All I can say about this plot is, “wow” here and then once more in the caption:
Valid at 5 PM AST, April 28th. Wow. The periodic storm threats will continue for AZ for the foreseeable future, which is about two weeks. Temperatures should be moderate, too, for April. Patterns like this also lead to tremendous storms in the Plains States. It might be time to get out there.
Began at 1:15 PM, ended at 1:40 PM. Then, a second round at 3:58 PM. Nothing more on tap today through June. Thought, too, since there’s been a lot of talk about the Southwest monsoon lately in the media, we’d check on that and see how its doing:
This as of June 15-17th (green lines, red lines are normal position. Things are not so good, seems to be running a week to two weeks behind schedule.
Hmmm. Not so well so far. Is this being impacted by the developing El Nino? Our summer rain season, more often than not, has been disappointing as well in El Nino summers. An El Nino is in formation as you likely know.
Your cloud day yesterday, in thumbnails:
A better way would be to go to our University of Arizona time lapse movie here.
5:55 AM. Now I didn’t mention yesterday because I didn’t want you to feel bad, but these crepuscular (aka, “crepsucular”) rays were due to a lot of smog in those clouds yesterday morning. Got mixed out as the day progressed. Likely, from tropical Mexico based on trajectories at cloud base level.5:55 AM. More smog and clouds, some virga. Ugh.6:18 AM. Could be called, I think, Altocumulus castellanus or Cumulus due to the large size of the elements. However, they are not Cumulus arising from warm air near the ground, but rather from the gentle lifting of the air over the Catalina Mountains.6:20 AM. One of the remarkably small, sprinkling clouds that passed over yesterday. To get rain to the ground from about 11, 000 feet there would have to have been graupel (small, soft hail) forming in those little guys. Single ice crystals, or fluffy flakes would never had made it all that way since they would have dried up. Think of how great it would have been for you to non-chalantly, in your morning walk with neighbors yesterday, to have dropped the bombshell that, “Must be hail, soft hail, up there in those clouds for rain to fall on us from so high up.” You can see your neighbors’ jaws dropping in disbelief at that point! But you would then be some kind cloud hero to them, never to be seen the same way again. You wouldn’t say anything more about it; you’d made your point, succinctly I might add, and they’d likely get bored hearing anymore about it. Its best to let them just think about it the rest of the day.
Afternoon…..
12:53 PM. Promising Cumulus congestus are forming over the Catalinas, some already spewing a little ice. Here, about 2 km thick, or something around 6,000-7,000 feet thick, tops already about -10 to -15 C.1:15 PM. Taken just after first thunder heard from this modest Cumulonimbus. Not much shafting yesterday at all, suggesting weak updrafts and modest condensed water in them. No cloud to ground strikes were observed, and the time between thunder was a few minutes, all adding up to marginal conditions for thunderstorms near us, anyway.1:15 PM. One of the signature shots for this website, added to the “cloud base” collection. Here, graupel strands are just barely dectable as they begin fall out.
1:37 PM. Just before the last thunder, this icy top to a cell approaching Mt. Lemmon. Since the transition to all or mostly ice has occurred, this Cumulonimbus would be termed a “calvus.” The outward transition to all ice happens very rapidly, just in a few minutes, kind of an exciting thing to see!1:37 PM. Here’s what the bottom of that top looked like. No major shaft yet, but there will be but out of view.4:02 PM. Second round of occasional thunder in progress. Nice to see a little rain on the Ridge (Samaniego).7:31 PM. After all the excitement, we were left with little rows of Altocumulus perlucidus to celebrate a great day of cloud scenery.
“Storms” at 30,000 feet, single ice crystals falling from various varieties and species of Cirrus clouds. That’s about all we got for “weather” in the next few days as Cirrus creeps up from the tropics into Arizona. But those Cirrus produce great sunrises and sunsets, so have camera ready. And while not much is happening, you should practice logging what you see up there.
Cirrus clouds are the first clouds we see when something is up with the weather, even when it stays up high, but even in these “storms at 30,000 feet”, the moist level tends to decline over time, meaning there might be a chance for mid-level clouds to appear….such as, you guessed it, say, Altocumulus clouds, clouds mainly comprised of droplets, in the near future. That would be pretty exciting; mo’ better sunsets!
Maybe if it was a “cold one”, an Altocumulus cloud with virga hanging out of it, would give you a great opportunity to talk with your neighbors about the Wegner-Bergeron-Findeisen1 precipitation mechanism (be sure to use all three names to attain the greatest personal stature with them).
