Here’s your cloud day for yesterday, a fairly complex day for your cloud diary entries:
7:27 AM. Looking SW along Equestrian Trail Road; Altocu with Cirrostratus above.7:45 AM. Altocumulus perlucidus over the Catalinas.12:38 PM. Stratocu begin to move in under the Altocumulus layer.2:47 PM. Altocumulus lenticularis began appearing, suggesting strengthening winds aloft. This was an odd location for such clouds, perhaps responding to uplift ahead of the Catalinas. Haven’t looked at Froude or Richardson numbers, though, to see if this is reasonable hand-waving.3:02 PM. Looking NNW at Stratocu (“the boring”; is State Cloud of Washington, and Oregon, for that matter) with a little Altocu on top.
4:33 PM. Stratocu. Kind of characterized the dull, dark, late afternoon and evening hours.
Intermittent R- to R– expected during the day today. Hoping for a quarter inch (forecast to friends early yesterday morning, 0.225 inches; will be ecstatic if more falls. Latest AZ mod has about that amount here, and over half an inch in the Catalinas. Usually, though, those amounts are on the high side. On the other hand, if the details about where the the rain band shown below are off a bit, we could do far better than the 0.10 to 0.25 inches predicted. Here’s the accumulated precip predicted for today from that model:
Accumulated rain until 10 PM AST tonight from the U of AZ model run at 11 PM AST, the latest. Much needed, nice heavy band of rain across AZ!
Next rain threat continues for the 12th, plus or minus a day.
Of course, only CLOUDS can rain, so the title is a little silly, but it sounded more dramatic like that. This is the first measurable rain, it fell between 9 and 10 PM here, in EIGHT weeks!
And you could sure smell that special fragrance from the ground and desert vegetation as soon as you stepped outside to do your exercises this morning!
Nice sunrise yesterday morning to start the day. In case you missed, of course, I am there for you.
BTW, in the captions below, I have included for you a discussion of climate issues in a kind of stream-of-consciousness format. OK, its a rant that came upon me out of the blue. CM sometimes gets mad and loses control for a few seconds; need to get some counseling maybe…
6:56 AM. Altocumulus perlucidus. Say no more. Might be a lenticular sort of on the right. Not the classic almond shape, but it did hang on for a long time in that spot. Say no more.
Kind of gray after that in Altostratus with an undercutting, lower layer of Altocumulus by mid-afternoon darkening the sky up some more. Some virga here and there with sprinkles-its-not-drizzle reaching the ground by late afternoon in the Catalina area. Here is your cloudscape for later in the day, very Seattle like during approaching storms that actually rain lightly on you for hours:
10:35 AM. Classic Altostratus translucidus, ice path in cloud all the way to the sun.10:39 AM, after walk down a slope to give YOU a view to the southwest, classic Altostratus as seen when not looking toward the sun. Hard to tell if its translucidus or opacus looking this way. By the way, even when you can see the sun, As clouds are thousands of feet thick, tops usually at Cirrus clouds levels.1:26 PM. Here come the lower, flocculent masses of Altocumulus clouds, ones composed of droplets.3:15 PM. It was all downhill for cloud bottoms after the Altocumulus moved in. Now, the bottoms are lumpy and much larger, casting them as Stratocumulus. There was some virga and very light rainshowers reaching the ground at this time, too. A few drops fell at 3:11 PM. Only the great cloud mavens of all time would have noticed. Lasted maybe one minute.3:15 PM again. Lot going on here, so I thought I would point out some things on a gray day, in particular for my fellow meteorologist Mark A at the U of WA who winters in the Tuscon smog plume. Mark is a super sleuth when it comes to snowpacks, but maybe doesn’t have so much moxie when it comes to smog. Mark, as you know may now, was fired as Assist State Climo for Washington when he demonstrated and kept complaining, along with two faculty members, that the claims of gigantic snowpack losses due to global warming (now repackaged as “climate change1“) in the Cascade Mountains were hugely exaggerated, likely the result of cherry picking a cold snowy beginning and ending with a run of El Nino winters, ones that lead to less snowpack in the Cascades of Washington and Oregon. Such cherry-picking led to a wonderful suggestion of huge declines that has led to a bounty of funding and continued employment, promotions, accolades, citations by Big Media, etc, because such claims, even if exaggerated and untrue, are what we want to hear! And, no one ever got a job for claiming they can’t find any sign of global warming, or only a little one, but rather are vilified for even suggesting exaggerations in the “global warming” domain. Mark, BTW, continuing his sleuthing has recently shown that similar claims for declines in snowpacks in Montana near Glacier National Park, have not been decreasing but rather increasing. He’ll get HELL for this one! So, more vilification is likely ahead for poor Mark, as well as more smog.
What’s ahead, besides the Big Pac 12 Fubball Game on Friday evening?
