Author: Art Rangno

Retiree from a group specializing in airborne measurements of clouds and aerosols at the University of Washington (Cloud and Aerosol Research Group). The projects in which I participated were in many countries; from the Arctic to Brazil, from the Marshall Islands to South Africa.

Models divine powerful mid-month storms

Here’s what we got now for a jet stream regime.  The jet stream, that raging river of wind between the deep cold air of the northern latitudes and the deep warm air of the tropics and sub-tropics,  is crashing into Washington and British Columbia from the Pacific.    We have remain in the quiescent warm air of a “ridge”, a slight poleward bulge of warm air in this case extending toward Montana at map time (5 PM LST yesterday).  This has been going on for the past two weeks.  Boring, but really nice, too.

When the jet stream extrudes itself southward, as over the central and eastern US, it drags cold air southward, too.   Here is an example of the US temperature change over the past 24 h associated with the current pattern from The Weather Channel:

But look below at what has happened, the models say, by mid-month, as shown in the following four panels!  The jet stream has buckled over the West Coast and has extruded down into AZ, a wet and cold pattern in the interior of the West has developed with lots of precip around here predicted.


 Since these storms weren’t on yesterday’s model runs, so’s you can’t count on them.  BUT, having said that, we can hope anyway.    I will interject that I have a feeling that this is going to be correct, no quantitative stuff here.  This due to the type of winter we have already been experiencing, a feeling it will return to that mode.

Here are some examples from IPS Meteorstar‘s rendering of the WRF-GFS model run from last night.  The greenish-looking maps are the ones showing where the high and low pressure centers are predicted to be and the green those regions where the model thinks it has rained in the prior 12 h.  Look at all the green in AZ.   The reddish orange maps show the jet stream, that river of storms and how they will be guided.  If correct, the storms will be steered from the interior of Canada down into the Southwest,which means that these storms will be not only cold, but damn cold, to cuss that bit for emphasis.

The first pair of maps are valid for Sunday afternoon, the 16th, at 5 PM LST, and the second pair for Tuesday morning, the 17th at 5 AM LST.

Enjoy dreaming about more rain…and probably low snow levels in a couple of weeks.

 

 

 

 

 

 

 

 

 

 



“(the reviewers)… are still unconvinced by these controversial claims.” A science story.

Alternate titles, choose one or all:

 1) The story of APIPs (Aircraft-Produced Ice Particles)

 2) They said it couldn’t be done, but they did it anyway

 3) ‘An embarrassment for the airborne research community’–Dr. John Hallett, 2008

OK, “baby I’m bored” with the lack of clouds and precip,  and so I thought I would share my boredom with this long tome on aircraft effects on clouds.  Why not bore other people if you’re bored?  I’ve thrown in some alternate titles above to peak and pique your interest.  Speaking of “thrown”,  Mr. Cloud-maven person was also thrown off his big (I mean huge1),  young horse lately; “JohnT”, as he is named, doesn’t like people to sit on top of him sometimes.  Not easy to sit at a computer these days, hence the lack of “acitvity.”

OK, on to the story of APIPs.  The title quote was written in 1982 by the Chief Editor of the American Meteorological Society’s, J. of Climate and Applied Meteorology (JCAM) summing up the opinions of the three reviewers at the bottom of a second rejection notice of a manuscript, one that had been fluffed up with more evidence of APIPs.   However, the Editor allowed us (me and Peter Hobbs, director of the Cloud and Aerosol Research Group at the University of Washington) another crack at it, and by the THIRD submission (requiring a bit of chutzpah),  a colleague and me had found photographic evidence of aircraft having produced icy canals in supercooled clouds, and that visual evidence really pushed our third manuscript, now as big as JohnT, over the top in getting accepted and  published.

The phenomenon came up again last summer in a Wall Street Journal article, one in which Mr. Cloud-maven person was asked his opinion.  This phenomenon (APIPs) is attracting more attention these days, so I thought I would pass this background story along.  I hope will encourage authors with rejected manuscripts, which I myself have quite a few.   You might have something really good.

Yes, that’s right, lucky Mr. Cloud-maven person was involved in this interesting chapter of science that happened way back in the early 1980s when he was part of the flight crew in the University of Washington’s Cloud and Aerosol Research Group (CARG).  Occasionally, and mostly in studies of ice development in Cumulus clouds, I got to direct the University of Washington’s first research aircraft, a 1939 manufactured, Douglas B-23, into Cumulus and small Cumulonimbus clouds.  It was heaven for me, a storm chaser type person, having done that here in AZ way back in the mid-1960s chasing summer thunderstorms all over the State with my camera and rain gauge.

We had a viewing dome on the top of the fuselage of that B-23 and I sat in a swivel chair, head protruding into the “bubble.”   I was kiddingly referred to as the “bubblehead.”  I think they were kidding, anyway…  Those who know me will understand that title.   Sitting there with head in the bubble, allowed me to see EXACTLY where we exited a cloud and could direct the pilot to EXACTLY that same cloud blob we had just exited.  The pilot was fond of turning the plane sidewise for this return so that one wing was pointed straight down in the turns and we often got back in within 90 s to two minutes.  It was an exciting as well as sickening experience.

We did that because we wanted to see how that element of the cloud had changed with time.  Did ice form?  Did the drops get bigger or smaller?

