A little “troughy” here on Saturday and Sunday

Best chance for rain here, and its not that great, is later Saturday and Sunday AM as an upper level trough comes by, one that includes that bit of poor Paul, who died at sea.  Here’s what that trough looks like when its about over Catalina at 8 AM Sunday morning, this map due to the U of WA Huskies Weather Department:

Now, I will be truly surprised if I don’t see some rain hitting the ground somewhere in viewing distance around Catalina between Saturday afternoon and Sunday morning as this little trough goes by with Paul’s ashes.  But mods don’t show anything, however, at least as of now (at 5:24 AM).  Certainly, we should see some nice cirriform clouds, and middle clouds like Altocumulus, Saturday and Sunday AM.

Elsewhere in the West

Since we’re all bored with our “pleasant weather” now days, I thought I would look around and see what else is going on that might get you excited…

Unusually heavy Nor Cal rains: begin on Sunday; last for about a week associated with purple monster (trough) in map above–it sags southward along the coast.  Many inches should fall in the coastal range north of SFO (aka, “Frisco”).  Maybe we should get a field trip going, some kind of “Rain Safari” to refresh ourselves on pounding rains.  I wouldn’t charge that much.  Also, during the trip, I would pack in a LOT of information, like that in the paragraph below, which provides some trip details.

We would go to Shelter Cove, CA,  and the King Range north of there to get that rain fix.  Now, I have linked to some nice photos of this area but you would not be able to see any of those because the clouds would be based at only 300-500 feet above the ground at the coast, and everywhere else would be mostly IN the clouds.  The King Range, 150 miles or so north of Frisco,  juts up from the ocean suddenly to about 4,000 feet, which causes a lot of water to be condensed in the clouds during onshore flow.  The drops get bigger in those clouds over and upwind of the King Range, bigger than 30-40 microns in diameter at which point they can collide and stick together forming a much larger drop that falls faster and collects more drops on the way down and,  before you know it, those drops have reached millimeter-sizes (real raindrop sizes) in a hurry.   This rain-forming process called the “collisions-with-coalescence” rain mechanism or “warm rain” mechanism because there is no ice involved and it is seen on radar as a situation where there is no “bright band” where level where snowflakes are melting into raindrops as is usually seen when its raining steadily.  This situation is also called, “non-bright band” rain, something that is quite common along the West Coast but you knew all this already.  That kind of rain formation rarely happens here in AZ because it takes extremely clean air in which few cloud droplets can form in the clouds and being fewer, are larger, and here we have too many sources of aerosols and “cloud condensation nuclei” to have really pristine clouds in which this can happen.  The result here is more  and smaller drops in our clouds, ones too small to bump into each other and stick together.  I will point out those days here when the warm rain process is active–our rare wintertime drizzle (tiny, close together drops that almost float in the air) occasions are due to that process.  Some periods of that heavy Cal coastal rain will certainly have a LOT of ice mixed with liquid droplets, and those liquid droplets are either collected on snowflakes as they fall, or evaporate in the presence of ice and that water vapor that evaporated from them then deposits on the ice crystal causing it to grow (the Wegner-Bergeron-Findeisen mechanism of precipitation formation), too, so it would be quite interesting for you to go there for that, too.  You would experience two of the three kinds of rain-forming mechanisms.  (The other one, often seen at higher elevations,  like in Colorado, is where precipitation, usually very light, is formed soley via ice crystals without any liquid droplet cloud being involved.  Many textbooks overlook this third one.  Its great being on the internet and having a blog where you don’t have to worry about packing in too much information and worry about where sentences/paragraphs should end and begin; just get it out there and you’re knowledge-hungry audience will dissect it eventually.

I suppose if we drove in a marathon drive, some people would want to jump out due to info overload now that I think of it.  Of course, I would not be providing “empty” info calories, but full ones.

 Yesterday’s Clouds?

Ci uncinus with moon shot; can you find them?  BTW, Ci uncinus and other forms of Cirrus clouds are good examples of the all ice precipitation mechanism.

5:43 PM.

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.