Learning from clouds, or lack of them; and the storm ahead

You probably should go here for your Sutherland Heights forecasts, brought to you by that great weather provider,  Weather Underground1.

Let’s begin with an exercise in excuses with this map from the Haight-Asbury District, aka, San Francisco State’s weather department, speaking of the 60s:

Map of the 500 millibar height contours (~18,000 feet above sea level pressure) for 5 PM AST yesterday when we were in the apex of a big trough with a minor pulse of curly air (vorticity maximum, to be provide some obscuration for layman, and for laywomen, for that matter) that was approaching.
Map of the 500 millibar height contours (~18,000 feet above sea level pressure) for 5 PM AST yesterday when we were in the apex of a big trough with a minor pulse of curly air (vorticity maximum, to provide some verbal obscuration for the layman, and for laywomen, for that matter) that was approaching.  That minor pulse , toward Vegas, was helping to produce a blob of clouds and light snow showers in the northern third of AZ yesterday.  The next storm is that bend in the contours.winds off SE Alaska.  Will drawn down cold air behind it across the whole US.  Some low temperature records likely to be set in the western US, though not here.

What is interesting to cloud maven person, in looking back retrospectively at yesterday, is that he has never seen a big trough like this that is SO DRY that not even the smallest of Cumulus clouds formed here in the area.  Not ONE!   It sky was so completely clear from horizon to horizon in the afternoon that it was truly astounding to CM.

Such a cloudcast humiliation (recall that C-M foretold of Cumulus that would develop and fill in, producing virga, and a few light showers in the area), of course, provides a learning opportunity, a chance to move forward, and as such, is truly WELCOMED by the persons working in science.     :{

So, we have seen the rare time when, with a 500 mb jet core south of us, that it does not circumscribe enough moisture for even a %#$! Cumulus fractus.  Therefore, we have seen that a jet core south of us is a necessary, but not a sufficient condition for precip in the area, something we learn every so often here.  (More than 95%, but not ALL, of the Nov-Apr precipitation at TUS falls with the 500 millibar jet core over or south of us.)

It is also evident that CM did NOT believe model runs that had little or no chance of precip and decent clouds around.  Very bad, a sign of unhumble thinking, possibly arrogance.

What’s ahead?

Well, as everyone knows, a major precip situation is building up for Catalinaland on December 31st through January 1st , as you saw from the Weather Underground’s forecast, one derived from our latest computer model run.  In  that you saw that a little SNOW is also forecast for here!  Nice, for a few hours afterward that is.  Get cameras ready.  Precip seems guaranteed here.   Bracketing amounts, should be at least 0.25 inches (things really go badly), and 1.5 inches as a top possibility.

The high end forecast by CM, whose recent diminished credibility should probably be taken into account,  is due to the possibility the main rainband in the system might stall for even just a few hours longer than currently forecast.  Typically, rainrates in the band are “moderate” here, technically defined as 0.10 to 0.30 inches per hour.  So, you can easily see that if the main rainband hangs on for just a bit longer than currently forecast, totals will climb rapidly.

And, this is a slow moving, major system by the time it gets here.  Exciting days ahead!

From two days ago, I thought I might fill in some of the photos from a Christmas Day hike into the Samaniego Ridge foothills that some reason WordPress had problems with:

At the well-known watering hole called the Cement Trough.
Water ran in every crossing of this tributary to the Sutherland Wash, on that hike on the Baby Jesus Trail though the wash itself was dry.
A lady bug? Wow, completely unexpected on Christmas Day, 2014.
Flowers like Desert Marigolds are still found blooming in some locations, though these are not them. I’d tell you what they were if I could remember, flower book loaned out.


The End



























The End


1They have nothing to do with the 1960s-70s radical folk with a similar name.



By 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.