They seem to go together every time we have Altocumulus clouds; aircraft flying through them create holes or canals! Have been photographing this phenomenon since the early 1980s, and I have not seen it so consistently occur every time there was a flake of Altocumulus around as has been the case here this winter! Its likely because our Altocumulus clouds have mostly been so cold, having temperatures lower than -15° C. Mid-level Altocumulus clouds can range in temperature from well-above freezing to below -30° C.
What was unusual about yesterday afternoon, if you caught it, was that you could make out the aircraft producing the “high temperature contrail” (aka, APIPs), a four engine prop aircraft flying just under the bottom of the Altocumulus layer. Even if you see a contrail in the Altocu, you can almost never make out the aircraft type for sure because its too high or in the clouds. But, because of our cool spell, those cold Altocumulus clouds were lower than usual, around 15,000 feet off the ground, or near the 500 millibar pressure level. The temperature at the bottom of this layer was -21° C. See annotated NWS sounding, courtesy of IPS Meteostar, below:
Here’s your aircraft shot, full size so’s you can really zoom in and see those engines:
The weather ahead, WAY ahead
Not a single model run since two days ago has produced a big trough in the SW US, in complete opposition to the interpretation of spaghetti ensemble output at that time. This would be, IMO, one the greatest busts of all time (not for me, of course), but for spaghetti ensembles (I was only foretelling what they told me), spaghetti considered to be one of the great forecasting advances of all time when computers became powerful enough to produce them in a timely manner.
If we believe these later model runs, it will be relatively hot and dry here, not cold and wet, as was suggested here.
But being of a stubborn nature, Cloud Maven Person is not yo-yo-ing on his forecast just yet. Surprises are almost certain in these model runs, since spaghetti still supports troughing beyond 10-12 days… Standing by for model yo-yo-ing….
A laugher (???) below from our very latest computer run (from IPS Meteostar again). This map in incredible in the lack of jet stream activity over most of the US!
0.22 inches was, indeed. how much rain fell in the form of drops from Nimbostratus clouds yesterday as a modest little rain band generated by a rapidly moving trough swept through during the afternoon. Regional precip values can be found here. Our local area got the most, up to about a quarter of an inch, as often happens in marginal storms.
Yesterday’s storm marked the beginning of the new, more normal weather regime for southern Arizona, as has been blabbed about here in recent weeks. No more week after week of droughty weather with temperature far above normal, the kind of weather that has marked this whole fall and winter so far! I. e., “Thank you very much, a snowbird might say, but get the hell out!”, the rest of us might conjure up, thinking about the needs of our desert’s wildlife and vegetation.
Indications are now that below normal temperatures and above normal precip are ahead for us and all of Arizona in late Jan and early February.
The evidence for these claims?
Below, the stunning, jaw-dropping evidence for this seemingly outlandish assertion in the form of an ensemble (spaghetti) plot generated by NOAA last night. I have followed these charts for almost ten years now, and I cannot remember when such a strong signal (clustering of flow lines) 15 days out has occurred before in our region.
So, excessively excited this morning when I saw it! Its been annotated with excitement text.
This troughy pattern begins to take place on January 30th. Until then, a strong but dry cold front with a lot of wind comes by in a few days, on the 25-26th.
The whole interesting, if excessively gray story is shown below:
The weather way ahead
The title sums up where we are now. Will we go have more rain? Oh, yeah. But not right away, as you already know.
“Rain on tap” does not refer to a microbrew, for those who’ve accidentally stumbled onto this site.
Our nice sunrise and sunset, featuring supercooled1 Altocumulus clouds:
Rain on tap? Oh, yeah….finally. One forecaster friend is predicting 0.5 inches! How nice would that be? The rain will likely begin toward midnight–check it here from our nice U of AZ Weather Department.
Looking for more rain in AZ after mid-month, toward the 20th.
A swatch of Altocumulus perlucidus translucidus (sorry, that’s the way we talk around here) passed over Catalina early yesterday afternoon, each “unit” nearly perfectly evenly spaced with its fellow cloud element creating a brief period of cloud awe for those Catalinans (or is it, “Catalina-ites”? “Catalinians”? Who knows, who cares?). Here it is, in case you work indoors and missed it. It was truly a fabulous sighting!
The afternoon was marked by a melange1 of middle clouds:
The weather just ahead
The local TEEVEE met men are, of course, pounding out the good news rain is just ahead for Catalina. Looks like, oh, 100% chance to CMP (Cloud Maven Person) starting after midnight Tuesday to Wednesday. How much?
This is a potent, but fast moving trough. Maybe will have only 2-4 h of rain with the passage of the cold front and its rainband. But, coming from the sub-tropics, should have a appreciable rain band with it.
I would expect rainrates to reach “moderate” as the heart of the band goes by for a coupla hours, anyway. Moderate rain is defined by the NWS as 0.1 to 0.3 inches per hour. So, only two hours of moderate rain should be at LEAST 0.2 inches, and most likely more.
We’re thinking here that there’s a 90% chance of more than 0.15 inches, and a 90% chance of less than 0.70 inches. So, averaging those two leads to a best estimate in CMP’s opinion of 0.425 inches! Wow. Nice.
Now, I will look at the U of AZ nested model and see what it thinks. Kind of game we play here, seeing how a seat of the pants forecast, made over a coupla minutes, measures up to a computer model with billions if not trillions of calculations:
The weather way ahead
After the nice rain just ahead, we have to get through the week-long dry spell before we move into a new stormy regime. First, a spaghetti depiction of the ridge after our nice storm:
Here’s what’s been exciting for a few days now, and below, from last evening’s global model output:
Let’s see what the actual and very latest model run from IPS Meteostar has for us:
How much these coming rains can benefit our spring wildflower bloom and spring grasses I don’t know, but I sure hope they can resuscitate what otherwise will be a dismal spring.
