snapshot of that rain day from Enviro Can (see lower right panel for 12 h rain totals and areas covered–would fallen overnight tomorrow night into Wednesday morning. The whole better than the US model runs is here.

Yesterday’s clouds

Another fabulous early winter day in Arizona. Out of state license plates picking up in number. Can’t blame ’em. Here’s a sample of yesterday’s skies and another great sunset:

Raining hard here at 4:08 AM

Little cell going by (aka, weak Cumulonimbus). I hope you’re up to enjoy the sounds of a good cellular rain on the roof. I feel like another song coming on. Ooops, same one, but its a good one because it not only has rain and thunder in it, but also pathos¹. (I thought the thunder in this song gave it a lot of dramatic impact, and we had some thunder NE of Saddlebrooke yesterday afternoon around 2:45 PM.)

Cell has added 0.03 inches to our 0.13 inches and this morning’s total is now a quite nice 0.16 inches on top of the 0.30 we got yesterday. Raining harder now after it let up! Oh, that didn’t last long. Dang.

Total here at 6:55 AM: 0.18 inches! Two day total here, 0.48 inches.

This is so great since this second part of this two part storm was “marginal” as a rain producer, might have only produced 0.05 inches as the bottom estimate for rain, made a few months ago (just kidding), with a top possible amount of 0. 40 inches. So, we’re getting close to the middle of the prediction range made so long ago, 0.225 inches, a prediction you may remember, one that was based on spaghetti.

This rain is associated with the strong cold front that passed through Catalinaland about 2 AM, just after those strong gusts occurred, 30-40 mph last night. Here’s what the nighttime temperature did, drop 14 degrees!

And, as you no doubt know, the atmosphere pressure goes up instantly as the cold front goes by and the colder heavier air piles on top of you. (Time hacks don’t match on these charts for some reason–have not noticed that before….)

annotated 2012101009_Cat temp drop — Arrow points to passage of cold front at Catalina, AZ.

annotated pressure 2012111012 — Atmospheric pressure on top of you here in Catalina, AZ. Arrow denotes cold front and rise. With this denser air, you may notice that you’re having difficulty getting up, moving around as you push more “molecules” of air around for any given movement compared with yesterday when the air was not so dense. It also might be because you have more clothes on today…. Hahahaha

Here’s a really nice link to radar happenings locally from The Weather “Underground” (nothing to do, BTW, with “The Weathermen” of the 1960s-70s even though it sounds like it).

Learning module….skip if bored already.

——————-

One of the things that is happening right now at 5:01 AM LST, is that cells are appearing on the radar or intensifying as they move toward Catalina. This happens a lot when the air at cloud height is moving toward the Catalinas and upslope toward Oracle and Mammoth, getting squeezed between the Tortolita Mountains and the Catalinas. That lifting makes the tops go up to higher colder levels, and when the tops to the west and southwest are too warm for ice formation, say above -10 C (14 F), then just a bit of lifting triggers ice formation making a cloud “visible” on radar as the ice grows in size into snowflakes, maybe collides, too, with some itty bitty cloud droplets (too small to be seen by radar) growing even larger and falling faster. This is maybe the biggest reason why Catalina has so much more rain than upwind areas (17 inches annual rain) compared with about 11-12 inches upwind. Most of that difference comes in the wintertime in situations like this, and so some extent, like yesterday’s more general rains.

——————

What’s ahead for today?

Back edge of this rain band, more or less solid clouds dotted with deeper ones producing rain, is on the doorstep.

Here it is as of 4:45 AM from the U of AZ Weather Department Satellite Facility, with a CONSIDERABLE amount of arrows and writing on it:

So, according to this “diagram” the back edge of this band on the sat image should be here by no later than 10 AM today, that is, chance of additional rain up until around 10 AM in a brief shower, but only a hundredth or two likely. After that, just clouds, probably a lofted Stratocumulus layer, then a widespread clearing with scattered to occasionally broken Cumulus.

Since it is so cold aloft now with the freezing level around 5,500 feet (snow shower now (7:29 AM) on Samaniego Ridge), ice will like form even in modest Cumulus clouds this afternoon, that means virga or maybe an ISOLATED light rain shower possible through around dusk.

Yesterday’s clouds

Here are some of the best cloud photos from yesterday, such a pretty day here in Catalina, where Cumulonimbus clouds stayed just to the north of us off and on all day.

The End, at last!

———————–

¹Actually, I made it sound like I wrote this song in yesterday’s blog, but in fact, I did not, though I WOULD have if I had thought of it. Note that the person who uploaded this song to You Tube, did not know how to spell, “Cascades.” No wonder we’re falling behind.