This viewing dome gave us a huge advantage over other research aircraft doing this kind of research.  Below, that B-23 aircraft sitting on the tarmac at Boeing Field, Seattle2.  The second photo is a view from the “bubble” located toward the rear of the fuselage.  Nice!  I was so lucky!

One day, while looking over our Brush strip charts from the flights, I noticed some odd spikes in the ice crystal detector we had. Also, since we were one of the first groups to get a probe that produced shadows of the particles in the clouds as we flew in them, I was able to see that the particles producing those spikes were oddly similar sized, as though they had formed simultaneously, something not seen so much in natural clouds. Pretty soon it became apparent that these spikes and odd particles ONLY appeared after we had gone through the same cloud for the second or third time.

I remember walking into Professor Peter Hobbs grand office with a strip chart with those ice spikes and saying, “I think our aircraft did this.”

He was unfazed; did not have a particular reaction.  Peter Hobbs was always open to new thoughts, and that helped allow me to go forward with a further investigation even if it meant some of our past data and publications might conceivably be compromised, ones however, I was not involved with as a fairly new (5-years in) employee at the U of WA.  No vested interests here!

After awhile, after aircraft plots showed that the spikes were within tens to a couple of hundred yards (meters) of where we had been before in a Cumulus cloud, a very short paper was written up on it and submitted to JCAM in late 1981.  It was quickly rejected.

Ours was a highly controversial finding due to both the high concentrations of ice that we found (hundreds  to over a 1,000 per liter) but most of all due to the temperatures at which we were reporting this effect, -8 to -12 C.   Our plane was,  in essence,  seeding these clouds with ice crystals, changing their structure.  Since the volume affected was initially quite small, it was likely that only having the viewing dome allowed us to find them on the second and third penetrations of the clouds.

This inadvertent aircraft effect had even been looked for by our aircraft group leader, Dr. Prof. Lawrence F. Radke before I had arrived and after the University of Washington acquired the B-23.  He didn’t find’em though.  Larry was also aware that an aircraft COULD do this in those early days with the B-23.

So, when I found them and a paper began taking shape, the skeptical Larry Radke called them,  “Art-PIPs.”  It was so funny.

Later, with the skeptical Larry at the helm, we got some money from the NSF to try to produce them in various clouds, and sure enough, we did.  It was amazing finding those crystals in those test flights since even I couldn’t be absolutely positive sure that this was real.  Why hadn’t this phenomenon been reported decades ago?   That, too, was part of our problem:  why you, why now?  And why hadn’t I seen the holes and canals of ice produced by aircraft as a cloud photographer for decades even by then?

Some ground observers had seen trails and holes in “supercooled” clouds like Altocumulus.   Those holes and canals were occasionally reported over the decades (!), but not in the technical journals.  A couple of really lucky observers had even seen the type of aircraft that had caused them.  But the airborone research community, ignored or did not know about these reports, ones that appeared in non-technical weather magazines like Weatherwise, Weather, and Meteorological Magazine (the latter two in England).

Furthermore temperature data were nearly always absent in these visual reports.  So, it could be reasoned they had occurred at very low temperatures, below -25 C or -30 C.  Clouds that cold, but still consisting of only or mostly of liquid droplets do occur, the ones in which an aircraft could leave an “ice canal” or a “hole” with ice in the center, falling slowly out.

If we had been reporting our finding at cloud temperatures of -25 to -30 C, maybe we’d have got into the journal on the first try and reviewers would have yawned.  But at -8 to -10 C cloud temperatures?  No way!

Why?

Research aircraft had been going back and sampling the same cloud, usually a Cumulus one,  for a couple of decades by the time of our report.   Furthermore, those aircraft re-penetrations were almost always in the same temperature domain that we were reporting this effect, to about -5 t0 about -15C.  And one of the main findings in those early days of aircraft sampling was that nature was producing far more ice in clouds than could be accounted for in measurements of ice nuclei, particles on which ice can form.  Concentrations of ice nuclei were largely determined from small cloud chamber measurements made on the ground.

These early cases of high ice concentrations in clouds with tops that were not very far below freezing (greater than -15 C) were called cases of “ice multiplication” or “ice enhancement.”   No one understood how such ice developed and many theories were put forward initially in the 1960s.  The issue was largely explained by the “Hallett-Mossop riming and splintering mechanism”, a mechanism discovered in the mid-1970s and today is still believed to be the primary reason for high concentrations of ice crystals in clouds with tops warmer than about -15 C.  Oh, yeah, ice multiplication is real and NOT due to aircraft penetrations!

But our paper on APIPs, if true and published,  would cause researchers to have to go back and look at their research data (even us!) and investigate whether their own aircraft had contaminated their published studies with artifact ice crystals.  An entire body of airborne literature would come under question.  This was not a pleasant thought for anyone who had  conducted such studies.

Why would you go back and sample the same cloud?

To see how it changed with time.   How many ice crystals formed as time went by?  Where, and when?  These were techniques used in trying to get to the bottom of the “ice multiplication” phenomenon.  In fact, the Chief Editor of JCAM himself was involved with numerous aircraft that sampled clouds in a huge summer Cumulus cloud study program in Montana in those days (called “CCOPE”-Cooperative Convective Precipitation Experiment)  That study, like so many other airborne studies, was to determine how ice onsets in clouds, how high the concentrations of natural crystals were in clouds with various cloud top temperatures, and the potential of cloud seeding to increase rain.