——–Warning! Beginning pedantic unit———-
What’s “WBF”, you say?
Hell, you see it all the time! Well, actually only once in awhile here in Arizona. Below, in a pictogram, is a representation of “WBF in action” from a few days into our cold spell just passed so you’ll know when you see ice virga hanging from a droplet cloud you’ll know what the HELL has happened up there. (Dry spells, such as we are in now, make me want to cuss that bit more.)
The background.
Your car has been parked outside all night, and the air was moist. You finally wake up and go outside and you see that dew has formed on your car windows, well, all over. But even though its a bit below freezing, not too much because we’re in Arizona, you also see that in a couple of spots, ice has formed; “horror frost” crystals as we call them here in Arizona because we don’t like frost and cold air of any sort. (The real name is “hoar frost”, and watch out how you use that in a sentence.) The remainder of the drops you see on the car are still in the liquid phase, or have JUST frozen.
But here’s the exciting, magical thing that happens around those “horror frost” ice crystals, demonstrated with a photo through a car window. I’ve added stuff on this jpeg to help explain the magic show going on when the two, liquid and ice, mingle.
A recent example of the WBF in action.
And what you see that has happened here is the same thing that happens in clouds when ice and droplets mingle, are co-located so-to-speak. When an ice crystal forms in a droplet cloud, it becomes a vapor hog, water molecule hoarder, because at water saturation, the condition that results in the drops forming in the first place, its SUPERSATURATED with respect to an ice crystal! Amazing, and CRITICAL for life as we know it on this planet because most of the precipitation that falls in mid-latitudes is related to this process. We would have virtually no precip here in Catalina ever without this process.
What does that mean? When the two phases are in proximity as here, the droplets nearest the crystal evaporate, and the ice crystal grows and falls out, usually, as precipitation. Most rain on this planet is due to that process! There are two others that are also important, all ice, all liquid, but today I’m only talkin’ WBF, the “mixed phase” process.
In a cloud, especially a flat one like Altocumulus, this “mixed phase” condition results in ice crystals that grow too heavy to stay in it–its kind of like a “Thanksgiving-for-ice-crystals” inside a mixed phase cloud, and they fall out in those fine strands because they are so fat.
In another way, the ice crystals in a mixed phase cloud are like a low pressure centers, the droplets high pressure centers and the molecules move from high to low pressures.
Mixed phase clouds would go away completely, of course, UNLESS there was some upward motion to keep new droplets forming. But, as in “Ghosts of the Perlucidus” blabbed about here a couple of days ago, sometimes there isn’t enough upward motion to keep the droplets “alive” and only a ghostly remains of the droplet cloud can be seen in a thin patch of ice.
Further detective work re the above jpeg.
Those ice crystals has to have formed when the drops around them were still liquid, probably just as the window reached a freezing temperature or a hair below. If all the dew drops had frozen at once as clear ice, you would not have seen this crystal growth happen because everybody is in the solid phase, no “high or low pressures.” So, while dew drops were forming and growing while the temperature dropped below freezing, there was something quite unique about a particle on the window that caused ice to form when most other places were quite happy to be liquid. We call those special particles that might have triggered an ice crystal, “ice nuclei”, though, too, there may have been a window surface imperfection that did it.
Anyway, ice nuclei are always much rarer in clouds than “cloud condensation nuclei”, particles that the cloud droplets form on. A demonstration of that is in that photo above.
Cirrus clouds, almost never having water, “don’t need no water” because its often supersatured with respect to ice above 30,000 feet without having a droplet cloud. So, even without the water phase, an ice crystal can get fat and fall out in many Cirrus clouds, such as the revered, Cirrus uncinus with its pretty trails. Veil clouds like Cirrostratus? Not so much growth.
———-End of pedantic unit———
Yesterday’s clouds
You may have spotted those creepin’ Cirrus at sunset yesterday. If not here they are, a classic example, ones that kind of drift up to the north out of the tropics into Arizona that from weak circulations down there, even in drought times here, periodically passing overhead, keeping our skies from being boring, particularly for those many of you who out there who are cloud-centric, head-on-a-swivel when outdoors:
5:48 PM. Distant Cirrus, loaded with a few contrails because there’s an airway down there, creeps toward Catalina. Outta be here by now. Its dark and I think I can make out something so this is not really a forecast because I kind of cheated by looking at the sky just now but I WOULD have said that without looking… And if those clouds did get here, there might be nice sunrise for you.
What ahead?