Expecting a snow event during the “new regime” that takes over after mid-month, too. Be ready!
I use that expression not only to draw attention to myself since my name is Art, or, “Artie boy” to mom, but also because I had a role in bringing this phenomenon to the attention of the scientific community; that is, that an aircraft could glaciate portions of clouds at temperatures as high as -8°C. This in a peer-reviewed article so controversial it was rejected twice by journal reviewers before “getting in “(pdf here)! Some background on why this happened is found in a footer way down below….
Its common knowledge today that an aircraft can produce in essence a contrail in clouds at temperatures down to about -10°C and must be avoided when researchers are sampling the same cloud over and over at below freezing temperatures.
Back to the beginning:
The day began well enough with a nice sunrise over the Catalinas:
Here’s the early morning National Weather Service balloon sounding from the U of AZ:
Then, as the Altocumulus layer filled in from the west, the aircraft effects roared to life. An example from yesterday, one that passed right overhead of little Catalina!
The weather ahead
More interesting middle and high clouds, probably a great sunset/sunrise or three, but no rain, just virga. The present mass of middle clouds passing over has some virga and sprinkles, but that’s about it from this episode. No real support yet for a change in our dry, warmer than normal weather regime in spaghetti plots though one trough a week or so out is forecast to bring a little rain.
Some background on “APIPs”
This phenomenon had been shot by photographers for decades, yep, DECADES, BUT, it was believed (apparently) by those doing cloud research, that it only happened at very low temperatures such as those when the normal contrails we see occur (at temperatures lower than -35°C), viz., it was ignored.
Another factor was that all of the rare photos of this phenomenon, dubbed “Aircraft Produced Ice Particles” (APIPs, by yours truly, though not the greatest name) appeared in lay or quasi-lay publications and were likely missed by those with big Ph. Ds. who only read technical journals. An example of this was on the cover of the Bulletin of the American Meteorological Society in 1968, a cover shot which drew the greatest amount of reader comments that the journal had ever seen! They went on for a couple of months, some suggesting that the ice and hole in cloud was due to a meteorite!
Also, it was a rare case indeed when the photographer could report the temperature at which it occurred.
I was thinking how great yesterday was for you. Started out with a spectacular sunrise (lasted just a couple of minutes), and then you could watch for pretty much the WHOLE day, orographically-formed Altocumulus opacus and castellanus transition to ice crystal clouds (in this case, Altostratus with virga and some mammatus) right before your eyes!
After sunrise….this odd scene below of an extended Altocu lenticular cloud:
More “pretties” below; yesterday’s sunset:
I hope you had a chance to venture out late yesterday morning and see some of the most spectacular Cirrus (uncinus) displays with HUGE streamers that you will ever see.
The early Cirrus cloud were nothing very special, not showing clues about what was to happen a few hours later:
But by mid-morning, racing in from the west, these:
There was an interesting contrail distraction later that day. Are these “castellanus” crenelations, or is it perspective? Those knobs are usually pointed downward due to the action of the wingtip vortices that take them downward behind the plane. Maybe they’re just sloped down at us, not puffed up.
Late in the day some Altocumulus advanced from the west, providing a nice sunset, but a layer once again impacted by aircraft holes. Can you find them (with their trails of ice slanting downward?)
Well, there is still a chance of some rain late in the month, late or after the TG holiday weekend….. FIngers crossed. Poor wildflower seeds.
Hope you saw them and recorded them in your cloud and weather diary. I’m thinking that at the next Cloud Maven Junior meeting we should devote a lot of time to this issue. It was a rare day yesterday that the WHOLE day had that phenomenon occurring as aircraft penetrated those clouds, usually on ascent or descent. Sharp descents/ascents produce holes. See the sequence below if you don’t believe me (ppt from a recent talk):
Yesterday’s clouds: lots and lots of aircraft-produced ice
(btw, see note below about pop-up ads in this blog, ones that started to appear after downloading latest WP software)
——————About those nuisance ads—————
Note to me and the two other people that drop by my cloud or “clod” blogulations: The embedded pop-up ads are due to a WP third party plug-in that needs to be repaired. It will likely happen today.
After consultations about ads…
Oddly, those pop-ups and blue highlighting and double underlining do not seem to be present outside of my personal view of my own blog, this according to hoster, “godaddy.” Even using a different browser other than FIrefox does not show them as I have just verified.
Been busy as a briefly unretired science worker (gave a stressful talk at a university last week) and thought maybe a lot of usual drop ins to this site might not anymore. So, in the title for today, am reaching out to a new demographic: persons interested in congealed soil matter. They might later, after stopping by, discover a new interest; that in clouds, pretty ones. Most of the cheap tricks I try like this don’t have any effect, though. Oh, well.
Let us go forward after backing up:
But the Cirrus kept coming and more odd sights were seen:
Heavier Cirrus, increasing and lowering to Altostratus finished off the day as a heavy shield of middle and upper clouds raced toward southern Arizona from the Pacific:
“Due to time constraints, we move ahead in the action…”
Sunday, November 5th:
4:26 PM. Perhaps the brightest example of iridescence I have ever seen! Just spectacular for a few seconds in this patch of Cirrocumulus. Iridescence is caused by diffraction around the tiny of droplets, less than 10 microns in diameter, as are present when a cloud just forms.
The weather just ahead