Return of the cut offs followed by a Pac blast

While waiting for the to the 10-15 day forecast to resolve itself, most reliably experienced by having those days that used to be two weeks away get here,  we can get a more reliable fix on the next few days to a week.

Take a look at these WRF-GFS model forecasts based on last evening’s global measurements of 500 mb flow rendered by IPS Meteostar:

In looking at those, its pretty remarkable that the “weather” has remembered to place some cut off lows down in the SW as it was doing off and on throughout November and December, ones that helped our rain and snow totals zoom above average!  Like a sad love affair you can’t get out of your mind, one that keeps coming back to remind you how bad it was, the weather, too, in something we weatherfolk call “persistence,” tends to keep coming back to the same pattern, even after long breaks like our recent three week sunny malaise, in which I thought the cut off pattern had been forgotten about.  In the first panel for tomorrow, an elongated bend in the winds is passing over Arizona.  Then part of that “trough” shears off into a circular whirl over eastern New Mexico and west Texas.  Cut off magic!

This is followed by another dollop of the jet stream that breaks away from over the Pacific NW (that bend in the winds in the second panel up there), shears off from the main current, and ends up as a whirl over southern Arizona by next Friday. the 13th.   As you know, ones in that position have a lot of promise for providing a decent rain, such as the 0.25 to half inch we’ve gotten out of several of the prior cut offs in that position.    The first trough is too dry and goes by too fast (tomorrow the 8th) to produce rain except well east of us.  We’ll only see the temperature plummet.

So,  here we are again in the cut off regime, at least in the week ahead.

Pac blast

Beyond our little cut off low spell, the models are starting to rev up the central Pacific flow that breaks into northern and central California, flow that would be associated with tremendous rains (ones you will read about it in the newspapers) if it happens like this.   And in this latest model run, some of that rain dribbles into Arizona (on Friday, the 19th) with SEVERAL more chances for AZ rain in quick succession after that during this Pacific blast that rips into the West Coast in the days ahead.  The change in circulation is stunning!  Below is an example of what is predicted to happen by Sunday, the 21st of January,  of one of my favorite patterns whilst growing up in southern California.  Overall, the rains begin to move into northern California on the 15th.

However, from the prior harangues you also know that these model forecasts have had an unusual degree of “eracticity”;  can’t be relied on too much, especially with regard to the placement of that incoming jet into the West Coast.  It will be interesting to see how this turns out (as always!)

However, it was a nice model gesture to show rain in AZ from this Pac blast this time around.

Weather 10 days from now remains uncertain

Hahahahah.    That is the funniest thing I have thought of in a long time, and its not that funny.    Take a look at this “spaghetti” plot for 10 days from now based on last night’s global data.   The map is for 500 mb, about 15,000 to 20, ooo feet above sea level.

“High predictability”, even as far as 1o days out, is indicated by those areas where the bluegreen and red lines are all close together.  For example, in the upper left hand corner, or in eastern Asia and the extreme western Pacific Ocean if you can make those areas out through all the lines.  Also, both the red and bluegreen lines themselves are pretty close together there, and that says the jet stream is extremely strong there, normal for that region in wintertime.  That jet stream is geographically anchored in that region and so not much changes there, even from winter to winter.

But then look what happens to that compact jet stream as it approaches the middle of the Pacific! It comes apart, line a twisted speaker wire that’s been untwisted.   The bluegreen lines, representing a colder portion of the jet stream, mostly head off to the NE, while the red lines, indicating a warmer portion of the jet stream, split off and continue more or less toward the east across the Pacific and into the Southwest.  However, the details of both flows, the northern one and the southern warmer one, are pretty unknown, as evidenced by all the “scatter” in the lines, the “bowl of rubber bands” you see in the east half of the Pacific and into North America (and elsewhere).  Note that the lines are tending to group that bit more over the eastern US, suggesting higher predictability, and the presence of an upper level trough (and cold in the East).

For the sake of contrast, here is the same kind of plot for just 48 h from now, showing high predictability.   Of course, things always go to HELL in the longer term, but today’s 10 day vagaries are more than usual.

So, what seems to be ahead for sure is a split in the jet stream in the eastern Pacific with one of the branches coming toward us.  That is the good part since that branch can be pretty wet if it is strong.  But, as you can see, exactly where it is, and that’s crucial, is really anyone’s guess at this point.  That warmer jet has to be south of us to have any rain with the disturbances that are shuttling along in it.  And if you look over AZ, the red lines of the warmer jet are all over the map, literally.

Hence, to use an old word there, particularly uncertain times ahead.  In fact the only thing that is certain, is with the southern branch of the jet in this area, there will at least be passing regions of clouds as upper air troughs go by.   Will they, like yesterday, only be Cirrus?  Or rainy Nimbostratus?

The second shot shows a nice “parhelia” or “sun dog” at the far right, caused by plate-like ice crystals falling face down, the normal mode.  The final shot has some the rarely seen Cirrus castellanus, Cirrus clouds with little turrets or humps at the top.

Its not worth mentioning…

…so I wasn’t going to say anything, but last night’s model run based on the 5 PM LST global data went into a dry mode for AZ over the next two weeks, sucking up all that rain that was predicted in a run just SIX HOURS before the run last night (shown on the left), and all those runs before that one!  Feeling like the model has punched me in the gut.  It was like having your favorite’s team running back score the winning touchdown with a minute left on a 79-yard run, only to be called  back due to a holding penalty.  Or, in the World Series, the Cubs have just won the deciding game on a homerun in the ninth inning, but then it turns out that the batter hit out of turn and it was an out instead.   Well, you get the idea.

Check the differences out between these two for the same time and day, Friday morning, January 20th from IPS Meteostar.  Its incredible.  That juicy, wet stream from the subtropics into California (right image)  is completely gone in a forecast made just 6 h later!

Unfortunately, the new run with nothing but an upper ridge along the West Coast, and a deep trough in the East, is a favorite mode of the Great Southwest Rain Repeller, La Nina.   In spite of the WILD fluctuations in model outputs over the past few days, you would have to give this latest one  from last night’s global data some credibility.  Its as though the model just woke up after all those predicted rainy scenarios in AZ and said, “I can’t do this, its La Nina time!”

However, with all these fluctuations, rainy scenarios for AZ may still come back.  Standing by, if a bit grumpily.  Maybe there’ll be some Cirrus clouds today to ease the pain.  Let’ look at a national satellite view from the bowl record-setting University of Washington Huskies’ weather department here:  Yep, a little band of Cirrus approaching from southern Cal.  Should be here in time for a nice sunset.

Don’t forget, too, those Cirrus clouds are usually the way the tops of winter storms appear, one with vast layers and produce hours of rain at a time, if you could slice off the topmost 1-2 km (about 1,000 to 2,000 yards, or about the same amount of yardage as given up by my former company’s (i.e., Washington’s) football team in the Alamo Bowl this December 30th).

Remembering that about Cirrus representing the tops of storms if we could only see them will help us get through today’s model disappointment I think.

 

Some more of that Catalina climo

Here is a 35 year record showing what days have had measurable rain in January.  Sometimes “singularities” in weather show up in these kinds of charts of tempearture or precipitation, such as the “January thaw” that seems to occur with some regularity in the East but is “unexplained.”  You would be looking at our chart for Catalina for example,  a cluster of days with higher or lower precipitation and it MIGHT be a singularity, something that Nature likes to do at that time of the year rather than a statistical fluke that represents nothingness.  Here’s January, a month that averages 1.65 inches in Catalina.  These data are almost totally due to the careful measurements made at Our Garden organic orchard here in Catalina–only the last few years here are from measurements on East Wilds Road.

Not much to see here.  That peak on the 6th looks more like a fluke rather than a singularity.  You would never say that one day represents a singularity, but maybe 5-10 days.

The reason why I wanted to see this was because of the striking changes that were foretold by the “WRF-GFS” model 36 h ago and were shown here yesterday.  Was there a singularity that might support a greater chance of rain in SE AZ in mid-January, and therefore, cast that bit more credibility on such a huge model change?

I would have to say “no.”  And, not surprisingly, that huge change has gone bye-bye in the models.  Nothing like it is shown now, though they do have a rain situation developing for here by the end of the 15 day run (around January 20th and beyond).    But this rain comes out of the lower latitudes of the Pacific, a completely different direction than was shown just yesterday, and if the models are correct in this pattern breakdown, it means flooding in California as the flow breaks through to the coast from the Pacific.

Below, what the models came up with based on last night’s global data, again, from IPS Meteostar, whose renderings I favor.

These are exciting times for those of us who peruse the models.

Why?

These vast changes indicate that there is something far, far upwind, perhaps a data sparse zone, errors in reported measurements that is causing a problem for the models and that more changes in their outputs may come down the line until that problem is better “resolved.”  (They are never perfectly resolved.)

So, every 6 h update of the models is a “must see”, with the persuser (me) holding his breath with excitement.  In these cases, its all “good” because a rain situation is foretold for us.  Take a look at where the jet stream is compared to where it is now, up around British Columbia.   You can see it barging into southern California and major rains ALWAYS accompany this pattern.  Also, you can probably count on at least two storms breaking through before this pattern changes much.   The reservoirists in Cal will be very excited to see this pattern develop since most of their holdings have much below capacity.  And these kinds of storms usually produce significant rain in Arizona, too, though here we would be a little far south to get the brunt of those storms in this scenario.

Pretty clouds yesterday

Can’t leave without a little cloud excitement.  I wonder how many looked up and saw this little beauty go by (shown below)?  So pretty and delicate-looking, as unusually thick virga (snow) fell from this little cluster.  It would be called, “Cirrus uncinus” at this stage.

That snowfall probably began developing one-two hours before it came over us, and the cloud patch would likely have been fluffed up on top that bit and as a mostly liquid water cloud, that is, an “Altocumulus castellanus” before becoming this “uncinus.”

Below we saw the dying remnants of that patch, the snow to finally stop falling out with the parent cloud mostly gone, and that snow continuing to dry up on the way down.  Lots of nice cloud sights yesterday, in fact.

Enjoy.

 

 

 

 

 

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.

 

 

 

 

 

 

 

 

—————————

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.