More clouds. Maybe a few more sprinkles especially tomorrow after dawn. See nice map below from the U of WA Dept of Atmospheric Meteorology (original colors on the map below by that big troublemaker, Mark Albright)
Valid for 8 AM AST, tomorrow morning, which is Thursday, in case you’ve lost count of the days of the week. The arrow denotes an upper level trough, or bend in the winds. Ahead of the bend (sometimes referred to as vorticity, or curling air, or red curly air) the air tends to rise producing cloud sheets, whereas behind red curly air, the air descends. See Seymour Hess, Introduction to Theoretical Meteorology, 1959, Florida State University Press. As you can see by the arrow, that slight bend in the winds is about to pass over your house in Catalina, and the U of Az model output from last evening sees a little rain here with that passage. Yay! Also note suggestion of bifurcated jet flow with a minor maximum in wind (slight bunching of contours) to the south of us, nearly always required for rain here in the cool season.
Beginning to wonder, with all the middle cloud thickness out there over and SW of Baja that’s headed this way if we won’t get sprinkles that produce a little measurable rain later today or overnight….
7 AM AST. Look at all those clouds over Baja and to the west of there.You can see this whole loop from the Washington Huskies here.
Models beginning to wetten things up here as well, like that Enviro Can model that sees our tropical surge high and middle clouds passing over us now, as deep enough for measurable rain later today and overnight. Huh. U of AZ mod, the best one for us, is still dry around here except on mountain tops. Our larger scale model, however, also has some very light rain in this area now, later today into tomorrow morning.
What’s intriguing is that a little jet core at 500 mb (up there at about the height of middle clouds) passes south of us as this happens, key for precip here1 in the cool season. The major jet stream is far to the north.
As you know, we have a bit of an El Niño going, both a “Classic Niño” as well as the “New Niño” going, and El Niños strengthen the southern portions of jet streams in the very way that we’re seeing in this situation.
They do that because its warmer than usual in the central and far eastern Pacific tropics due to heat in extra big Cumulus and Cumulonimbus clouds that pump away down there over that extra warm water, and that rising warmth produces a greater than usual difference in temperatures throughout the troposphere between the tropics and the mid-latitudes. Since jet streams are the products of temperature differences between warm and cold air around the globe, so unusually deep warmth in the tropical eastern Pacific gives a little strength tweak to jet streams coming into the coast2.
SInce there are two of these lower latitude “waves” traveling along in the southern branch of the jet stream, there are TWO chances for slight rains including that for later today. The next one barges in on the 6th of December. Will again be dense middle and high clouds with virga at its worst, like this one, though again a hundredth or two could happen.
Next real rain chance, and major front passage with air that’s too cold for us, will be on the 12th. Spaghetti folk, or “Spaghetti Busters”, those who can make sense of these balls of yarn, can EASILY see that trough on the 12th and a cold front with are “in the bag” even though that’s ten days away. Rain occurrence is more dubious, since the trough may land a bit too far east to produce rain, only a lowering of temperatures. Here is that plot from last evening. Enjoy.
Valid at 5 PM, December 12th. Pretty clear a nice trough will be in the area then.
Your yesterday’s clouds
11:44 AM. Up and down, up and down, those wavy air motions that produced this interesting line.3:37 PM. Classic Altostratus translucidus (sun’s position is visible).5:20 PM. Sunset Altostratus (ice clouds) and Altocumulus (droplet clouds).
BTW, for horsey people, the Cement Trough had water in it yesterday after being completely dry ten days ago:
11:44 AM. At the Cement Trough headed to South Gate.
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1See Rangno, 1973, unpublished manuscript and figures for the whole US using only the horizontal shear in jet stream at 500 mb as a definer of precip occurrences. Its really quite something, though, I guess you can’t see it.
2This was figured out by the Great Jacob Bjerknes of the Norwegian School of Meteorology while he was cruising into retirement (“Emeritus” status) at UCLA in the 1960s, though Chuck Pyke3,4, his grad student, did most of the work. Did a lotta work on the big “Classic” El Niño of 1957-58, which, per chance turned out to be an International Geophysical Year with a lot of extra observations! How lucky wazzat?
3Chuck, as you may recall was in the National Guard whilst at UCLA and was sent to Biloxi, MS, for two weeks of training and while there, was “gifted” with the passage of the eye of Hurricane Camille, one of the strongest of the century. Later the remnants of Camille, to go on and on, produced 31 inches of rain in 6 h in Virginia.
4Chuck P, who now lives in Arizona, also was very thorough in his evaluations of rainfall in his other studies concerning the seasonal timing of rainfall throughout the West. He once told me when I visited UCLA once to get Bjerknes autograph5 that he had gone to every rainfall measuring site in his study! Now some people go to every baseball park in America, but going every rain gauge site would be more interesting to cloud mavens. He further told me he found one that had not moved for 30 years, but the rainfall had been decreasing. When he went to that gauge, he found that it was being overgrown by a tree! This is why you have to check things.