Of course, there’s some rain on the model “horizon” (IPS MeteoStar rendering of WRF-Goofus model), but like that “puddle” on a desert highway on a hot day that you never get to, and I’ve tried, because it moves away as you speed down the road, the “puddle” staying the same distance away, our model rains seem to do the same thing. I’ve used this metaphor before, but I can’t think of a better one. I think its pretty good, too; damn good, really, to cuss a bit more. :} Here are a couple of examples of rain in southern Arizona from last night’s global model run to get your hopes up, most likely to be dashed:
Valid for 5 PM AST, January 28th, Monday. Green areas denote the rain the model thinks has fallen in the prior 12 h. Yeah, right.
Valid for 5 PM AST, February 1st, Friday. I would gladly eat my words with whipped cream on them if this happens.
The END, FINALLY!
—————————-
1They’re not “mostly dead” now, but “all dead”, to crib a line from “The Princess Bride.”
One of the things I like to do when I am wrong, yesterday having predicted a trace to a few hundredths of rain last night from that disturbance going by to the south, is to spend a LOT of time talking about how close I was.
Its true the zuperkomputer, the Beowulf Cluster, at our U of AZ Weather Department, did NOT predict rain here at all, but it did not have the sprinkles as close as they came to us, either! Exulting here that bit. Going to look on “trace detector” (car parked in dust and sun outside) now, just in case there is a drop image somewhere. Will report back on that later. Stand by.
Also, you should be looking around for drop images in the dust on stuff, too. If you’re going to be a “trace king”, you have to look hard in AZ so you don’t miss anything. A lot of reported traces shows that you are indeed a true CMJ! A trace of rain is incredibly important to microbes; a drop is like the ocean to them. Think about it the next time it sprinkles on you.
Below, the evidence of how close we came to one drop of sprinkle-rain last night (remember, it would NOT have been “drizzle” had it occurred; drizzle falls from LOW-based clouds that hug mountains, not from Altostratus clouds such as we had):
Sprinkle from Altostratus deck just to SE of Catalina at 1: 40 AM AST last night.
Arrow added into the SAME image as the first one in case you did not see how close that sprinkle came to us when you first looked at it. I really want you to know. I feel its quite important.
As a CMJ (Cloud Maven Junior), you would have seen and logged the low hanging virga extruding downward in one spot from that thick layer of Altostratus at sunset, that As band that also had something that looked a bit like an anvil extruding from it. Here is the “documentation” for these claims:
5:16 PM. Heavy Altostratus with scary anvil-like feature and VIRGA just to SW of Catalina about 50 miles.
Finally, this sunset shot of the same band 30 minutes later, making the same points as above again to better imprint them on you:
5:36 PM. Same band of Altostratus with anvil-like feature and virga (to right) at sunset.
The above has been, in effect, a burst of altruism. Let’s say I am hiking on the trails, I’ve missed a forecast, and you’re heading in my direction. At about 100 yards you will want to exit right or left and bushwhack it for awhile until I have passed to avoid an extended “in hindsight…”, hike-delaying conversation in which you have no real interest. Its gonna happen. It would be kinda like this blog-blab right now….
Now, feeling better, some REALLY pretty Cirrus uncinus from last evening:
5:17 PM. Pretty Cirrus uncinus along with some other varieties/species.
Now that I have gotten yesterday’s burr-under-my-saddle dispensed with, can ahead now, not stuck anymore, clouds moving away, can have new thoughts…
Will look at model outputs and see which one has the most rain/snow in it for us on the 11th-12-13th, with that Arctic blast, and think about the onset of that new “zonal” pattern after that, that pattern that will mild us1 quite a bit after the Arctic blast. Beginning look at mods now….
WHAT?!!! Its back! That “trough bowl” collecting area for storms in AZ and the Southwest, after only short respite from cold storms. What happened to theThis is remarkable, check this prog for January 22nd at 5 PM AST. If it looks familiar, its almost the same as the map for yesterday afternoon, the 7th, but 15 days later! I repeat myself in the gif for emphasis now that I see I have repeated myself.
Valid for 5 PM AST, January 22nd.
What’s the gut check here? “Spaghetti”, which seems appropriate for a “gut check.” Yesterday we saw that the NOAA spaghetti plots varied wildly 15 days out, making ANY model forecast that popped beyond about a week out pretty unreliable.
But what aspect of the atmosphere do we know about that makes a prog 14 days out that looks like weather we had yesterday look that bit more credible: the mantra, “the atmosphere remembers.”
