In case you don’t believe me that over an inch fell, this digital record from Sutherland Heights with writing on it:
Your last 24 h of rain in the Sutherland Heights, Catalina, Arizona, USA. Total resets at midnight.
Probably a little more to come, too. Got some blow damage, I’m sure. Will be looking for roof shingles around the yard today.
12:45 AM. Your radar and IR satellite imagery for our blast last night from IPS MeteoStar . That tiny red region near Catalina represents hail and/or extremely heavy rain.
And, as everyone knows from their favorite TEEVEE weatherperson, “New Storm to Pound SE Arizonans!” Begins Monday night, Tuesday AM. May have snow in it as it ends.
Your know, its no fun telling people what they already know, so lets look ahead beyond the normal forecast period of great accuracy, beyond not seven days, not eight, but beyond TEN days!
First, we set the stage with a ten day look ahead (from last evening) in a NOAA spaghetti factory plot:
Valid for 5 PM, Monday, January 30th. If you’ve not seen this, you’ll be screaming “warm in the West, and damn Cold in the East.” Its a common pattern often associated with some of the driest years in the West when it recurs over and over again during a winter.
This plot indicates that the pattern of a towering, storm-blocking ridge is certain along the West Coast by ten days–will be developing for a day or three before this, That ridge represents an extrusion of warm air aloft over the entire West Coast extending all the way into Alaska. The couple of red lines in and south of AZ are due to the change of a minor, likely dry, cutoff low in our area about this time (plus or minus a day).
In other words, this plot suggests a warmer, dry period develops over AZ, and storms are shunted from the Pacific Ocean, located west of the West Coast, all the way to Anchorage and vicinity, They will be welcoming a warm up in weather up thataway at some point in this pattern.
Is that it, then, for the AZ winter precip? It could happen. Just one more storm after the current one fades away today?
Hint: Sometimes anticyclone ridges like the one in the plot above get too big for their britches, and fall away, or, break off like a balloon from a tether, and a warm blob of air aloft sits at higher latitudes, often floating off to the northwest.
The exciting ramification of this latter scenario is that in the “soft underbelly” of the “blocking anticyclone” (as in American football), the jet stream throws something of a screen pass, goes underneath the belly of the blocking high, and races in toward the West Coast at lower latitudes. Having done so, such a break through pattern (“Break on through to the Other Side”) results in heavy rains in Cal and the Southwest.
Izzat what’s going to happen?
Let us look farther ahead, unprofessionally, really, and see if there is evidence in spaghetti for such a development and you already know that there must be because it would explain why I am writing so much here. Below, the EXCITING spaghetti plot strongly indicating break through flow breaking on through to the other side, i.e., the West Coast, from the lower latitudes of the Pacific:
Valid on Thursday, February 2, at 5 PM AST. Flow from the lower latitudes of the Pac will, in fact, break on through to the other side, as told in song by the Doors1. Who knows what they were talking about but here we’re talking about a jet stream….
Well, we’ll see in a coupla weeks if CMP knows what he is talking about.. I think this is going to happen, resembles what’s happening now, and weather patterns like to repeat, more so within the same winter. However, how much precip comes with this pattern will be determined by how much flow breaks on through to the other side….
Yesterday’s clouds
Let us begin our look at yesterday’s clouds by looking back three days ago before the Big Storm. We had a nice sunrise. Here it is in case you missed it:
7:21 AM. Altostratus sunrise. Virga is highlighted showing the precipitating nature of Altostratus. Amount of virga can vary.7:31 AM. Same kind of view, different colors.7:40 AM. Highlight on the Tortolitas. This is why you carry your camera at all times.9:04 AM. Pretty much solid gray after that nice sunrise for the rest of the day with cloud bases lowering and raising. Early on, cloud bases were well above 10,000 feet; i. e;, above Mt. Lemmo, and would be called, “Altostratus opacus.” The virga is very muted, and there are embedded droplet clouds as well as a droplet cloud layer (Altocumulus) encroaching on the right. Estimated ceiling here: 12,000 overcast.” (Pronounced, “one-two thousand overcast” if you want to make your friends think that maybe you were a pilot at some time in your life.)12:58 PM. Clouds began to appear on Samaniego Ridge as the moist air above us lowered steadily. However, due to lowering cloud tops, the ice in the higher overcast layer was gone. Here there are two layers above the scruff of Stratus fractus (I would call it) on the ridge. The lower one looks like its a Stratocumulus, and the higher one a solid layer of “Altocumulus opacus.” Its already rained some, and we were in between storm bands.2:48 PM. Looked like the Altocumulus opacus (stratiformis, if you want to be exactly correct) was breaking up just enough for a sun break. But no; it kept filling in as it headed this way from the southwest. No ice, or virga evident, so tops are pretty warm, probably warmer than -10° C (23° F) would be a good guess. Hah! Just now looked at the TUS sounding and tops were indicated to be at -11° C, still very marginal for ice (absent drizzle drops in clouds, which causes ice to form at much higher temperatures, but you already knew that.)4:24 PM. Small openings allowed a few highlights to show up on the Catalinas underneath that Altocumulus opacus layer. And clouds were still topping Ms. Mt. Lemmon, indicating a good flow of low level moisture was still in progress.
Moving forward to only two days ago, the day preceding the nighttime blast: a cold, windy day with low overcast skies all day, shallow, drizzle-producing clouds, something we don’t see a lot of here in Arizona.
8:08 AM, January 20th, 2017, btw. “Gray skies, nothin’ but gray skies, from now on”, by Irving B. Stratus fractus underlies an overcast of Stratocumulus. Some light rain is falling toward Romero Pass on the right.8:10 AM. A really special shot. Stratus with drizzle, shown here, is a very difficult photographic capture. I can feel how enthralled you are with this scene toward Oro Valley. You know, I do this for YOU. Look how uniform the gray is! It just takes your breath away!9:44 AM. Before long, drier air down low moved in, eradicating our beautiful Stratus layer, leaving only holdouts (Stratus fractus) along the Catalina foothills below the heavy layer of Stratocumulus.10:20 AM. The wind had now shown up, and these ragged, shredded shallow Stratocumulus shedding drizzle or very light rain showers stormed across the Catalina Mountains. This was quite remarkable sight, since such shallow clouds as these are more often seen in clean maritime locations like Hawaii. Scenes like this suggest that the cloud droplet concentrations were very low, and that there were larger than normal cloud condensation nuclei on which the drops could form, getting a head start in the sizes needed to produce collisions with coalescene (larger than 30 microns in diameter (about one third to one half a human hair in diameter, for perspective.)
3:12 PM. Lower, drier air moved in, eradicating the Stratocumulus and revealing the rarely seen Nimbostratus precip-producing layer. This layer, considered a mid-level cloud, is usually obscured by, you guessed it, Stratocumulus clouds.