5I failed. He was “Emeritus”; too good to be in his office that day. You see, your Catalina cloud maven was a strange person even then, wanting an autobgraph by Bjerknes rather than one by Mickey Mantle, though one by Mickey M would be worth a lot more today.
(Formerly titled: “Storms lining up for Catalina in early December”)
Things change.
Confidence was never real great in the spaghetti plots we rely on for hints about the reliability of our longest range “wishcasts,” as a friend puts it. Now it seems we’ll only see high (Cirrus) and middle (Alftocumulus and Altostratus) clouds on the edges of the rain areas that move across California, maybe the NW corner of Arizona, too, during the first week in December. Oh, I suppose there could be some virga with a sprinkle here from the thickest of those middle clouds, but that’s about it now.
But, on the happy side, we’ll see our usual array of stunning sunrises and sunsets under warm conditions when those high and middle clouds begin arriving about Saturday, the envy of many northern “climers”, or “northlats” this time of year. (Starting to see those Illinois, Minnesota, Ohio, license plates now, aren’t we?)
Our next chance at rain after that is not good but revovles, and the air does, around a cutoff low that gets stuck out of the mainstream here in the SW in mid-December. Those, unless you’re in the exact right position, or are gigantic like that one back in ’67, often have limited amounts of moisture. If you’ve never seen a cut off low, here’s what they look like in the middle troposphere, a forecast valid for this Monday afternoon:
From the University of Washington Huskies Weather Department, this example of a cut off low at 500 millybars, or around 18,000 feet above sea level. They kind of meander around not doing much, then eventually dissipates/”opens up” into just a bend in the winds up there, as this one does as it begins to move eastward and then northeastward (the killer for us) as it comes into the Cal coast. Most of the jet stream, as indicated by numbers of contours, is far to the north, something that allows lows like this to pretty much have a mind of their own for awhile. The bulging northward contours over us mean that it will be toasty and dry here, maybe some Cirrus clouds around..
So, it would kind of lucky for us to get something out of it. And, when you’re in a droughty period, as we have been in for the past EIGHT weeks, things like that don’t usually work out in your favor. Its like being a football team that loses the close ones but also gets blown out in other games. Since we’re talking about sports now, a pause for a sports exultation: Washington1 volleyball somehow beat No. 1 Stanford on Wednesday!
Special Scientist, Bob Maddox, who is an actual expert and does a superb weather blog for this area, has passed me a long range forecast from the CPC (Climate Prediction Center) recently that I will share with my reader:
A wet mid-winter in the Tucson area been forecast!
How wet? 2 inches in December, 4 inches in January, and a colossal 6 inches in February. Wow. There would certainly be flooding at some point later in this period.
These results derive from a longer range forecast model the CPC runs. Although the fantasy factor is high here, still, something to hope about. With a bit of an El Niño in progress, and this forecast resembling the tendency for El Niños to act up in aiding wetness in the Great Southwest in the mid-winter to spring, there is some SLIGHT credibility here.
Too, such forecast amounts resemble the great El Niño winter of 1992-93 that helped ruin the Biosphere 2 experiment, then in progress because there were too many clouds and not enough sunshine to make it “work.” Imagine.
OK, already getting too worked up about this. Will quit here.
The End
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1The writer was employed in studies of clouds by the University of Washington’s Cloud and Aerosol Group, and quickly adopted the company teams as his own, one of the signs of a great employee, one who wore Washington this or that sports Tees in the off hours, no doubt helping to enhance Washington revenue streams.
I wanted to add some suspense to this blog today, and to enhance readership beyond one, I would do like TEEVEE news and weathercasters do who get people to hang around by saying silly things like:
“Will it rain for the Arizona fubball game tomorrow? We’ll tell you at 11”
when an answer consisting of a single word would do.
These are one of the dumbest, outrageous and annoying lines that weather and newscasters come up with over and over again, and I hope I am NEVER on TEEVEE and have to say something like that unless I am making a LOT of money, and then I might say almost anything! (Haha, just kidding, I think, but not positive.)
Valid for 5 PM AST Thursday, December 4th. The location of Arizona and Catalina on a map of the United States is shown. Areas of rain are generously pointed out by arrows to help the reader comprehend this map.
Well, since the supercomputer calculations, these based on earth data from last night at 5 PM AST (00 Zulu, Greenwich Time, Central Universal Time, etc.) continues to show early December rains in Catalina (see illustrative figure above), we need to have some spaghetti to see if a trough in the middle troposphere has much chance of being here:
Also “valid” for 5 PM AST, Thursday, December 4th, corresponding to the storm map above from NOAA, and also based on earth data from last evening at 5 PM AST. Areas of high confidence and cluelessness are pointed out, FYI. The yellow lines are what the model actually predicted. (Hint: doesn’t match up that well with itty-bitty error-laden runs, one that try to account for “chaos” in the atmosphere (where itty-bitty things like a single thunderstorm mislocated in the initial run can cause the forecast to go bad; and, of course, real errors in measurements. Sometimes this strange plot, deemed a major advance in weather forecasting, is called by CM, anyway, a Lorenz Plot, after E. N. Lorenz who liked to publish papers on chaos. OK, as you can see, I hope, not a lot of confidence is suggested for a storm on December 4th at this time; mods will continue to see it come and go. Here, you will only see those forecasts that have a storm for Catalina.