Persistence, a forecast based on weather you’ve already had for the past week or three, and projecting it into the future is one of our more reliable forecasting techniques. Sounds silly, but its true. The pattern eventually changes, but its hard to catch that tipping point when it does. Yesterday, the mods had that pattern change and it was some support for that in the NOAA spaghetti plots. That support has weakened, though not gone, seen here if you dare.
——————Module on conversational meteorology——–making the past the future
Imagine, that on January 1st last, a neighbor asked you, knowing that you were a cloud maven junior, maybe have Asberger’s Syndrome, and in your case, focus on itty-bitty weather details and data:
“What kind of weather do you think we’ll have in January?” Without divulging details of your forecasting methodology, hindsight, and then trying to remember, if you could, what the weather had been like in the two weeks leading your neighbor’s question, i.e., the time when the new flow pattern began here, you could have furrowed your brow and said, with at least feigned authority:
“I see below normal temperatures, perhaps much below, with a good chance of above normal precip. “‘Hey'”, and then going a bit too far, you might have ventured into, “…and I think there’s a good chance of a real snow here in Catalina this month with all that cold air we’ll have.”
Today, with a severe cold spell ahead, you would be the forecasting guru of the block, icon of the next block party, and all you had to do was remember, which can be hard sometimes.
In weather, it really is true: the past is often the future.
—————-End of conversational meteorology module———————————————————–
So what to think?
Its not a bad idea to hedge your forecast longer term forecast with “persistence”; continuing below normal temperatures, maybe not as severely cold as what’s immediately ahead on the 12-14th, precip on the 11th. Amounts, due to the speed of this thing, still 0.10 inches at the bottom, but I’d reduce the max potential to 0.40 from 0.50 inches, median then 0.30, about the same as the last prediction. The flow pattern with this will be like the last front on the 31st, and so we’ll do better than most of areas around us in amount because the clouds will bank up against our side of the Catalinas more than elsewhere. Still expecting rain to change to snow at the end of the FROPA on Friday morning, the 11th, but amounts likely to be an inch or less now. Dang, again.
Because it will be so cold aloft, and here, and there are minor disturbances that blow on through for the two days after the 11th, a passing flurry is likely (that from, as you KNOW, from “heavily glaciated clouds”, at least at times.
A bit much today, so will gift you by quitting here.
The end.
———————–
1Using “mild” as a verb here; might be first time ever such use–William Safire, language-maven, where are you now that we need you? Remember when we made fun of Alexander Haig, the Nixon admin Chief of Staff, about the way he used nouns as verbs, i.e., “gifted him.” Now he can be considered a language pioneer since we hear that usage all the time. Don’t forget to use “mild” as a verb today at least once: “the weather pattern is going to mild us for awhile before the big freeze hits.” That would be great! Thanks.
Some 8 days ago a spaghetti plot indicated with confidence that a “warm in the West”, “cool in the East” pattern would develop. Well it has materialized. Thanks to Hamweather, this chart shows the records set with that pattern so far. They’re not so numerous, but the forecast of a strong trough off the West Coast pulling warmer air north into the West and a trough in the East dragging down cold air from Canada has verified. The point of this is that those strange looking “spaghetti” plots can have some power if you’re not overwhelmed by all the lines.
————————-crass commercial break, just in time for Christmas————————————–
BTW, after learning about this spaghetti verification, you might want to consider adding to your collection of cloud maven junior tee shirts this new attractive—well, stunning really — “I love spaghetti” black Tee offering with a truly gorgeous multi-colored example of the NOAA-NCEP “ensembles of spaghetti.”
Here’s last night’s example from NOAA-NCEP to get you excited about getting that tee:
I think you’d look great in it, and, of course, most sophisticated when it comes to being a cloud maven junior and advertising that you know about something like this. Most people have never heard of these plots, which puts you ahead of masses.
Remember the “You are here” Milky Way Galaxy tee showing where the earth was? Well this one would be as good for you to be seen in as that one! And this new cloud maven junior tee is only $29.95 plus shipping and handling, which brings the total to $75.42. (I’ve been studying how the online vendors do it….)
Think of all the people you might meet that would ask you about your tee by saying, “Huh?”
Then you would go on a long spiel, making new friends, by pointing out areas on your tee where the signal is strong and the forecast reliable, and where the forecast model is clueless. In the above example tee, that trough north of the Hawaiian Islands 15 days from now looks pretty solid while things are pretty clueless in central Europe, roughly diagonal from the trough north of Hawaii. You know where Hawaii is, don’t you?