While academic scientists did not particularly welcome these reports and were dubious and largely ignored them (did not change their aircraft sampling strategies), or when they looked could hardly find any APIPs, it was soon evident that purveyors of cloud seeding services were elated!   Our finding suggested to THEM that all that natural ice formation reported in re-penetrated clouds  in research articles over the years might be wrong, and rather due to ice produce by the aircraft!  Maybe those clouds that had been reported with a lot of natural ice, which made them unsuitable for seeding, was because the researcher’s aircraft had produced it, not nature.  Purveyors of seeding would like clouds that are below freezing, about -5 C and colder, with no ice in them.  If the concentrations of natural ice crystals forming in clouds ice get to 10s to 100s per liter,  those clouds are deemed unsuitable for seeding to add more ice.  The crystals might be too small if you add more in those cases, and not fall out.  If surveys of clouds in a region find that they have lots of ice in them, its “no paycheck” for commercial cloud seeding interests. (Usually, cloud surveys aren’t done before commercial programs begin.)

Thus, those who had interests in cloud seeding actually saw our result as a way to discredit findings of high natural ice concentrations in clouds, findings that made them appear unsuitable for seeding.  It was a bogus argument since numerous FIRST penetrations of clouds had encountered high ice particle concentrations, still, they had SOMETHING to hang a hat on.

This was indeed an ironic twist, being supported by the cloud seeding community!

Me, usually with Peter Hobbs as a co-author, had been discrediting various published cloud seeding results in the literature via reanalyses and journal commentaries for several years (e.g., here) when our APIPs finding finally hit the “streets” in 1983.

Given these a a priori possible biases between academia and in the commercial cloud seeding world in detecting APIPs you can imagine where the major “confirmatory” studies of this phenomenon came from. Yep, those associated with cloud seeding programs!  It took 8 years (1991) for our finding to be independently confirmed (the best way) using several types of aircraft in marginally supercooled clouds.   Then pretty much the same workers amplified their findings with another paper in 2003 WOODLEY et al. 2003.  For those of you who don’t know the cloud seeding literature, Woodley and Rosenfeld and Peter and I have had a major clash in the cloud seeding literature (i. e. and big i. e., and bigger still)

We loved it!  They loved it!  Even the great John Hallett got involved and found in lab experiments that the mechanism was the extraoardinary cooling at the prop tips, momentarily down to -40 C, a temperature at which ice forms spontaneously in high concentrations (here).  It had also been suggested that prop aircraft could do this by the late Bernard Vonnegut back in the late 1940s in a less widely distributed report from a General Electric research lab and in the J. Applied Physics.

Today this phenomenon is taken pretty much for granted, and has been more widely detected from time to time in satellite imagery in thin clouds as here.  In thicker clouds, the effects of aircraft go largely undetected.  Recently, in a widely distributed news release that accompanied their formal publication, Heymsfield et al reported a case in Colorado in which aircraft-produced ice effected a snow shower on the ground instead of just being a hole or canal in some thin clouds as we normally see.  They opined that aircraft could actually help delay flights from the airports that they were taking off from or landing at in special conditions.  (That’s what the Wall Street Journal article was about.)

Why was it an “embarrassment” to the airborne research community, as John Hallett (of Hallett-Mossop) asserted?  Because they should have found out about APIPs right from the get go, especially in view of the occasional lay publications that had photographs of ice canals in supercooled clouds even in the 1940s, ones  that could only have been produced by aircraft.  It turned out to be a major oversight.

Below, a cartoon I did before the paper was accepted making fun of how a researcher, thinking that natural ice multiplication processes were taking place (i.e., the Hallett-Mossop riming splintering mechanism) might overlook all those ice crystals streaming off, in this case, the Husky 1 aircraft.

Below, some photographic evidence of what aircraft can do to supercooled clouds, the last one taken about two weeks ago over the Cat Mountains.

Finally!  The End.

 

 

 

 

 

 

 

 

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1The 6-year old horse in question is about 15 hands, 1200 lbs, not really a Clydesdale.  I have overemphasized our horse’s size for personal reasons.   You don’t want to be injured getting bucked off a Shetland pony, but rather something HUGE!  It just sounds better.

2That B-23 aircraft, wherever it went, brought a crowd out to see this antique “tail-dragger.”

So Seattle

Seattle nostalgia part

Got a little homesick yesterday with the weather the way it was here in Catalina.  Well, after 32 years in Seattle it seemed like home.  The dank, gray, low-hanging, lifeless, overcast skies of Stratus and Stratocumulus clouds hour after hour (spoken with emphasis on each descriptor using a whiney kind of emotional voice) reminded me of all the great times in Seattle, the friends, the occasional unsatisfactory girl friend (hahaha), the sports glory days in the Western International League semi-pro baseball league (well, there was one day in particular), the days as a Mariner batting practice pitcher in the equally dank Kingdome, an edifice that mimicked the skies outside, the 25 years or so of bike trips to and from the University of Washington under those same kinds of dank, gray, lifeless skies, and piddling rain we saw here yesterday.

And with people here driving around in the middle of the afternoon with their car lights on, it was the perfect replica of a Seattle winter day. Even the temperature cooperated here to mimic Seattle;  it only changed a couple of degrees from dawn to the mid-afternoon high of 47 F, some 20 degrees or so below normal.  Sometimes in Seattle, the temperature is the same all day because the sun is so weak and the layers of clouds, piled one upon the other, seemingly impenetrable to light and heat.