Went on a hike yesterday morning, about 4 h worth up the Baby Jesus trail to the Deer Camp trail and back down again. Here are some scenes from later November from a desert having a lot of rain in September and October. Octotilloes are blooming here and there! Amazing! Morning glories hanging on, too. Cement trough, though, was dry. Boohoo. Didn’t expect that.
Ocotillo in bloom, November 22nd, 2014.Arizona fall color as evidenced in a coral bean bush.More Arizona fall color in something, maybe a wild cotton bush. Was hiking with the Cottons, too.Some kind of green grass. Most of the grasses, though, were dried up.Morning glories still abound!Typical riparian scene seen on the hike. Crossed this wash several times, and all of the views were as good as this.A weed. Burrowweed in bloom. Kind of pretty, I thought, but who cares what I think?Expected to see water here at the old “Cement Trough” where water is often counted on by horsemen and horsewomen.People from all over gather at the Cement Trough scenic area for a hike respite.Two stage arrowhead.
6:52 AM. Altocumulus cloudlets over and east of the Catalinas.6:52 AM. Sprinting to the other side of the house, this spectacular scene of virga falling from Altostratus. Breathtaking!6:53 AM. To the NW, the virga roiled downward into mammatus bulges under lit by the sun.6:54 AM. The color was fading just in a minute or two, but it was still a breathtaking panorama I thought you should see.
Some additional commentary about these scenes. One of the remarkable things about clouds, a real unknown, is how clouds such as Altocumulus (1st photo) can get so cold, colder than it was this mid-November in Wyoming, and can remain all or mostly water drops, which is what you are looking at in those cloudlets over and beyond the Catalinas. Pretty amazing. This phenomenon has been known about for decades, but not fully explained. We expect to see a lot of ice in clouds with tops colder than -30 C (-22 F) as you might imagine.
Here’s the sounding near the time of these photos, with writing on it:
———-Begin learning module———————————-
The Tucson balloon sounding, launched around 3:30 AM AST yesterday morning.
As a CMJ, you need to be armed with explanations if, on a morning walk, your neighbor, at first overwhelmed by the morning beauty, but then instead of being quiet, goes on to ask, “Hey, aren’t those clouds composed of droplets; they must be pretty low and warm?”
Since you’ve already seen the TUS sounding for the hours just before this, you know those cloud bottoms are real cold and high, -26 C, and 19,000 feet above you here in Catalina, and tops are really cold, about -32 C (-26 F), you cringe. What to say? How do you explain clouds that can sit there at -32 C and develop little or no ice, while knowing that Cumulus clouds, ones whose tops have never been colder than -7 C, can be completely composed of ice just after reaching up to that temperature?
—————-End of learning module, such as it was———————
Here’s another example from yesterday of extremely cold clouds with few ice crystals:
9:36 AM. Altocumulus perlucidus opacus (sun’s position is not detectable). The TUS sounding for the morning would not be valid at this time since the cloud bases were slowly lowering but they would still be about -20 C at this time, height about 17,000 feet above ground level. And, at this temperature, such clouds are ultraripe for ice production by aircraft that may flay threw them. See next photo for a POSSIBLE aircraft production of ice in these cold clouds.
10:43 AM. Of course, all of you were looking for some aircraft perturbation I’m sure, and this seemed “too linear, too uniform, the crystals too small (as deduced by the sloping lines of virga underneath this line for the ice to be natural. No other virga looked like this having straight fine lines underneath, the thing typical of contrails. However, its not the typical ice canal, either, with clearings beginning on the sides. In fact, the cloud seems thicker here where an aircraft may have traversed it, posing an explanatory challenge. Also counter to reason, why would an aircraft fly so far in what would have been light rime icing conditions in those Altocumulus clouds? Lots of questions, no really good answers.
11:07 AM. Linear feature passes over Catalinaland. Was hoping for a drop so I could claim it had rained in November, even if it had been a phony rain.
11:32 AM. Looks phony to me! Not a real cloud. I think we’re looking now at the tube of high concentrations tiny ice crystals that slowly settled out from that Altocumulus layer after an aircraft went through it–this tube to me appears to be BELOW the general layer, due to settling out after a few larger ice crystals fell out first. Am about 60 % sure that’s what happened and caused that linear feature. Getting pretty worked up about, too.
Well, Shakespeare said it: “Much ado about nothing,” so it must be important if he said it.
Had some really nice cloud scenes after the big clearing came through in mid-afternoon:
3:38 PM. Our typical spectacular lighting on the Catalinas scenes as storms move away.
