More March rain ahead; and not so far ahead

High cold ones that are headed this way in a curvilinear path. Image was made at 5 AM AST, annotation later.

That means that a deep Altostratus overcast will be in place by tomorrow with a load of virga and sprinkles, not really much rain since the bases will also be cold and…high. Top possible rain amount from these high cold ones is a tenth of an inch, but more likely will be traces. Chance of a trace in the area? Oh, about 99% IMO.

But that’s not our full rain destiny.

On the horizon, only a week from now, is the likelihood of a significant rain. Check the models and the spaghetti:

Valid at 5 PM AST, March 16th. You don’t need the precip prediction for this day when the 500 millibar pattern is like this, the core of the wind at that level south of Tucson. Its not a sufficient criterion for rain, but a necessary one in the cool half of the year. (Only about 5% of the rain in TUS falls outside of this criterion in the cool half of the year.

Here’s the rain prediction which I have not looked at until posting now to make the point you don’t need to look at it:

Where the model thinks it will have rained in the 6 h prior to 5PM AST on March 16th. I hope you’re happy now.

Valid at 5 PM AST March 16th. Blueish lines of cold and rain (546 decameter geopotential height contours) way down the Cal coast, and somewhat bunched (confidence indicator) for a major trough to affect all of Arizona, keep the current greening underway.

Would say the chances of measurable rain from this “incoming” are at least 90%; i. e., virtually certain. (Note that “virtually certain” is not the same as 100% certain, but its damn close.)

Problems with hoster and connections to hoster continue–must wait seconds to see what I’ve typed, then have to go back and correct the gibberish. So, not doing much as a result.

But here are a couple of cloud shots from yesterday anyway:

6:17 PM. Altocumulus perlucidus appearing to spread out, though likely a perspective tomfoolery. Thin Cirrostratus above.

Addendum: Coupla of days ago saw the rare “Cumulo-cirrus” clouds, ones that appear to be Cumulus but are fakes, up at Cirrus-levels. You might call them Cirrus castellanus. I feel these are worth sharing so that the young cloud maven person doesn’t embarrass himself or herself when making a cloud call to friends and neighbors, as you would do. They occurred on March 7th between 11:30 AM and Noon. Can you tell, upon “zooming big” that these are mostly ice clouds? If droplets were present they were there for only a short time, thus (is that still a word?) indicating that these rag clouds were at very low temperatures.

Some sounding detective work below

The 5AM AST sounding for March 7th. The sliver of moist air at 16,000 feet above sea level is not deemed the source of those rag clouds.

5 PM AST, March 7th sounding with writing on it.

The End

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.

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By Art Rangno

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