The Seattle mimicry was completed with some light rain in the morning here, raining just like it does in Seattle, barely accumulating hour after hour but there to annoy you.  We only had 0.02 inches after 7 AM LST, but it stayed wet all day here just like back at my old Seattle home.  The grass in the backyard there might be dry sometime in April, otherwise your shoes and your dogs come in wet everytime.

Yep, that’s what Seattle is like.   I loved it there….  Hmmmm.

Well, what I really loved was being at the University of Washington during the glory days of the Atmospheric Sciences Department when all the “big guns” in meteorology were there it seemed;  Holton, Hobbs, Wallace, Reed, Charlson, Fleagle, Bussinger, Leovy, Houze, and the job of flying around in clouds in the “CARG” aircraft, etc.  Their kind will not be seen, clustered together like that, anyway, again.  As a kid I tried to get autographs of the big stars in meteorology like Jacob Bjerknes at UCLA so that’s why being at the U of WA was so exciting.  They were to me like major league ball players were to other kids, though I did like Ted Williams and the Bosox in those halcyon days. Egad, enough!

A review of yesterday’s clouds below.  The first photo toward the Tortolita Mountains (obscured) and a near perfect example of Stratus, followed by two shots of Stratocumulus.

Weather and clouds part

Yesterday was interesting in several ways.  First the rain fell from clouds topping out at a modest -10 C, something we don’t see much of in Arizona.

Second, it was so dark during the day even as the clouds became shallower as the day wore on. Below are the two soundings from TUS for yesterday from the U of AZ, the first at 5 AM and the second 12 h later at 5 PM LST.  Where the green and white lines come together mark where the clouds were.  From that description you can see that they were topping out around 700 mb, or around 10,000 feet above sea level in the morning, and maybe 9,000 feet by evening at about -6 C.  No echoes were being observed by the afternoon.

But why?

Well, the cloud savant will know that there must have been a lack of ice crystals in those supercooled clouds in the afternoon (ones whose tops, at least, were below freezing.)  But why no ice?  Almost certainly it was because the cloud drops in those clouds were smallish, less than 25 microns in size, there were no “ice nuclei” active at those higher temperatures (a normal situation).  The lack of drizzle (fine misty rain that appears to float in the air) is evidence that the drops in those clouds did not reach sizes larger than 30 microns in diameter. Drizzle drops (those between about 100 and 500 microns in diameter, have often been associated with the onset of ice in clouds at temperatures of -4 to -10 C over the years.  But not always.

BTW, the formation of drizzle helps eradicate clouds by draining them of their liquid water, causing clearings.  So the absence of drizzle due to smaller drops helped “seal the deal” on a long day of overcast.  Also surprising to me was the amount of underlying haze yesterday, again evident in very strong crepuscular rays late in the afternoon.  See below, along with the rare example of liquid cloud mammatus formations.  That haze suggested to me that the drop concentrations in yesterday’s clouds were also pretty high, and helped keep the sizes of the droplets down by spreading the “condensate” on more particles. And guess what, those likely more numerous and smaller cloud drops helped make those clouds darker than clean clouds.   More sunlight is scattered back into space by dirty clouds than by clean clouds, so the bottoms of dirty clouds are darker even given the same thickness as clean clouds.  (This is a HUGE issue in global climate models, drizzling and not drizzling clouds because it effects the cloud cover, and the more cloud cover you have, the more CO2 warming is offset.)

So several factors likely went into making yesterday “so Seattle”; lack of precip later in the day, small cloud drop sizes, likely due to high droplet concentrations in those clouds, at least later in the day.  Lets hope it doesn’t happen again.   The End

Addendum on cloud seeding potential for yesterday

Yesterday was the perfect day for seeing what you can do by seeding clouds with dry ice–dry ice is more effective on days with marginally supercooled clouds.  Would there have been some rain on the ground?  You betcha with those low bases.  However, it is virtually certain that any rain would have been but a trace, or barely measurable.  The main thing that would have happened is that clearings would have ensued in the seeding zones, seeded by the way, by aircraft dropping dry ice into those tops.  So, a little precip, and some clearings, and those clearing would have likely triggered a widespread natural clearing if you could get enough holes produced by your aircraft.  The last photo shows would you can do when you glaciate a relatively thin layer cloud.   Were yesterday’s clouds thin enough for holes?  I think so.


31 hundredths and counting; December total for Catalina now 2.59 inches (normal, 1.72 inches), Seattle has only had 0.25 inches this month! We had more last night than Seattle has had all month! Planet, CPC, out of control!

Pretty excited there in that title, and haven’t had that much coffee yet.   Whenever strange weather occurs, I always like to kid friends who might ask, “What’s causing this strange weather?”,  and say that the best explanation is that the “planet is out of control.”  hahahah.   Oh, well, its the best I can do.  No one really can tell you why we have had so many (great) cut off lows this year in the Southwest.  Totally unforeseen.  I didn’t expect that it would still be raining this morning at 6 AM either.

Also, remember the CPC’s (Climate Prediction Center) prediction for November, December and January made back in late October?   Due to the La Nina regime in the east Pacific, Seattle and the whole Pac NW was supposed to get hammered with excess rain and snow, and the SW was supposed to experience “intensifying drought.”

Didn’t happen, and can’t happen, even if it dries out in January.  It just goes to show that these several monthly type predictions are dicey, probably more often right than wrong, but they can’t be counted on too solidly.  Also, we know that the La Nina regimes exert their greatest influence in later winter and spring, so we could still dry out a lot after December’s excesses.