4:49 PM. A dramatic finish to the day; light showers hit south and southwest of Tucson, but faded before arriving here.
There were some light showers that produced as much as 0.20 inches of rain in the south and east parts of Tucson late yesterday afternoon and evening. Nice for them.
The weather way ahead
Nothing in the way of rain in the immediate future. Have to wait until December for any real chances. See this bad boy for December 6-7th, this panel only 360 h from now1!
Valid at 11 PM AST December 6th. Note that the heaviest rain in Arizona is over Catalina! These are totals that accumulated in the 12 h prior to 11 PM AST. Hope I made you that bit happier showing you this. It’s a pretty cold system, too, might be a close call for snow here.
The End.
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1360 h in advance, even using our best model, is about in time like the distance to Betelgeuse in light years. Hence, caution when the writer says, “only.”
Started out clear yesterday. Below, an example of that completely clear sky in case you missed it.
10:06 AM. Clear skies are evident as we look in the general direction of Baja California. HOWEVER, note shallow smog plume exiting Tucson and flows northwestward across Continental Ranch over there by Twin Peaks where fellow University of Washington meteorologist, Mark Albright, lives.
I think it is interesting that Mark would chose to live as a snowbird in a smog plume rather than here in Catalina where that Tucson smog plume rarely strikes. Its pretty regular down there because the normal morning wind in Tucson is from the southeast and that wind shoves the urban smog over to Mark’s house on many cold mornings. Pretty funny, really.
Yesterday’s clouds
In the mid-afternoon, a stream of patchy Cirrus was beginning to creep over us. If you don’t believe me, you can see it in the University of Arizona time lapse film for yesterday.
And, in those leading Cirrus clouds were some spectacular, stupefying really, complex patterns of cloud formation and and holes in them, ones like CM had never seen before except maybe that one time in Durango back in the 1970s. Here are some examples of those odd that were up there:
3:14 PM overview of Cirrocumulus and Cirrus clouds with oddities.3:14 PM Close up of previous cloud scene. Note all the weird stuff going on.3:22 PM. More oddities. Going crazy trying to understand what the HECK is going on!3:23 PM. Close up of rectangular “fringe.”
Started to breath a sigh of relief when this melange of complexity moved off rapidly worrying that someone might call and ask me to explain it. So, when some Cirrus uncinus and/or the rarely seen Cirrus castellanus came by I started to relax, feel confident again. Here are some of those pretty shots of little, icy clouds trailing light snow showers, likely, to repeat again, crystals called bullet rosettes. The ones in the part of the cloud from which they spew are likely tiny prisms, side planes, and tiny solid columns, thick, but tiny hexagonal plates with little fall speed, so those hang up there, while the favored ones in the best tiny updrafts in these clouds that resemble tiny glacial Cumulus clouds grow from those kind germ crystals into bullet rosettes, complicated crystals with multiple tiny columns sticking out of them. If you would like to read all about the crystals that form in high icy clouds like these you should spend some time browsing this paper, co-authored by the great John Hallett1 I really like footnotes–yes, of the Hallett and Mossop riming and splintering mechanism, discovered by them in 1974. Helped explain why there was a LOT of extra ice in clouds that shouldn’t have it.
Here’s one more weird scene in Cirrus before moving on to something explicable:
3:43 PM. Holes, plops of downward moving air amid the Cirrus/Cirrocumulus. But why so round?
Thankfully, here’s what transpired next at Cirrus levels:
4:02 PM. Cirrus uncinus (one with tufts or hooks at the top and long streamers of ice below them) followed the strangely patterned sky.4:03 PM. Look at all the larger ice crystals pouring out these little guys! Its amazing. Notice how FINE those strands are. Airborne work we did indicated that the cores were only a 5-20 meters wide!4:20 PM. Reminded me of a ballet the way the clouds and the streamers were arranged around one another.4:17 PM. Just a little before the dancing clouds came by, there toward the Gap was this CIrrus castellanus mimicry of a full grown Cumulonimbus capillatus (tuft in center of photo). Look, it even has a tiny anvil spreading out, to use the word “tiny” for the 18th time! How fun was that to see!
Of course, with all the patchy Cirrus around we were guaranteed a nice sunset and it did not disappoint:
5:29 PM. Sunset.
Today’s clouds
Heavy ice clouds, several kilometers thick at times. We call that kind of fray, often full sky-covering layer, Altostratus. Likely some Altocu around, too. Will look now and see if I see any of those latter ones. Oops, too dark.
With clouds kilometers thick, tops at Cirrus levels, you can expect to see virga, and the chance of a few “sprinkles-its-not-drizzle” later in the day. The whole progression of clouds can be seen from the U of AZ model output from last night in these forecast soundings for Tucson. As per usual, the bottoms get lower and lower as the day goes by, but are still up around 13, 000 feet above Catalina by around sunset. So, will be tough to get a drop to the ground before then. U of AZ mod thinks all measurable rain will be to the south of us. Oh, me.