By the end of the day, the clouds had lowered again, and we were about to have a very interesting night!
5:01 PM.
The End
———————- 1Remember how great we hippie relics thought that first Doors album was? Later, the Doors, and that era were to be made fun of by 80s punk and humor group, The Dead Milkman in “Bitchin’ Comaro.” (Its worth a listen.)
What a nice steady rain with honest-to-goodness drizzle mixed in over the past two days. We’ve now had 4.24 inches in the past 30 days!
And yesterday, you saw the rarely captured on film, drizzly Stratus clouds, essentially something akin to wallpaper in the sky, but with misty visibility below its base. I hope you got a lot of photos of it; occurrences like that in Airizona1 its like finding a clean-shaven Lincoln penny.
And, of course, you knew that with misty, drizzly rain, clouds were shallow, no matter how dark they looked! Here’s the afternoon TUS sounding (from IPS MeteoStar) confirming that assertion2:
Tops are indicated by this sounding to be around 12,000 feet above sea level and at about -10°Ç.
The drizzle likely fell from shallower parts of this cloud, while the accumulating rains, ones that “tip the bucket”, were likely associated with clouds all the way to that -10° C, where lots of ice would have formed. Drizzle occurrences and lots of ice in clouds at surprisingly high temperatures such as those tops we had yesterday are common, mutually inclusive observation in airborne studies of clouds then the tops go much below -4° C. But, its an unusual occurrence in AZ since we rarely have shallow clouds like yesterday’s with droplets in them large enough to form drizzle.
So, drizzle and what we call, “ice multiplication” occurring in our clouds yesterday made it a rare day, indeed for Arizonans to enjoy even if the mid-40s temperature all day was “less than optimum.”
Next up, more substantial rain after a couple of pretty nice, but maybe not thermally optimum days. Below, the latest output from the U of AZ supercomputing weather calculator showing the cumulative precipitation over the whole SW during the next week, starting from last evening. Quite fun to see the totals build up in that link above:
Cumulative precip ending by 5 AM AST January 23rd. Our precip is pretty much over by late on the 21st.
Being from southern Cal, what I find interesting is that another 10-15 inches of precip is forecast by this model’s output in the northern mountains of Cal, on top of the 20-30 inches they’ve already had JUST THIS MONTH!
Some cloud highlights
11:59 AM, yesterday. This is just an astounding scene. You can hardly have a more spectacular, photogenic photo of Stratus! I get goose-bumps looking at this scene! The view, if you can’t tell, is toward Saddlebrooke. The dismality of yesterday’s skies is also well captured.
It pretty hard to top a photo like this one, so maybe I will just quit here. Wait to see what interesting clouds today brings for us. They’ll be shallow again as an inversion clamps down on the tops even a little more so than yesterday’s afternoon sounding shows, and the Stratocumulus and Cumulus clouds will be thinner, higher bases, lower tops, marginal for ice formation. So, not expecting to see ice in clouds today, but, then I wasn’t expecting so much rain, either from this little system that went through….
OK, one more:
2:14 PM. Horse and drizzle.
The End
————————— 1Misspelled on purpose to emphasize the quality of the air we have in Arizona, at least yesterday. Chamber of Commerce, are you listening? “Airizona,” as our new State name, would work great to attract people from smog-laden regions. I’m sure! Hmmm, or maybe just a good, new athletic shoe would do it, “Nike Airizona”… Nike, are you listening? 2One of the great moments in a life, as we all know from time to time, is in confirming an assertion, which also might be accompanied by gloating.
3:55 PM. Rainbow fragment and solar home, an extraordinary combination.. It was yesterday’s visual highlight. Yours for $1995.95. And, if you order now, we’ll throw in a second, exact copy of this extraordinary, magical scene FREE!
Here’s a nice one from the day before as the clouds rolled in, starting with Cirrus and Altocumulus, lowering to Stratocumulus later in the afternoon.
Yesterday’s clouds; an extraordinary day with a little drizzle amid light showers
Hope you noticed the true drizzle that occurred yesterday, namely, fine (larger than 200 microns, smaller than 500 microns in diameter), close TOGETHER (critical to the definition of “drizzle”) drops that nearly float in the air. They may make the least impression, or none, when landing in a puddle.
When you see drizzle, you have the opportunity of chatting up your neighbor by educating them informally to what drizzle really is (many, maybe most, TEEVEE weatherfolk do NOT know what “drizzle” is, btw), and 2) by telling your neighbor, if he/she is still listening to you, that the droplets in the clouds overhead must be larger than 30 microns in diameter, or better yet, “larger than the Hocking-Jonas diameter of 38 microns, at which point collisions with coalescence begins to occur” and “drizzle is not produced by ice crystals in the clouds overhead; they’re not enough of them to produce ‘fine, close together drops.'” Your neighbor has likely left the building at this point, but, oh, well, you tried.
Here, in Arizona, shallow clouds, such as we had yesterday, hardly ever can produce the broad droplet spectrum in which clouds have droplets larger than 30 microns in diameter. Its because this far inland from the ocean, where the air is very clean, the air has picked up natural and anthro aerosol particles that can function as “cloud condensation nuclei” (CCN). As a result of ingesting dirt and stuff, clouds have too many droplets here as a rule for the droplets in them to grow to larger sizes. They’re all mostly less than 20-25 microns, sizes in which even if they collide, they can’t coalesce.
In “pristine” areas, if you go to one, such as on a cruise out in the oceans, droplet concentrations in clouds are much lower, and even a little water that might be condensed in a shallow cloud can produce a broad spectrum, one that extends to droplet larger than 30 microns.
So even little or shallow layer clouds can precip over the oceans, produce drizzle or light rain showers (in which the larger drops are bigger than 500 microns in diameter). Of course, here we recall that the (whom some consider “villainous”) geoengineers want to stop drizzle out over the oceans so that clouds have longer lifetimes, are darker on the bottom, and reflect more sunlight back into space.
Those guys can be lumped into the same ilk as those who want to change the color of the sky from blue to whitish or yellowish by adding gigantic amounts of tiny particles in the stratosphere, again for the purpose of cooling the planet! Unbelievable. Please ask before doing this!!!
A Pinatubo sampler for what “geoengineering” would do to our skies, say, sunsets in particular. I took this photo from the University of Washington’s research aircraft in 1992 off the Washington coast in onshore flow. But we saw these same sunsets, sunrises, yellowed by the Pinatubo eruption of June 1991 everywhere we went, including in the Azores in June 1992.
OK, pretty boring, whiney, really, so inserting picture of a nice horse here to make people feel better if you’ve been depressed about what our scientists have been pondering to do about global warming other than controlling emissions:
8:57 AM. Zeus. Led cloistered life for 13 years; likes to bolt, now that he’s getting out on the trails.7:40 AM, yesterday, Dec. 31st. The low hanging Stratocumulus clouds, about 1500 feet above Catalina, and the mountains had a bit of an orange tinge. It was probably due to sunrise color on a separate much higher layer.
Later….drizzling Stratocumulus, same view:
10:30 AM. Stratocumulus praecipitatio, if you want to go “deep” into cloud naming. “Stratiformis”, too, covers a lot of the sky. Note misty-like view, lack of shafting.12:48 PM. More Stratocu P., an example of those clouds in the distance that kept dropping little and light rain showers on Catalina.1:01 PM. Highlighting amid the RW– , (weather text for “very light rain showers”). Stratcu P., with maybe Stratus fractus or Cumulus fractus below. The shadowed, dark shred clouds in the mddle would be Stratus fractus IMO.3:55 PM. Zooming in on that pretty rainbow. You know, this is a cloud heaven here. I hope you all appreciate it! Maybe that’s why I get upset over “geoengineering” and changing the sky anywhere.3:57 PM. Between showers, but new ones erupted upwind. This one have a shaft, implying a higher cloud top than the prior, non-shafting clouds that brought us semi-steady RW–.
The second extraordinary thing about yesterday was that the top temperatures of these clouds was around -10° C (14° F), temperatures that ice does not form act as a rule in Arizona. To get ice at temperatures that high, you also need larger cloud droplets, and they have to occur in the -2.5° C to -8° C range. In this range, it was discovered that falling ice crystals, mostly faster falling ones like “graupel” (aka, soft hail) when colliding with larger drops, ice splinters are produced. The cloud droplets must be larger than 23 microns in diameter in THAT particular temperature zone, something that would occur more often in our warm, summer clouds, but would rarely be expected in our winter ones.
Why?
Again, it goes back to clouds in inland regions ingesting lots of natural and anthro aerosols that cut down on droplet sizes in clouds (by raising droplet concentrations in them). Our recent rains have helped cut down on that process on ingesting dirt, for sure, and was a likely player yesterday. Furthermore, our winter clouds are moisture challenged relative to the summer ones with their tropical origins and high cloud base temperatures, a second reason not to expect larger droplets in our winter clouds.
Here is the TUS sounding with some writing on it for yesterday afternoon from IPS MeteoStar. (Satellite imagery was also indicating warmer than usual tops for precipitating clouds yesterday.):
The TUS balloon sounding (“rawinsonde” in techno speak) launched at about 3:30 PM yesterday afternoon. Balloon rises at about 1,000 feet a minute, FYI. Typically they pop up around 100,000-120,000 feet! Instrument package is parachuted down so it doesn’t conk somebody on the head. Sometimes they are found and returned to the NWS and re-used! How great is that?
Here’s the punchline: If clouds are drizzling, then they are ripe, if the tops get to lower temperatures than about -4° C for what we’ve termed “ice multiplication” or “ice enhancement”. A very few natural ice nuclei at temperatures between -4° and -10° C, say, starts the process, those forming “soft hail” which then leads to ice splinters. This is the leading theory of this anomaly of ice in clouds at temperatures only a little below freezing, if you think 23° to 14° F fits that definition.
There are exceptions where this process did not explain the ice that formed at such high temperatures, so standby for further elucidation about how in the HECK ice forms in clouds at some point in the future.
As usual, no time to proof, so good luck in comprehending what’s been written.
The weather just ahead:
The second main rainband is just about here at 9:25 AM. Cloud tops will be deeper and colder than in the prior rains, raising the possibility of some thunder today, and maybe another third of an inch of rain. Watch for an windshift line cloud (“arcus” cloud) might well be seen today. That’s always dramatic and exciting here in Catalina cloud heaven.
Former Hurricane ‘Newt’ brought some real humidity, low clouds with unusually warm bases (around 15-20 ° C) to Tucson and Catalina yesterday as its remnant center passed just about over us.
Old Newt was “dragging” here as a tropical storm, aloft it was pretty strong still, brought near hurricane force winds on isolated, high, mountain tops. Mt. Hopkins reached 59 kts from the ESE before the “eye” passed nearby and the winds turned to the west. And in the Rincon Mountains a gigantic 6.39 inches was logged, and a site on Mt. Graham reported 6.43 inches. (Thanks to Mark Albright for these reports.)
While Sutherland Heights received only 0.29 inches in that all day rain, there were eye-popping totals in the Catalinas. Take a look at some of these, Dan Saddle near Oracle Ridge, nearing 6 inches in 24 h! Below, 24 h totals ending at 2 AM this morning, which pretty much covers Newt:
0.28
Golder Ranch
Horseshoe Bend Rd in Saddlebrooke
0.59
Oracle Ranger Stati
approximately 0.5 mi SW of Oracle
0.24
Dodge Tank
Edwin Rd 1.3 mi E of Lago Del Oro Parkway
0.35
Cherry Spring
approximately 1.5 mi W of Charouleau Gap
0.79
Pig Spring
approximately 1.1 mi NE of Charouleau Gap
0.47
Cargodera Canyon
NE corner of Catalina State Park
0.31
CDO @ Rancho Solano
Cañada Del Oro Wash NE of Saddlebrooke
0.39
CDO @ Golder Rd
Cañada Del Oro Wash at Golder Ranch Rd
4.13
Oracle Ridge
Oracle Ridge, approximately 1.5 mi N of Rice Peak
4.25
Mt. Lemmon
Mount Lemmon
1.61
CDO @ Coronado Camp
Cañada Del Oro Wash 0.3 mi S of Coronado Camp
2.17
Samaniego Peak
Samaniego Peak on Samaniego Ridge
5.91
Dan Saddle
Dan Saddle on Oracle Ridge
3.54
White Tail
Catalina Hwy 0.8 mi W of Palisade Ranger Station
3.66
Green Mountain
Green Mountain
1.77
Marshall Gulch
Sabino Creek 0.6 mi SSE of Marshall Gulch
Your cloud day yesterday; we don’t talk about today. That’s for tomorrow.
The day began with one of the great examples of Nimbostratus, that technically a middle -level cloud greeted us at daybreak in what was one of the great examples of the phantom cloud, the true precipitator, usually hidden from view by lower clouds such as Stratocumulus. But, yesterday morning, there it was, “Ns” naked as could be. I know many of you have been looking for a good shot of Nimbostratus to add to your cloud collection for a long time and I could feel the joy out there when I saw it myself. I only took a couple of shots myself, wish now I had taken more of an extraordinary scene.
6:49 AM. Nimbostratus! Note how high the bottom is, a bottom marked mostly by falling precip, usually snow because steady light rain is so relatively transparent.6:52 AM. Looking NNW toward parts of Saddlebrook/Eagle Crest developments. Notice the nice, relatively uniform, blurry gray, the “blurry” look due to falling rain, the perceived bottom, at the melting level, snow is melting into rain. In winter, therefore, the “bottom” or base of Ns, absent lower clouds, appears lower to us because the snow level is lower.
Then, as the light rain here moistened the air hour after hour, low clouds, such as Stratocumulus and Stratus fractus began to form along the mountains, producing some interesting “tracers” of the chaotic air movement over there by the Catalinas under nearly calm conditions. Newt disappointed in his wind accompaniment.
1:41 PM. Stratus fractus clouds lined Samaniego Ridge, Stratocumulus or weak Cumulus topped it, with a higher layer of Stratocumulus above that, That highest layer was once the much deeper Nimbostratus, but now has lost its deep part, so its no longer “Ns” since its not precipitating.1:42 PM. The deep stratocast has departed, the remaining clouds in the foreground are Stratocumulus. The darkening bases on the horizon southwest of Pusch Ridge are where Cumulus and Cumulonimbus clouds filled with rain are piling up, likely due to the light winds coming together down there, maybe in the low center that was once “Newt.”
Later in the day, as the highest, coldest cloud tops associated with those beautiful Nimbostatus clouds moved off to the NE, and our cloudscape became a mix of deeper Stratocumulus with Cumulus and isolated Cumulonimbus cells, they produced true drizzle and misty, visibility-reducing “warm rain”, that rare type of rain that falls here from clouds lacking in ice, began to be observed producing Hawaiian looking rain on our mountains, delicate shafts of rain whose small drops slanted away from the base.
2:32 PM. Misty drizzle and very light rain! When did this transition happen?2:32 PM. Hard to tell the difference here in a photo between the pure, naked Ns, and this lower drizzle,misty rain producing cloud likely topping out well below the freezing level. I’ve seen these transitions before, but I missed this one, where a Stratocumulus deck starts to look a little fuzzy on the bottom as the drizzle, very light rain starts to come out (due to tops rising, drops at the top getting larger, at some point crossing over the “Hocking” droplet threshold of larger than about 38 microns in diameter, where they begin sticking together when they hit). Here, the transition from non-precipitating Stratocu to I-don’t know what has already taken place during between the photos at 1:41 and 1:42 PM. Should drizzly, relatively shallow clouds like these now be termed, Nimbostratus? Or Stratocumulus praecipitatio,to emphasis the shallowness? A question definitely for the cloud philosophers to haggle about. No member of the cloud maven club would be punished for calling this scene one showing “Nimbostratus.” However, the drizzle and very light misty rain should have told you it was from a far different cloud structure than that associated with true Nimbostratus, always a deep cloud with ice in it, often topping out at Cirrus levels.
Here, you might well erupt with, “This doesn’t look like Hawaii, but Ocean Shores, Washington, or some other coastal location along the West Coast on a spring day having Stratocumulus with drizzle!”
You would be correct in that eruption.
Below, an example of drizzle drops on your car’s windshield:
3:50 PM. The tiniest drops you can make out on the window are drizzle drops. I focused on them and you’ll have to click on it to get the full size to be able to see them. I was so excited to see some more of them!
Later, it was to look little more “Hawaiian”, but if you’ve been to Hilo, you know its mostly cloudy all day.
“Warm rain” or rain due to the colllision-coalescence process, is also mainly associated with “clean” conditions, ones low in aerosol particles that can act as cloud condensation nuclei. The fewer the “CCN” the fewer are the droplets in clouds, and the larger the individual cloud droplets are when saturation and cloud formation occur. So, by yesterday afternoon, certainly, it was doggone clean here, no doubt aided by washout in that light rain we had.
Particularly heavy rain with low visibility fell just south of Catalina yesterday afternoon around Ina and Oracle just after 4 pm. However, that rain did not have those HUGE drops that we see from unloading, deep, Cumulonimbus clouds making this observer think as heavy as it was, it may have been due to a Cumulonimbus topping out at less than 20,000 feet, where the temperature would have been too warm for ice. The 500 mb temperature yesterday was a tropical-like -3.7° C on the TUS sounding, almost unheard of with a rain situation here. This, another sign of tropical Newt, since tropical storms/hurricanes have warm cores.
lacking in those huge drops we see in our thunderstorms, this rain likely formed from the “warm rain” process except maybe in the very heaviest rain areas. It was a special day.
You probably noticed how quiet it was; no thunder around, for one thing, indicating the updrafts in the clouds were not very strong, and that was another indicator that the clouds may not have contained ice. Without ice, hail and graupel, soft hail, you don’t have lightning.
The lack of lighting, the all day off and on rain, such as you might experience at Hilo, Hawaii, on the windward side, made it seem like you were in Hilo, Hawaii, or one of the other wet spots on the windward side of the Island.
3:27 PM. Another, to me remarkable misty scene reminiscent of oceanic and coastal Stratocumulus with drizzle and light rain3:52 PM. In the meantime a much deeper cell had developed to the SW of us, down around Ina and Oracle, where an inch and a half of rain fell. Look how the bottom is so close to the ground, like at a temperature near 20° C, about as warm as a cloud base can be here! And the warmer the base, the more water is going up into that cloud! Very exciting scene! Well, they all are to people of cloud maven persuasion.4:24 PM. Into the bursting cloud. Still, drops were not HUGE, as you would expect, but extremely numerous, rain rate over an inch an hour in the heaviest parts. Was taken I around Oracle and McGee, and of course, not while driving. That would be crazy. Only looks like it.6:32 PM. One of the more Hawaiian looking scenes, fine trails of rain dragging along the Catalina Mountains. The slope of the rain coming out absent much wind down low tells you the drops are small, probably near drizzle sizes. And the “shaft” if you will, is diffuse, indicating the small drops are spreading out due to the little turbulence there was making it fuzzy around the edges. Maybe, anyway.
The “perfect storm”? Well, maybe the perfect rain, and it kept giving fro several hours yesterday after our best model said it should end yesterday before 11 AM. And what a nice rain! 1.18 inches total here in Sutherland Heights, as measured by a CoCoRahs plastic 4 inch gauge. (You might consider getting one, btw, or one from the U of A’s rainlog.org)
Went down to the CDO and Sutherland Washes to see what was up after seeing the gargantuan 4.96 inch total on Ms. Lemmon, and the 3.62 inches at the Samaniego Peak gauge. Below is the resul for the Sutherland, both were the same, nary a drop in them:
8:15 AM. Looking upstream in the Sutherland Wash at the back gate of Catalina State Park. I could hardly believe that there was no flow with so much rain having fallen in Catalinas! But it was good in a sense; all that rain mostly soaked in.
6:37 AM. A photo of drizzle falling from Stratocumulus clouds. Hope you got out and jumped around in our rare drizzle occurrence. Big hat, no bicycle, works in drizzle, too, the tiny drops won’t get on your glasses. Note how uniform the fuzziness is toward Catalina/Oro Valley, only gradually thickens to the left. Took about 2 h to get a hundredth when this was going on.
7:23 AM. Drizzle drops as seen by your car’s windshield after about 1 sec at 1 mph. Note how close together they are. The tiny drops and how close together they are is what differentiates true drizzle from the phony labeling of spares large drops as “drizzle” we sometimes get from our TEEVEEs by semi-pro meteorologists. Sorry to bang on them again, but REALLY, folks, they should know better. Sure, I’m a drizzle-head, but it really does matter since its a whole different process that produces drizzle compared to sparse large drops. Sorry, too, for another mini-harangue on this, but REALLY folks, we should know the difference! Feeling better now, got that out.
8:02 AM. Heading down to the Sutherland Wash on Golder Ranch Drive with temperatures and dewpoints in the mid-60s, there really was a feel for being on the wet side of the Hawaiian Islands, maybe above Hilo, HI, at 3,000 feet elevation, except for the dead grasses.10:20 AM. One of the many dramatic scenes yestserday, this one looking toward the Charouleau Gap NE of Catalina.10:19 AM. While it was nice to see all the water glinting off the rocks on the side of Samaniego Ridge, a deeply troubling aspect was the amount of aerosol that had moved in suddenly it seemed, evident in the crespuscular rays. How could it be this dirty so soon? Seems like a weather oxymoron after such a long period of rain. Also, one wondered if this aerosol loading would stop the warm rain process by providing too many, and smaller droplets in our clouds. Fortunately, that did not happen, and what appeared to be warm rain events, or ice formation at relatively high temperatures in our clouds, also requiring extra large cloud droplets, for the most part, continued intermittently into mid-afternoon.
10:32 AM. Close up of aerosols and sun glints on wet rocks.
12:23 PM. Glimpse of ice-forming top (smooth region above crinkly top). Types of crystals visible here? Needles and hollow sheaths because the top temperature was likely equal to or warmer than -10 C (14 F) and cooler than -4 C, and that is the temperature range that those crystals form under when there is water saturation, as there is in a Cumulus turret before it glaciates. OK, a lot of hand waving, but that’s what I think and I am here mainly to tell you what to think, too.
5:36 PM. The day ended quietly with a little, but pretty scruff of orographic Stratocumulus castellanus on Sam Ridge, the clouds mashed down by the subsiding air at the rear of our little trough that went by yesterday afternoon.
The weather WAY ahead, too far ahead to even speculate about:
NOAA spaghetti plots still suggesting a pretty good chance of rain here around the 23-25th of this month. Nothing before then.
Yesterday, in the wake of TD Odile, it was about as Hawaiian a day in Arizona as you are ever likely to see. First, the high dewpoints, ones that replicate those in HI, mid and upper 60s (69-70 F in HNL right now), cloud base temperatures of around 60 F, and with misty, even drizzly warm rain around at times. The only thing we didn’t see was a rainbow, so common in HI they named a sports team after them.
If you thought the clouds looked especially soft-looking yesterday, I thought they were, too. That soft look that also characterizes clouds in Hawaii and other pristine oceanic areas arises from low droplet concentrations (50-100 per cc), characteristic of Hawaiian clouds.1 Both low updraft speeds at cloud base, and clean air result in low droplet concentrations in clouds.
The result of these factors?
The droplets in the clouds are larger than they would be forming in air with more aerosols (having “cloud condensation nuclei”, or CCN) and stronger updrafts at cloud base. Yesterday, you could have remarked to your neighbors late yesterday morning, as the rain and true drizzle began to fall from that Stratocumulus deck out to the SW-W, that the droplets in those clouds, “….must’ve exceeded Hocking’s threshold” of around 38 microns diameter. Lab experiments have demonstrated that when droplets get to be that large, which isn’t that large at all, really, that they often stick together to form a larger droplet, which in turns, falls faster and bumps into more droplets, and collects them until the original droplet is the size of a drizzle (200-500 microns in diameter) or raindrop (greater than 500 microns in diameter) and can fall out the bottom of the cloud.2
6:10 AM. Light drizzle or rain due to collisions with coalescence rather than due to the ice process falls from yesterday morning’s Stratocumulus deck (fuzzy, misty stuff in the center and right; eyeball assessment). Quite exciting to eyeball. 9:46 AM. So clean and pure looking, these clouds during a brief clearing yesterday morning. These might well have been seen off the coast of Hawai’i. 10:23 AM. One of the Hawaiian like ambiance of yesterday was both the low clouds, the humid air, and the green texture on the mountains highlighted by the occasional ray of sunlight. Fantastic scenes!
11:31 AM. Being a cloud maven, I wasn’t too surprised to see drizzly rain start to fall from our Hawaiian like Stratocumulus clouds, but I was excited!
11:41 AM. Stratocumulus clouds mass upwind of the Catalinas. Hoping for a few drops at least.
12:07 PM. An especially tropical looking scene I thought, with the very low cloud bases, the humid air; the warm rain process likely the cause of the rain on Samaniego Ridge.
6:08 PM. As the day closed, this fabulous scene on Samaniego Ridge. Clouds might be labeled Stratocumulus castellanus.
6:25 PM. As the air warmed in the clearings to the southwest and west of us, King Cumulonimbus arose. Expect some today around us.
Mods still coming up with cold snap at the end of the month, even with rain as the cold front goes by. How nice would that be to finish off September? Still have a couple of days of King Cumulonimbus around as tropical air continues to hang out in SE Arizona. Hope trough now along Cal coast can generate a whopper here before that tropical air leaves us. Am expecting one, anyway, in one of the next two days, probably our last chances for summer-style rain.
Speaking of Odile….
the thought that inches of rain might fall in Tucson, something we all heard about two eveings ago WAS warranted by the gigantic amounts that occurred as Odile slimed its way across extreme southeast AZ. In modeling terms, the error in its track was pretty slight, but the predicted amounts that we COULD have gotten were pretty darn accurate. I did not see these amounts until after writing to you yesterday. Note those several four inch plus values around Bisbee, and the one in the lee of the Chiricahuas. That one 4.45 inches over there suggests to me that the Chiricahuas like got 4-6 inches. Check’em out:
24 h rainfall ending at 7 AM AST yesterday for SE AZ (courtesy of the U of AZ rainlog.org site).
The End
———————— 1Except those affected by Kilauea’s “VOG” which have much higher concentrations, and look a little “dirty.”
2A thousand microns is a millimeter, in case you’ve forgotten, and that’s only about 0.04 inches in diameter. Most raindrops are in the 1000 to 3000 micron diameter range, though the largest, measured in Brazil, the Marshall and Hawaiian Islands, can be about a centimeter in diameter.
Yesterday was equal to the most potent cloud day that cloud maven person has seen since moving to Catalina in 2008; from clear skies to thunder before 10 AM! Fortunately, in spite of all the incredible cloud scenes around, fine, tall clouds so early in the day, CMP was able to control himself and only take 190 photos yesterday, and will share only a 100 of the best with you.
Kind of lost interest, though, when the sky went gray in Altostratus opacus cumulonimbogenitus after about 3 PM. Didn’t get any rain here, either, which was a disappointment.
Oh, well, “Today is another day”, to paraphrase Scarlet O. And another chance for an isolated TSTM to land on us.
Saw some of the most intense rainshafts that you can see here, likely producing 1.5 to 3 inches over there on the Tort Mountains around 2 PM and thereafter yesterday. Thunder was continuous from it for awhile.
But, in poor little Catalina, not even a drop. Even though Altostratus opacus cumulonimbogenitus (copied and pasted that linguistic monstrosity to keep things moving) did not rain here, there were a few drops that got to the ground from it around James Kreig Park where CMP taking batting practice for some reason with a friend. The balls were winning.
In spite of the boring cloud scene in mid-late afternoon in Altostratus opacus cumulonimbogenitus, the skies were open far to the west and allowed a sunset display that was pretty much unequaled in CMPs experience anywhere. So, though it didn’t rain here, we got a nice light show. Hope you saw it. Go to the end to skip a lot of excess verbage and less interesting photos.
The end of the day, BTW, was ruined when a TEEVEE meteorologist came on during a local news program told his viewers that “drizzle” was falling somewhere in the area. My faced turned red, I clinched my fist, and pounded the dining room table, veins standing out. This is exactly why I don’t watch TEEVEE. Under my watch, he’d have been fired before he got off his next sentence off.
But that’s me, CMP, a person who cares deeply about educational standards. As a public service, once again I begin this blog with a photo of what’s not “drizzle”, its that important. Remember that guy (actually, a world famous prof) I told you about that asked me to leave his office and never come back right after CMP told him that it had been drizzling outside? Q. E. D. (The occurrence of drizzle meant that all of that professor’s peer-reviewed body of work in clouds was in error. OK. enough past interesting personal history… Well, maybe this; told him there was a lot more ice in his clouds than he was reporting before the drizzle comment. You could see why that prof might be “concerned.”
Evidence of a “sprinkle”, or as we would officially call it, RW–, a “very light rainshower”, July 30th, 2010. “Its not drizzle, dammmitall!”, as we say around here. Thanks to JG for this photo.
Drizzle, of course, is fine, CLOSE TOGETHER drops smaller than 500 microns in diameter (0.02 inches!) that almost float in the air. You can get really wet biking in drizzle, and forget about a baseball cap keeping those drops off your glasses. They can barely fall out of a cloud; you have to be real close to the base to even experience them and that’s why drizzle is commonly experienced falling from very low-based clouds along coast lines.
You can tell how much that erroneous report of “drizzle” falling in Tucson affected me in how I am starting this blog with an educational soliloquy instead of jumping into cloud photos.
By now, you’d probably like to skip to the chase, and going to the U of AZ time lapse is a good way to do that. Unfortunately, as the storm hit the campus, the power went out for a couple of hours and you miss a good part of it and end of skipping from the middle of the storm to, let’s hear it, “Altostratus opacus cumulonimbogenitus.” Its great when you can say big terms like that; it’ll make you sound more educated than you probably are!
OK, after LONG diversionary material, a sampling of yesterday’s fabulous clouds, so many will post them as thumbnails so’s I can cram in more, and, that glorious sunset, too:
7:34 AM. Cu already starting!8:27 AM. I’ve already taken a hundred photos! I am beside myself on how these clouds are growing so early in the morning!8:49 AM. Go, baby, go, make some ice.
9:30 AM. Unbelievable, this tower piling up like that over the low Tortolita Mountains, especially since CMP was clueless about an early start to convection like this!9:32 AM. Cu congestus are converting to Cumulonimbus capillatus, the ice machine is on! See writing on photo.9:46 AM. Sprouts! That background turret is far higher, has reached maybe 30 kft, compared to the one in the prior photo. Thunder on the mountain beginning! Unbelievable. What a day this is turning out to be.10:25 AM. Oh, so pretty. Note ice anvil, but little rain has fallen out yet. Watch out below, its a comin’!10:33 AM. Rain on mountains getting closer to Catalina…10:39 AM. Load has dropped, though mainly from the turret on the left shown in that 10:25 AM shot.1:17 PM. Storms to the left of me, storms to the right, stuck in the middle again.1:46 PM. Storms to the left of me, storms to the right, stuck in the middle again. This is a pretty clever shot where it looks like I’m driving and on my way to James Kreig Park and just kind of holding the camera any which way. This storm is toward the Tucson Mountains.1:59 PM. After arriving at James Kreig Park, I see this massive storm over the Torts. Storms on the left of me, storms on the right, stuck in the middle again! Thunder was continuous at this point.5:13 PM. After a couple of hours of BP, and a few sprinkles, or RW–, the sky went dull as the convective roots died and left all this heavy, ice debris cloud (Altostratus opacus cumulonimbogenitus, of course, technophiles). Thought the interesting part of the day was over. Clueless again! See below.6:56 PM. Self portrait in interesting lighting. Kind of goes along with a tendency of megalomania sometimes seen here.6:58 PM. Not a self-portrait, but rather a celebration of lighting.7:03 PM. Words aren’t enough.7:08 PM.7:10 PM. Landscape view.7:11 PM.
And we might even end up with TWO inches total for this storm! Amazing! I couldn’t imagine it, even as a precipophile with a known bias, that more than 1.5 inches would fall from this situation (10% chance of more than that I wrote), with a best guess of only about an inch.
Even the mods grossly underestimated the amount of rain that would fall during the day yesterday, and THAT was the huge surprise in this situation, with several inches falling in the Cat Mountains in the first 18 hours. It appeared in the models that the major rains would occur overnight and this morning, rather than during the day yesterday.
Three to five inches of rain have fallen in the Catalina Mountains since the storm began about 36 hours ago. Is the CDO flowing? Sutherland Wash? Streamflow reports for the CDO don’t show anything at this hour, surprisingly.
We’re now in the main cloud and rain band wrapping around the upper low near San Diego and more showers, maybe a roll of thunder, will continue through this evening. This band was supposed to be the major rain producer, in the mods, but likely won’t now, though won’t be as great a rain producer as yesterday. Probably a tenth to half an inch likely during the day as the band continues over us for another few hours. And here is your U of AZ mod rain forecast, hour by hour.
While not forecast in this U of AZ mod run, sometimes secondary bands develop separate from, and behind the main one we’re now in, and I think there is a pretty good chance of that happening today. Often, there’s a nice sunbreak as the main band departs and before the second separate one comes through, so watch out for that possible surprise in case you think the storm is over.
Pity the poor Oregon Donald DuckTM football team, playing in “Eugene weather” against the Cats today in Tucson, Arizona. Imagine what they expected the weather to be here even a week or two ago! And those poor Tour de Tucson bicyclers, too, peddling around flooded streets!
Upper low passes overhead later in the day tomorrow, which means a day with the coldest air will be over us then, and with that, we’ll have some great looking Cumulus and small Cumulonimbus clouds, scattered showers, maybe enough depth for some graupel and lightning before the weather dries out again for a few days.
Sometimes in these situations like we have today, dramatic line of showers/thundershowers with a fronting arcus cloud can develop to the west and southwest and roll across Marana and Oro Valley in the afternoon. Will be looking for something exciting like that today.
Coming up, another forecasting conundrum….
While the US model has a trough passing over Cal as November closes, while the GEM Canada has the SAME trough offshore of Baja at the same time, a huge dispersion in model results we don’t see very often when they start with the SAME global data and its only five or six days away!
Recall the USA model was in error for the current storm early on, showing it to come inland and be rather dry when the Canadians came up first with a monster using that same global data. So, leaning toward the Canadian model this time around; that the incoming low at the end of the month has a good potential to produce more rain here by having a more offshore and southerly trajectory before arriving.
Below, the Canadian solution, and below that, the USA one, FYI as an example about what weather forecasters have to deal with sometimes:
Valid at 5 PM AST, November 28th. Low of interest (LOI) off Baja Cal. In USA GFS mod, its over Fresno, Cal at this same time! Can’t be two places at the same time. Believe this depiction will be closer to the truth.Valid for the same time as the map above. Quite a difference, huh?
Yesterday’s clouds
11:43 AM. Characteristic cloud shot for November 22nd, 2013.And with the massive amounts of rain and puddling, the desert quickly responded in unexpected venues. Here on Equestrian Trail Road, prickly pear cacti emerge from a road puddle.
Yesterday, too, after the light to moderate rain in the morning, was a rare episode of Arizona drizzle. I am sure the best of the CMJs noted this. And what does it tell you? The clouds overhead are exceptionally “clean”, droplet concentrations are LOW, likely less than 150 per cubic centimeter, or 150,000 per liter, which we consider low, though it probably sounds high to normal people.
The aerosols on which cloud droplets form on, called “cloud condensation nuclei”, or CCN, got pretty much wiped out by rain, as you would guess yesterday, and so air involved in cloud formation hasn’t got a lot of CCN available. Normally in inland areas, clouds with 300, 000 to a million droplets per liter are common.
When droplets are few, the water that condenses in the cloud is dispersed on fewer drops, and so each drop tends to be larger than in polluted clouds. When they are larger, and reach diameters of 30-40 microns (about half or so of a human hair) they can collide and stick together, form a much larger droplet that falls faster and collides with more and more droplets until it falls out of the cloud. In this case, because its a thin Stratus cloud, the droplet only can grow to drizzle size, one by definition that is smaller than 500 microns in diameter (about five human hair widths. They don’t or BARELY make a disturbance in a puddle. So, when you saw those drizzle drops falling out, you KNEW that the largest droplets in that shallow Stratus cloud overhead had attained 30-40 microns in diameter.
Do you need to know this? No.
12:33 PM. Very exciting scene. The rarely seen Stratus deck, AND a drizzle occurrence in progress!
Some rare drizzle precip1 fell yesterday. Suggests clouds were pretty “clean”, that is, didn’t have much aerosol loading and the concentrations of droplets in them was low (likely less than 100 cm-3) Also likely, in view of the recent strong winds, some of the aerosols in those clouds might have been large dust particles2 rather than those due to just “smog” and other tiny natural aerosols. Large dust particles can not only influence the development of ice at higher temperatures than normal (above -10 C), but is also known to aid the formation of rain due to cloud drops bumping into each other and sticking together; collisions and coalescence because large dust particles can accelerate this process by forming large initial drops at the bottom of the cloud where drops first condense. Here, drops are nearly always too small to bump together and join up unless clouds are deep, like our summer ones, and ice is going to form anyway.
So, yesterday, was a bit of a novelty. Some photos and story telling:
1:34 PM. Drizzling from Stratocumulus!
1:35 PM. Drizzling here. Hope you noticed and wrote it down. I remember how excited I was in 1986 when I was in Jerusalem and it drizzled! I did not expect to see drizzle there, and I remember how I screamed out, “DRIZZLE?” after putting my hand out the window of the modest hotel I was in. In those days, the cloud drops were reported to be too small by researchers there to form drizzle in them. Yes, Mr. Cloud Maven person was the first person in the world to report in a journal article3 that it DRIZZLED in Israel! One of the great things about blogging is that you can write ALL of the things that you like to read about yourself, and this one is no exception. I am really enjoying today, reliving past efforts and accomplishments since there don’t seem to be too many ahead….The late Jack Russell, flight engineer, listening to Art tell another cloud investigation story.
2:43 PM. Cumulus humilis field over Saddlebrooke.3:06 PM. Drizzle precip just a memory. These clouds too shallow to rain via collisions, and too warm to form ice.
Looking ahead….
Mods paint dry weather for the next 15 days, and so yesterday’s disappointing “trace” (don’t recall here that Mr. Cloud Maven person had predicted at least 0.02 inches!) may be it for October. Phooey.
———————-
1Drizzle: Fine (size range, 200-500 microns in diameter drops) close together, that nearly float in the air. Very difficult to bicycle in drizzle even with a cap or big hat. Fallspeeds, just a few mph. Smaller sizes can’t make it out of the cloud, or evaporate within a few feet almost if they do. Even true drizzle occurrences, you can’t be too far below the base of the clouds or those tiny drops won’t make it down to you.
2What is a “large” dust particle in a cloud? Oh, 1-10 microns in diameter, real rocks compared with the other stuff normally in them. So’s you get a drop that’s already pretty large as soon as condensation takes places. And, if the updrafts are weak at the bottom, then only them big ones might be activated, keeping the whole cloud’s droplet concentrations low! Happens even in places in the middle of huge land masses where in Riyadh, Saudi Arabia, we saw this happen on a dusty, moist day in shallow Stratocumulus clouds. They developed some drizzle drops. I was with the National Center for Atmos. Research on a field project then.