Regional precip reports are here where you can see some places got 2/3rds of an inch out of the little (cut off) guy.  How fine is that?Also, what’s really great, too, is all the rain that has and will be falling in NM and TX, taking a bite out of drought thanks to this same storm.   Below, 24 h precip totals fro the US and AZ deduced from radar from those WSI Intellicast weather guys and gals below.   Note that the Tucson area and Cat Mountains got the most of anywhere in the state.

More detail on the AZ rain can be had at the U of A rainlog site here.   BTW, joining this org as a measurer-reporter would be a nice thing to do.  How about getting a rain gauge for Christmas and joining up with the rainlog gang?

Quitting here for awhile.

Yesterday’s contrast to “the most interesting” clouds of three days ago

Forgetting about the fact that not one of the cloud types the so called “cloud maven” predicted showed up yesterday–perhaps he is not really a cloud maven after all–today we will look at cloud microstructure again which will help us to forget.

First, the rain:  Baja low beginning to spin toward Catalina, nice rainband forming in western AZ, should get here this afternoon.  Monitor it here.  Also, current clouds overhead will be getting colder on their tops as they deepen upward, and so showers are likely to begin appearing on radar before that rainband gets here, especially on the Catalinas.  Monitor those local shower formations here.

Today’s “lesson” will be that it was interesting that the TUS sounding for yesterday afternoon was almost exactly a replica of the day in which we had slightly snowing clouds and I wrote a kind of long, boring piece about how exciting it was  for ME to see shallow Stratocumulus clouds here in Arizona snowing when the tops were only -10 C  (14 F).   See fine, hair-like virga emanating from Stratocumulus clouds at right on that day.  They were the most interesting clouds.

Not supposed to happen, or is very rare here in AZ. I blamed it on clean air  after the rain in that tome, and that extra clean air likely led to larger cloud drops (cloud drops are defined as those smaller than about 50 microns in diameter; they don’t have appreciable fallspeeds).  “Larger” cloud drops,  to us met men,  would be ones bigger than about 25 microns.  Between 30 and 40 microns in diameter, they can then start bumping into each other and coagulate-coalescence to form drizzle drops (defined as those bigger than 100-200 microns in diameter because they then have appreciable fall speeds, a coupla meters per second), or grow into even rain drops (defined by met men as bigger than 500 microns in diameter).  These definitions are somewhat gray, not exactly black and white; not because the drops are in gray clouds, but because these are based on a continuum of fallspeeds.  For example, some scientists such as the great Judy Curry, have referred to drizzle as a drop but 50 microns in diameter.  BTW, to add some human interest to this dry piece, I know an awful lot of Judy’s these days and the first girl I had a crush on was named Judy.

So, with yesterday’s afternoon sounding we had these clouds below, tops according to the TUS sounding at -10 C, probably even a little colder over the Catalina Mountains, and nary one ice crystal was to be seen.  These clouds resisted ice formation even though they were cold enough to require quite the bundle of clothes had you been up there.  What happened?

I blame it on air again, but this time, “bad” air, air full of particles.  Take a look at this photo from yesterday.  You can just see that bit of haziness below the Stratocumulus clouds.
A real cloud maven might have started to ruminate that, “Its gonna be harder today for these clouds to form ice.”  I had no such thought myself, but was still looking for all those “no show” clouds.  Then at the end of the day, as the clouds filled in I took a couple of shots of “crepuscular rays”, those rays of sun between the clouds that illustrate the presence of dirty air.  Here is one of those shots.  By this time I was looking for virga, knowing full well that those clouds up there had to be “supercooled” (still composed of liquid drops though below freezing–the kind of thing that causes icing on aircraft.

Contrast the strong  “rays” of yesterday with the fainter ones of those on the “clean  day” shown next.  Note, the air always has some particles in it and there will always be something in the way of “crepuscular rays.”  I hope you can notice some differences here.  What that dirty air meant was smaller drops in those clouds than we saw on the clean day, and the smaller the drops, the lower the temperature at which ice forms.

Cloud seeding potential yesterday because the clouds were below freezing and not shedding ice?

Yep.   However, because of the realtive high bases of those Stratocumulus clouds yesterday, little rain would have reached the ground in Catalina or elsewhere in the lower areas.  Mt. Lemmon?  I think you could have produced a couple of inches.  Also, the SE flow was creating the “best” thickest clouds over and upwind of Pusch Ridge rather than over Mt. Lemmon as seen here in the U of A time lapse movie to some degree. Gee, I did see some brief Altocumulus lenticularis here.  So, one of the clouds mentioned did show up.

Below the TUS sounding for 5 PM LST yesterday, one that shows the clouds were based around 10,000 feet, above Mt. Lemmon as you could see, and topped out at -10 C.

Low spin cycle continuing off Baja; water being added

That enfante terrible now dawdles over the coastal waters of California and northern Baja today, adding some water to its central system as seen here from IPS Meteostar.  Note, too, a scruff of Stratocumulus clouds racing northwestward in the Gulf of Baja abouit the latitude of the border between north and south Baja.  This is good.  Still, this is a marginal storm as it trucks through on Sunday evening and I will be happy if we get a quarter of an inch.  Mods don’t think rain will get here until the upper center is upon us later Sunday.   Here is the whole map forecast sequence showing temperatures and winds aloft at 500 mb from the U of Washington unranked Huskies who play #12 Baylor in the Alamo Bowl –what a horrible bowl game that is for Baylor–on Dec 29th.  Still, as a spin off myself here into the SW like all of our lows this year, but from the U of WA, I will be rooting, of course,  for the “company team” along with my friends and former grad students with whom I worked.  BTW, these are pretty maps with lots of color as you will see.