BTW, and this is an embarrassment, it was asserted by this keyboard that rain would fall in November at the outset of the month. This is the last chance for that! Egad. But forgetting that possible gaffe, moving ahead anyway to what’s going to happen in December (of this year).
The storms way ahead, that is, ones in early December.
Those early December storms for us are coming and going in the WRF-GFS runs. But I am counting on rain here in early December myself due to an interpretation of those weird in so many ways, “spaghetti plots.” I think they’re showing, and continue to do so, significant troughs coming through the Southwest in early December.
The End
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1Later after the referenced paper above, and this is quite interesting, the great Hallett was to claim that me and Pete Hobbs had embarrassed2 the entire field of airborne researchers due to a paper published by us way back in 1983 (J. Hallett, 2008, communicated by him during his presentation at the Pete Hobbs Symposium Day of the American Meteorological Society, New Orleans.
2But it was a good embarrassment, not a bad one due to incompetence, I think.
6:55 AM. A surnrise glow from receding CIrrus spissatus highlights Samaniego Ridge. Very pretty and dramatic.
8:19 AM. Forming uncinus, CIrrus that is. Note trails of precip beginnng to form under these tufts of Cirrus castellanus clouds.9:06 AM. Jet contrails begin to show up in a Cirrocumulus cloud composed of supercooled cloud droplets. You know what going to happen….something special for you to log in your cloud diary.
9:20 AM. Another patch of supercooled, very supercooled for that matter, Cirrocumulus with evidence of a jet contrail. But, is the jet above or IN the Cirrocu? TIme will tell.
How cold were those Cc clouds? See below.
(Begin technical module)
The Tucson balloon sounding1 for 5 AM AST, November 19th with writing on it. The height of these clouds was slightly lower in the mid-afternoon, but (as Altomumulus then) were still about -23 C. As we know, cloud bottoms almost always get lower with passing time because the higher parts of cloud shields are moving faster.
In the mid- -20s C, around -15 F. Height, about 21,000 feet above the ground here in Catalina. Hope you got that estimate of cloud height right.
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Continuing…
9:21 AM. ANOTHER jet streaks by! This is going to be darn interesting, a rarity, like seeing a grey parrot in Catalina! The secret about what height the first jet was flying at is beginning to be revealed. Can you see what’s happening to that first contrail a little below the new one? This is a great test to see how far you’ve come as a CMJ (cloud maven junior)!
Here’s what happened in the Cirrocumulus cloud layer in yesterday’s special day, a pretty rare one, after the jets flew through it:
9:30 AM. OK, mystery’s over. Even the average CMJ Joe can see that 1) the jets were IN the Cirrocumulus cloud, and more importantly, the aircraft contrails consist of ice. Yes, that’s right, the passage of the aircraft has caused a phase change from liquid drops to ice crystals, a lot of them.
9:47 AM. Now those contrails are looking like real and icy Cirrus clouds. In this case they’re called “ice canals” but sometimes, when aircraft are ascending or descending and do this, they make round clear holes with ice in the middle, called “hole punch” clouds.
Lessons to be learned from yesterday’s supercooled clouds and the aircraft interactions inside them:
Cloud seeding works! You CAN make a supercooled, non-precipitating cloud produce a little precipitation that would not otherwise have occurred.
But in those situations where the clouds, say, are topping the Catalinas, they are often quite thin, and whether there is an economically worthwhile amount of precip is not known. However, an experiment targeting those clouds would be the perfect “baseline” one in cloud seeding to establish how much we can wring out of non-precipitating clouds. Things become kind of a mess when even randomized seeding takes on already precipitating clouds.
“Overseeding”, as here in these clouds when aircraft produce prolific numbers of ice crystals in a small volume, it leads to tiny ice crystals with low fallspeeds. Sure, they fall out and leave a hole, but they virtually never reach the ground except in one a in billion cases when the very cold clouds are real low, practically on the ground.
The Wegener-Bergeron-Findeisen mechanism produces precipitation.
Alfred Wegener, 1911, and later Bergeron3 and Findeisen in the 1930s, came up with the hypothesis that adding ice to a supercooled cloud results in the growth of the ice crystal at the expense of the droplets. They’ll tend to evaporate while ice is being added to the crystal via deposition of water vapor that was once liquid. So, an awful lot, maybe most of the precipitation that falls on earth, involves “mixed phase” clouds. This process has also been called the “cold rain process.”
However, let us not forget the two other processes that produce precipitation, the all ice process (no liquid required–helps produce “powder snow”, and the all liquid process, where cloud drops collide and grow into raindrops–the biggest measured drops in the world (about 1 cm in diameter) have formed soley through this process. It is likely that most of the rain that falls in tropical locations like the Hawaiian Islands and in hurricanes is due to this process even when ice is present in the top part of storms.
