Expert: Dave Dombek - 5/9/2007

Question
Hey Dave,

It would be great if you can help me with these few questions that have been bothering me.

1) How does a MCV (Mesoscale Convective Vortex) form and how do you spot it?

2) How do you locate boundaries on satellite that may have thunderstorms form on them, and outflow boundaries?

Thanks so much for any help!

Answer
Mark,

Those are good questions. Here is my  best shot at the answers...

(1) An MCV is basically a mini low pressure system, within an MCS, or MCC, the term we used back in the '70s and '80s. There is still a lot that we don't know about MCV's, but obviously, they are a small circulation center, with winds blowing toward the middle. That means that the pressures in the center of the MCV must be lower than the pressures surrounding it, since air ALWAYS blows from high pressure to low pressure. Therefore, the lower pressures in its center probably come from the latent heat of condensation due to the thunderstorms, since condensation is a warming process. Warm air has lower pressure than cool air.
(2) There are a number of different boundaries that can be seen on satellite pictures, especially on visible shots. The key to finding these boundaries is to examine places where there is a noticeable difference in the clarity of the air, or the texture of the clouds. Sometimes, an outflow boundary will separate clean air from a "dirty" or hazy air mass, and the boundary shows up very clearly on a visible satellite shot. Many times, a well defined outflow boundary from the night before will be the focal point of new convection to fire up that day. A scattered to broken line of cumulus clouds often shows where the boundary is.
I hope this answered your questions.

Sincerely,

Dave Dombek
Expert Senior Meteorologist
AccuWeather.com