You will also notice in this 4 day series of forecast maps for 500 mb that yet ANOTHER low drops into the Yuma area replacing the current one that begins to move toward us later today.  That new low develops via the back door from Colorado and nests over Yuma as a cut off at the end of the forecast cycle above.  That ‘s an unusual trajectory for a low! However, mods think its too dry to produce any rain as you might imagine.   But with another low center aloft ending up in the SW, it demonstrates again our characteristic pattern for this early half of the winter, having become something of a low magnet.  It certainly has been strange to see so many cut off lows.

BTW, the longer term picture after our little rain is a dry one for the next two weeks;  it may well mark the end of our cut off low fantasia.  Hope not.

Today’s clouds…

The marginal amount of moisture circulating around the periphery of this Baja low, I think will spin out some spectacular middle and high cloud streaks and patches over us such as Cirrus, Cirrocumulus with its tiny granulations, and Altocumulus lenticularis here and there, ones that often break up into small and interesting cloudlets downstream.  Get yer cameras ready!  Some of this began to happen yesterday afternoon.  Sometimes you see the most amazing tiny delicate patterns, very photogenic.

Here are a few shots from yesterday, beginning with that sunrise patch of Altocumulus and ending with a sunset shot.

Dry low in spin cycle for two days over Baja; WATER in the Sutherland!

Our latest cut off is now “in place” over northern Baja, California.  Below is the latest map (5 am today) combining satellite images with the 500 mb contours from the U of WA.  Now it will sit and spin before moving off to the ENE and the center passing right over my house here in Catalina Saturday night into Sunday morning.  Makes me feel important to have a low right over me because me and you will be the center of attention as well as under the center of the low on all the weather discussions around the country.

Now, it is true that this low is pretty dry right now, not much going on in the way of rain anywhere (check here), but, sitting where it is, that will change and we should get another “decent” rain out of this beginning Saturday night into Sunday morning.  SOP QPF?  Maybe a quarter of an inch of rain.  “SOP QPF”?   Just a quick eyeball assessment based on patterns, not on models right now.  But our great model output from the U of AZ here will have something to say about this later this morning when the model run is finished.  But why wait for it to finish and have a better forecast?  Because you wanna know NOW, and I have to go on and do something else.  Besides your favorite TEEVEE person and the NWS will have all the gory details when the model run is finished anyway.  So, really, I am of no use whatever here.  I’m feeling sad now.  But I’ll get over it.

Note in that satellite loop how high clouds are appearing in central AZ.  Those will be increasing and appearing more upwind as the low sits where it is, eventually deepening into rain/snow showers over the high terrain in the north and in the western part, and then as it moves off, a nice band of rain should move through here Saturday night.

 

With this low sitting there for awhile, we could see some really interesting Cirrus and Altocumulus clouds in delicate patterns I hope, and great sunsets before the rain gets here.  I really hope to see some Altocumulus castellanus this time.   That will be one of the best parts to this little guy spinning down there.

Another great sight is all the rain and snow predicted for NM and TX as this low finally, and slowly, trudges across the Southwest (seen here–hit the play  button to see the whole loop).   Once again this should do wonders in helping to knock out the awful drought in those areas.

The End.  Maybe some nice cloud shots tomorrow for tomorrow’s harangue.

Actually, its not the end because I just remembered that I forgot to mention that I saw WATER in the Sutherland Wash and one of its tributaries on a horseback ride yesterday!  How great is that?  Below, a former riding partner’s horse that I bought and now ride, “Big JohnT”, romps in a tributary to the Sutherland.

The most interesting clouds–technical discussion ahead; skip now if you have a headache

Well, to me, anyway, those flat, thin ones yesterday (Stratocumulus, and Cumulus fractus, humilis, mediocris, if you want some names).  The thicker versions of these clouds were shedding ice and snow but weren’t very cold and that’s what made them interesting.  Take a look.  If your eye is calibrated you can see that light snow is falling on the Catalina Mountains in the first two photos, and in the third photo, one that better illustrates how thin these clouds were (probably 2,000 to 3,000 feet thick is all), snow is seen falling in the distance from the cloud above and to the right of the white roof of the shed in the foreground.  Quite remarkable.

Why?

According to our TUS sounding data, these clouds, at least at 5 AM LST, were topping out at only around -10 Celsius (14 F), a very marginal temperature for ice formation in clouds in Arizona.  By the afternoon, the TUS sounding was suggesting the clouds near the sounding balloon were as warm as -3 C (28 F), too warm for natural ice formation.  (Where the temperature and dewpoint temperature lines come together, right now, over me.)

If you go to the movies, the time lapse one from the U of AZ here, you will see that the clouds were coming toward TUS from the Catalina Mountains by the time of the afternoon sounding, and therefore its not valid for the heights of those clouds over the mountains–the air has sunk coming off them.  So, the best we can do is probably with the morning sounding and assume the clouds were topping out at the -10 C level with bases about 0 C to -2 C.  You can get base height from where they were intersecting the Catalina Mountains (the cloud, not the snow!).  That was at about 6,000 to 7,000 feet elevation, roughly 4,000 feet above ground level here in Catalina.

So, we had pretty cold bases, and not very cold tops.  When we see ice coming out of clouds like these (and I would estimate from airborne experience at the U of WA, that those concentrations of ice coming out of those clouds were a few to 10 per liter).  If that estimate is correct, then we would say that these clouds exhibited “ice multiplication” or “ice enhancement.”  That’s because we don’t expect concentrations that high in clouds with tops around -10 C.  That is,  unless something “extra” is going on to add to the very few ice crystals that might have formed without “multiplication”; perhaps only 1 in 100 liters at -10 C.

So wha happened?

Our most accepted theory is that the very few lead to the many in collisions with cloud drops.  Those cloud drops, when a bit larger than usual (24 microns in diameter for a number), shed ice splinters, and those splinters go on to populate the cloud.  It takes a long time because the itty bitty splinters have to grow to sizes where they can collide with cloud drops, too.  This ice enhancing mechanism, referred to the Hallet-Mossop riming splintering mechanism, named after two scientists named Hallett and Mossop (hahaha), is known to only occur in the temperature range of -2.5 C to -8 C.

Those temperatures were indeed found in our little clouds.  So, too much ice explained!

Not quite.

In little, cold-based clouds deep into the continent as we are here in Arizona, it would NOT be expected that the droplets inside those thin clouds would be large enough (as big as 24 microns in diameter) so that ice splinters would occur when colliding with the rare ice crystal, the 1 in 100 liters one.

So, that’s the mystery of yesterday.   These clouds DID look kind of “maritime” to me.  In maritime clouds, such as those found in onshore flow along our coasts, drops reach that critical size for riming and splintering just above the bottom of the cloud.  That’s because the air is clean over the ocean as a rule,  and so there are few particles for the moisture to condense on, leading to larger drops right away, and many fewer in a liter than in continental clouds.   A typical maritime cloud has less than 100,ooo drops per liter, whereas a “continental” cloud would have several hundred to a half a million drops per liter and even more in some polluted areas.  So, as a drop, its hard to be a big deal in a “continental” crowd like THAT!

Best thought is that the heavy rains of late cleaned the air hereabouts and those clouds that looked soft and “maritimey” yesterday REALLY were like maritime clouds found over the oceans away from land.  Maritime clouds, as ours might have been,  have large drops in them, and even drizzle and raindrops before reaching the freezing level.  Therefore,  ice forms in maritime clouds at the highest known temperatures for natural ice formation, -4 C to -7 C.

The End.  You might want to rest for awhile if you got this far.

The weather ahead?  More rain, continued below normal temperatures as another “cut off” low rolls off the jet stream table in the north Pacific and falls into the Southwest and Baja area in the next coupla days.


Drought staggering after heavy rain/snow punch, may go down someday; more blows ahead

Any winter storm that drenches the Catalina area, including Saddlebrookians, Oro Valleyians, with more than an inch of rain in 24 h has to be one of the greatest.    Haven’t seen this much winter rain in since the so-called “Frankenstorm” of January 2010 when we got over 2 inches of rain in two days.  Here are the gaudy 24 h totals from the Pima County Flood Control District, ending at 3:34 AM this morning, about 24 h after the rain started Pima rain.  Other interesting rain totals can be found in the network established by the rainlog folks at the U of AZ here.  These totals are a bit smaller than those I culled from the Pima folks since the ob time for the rainlog network is at 7 AM LST, and here, 0.41 inches had fallen in the first few hours yesterday, and then 0.99 inches for the rest of the storm (0.01 inches just now!), for a total of 1.40 inches here in Catalina.  So, the storm totals at rainlog are broken up into two days (the rain pretty much fell in the 18 h from 3 AM yesterday to about 9 Pm last night).  BTW, a nice way to look at the comings and goings of the local rain is via the Weather Underground’s maps with animations of the TUS radar superimposed on a regional map showing our many “personal”  weather stations (e. g., here).  Its interesting that many of you do not have a personal weather station.  Well, the holiday season is here, and the economy can always use some impulsive buying and so maybe now is the time to pick one up before more storms hit.  And they will, as our models continue to show.  BTW2, a rainbow landing on a personal weather station.  Think about it.

In  just 36 h from now another low center barges into Arizona from the NW.  Due to its long overland trajectory, it’s going to be a lot drier than “Frankenstorm Junior”, once again, as another in a winter long series, stagnates in our area as a “cut off” low spinning around flinging rain around its margins for a couple of days (Friday and Saturday mostly).  So with luck, we might pick up another quarter of an inch or so.  Here is a quick look at that whole sequence, and one of the panels below, valid for Friday afternoon at 5 PM LST, for your viewing pleasure.I like this format with the four panels since you got yer upper map in the upper left hand panel showing yer cut off,  and you got yer precip in the lower right hand panel, all  in one jpeg; more cumbersome in the US model presentations I’ve found to have this much info in one jpeg.

So, what about our drought status after all this early winter rain (see below)?

Well, as I have learned from the State Climo office in 2010, not much changes due to a couple of months of wet conditions here, such as we had in 2010 when water was flowing everywhere in southern Arizona later that winter.   Seems for those folks that designate whether an area is in drought, there have to be almost years of wet conditions for the designation of droughty conditions to be removed from their maps.  Its pretty discouraging.  Perhaps it takes wide tree rings to indicate the drought is over (hahahaha, sort of)  ((just kidding!)) (((Really))) ((((Not being sarcastic at all))))

Below is the latest drought map from the Drought Monitors at the University of Nebraska-Lincoln as of December 6th, when they last released a map, we here in southern Arizona were still in an “extreme drought” in spite of all the rain in November and early December.  It will be interesting to see how this map changes after our “Frankenstorm Junior” of the past two days, and with all that rain that has, and will be occurring in the droughty areas of NM and TX.   The longer term model forecasts punish (delight?) those areas with widespread heavy rains over the next two weeks.  Will it remove any of the “extreme” and “exceptional” drought designations for them?  Stay tuned.

At LEAST we have avoided the Climate Prediction Center’s fall forecast of intensifying drought here in AZ over the period of November-January.  Seven weeks into that forecast, we have dispelled that notion, anyway.  It ain’t happening.  It would be hard to take another NDJ like that of 2010-2011 when only December had any rain at all!

Well, Mr. Cloud Maven person had better post some CLOUD photos if he is to remain that and stop squawking about drought…

Here are a couple from the
 storm.  The Catalina Mountains are so wonderful when draped in precip and snow!  I would like to report that I am very happy living here full time in Catalina.

The End, though the image organization will be a mess for awhile, will “publish” now anyway.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Grandson of “Frankenstorm” knocking on Heaven’s door (Catalina, Arizona)

Well, I think Catalina, AZ,  being next to the Catalinas, is “Heaven’s door”.   I think, too, to have a second consecutive thought,  that we’ll get more than an inch out of this Big Boy which is rare here in Catalina for a storm in the wintertime.  Not close in areal extent to the original “Frankenstorm” that struck the West Coast in January 2010 with record setting low pressure, but a potent one anyway.   In the January 2010 storm we received 1.41 inches the first day and 1.18 inches the second to “ice” a fabulous wildflower bloom that year.  We sure seem headed to a fabulous bloom season this year, too.

BTW, there has been a lot of rain in droughty Texas.   We are brothers/sisters in drought relief it seems these days.  How nice; adds to the holiday cheer.  Maybe the price of hay will go down..  It seemed interesting to throw something about Texas in there.  Here is a map showing that great TX rain of yesterday from WSI Intellicast1.  These radar-derived amounts precipitation are pretty much spot on–I’ve checked ground gages a number of times.  We should be seeing “green”,  1-2 inches) over much of AZ in the next couple of days, too.  So, the map below is like a preview for AZ.

Speaking of green, look at the “green-for-rain” in AZ in the lower right hand panel of this forecast for this afternoon ending at 5 PM MST.  During the prior 12 h, beginning at 5 AM MST, the entire State of AZ is virtually covered.   I am just beside myself when I see a map like this!  And look how far to the south of Baja California the circulation of the storm extends.  Its gorgeous to see this.   I guess there could be some flooding here and there, and some “snow birds” might complain about the “crummy AZ weather”, but….you can find people who will complain about anything.  See the whole wonderful model sequence of rain and mayhem in AZ here, and in much more detail from the U of A weather department, here.

Look, too, at how excited the National Weather Service, Tucson is!  They must have 50 bulletins out–be sure to keep reading them.  They are really having a lot of “fun” down there, too.

Late breaking storm bulletin:  We have sprinkles in the area (0425 LST).  Check this radar-cloud map out from IPS Meteostar.  What a great day this is going to be!  Enjoy.   Good chance we’ll see water in the CDO and Sutherland Washes, and maybe some snow mixed in with the rain as the storm closes out Tuesday evening now.

But is this storm the end of our “fun” weather?  Oh, no, my friend.  Another cut off low develops in our area after speeding down as a trough out of the NW in five days.   Another round of significant rain is likely, though not as much as this one.

Some cloud notes from yesterday, including some chat about the unusual streaks.

In that warm afternoon yesterday, it was so great seeing sheets of Cirrus and Altostratus (ice clouds, Altostratus with heavy shading) massing on the horizon, knowing that this time it was NOT just going to be a sky decoration for a nice sunset, but were clouds filled with stormy portent. You probably noticed the lack of sunset color due to the extensive coverage of those clouds upwind. No break allowed the sun to under light them, a sign of extensive clouds upwind to the southwest.

Also, unless you were blind you saw some unusual events in the thin Altocumulus (translucidus) layer yesterday: ice canals and splotches of ice produced by aircraft that flew in them. When so many happen as did yesterday mid-day, its a good bet those Altocumulus clouds, though comprised of liquid droplets, are terribly cold. While the TUS morning sounding did not pick up this mid-day layer, one can be confident that it was likely colder than -20 C or -4 F.

What you also saw was examples of how the presence of ice within a droplet cloud, causes the droplets to evaporate, and the ice crystals to grow and fallout, something that happens on our rain days. However, because there were so many ice cyrstals produced by these aircraft (almost certainly all jets) they compete for the tiny amount of water available at -20 C and form small crystals with little fall velocity.

So the trails of precipitation are very fine and don’t go very far. Here are some examples of that rare phenomenon, rare because for us to see it, takes a thin, cold water droplet cloud, and it has to be high enough so that aircraft are frequently penetrating it. One wonders why, in some of these cases, the trails yesterday were so long with an aircraft probably could have climbed or descended a couple of hundred feet to avoid flying in a light icing producing cloud (the Altocumulus layer composed of supercooled droplets)?  Note “ice optics” in ice canal in the first photo, a weak sun dog so I didn’t just make it up that the canal was ice.  I you wanna know more about this phenomenon, go here and/or here.