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Later, we had some Altocumulus castellanus clouds with virga as the moist level lowered, though they were long gone before they could provide us with a nice sunset:
2:32 PM Bands of Altocumulus castellanus approach Oro Valley from the west. These clouds, while based at just about the same level as the Cirrocumulus clouds earlier in the day had three things going for them to produce so much ice (right side of photo–and really, convert to Cirrus clouds). The cloud bases were slightly warmer (the TUS sounding suggests, -22 C), meaning more water was available to the cloud, something that would impact the drop sizes in the turrets of the Altocumulus clouds (left side of photo); 2) the tops were higher than the Cc clouds (ones that were paper thin) and therefore, slightly colder (probably about -28 C) than those of the Cc clouds, and perhaps as importantly, the drops near the top of the Ac turrets before they converted to ice, were larger than those in the earlier Cc clouds. The larger the droplets, the higher the temperature at which they freeze. So, ice is more likely to form in a cloud with larger droplets in it than one with tiny droplets in it even though they are the same temperature. That might explain the difference ice-forming behavior of yesterday’s very thin Cc clouds which mostly had no ice (until an aircraft came along in them) and these prolific ice-producing Altocumulus clouds, ones that converted to all ice. Just educated guesses here.
Still looking for scattered very light showers in the vicinity tomorrow as a Mr. Troughy goes by.
The End.
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1Through the oral history tradition I learned while viewing the Washington Husky meltdown2 at AZ stadium on Saturday from a Mr. Mark Albright that the Tucson weather balloon launch site has been moved from Davis-Monthan Airbase to the University of Arizona campus next to their weather department.
2Late in the proceedings, with about 2 min left and the Huskies starting a play, and in the lead, CM was visibly moved to jump up and say, “Don’t hand the ball off!”, as a gift to Arizona fumble occurred simultaneously. But, being bifurcated in his loyalties now that CM is in Arizona and not with the University of Washington, he had to be somewhat “glad” that the Cats maintained their somewhat suspect but great win-loss record.
3From the Historic Moments in Weather collection:
Your Catalina CM and Tor Bergeron meet for the first time in Goleta, CA, in 1968 at the headquarters of North American Weather Consultants. Yours for $2,100 dollars, today only. I remember thinking that his head was gigantic! No wonder he was so smart. CM, not so much.
Been away from you for a couple of days, wanting to see how you do on your own, perhaps see you grow in your cloud watching obsession, namely, that you want to name everything you see, as though you were Luke Howard himself. Hope you logged all cloud genera, varieties and species, 27 all told, over the past 48 h. You can bring your photo log books to the next meeting and CM will go over them with you.
Measurable rain chance still pretty reasonable for the window of Nov. 20-21st, too, as we have purported for some time here, but it will be pretty minimal.
The weather way ahead; a promise of substantial rains
However, as often happens, on the horizon is a substantial storm for Arizona, ones that have a habit of disappearing it seems as the foretold event gets closer. Here it is depicted below in plots from our cherished NOAA spaghetti factory:
Valid at 5 pm AST, December 2nd. Pretty cool, huh?Same spaghetti plot, annotated. Recall that these plots are ones where the model input has been deliberately errorized to see how big little errors make in the outcome of the model. Why do that? Because we know at the outset that our measurements are not perfect, and have all kinds of actual little errors in them. These plots are a way of seeing how robust a predicted pattern is, and those areas where the forecast is pretty reliable, is indicated by bunched lines (key contours of the airflow at 500 millibars, or around 18,000 feet above sea level in the mid-latitudes, lower near the poles, higher near the equator. Why do we use a pressure level instead of the pressure at a height? Go here. CM would like to see as well, in the 21st century, maps of constant altitude (3 km, 5 km, etc.) with the high and low pressures on them as we have on our sea level maps! Is anybody listening? (A google search just now could not locate, constant altitude pressure maps….)
While the above forecast of contours is two weeks away, and numerical models are often unreliable at those long horizons, we see that the red lines (not to be confused with political markers) have dipped down in great bunches over the extreme eastern Pac 12 Ocean, and continue all bunched up across Baja Cal and thence into Texas. In the plot above, the red lines represent a 500 mb height of 5760 meters, one that’s on the southern periphery of the jet stream. So, when its well south of us, our chances of rain are engorged. Recall, too, that the 5640 meter contour, just that bit lower in height, is associated with leading edge of rains in the central and southern California area–remember Brier and Panofsky, Some Applications of Statistics to Meteorology? Well, in that book you will learn that contour is what the LA weather service used to use as crib for when rain would occur in southern California.
I am sure you remember two things, maybe more than two. We have an El Nino in progress, not a great one, but an OK one, AND that El Niños strengthen the southern jet stream in the eastern Pac and across the southern latitudes to the east. So, we expect to see this pattern, one of a stronger jet stream in the sub-tropics carrying stronger disturbances as a result, evolving as the winter develops, that is, more disturbances in the lower latitude band of the jet stream (sub-tropical part). The plot above is a classic one for predicting that kind of regime, maybe with a bit of a split in the J-stream with northern and southern branches being pretty vigorous at this map time, and before, for that matter.