———————-

A couple of cloud pics, and the next pretty big US-Canadian model divergence coming up (updated)

Updated-at-lunchtime bulletin

This is tremendous, filled with rainy portent for AZ. I am getty excited again as I perused the 6-day (144 h) mod output from Enviro Can, our friends to the north, most of whom live close to the US border because they like us so much and we like them: Take a look at this map, valid for 5 AM, Oct. 2nd. The main things to note and get excited about yourself is that the flow is “caving in” over the Pac NW. Our little low is sitting off Baja, awaiting the southward moving trough over British Columbia. As that trough edges south and southeastward, that low will “open up”, stop being a circle of flow and be a “trough” like its big brother over BC and eject to the northeast. And, if that is not enough, this model output also has a tropical storm that will, in the event these things fall into place, be swept up by the trough off Baja and rake Arizona with substantial rains! OK, so I have filled in some “blanks” here, but, with a victory in the weather computing wars by the Canadians vis a vis our USA model recently, why not ride their coattails into the next major AZ rain? Rain would get here most likely beginning on the 3rd. Could be a little floody here, too, if it works out the way I am projecting, but then I have just had some extra coffee and am a little overexcited right now. In fact, look at the size of this paragraph!

annotated_2012092612_12_054_G1_north@america@zoomout_I_4PAN_CLASSIC@012_144 — I’ve added arrows as one would drawing up a play in touch football. I’ve shown where I think things will go based on this output valid for 5 AM AST Ocotber 2nd. The Canadians don’t post longer range views from their model, so I had to become an weather offensive coordinator to show where I think they should go.

The weather ahead; will it rain or not in a week?

Still a chance of rain of rain between October 4 and 8th as two pulses were shown in yesterday’s WRF-GFS 5 AM AST outputs. Of course, those AZ rains are gone now in the 11 PM AST run from last night, but does that mean it won’t be back in a future model output? Of course not.

The computer models are flummoxed by these weak patterns we have now and we again have a model “divergence” between the USA! and Canada. While the USA NOAA WRF-GFS model has backed off rain in AZ as of last night’s run, the Canadian model, ironically is pointing TO RAIN in AZ (instead of taking it away, as it did with the remnants of poor hurricane Miriam, winding down, lost at sea). It will be interesting to see which one pulls the “trickeration” this time.

The conundrum involves whether a weak upper air circulation that could rotate tropical air in here by the 4th, stays along the southern California coast, or recedes to the west, as the latest US models are indicating. The Canadians think its going to hang around, not go west, at least so far.

upper air panel from ec prog — Environment Canada model has an upper low (at 500 millibars) hanging around off southern California at 5 PM AST October 1st (upper left panel). Westerly jet stream, shown by bunching of lines in western Canada on that panel, bulges ever so slightly to the south and a big fat high is west of the Duck-Beaver nations (Oregon). Note winds over AZ are from the SW, always a good thing.

144 h NOAA prediction — In the NOAA WRF-GFS model for the afternoon of October 1st, the same time as the Enviro Can map above, that upper center is a tad farther west, but is blocked from eastward movement by a big fat ridge of high pressure with no real center as was shown in the Enviro Can map. Also, here, the jest stream in western Canada bulges to the north. That jet stream “needs” to collapse toward the south to help bring that wandering low off California toward Arizona. In this US model run, it doesn’t shift southward until its too far away from that wandering low. Note, too, that the winds over Arizona in this prediction, are from the north-northwest, not from the SW as shown in the Enviro Can map. Air from the north tends to sink and dry out; air from the SW tends to have clouds and rising motion.

Yesterday, that rain for AZ predicted by the WRF-GFS model happened because that jet stream coming into the Pacific NW and western Canada collapsed southward and literally grabbed that low off California and threw it toward Nevada and its tropical moisture came roaring up into AZ as that happened. Last night’s run is not even remotely similar to yesterday’s! Oh, well. Such is weather forecasting in the modern era.

Hoping for another “retro” model solution today or down the road.

The End.

Day of early and late storms

First, the rain report: 1.73 inches on Samaniego Ridge in the 24 h ending at 3 AM this morning; 0.42 inches here! Fantastic. We’ll keep those watery, glistening rocks on the sides of the Catalinas for a few more days. How nice is that for mid-September? Some rain 24 h totals til 3 AM, catches the early yesterday storm period from some of the Pima County ALERT rain gages (a bit chopped up, sorry):

Today? Lots of incoming stuff, should be another day of major rains! (Maybe our last of the summer season. Enjoy.)

Reviewing yesterday…..

Looks like afternoon but its not; yesterday morning just after dawn:

Later that afternoon, after the morning Altocumulus clouds thinned and skies became sunny, there was explosive cloud growth over the Catalinas as the temperature recovered from our pre-dawn rains and clouds. Below, a few shots, the first three showing the transition from Cumulus congestus clouds lacking in ?????? (Answer: ice), to ones just starting to show ice in their tops (which means snow and then rain formation).

Now I am going to transition to tiny thumbnails, so you’ll have to work harder to see what I am talking about. But if you work hard, you might remember it better. Also, to help you, I have added an arrow in one shot, really going that extra mile for you today since usually I am too lazy to do that.

The Cumulus congestus clouds you see in the first couple of photos, though quite pretty, are oriented ALONG the Catalinas, not trailing over us from Mt. Ms. Lemmon. This tells you that should rain develop in these clouds over the Catalinas later on will stay ALONG the Catalinas, and not dribble over this way as it often does. That means incoming storms for us here in Catalina will be to the south, toward Pusch Ridge. Still pretty much the same today, except a bit more toward the right of Pusch Ridge, and toward Twin Peaks.

Below, another example of a cloud photo diary, pretty much like the one you should be keeping: