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Neil
07-14-2008, 05:23 PM
A bit of a knit pick but I am almost positive that todays comment picture ,entitled "can you see the virga," is not actually a picture of virga but of genuine rain shafts.
The clouds at ground level clearly demonstrate that the column of air through which the rain droplets are falling is mostly at saturation. Thus it is all but impossible for the rain droplets to be evaporating on their descent, which is the definition of virga.

True, the air just above these low clouds is not at 100% saturation, but I'd put money on the fact that these rain drops are making it to the ground.

I'll shut up now.

-Neil

Bill O
07-14-2008, 08:34 PM
Neil should know, he lives in virga country.

Brad
07-14-2008, 10:27 PM
Okay, I am not a weather guy. It is not fair to post a comment about seeing the Virga and not give a clue as to what it is. At first I thought it was mistyped and missing the "n" at the end. Or maybe this thread was spam that got through the Bill O filter. But, it seems to be a real topic. Just that I am clueless.

Steve M
07-14-2008, 10:52 PM
It's ok Brad, I'll fill you in. Virga is a drug that helps men stay happy longer. Or is that Viagra? Now I'M confused.

Neil
07-15-2008, 12:10 AM
From the American Meteorological Society Glossary:

virga—(Also called Fallstreifen, fallstreaks, precipitation trails.) Wisps or streaks of water or ice particles falling out of a cloud but evaporating before reaching the earth's surface as precipitation.
Virga is frequently seen trailing from altocumulus and altostratus clouds, but also is discernible below the bases of high-level cumuliform clouds from which precipitation is falling into a dry subcloud layer. It typically exhibits a hooked form in which the streaks descend nearly vertically just under the precipitation source but appear to be almost horizontal at their lower extremities. Such curvature of virga can be produced simply by effects of strong vertical wind shear, but ordinarily it results from the fact that droplet or crystal evaporation decreases the particle terminal fall velocity near the ends of the streaks. Under some conditions, virga are associated with dry microbursts, which are formed as a product of the evaporation. See cloud classification.



As Bill alluded to the air here in Utah is frequently very dry at the lower levels and much would be precipitation from high based thunderstorms fizzles out as virga. Second to last line of the definition/explanation mentions dry microbursts... yup those happen here frequently often producing severe criteria winds with little or no precip reaching the ground.

The phenomena is also quite prevalent in the hours before a nor'easter lets loose. With cold dry air in place being over ridden by warm maratime air much of the first snow evaporates before reaching the ground. This actually serves to both moisten the layer of previously dry air and further drop the temperature because evaporation is cooling process (energy goes into the phase change of water from liquid to gas).

Incidentally Virga is also Jim Salge's dog.

-Neil

Brad
07-15-2008, 06:08 AM
From the American Meteorological Society Glossary:
Incidentally Virga is also Jim Salge's dog.

-Neil
I knew Jim was on some kind of drug hoping for success - and a happier life.

Jim, did he fall out of the sky and fail to evaporate?

KD Talbot
07-15-2008, 10:51 AM
On a quick google search the first hit that would have shown up is:

Virga- Jim Salge's dog.

Wikipedia definition:

Virga - Jim Salge's dog.

It goes on and on...

I thought you'd have come up with that, Brad.

KDT

fifteendays
07-15-2008, 11:17 PM
Today I saw Virga (the dog) from my office window and I saw Jim Salge (the person) in my office. And I'm not even an observer.

Scot
MWO Staff

Brad
07-16-2008, 05:36 AM
Today I saw Virga (the dog) from my office window and I saw Jim Salge (the person) in my office. And I'm not even an observer.

Scot
MWO Staff
Yes, but you have an advantage - your office window faces south.