Valid at 5 AM AST, Monday, December 1st. Colored regions are those in which the model has calculated that precipitation has fallen in the prior 12 h.
The plot above, it has laid a foundation of credibility for what is show below, from IPS Meteostar’s rendering of our WRF-GFS forecast model output based on the 5 PM AST global data. It shows 24 h of substantial Arizona rains, including here in Catalinaland, at the beginning of December. You’d be pretty cool to inform your friends about this, ones who might be heading back somewhere after a TG visit to sunland1. (Besides, they won’t remember what you said anyway by the time December gets here.)
Valid at 5 PM AST, Monday, December 1st. Colored regions are those in which the model has calculated that precipitation has fallen in the prior 12 h.
Today’s clouds
Lots of pretty Cirrus.
The End
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1By the way, the Great Lakes are freezing over already, a month earlier than normal due to some astounding cold back there, so TG visitors from back East, upper Midwest, may look for reasons to stay longer. Well, at least until the rain and cold hit here.
Here we go…..some pretty, but also dull, photos, along with some novella-sized captions as mind wandered into the obtuse while writing them.
6:44 AM. Nice sunrise due to Altostratus/Cirrus ice clouds.2:00 PM. Kind of a dull day yesterday, kind of like this blog. Stratocumulus (Sc) clouds topped Samaniego Ridge most of the day, below that gray Altostratus ice cloud layer. But those Sc clouds were too warm to have ice in them, and droplets were too small to collide, stick together, and form misty drizzle. Have to get to at least 30 microns in diameter before they stick to one another. Misty drizzle? Could be a great name for a late night female vocalist doing earthy songs like Earthy Kitt back in the ’50s. “Earthy” was much hotter than global warming.3:29 PM. An Altostratus translucidus to opacus, mostly ice-cloud with a dark patch of Altocumulus droplet cloud blocking the sun. If you look closely, (upper center) you can see a that there’s this Altotratus layer may be topped by a Altocumulus perlucidus droplet cloud layer. Yes, droplet clouds at the top of As where the temperature is lowest? Yep, this counter-intuitive finding happens all the time, up to about -30 C -35 C. Been there, measured that; in aircraft research. Ma Nature likes to form a drop and have it freeze before forming an ice crystal directly from the water vapor.4:40 PM, shot taken as we entered a local restaurant. You’ve got your two layers of Altocumulus, with some Altostratus translucidus above those, filling in the gaps. Gaps? Huh. I am reminded that I have a failed manuscript about “gaps”, these kind; Cloud Seeding and the Journal Barriers to Faulty Claims: Closing the Gaps., rejected by the Bull. Amer. Meteor. Soc. way back in ’99. It was an instruction manual, in a sense, about how to prevent all the bogus cloud seeding literature that got published in the 1960s through 1980s, and was not only published, but cited by our highest national panels and experts, like the National Academy of Sciences. Amazing, but true. I give examples. You can read about this chapter of science in Cotton and Pielke, 2007, “Human Impacts on Weather and Climate”, Cambridge U. Press, a highly recommended book. That cloud seeding distortion of cloud seeding science was due to many factors, of which perhaps the primary one was, “nobody ever got a job saying cloud seeding doesn’t work1.” This was a great segue. Of course, we have similar stresses on those researchers looking for effects of global warming nee “climate change” now days. Nobody will ever get a job (a renewed grant) saying they can’t find evidence of global warming, “Can I have some more of that money to keep looking?” And beware the “Ides of March” if you criticize published work in that domain! Think of poor Judy C , a heroine to me, and how she’s been vilified for questioning climate things.
5:29 PM, took leave from Indian food there in R Vistoso for this. Its not just anyone who would excuse himself from dinner to do something other than visit the laboratory.
That’s about it. No use talking about the rain ahead again. Seems to be a couple chances between the 20th and the 30th.
The End
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1You can make a cloud snow a little by seeding it with dry ice or silver iodide. This has been shown since the earliest days of experiments. Below, to demonstrate this, an aircraft inadvertently “seeded” this Altocumulus cloud layer. However, whether the small amount that falls out from previously non-precipitating clouds is economically viable is not known. Increasing precipitation due to seeding when the clouds are already snowing/raining has not been satisfactorily proven. As prize-winning stat man, Jerzy Neyman, U of Cal Berkeley Golden Bears Stat Lab would tell you, you need a randomized experiment and followed by a second one that confirms the original results, with measurements made by those who have no idea what days are seeded and evaluations done by those who have no vested interest in cloud seeding. Wow there’s a lot of boring information here. Getting a little worked up here, too.
Ice canal in supercooled Altocumulus clouds over Seattle, bases -23 C, tops -25 C (from PIREPS). Photo by the Arthur.