——————–End of crass commercial break————-
The weather ahead, way ahead…grasping for a switch to be turned on
A great pattern popped out yesterday. Hasn’t been seen since, but it was so exciting that I thought I would share it with you. We’ve been in a stagnant pattern for a LONG time now; storms racing across the Pacific into the northern half of the West Coast. As a weatherman, we’re always looking for the switch; patterns like that just don’t last ALL winter, but a tipping point happens, and boom, everything is suddenly different.
In this model run from yesterday, a tipping point happened and the storms began moving southward along the Alaskan coastline to off California in about 10 days. One of those is shown here near San Francisco. At this time in the run, December 15th, 5 AM AST, extensive rains are shown in Arizona!
While it might verify, there has not been support for this pattern since, and the ensembles of spaghetti, shown above, are not very encouraging, actually not at all, only suggesting a trough in the northern Plains States. A trough is suggested in the southern Rockies, and not a strong one at that since that trough is mainly confined to the red lines, those demarcating the periphery of the jet stream, or may even be a weak southern branch separate from the northern one. Usually doesn’t rain here with those.
But, this quasi bogus output looked so great, I had to post it anyway. I was so excited yesterday when it came out, because we know there WILL be a pattern change. There always is, even if its short-lived and isn’t a total drought buster. I guess this indicates a degree of desperation when you’re posting model outputs with little chance to verify.
The summer rain season has departed from us here in Catalina, but its still evident on the horizon in Mexico, and even here in Arizona. Take a look at these distant Cumulonimbus cloud tops yesterday.
4:59 PM. Arrows denote Cumulonimbus tops protruding from anvil Cirrus shield, “over the border, down Mexico way”, as the song says.7:00 PM. Looking WSW from Catalina at a massive Cumulonimbus top.
So, as we like to say around these parts, someone’s getting shafted (rain shafted, that is)
An example of conversational meteorology for everyday use:
Person 1: “Did you get shafted yesterday?”
Person 2: “Yeah, it was GREAT! Got more than an inch in just over 30 minutes!”
End of example.
Looking a few days ahead
While we are dry now, the summer rains are really pretty close (as represented by green pixels in this rendering of the WRF-GFS model, our best one).
Unfortunately, it keeps the “green pixies” away until the afternoon of September 4th; Elena, our hope for rain just after the first, stays too far west now this mod says.
However, as close as the rain is day after day in this mod, even a slight model flub, a “fumble” really, in keeping with the emerging college football season, could mean a random shower between now and the 4th. That’s our only hope from that one. But, to the rescue our Canadian friends and their model. That model still drags a part of tropical storm Elena’s moisture into AZ with a couple of showers indicated around here on the 1st and 2nd of September.
Looking farther ahead at less reliable results: green on green
The dry spell ends and a series of wet days are foreseen beginning on the 5th in SE AZ, and then spreading over various portions of the whole state (green pixels on the green of our State right now) from the 9th through the 14th in this same model. I mention this only because it was also predicted from yesterday’s model run from global data taken at 5 AM LST. Its not much to go on, but something. An example for the afternoon of September 12th where so much rain is predicted the pixels have turned blue (see scale at bottom to interpret amounts).
Not so good is the fact that this later predicted rain is associated with rather weak flow patterns, ones that inherently degrade the model’s reliability. So, don’t count on these rains, but it is there for now and has an itty bitty amount of credibility. Namely, its not hopeless that we are done with our summer rain season, as we know, can happen anytime now.
Yesterday morning’s sounding when the Altocumulus clouds were overhead. Bases about -18 C, tops -27 C. Lots of ice visible along with widespread virga. Whenever you see this much ice in small Altocumulus clouds like these, you should automatically assume that the temperature at the top is less than -20 C.
Usefulness of this information in everyday conversation, a module I call, “Conversational Meteorology.”
The scene: you’re walking/hiking with a friend on a warm morning when sunrise occurs. You see these clouds. The conversation has died off since you’ve been walking for several hours. You’re looking for something to say to re-energize the conversation. Suddenly, you look up and see this scene below and blurt out, “Man, those clouds are cold!” The volume of your blurtation has surprised even you, and startles your friend who was thinking about that tortoise on the trail ahead of you. You rattle on about how cold the clouds with a followup, “Man, they must be at least colder than -20 C!” Your friend seems puzzled at your excitement, but listens politely’ after all he is your friend. You quickly add, “Almost every cloud has some snow coming out of it, no matter how small it is! Wow!” Your friend, now saturated with your exuberances, asks if you saw the last episode of NCIS last night?