31988: Rain from Clouds with Tops Warmer than -10 C in Israel (Quart. J. Roy. Meteor. Soc.)
Yesterday, that is. It felt like I never left. Only 49 F here; was 55 F in Seattle yesterday.
But the main thing that made it seem “so Seattle” was the persistent low Stratocumulus overcast, almost no sun whatsoever, and a little rain. We picked up another 0.03 inches in a couple of morning episodes of R– (an old weather texting1 shorthand for “very light rain”) to bring the storm total here to 0.55 inches. Of course, the best part of that overcast was that it allowed the ground to be damp for another day, helping the spring grasses and wildflowers by keeping the soil moisture in the soil and not flying away under a hot sun. The worst part of the overcast that lasted almost all day, was that Mr. Cloud Maven person had the day completely wrong–thought it would break open in the afternoon to “partly cloudy” and so he was as gloomy as the sky. You see, as a weather forecaster, you can’t even really enjoy a nice day if you didn’t predict it. Had some sad 75 F days in Seattle when I only predicted 69 F; everybody having summer fun but me.
Enough nostalgia, here are the clouds, even if you have no interest in seeing such boring clouds again:
6:56 AM. Interesting little punctuated lenticular. Mr. “CMP” has just finished his long blog and thinks the sky will break open in the afternoon. Hah!
8:00 AM. Stratocumulus tops Samaniego Ridge–with the turrets, you might lean toward adding the descriptor, “castellanus.” Note blue sky here, if you didn’t see any at all yesterday. No precip evident.8:02 AM. Looking north toward S-Brooke. Fine shafts of precip emit from Stratocumulus clouds indicating those regions in the cloud where there was more liquid water at one time, that is, where these clouds are humped up like those Sc clouds on Samaniego Ridge in the prior photo (the precip from those clouds may have been out of sight). But, was the precip shown here due to ice or the colliding drops process? I wasn’t sure at this point. You see, after a storm, the clouds can be real clean, almost oceanic-like meaning they have LOW droplet concentrations, and when the droplet concentrations are low, the drops are usually larger and can get to sizes where they can stick together when they collide (think 30-40 micron droplet diameters). You probably don’t have a clue about those sizes, but it sounds great if you see rain like this and tell a neighbor that, “those clouds might have drops larger than 30-40 microns in diameter near cloud tops.” Instant neighborhood expert!
8:06 AM. Then the clouds to the west of Oro Valley and Catalina began to produce fine precipitation and advance on Catalina. How nice. Definitely was looking like a true drizzle event (caused by colliding drop rain formation process), at least to me at this point. That process is a rare event in AZ when very light rain or true misty drizzle (tiny drops, close together) forms like that. Usually our clouds have too many droplets from natural and anthropogenic sources and the cloud droplets stay too small to collide and stick together, instead bumping around like marbles with all the surface tension they got. And then because they’re all tiny, they don’t have much impact when they hit, there’s not a lot of velocity difference like there would be in a cloud with a broad droplet spectrum, the kind of spectrum we see in “clean” clouds where drops bigger than 30 microns are a plenty. Note trails of precip coming down in center. BTW, to go way off topic, to distract from how bad my forecast was, in “hygroscopic” seeding, particles like salt are introduced at cloud base to encourage the formation of rain through this process in polluted Cumulus clouds. Worked in Saudi, based out of Riyadh, winter of 2006-07, flying in a Lear jet, helping to select Cu for random seeding using that methodology2. Our office at the government met building, I recall, was cleaned by the “Bin Laden” group. Hmmmm. Maybe its a common name there, to go even farther off topic.10:09 AM. So Seattle! (Have to make up for that last bloated caption.)4:49 PM. And that’s your entire day.6:27 PM. Sunset tried to do something. But, like the day, it was like that sugar icing on a stale dried out cinnamon roll, just didn’t quite make it, though cinnamon rolls are quite good as a rule.
Today’s clouds
Some residual small Cumulus, maybe clumping into a larger group this morning for a bit, which you would then refer to as Stratocumulus. Should gradually diminish in size and coverage until almost completely clear in the afternoon. Expect a north wind in the afternoon, too.
The weather ahead
There isn’t any, well, not right away, but WAY ahead….
Chances for rain begin to pick up after the 19th as we enter the “zone of curl”, “cyclonic curls” in the upper atmosphere with a lot of “vorticity” in them again, with temperatures falling back to normal values. Pretty tough to have warm weather for long at this time of year in AZ. You see, its troughs like to “nest in the West” in March, April, and May, even when they’re not strong and far enough south to bring rain, maybe only wind. Its a climo thing, and it causes many areas of the West to see an increase in precipitation in March from February, and also halts the rapid rise in spring temperatures (especially in Seattle, hahahaha, sort of).
This because the global circulation pattern, responding to the climb of the sun in the sky and warming continents in the northern hemisphere, those forces acting on the position of the jet stream, and weakening it here in the NH (northern hemisphere), is changing the jet stream pattern so that storms begin to move southeastward from the north Pacific across the Pac NW into the Great Basin area in the spring, bringing cold north Pacific air into the West. There was a great report about this phenomenon by old man Bjerknes out of UCLA with his Ph. D. grad student, Chuck Pyke, back in the mid-1960s. Pyke was a UCLA sports nut, BTW, to add some color to this account.
We won’t see that “trough in the West” pattern for awhile here in our “oasis of warmth” now about to begin, but count on it returning, as it appears to do late in the model runs from last night. Climo is forcing it.
The End, except for footnotes.
——————————————- 1Yeah, that’s right. Weathermen, as we would say it then, were way ahead of their time, “texting” each other long before kids thought of “texting.” You might write a weather friend, if you could find one: “We had a TSTM to the S with FQTLTGCCCG ALQDS last night for a few H. MVD N.” PIREPS, SIGMETS, too, were all “texted” and texted by teletype! Tell your kids.
2Was under the aegis of Research Applications Program (RAP) at the National Center for Atmospheric Research (NCAR) in Boulder, CO. Money was good…though not nearly as much as you would make as a TEEVEE weather presenter (hahaha). I was a post retiree guest scientist for RAP NCAR. Clouds could be real bumpy there in Saudi, thought I was gonna die once as bottom dropped out of the Lear going into Cumulonimbus at night that one time. Pilot liked to cut it close between the hail shafts and the rising parts of the Cu with little or no precip, using his aircraft radar. But sometimes, it was a little too close…and we got into the shear zone between a strong updraft and the downdraft.
