Weather

YOUR PHOTOS: Virga, or “jellyfish clouds” spotted over Metro Atlanta Tuesday morning

Ready for a little bit of science?!

Clouds in the sky give a clue to the state of the atmosphere. On Tuesday morning, Smilin’ Mark McKay spotted this interesting cloud feature, which he described as looking like an “ice cream swirl” over Downtown Atlanta.

I agree that this clouds appears like an ice cream cone, but often I see these clouds and think “ooh, jellyfish clouds!”.

But these clouds are actually virga -- precipitation (including rain and/or snow) falling but evaporating before reaching the ground. Virga illustrates a dry layer in the atmosphere, but once the air column moistens up, that precipitation survives its journey to the ground.

Something I monitor in the Fall/Winter/Spring months (think cold temps but with precipitation nearby) is the “Dry Air Monster” (hat tip to Nashville Severe Weather for the “term”).

The Skew-T plot below is generated twice a day by the National Weather Service. When the NWS releases their weather balloons, the data packs tethered to the balloons track various atmospheric data as they rise from the ground to the upper atmosphere.

The green line is the dewpoint, and it’s much lower than the red line temperature about a mile above the ground. This is the Dry Air Layer, or for those who are wishing for snow and don’t receive any, this is the “Dry Air Monster” eating your snow!

During winter weather events, I often check the radar. When the radar is depicting rain or snow, I check the dewpoint at the surface and the dewpoint on the Skew-T to see if that precipitation is surviving, or evaporating before reaching the ground.

The Dry Air Layer will “eat” the precipitation, producing the virga -- in other words, the precipitation is evaporating as it moves through that super dry air layer above the ground.

Y’all, the atmosphere... It’s FASCINATING!! Share your view of the sky with me!!

Facebook: Christina Edwards WSB

Twitter: @ChristinaWSBwx




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