> "Sometimes very ominous in appearance, mammatus clouds are
> harmless and
> do not mean that a tornado is about to form; a commonly held
> misconception. In fact, mammatus are usually seen after the
> worst of a thunderstorm has passed."
Partially true. In most parts of the US, cyclonic type storms
tend to move and the tornados "usually" form on the southern
trailing side of the storm. Rule of thumb, if the wind at your
location is coming from a northerly direction you're most likely
safe. When the storm is hauling the mail, the tornados can drop
out way behind the storm as the storm is tilted quite a bit
forward.
However, if the storm is relatively stationary or slow moving or
still in the building stage, the tornados will form from where
the wallcloud drops. These mammatus clouds typically happen when
a storm tops out and the anvil kicks out. The anvil can blow a
hundred miles in FRONT of the storm. Depending on the altitude
of the "cap" these cloud patterns don't have to be all that
high.
The "tornados" seen dropping from this type of cloud are thermal
in origin and not cyclonic in origin. You can see these funnel
clouds drop out from standard cumulus clouds on a cool windy
day--especially when you have a thermal inversion in place.
Rarely do they reach ground and when they do, they're usually of
the F1 type that knock down old trees and form crop circles.
Over water, these are your typical waterspouts. One late fall
day up in Michigan I saw a dozen of these things at one time.
Of course, we also had patchs of quicksand up there too...
AG
__________________________________
Yahoo! Mail - PC Magazine Editors' Choice 2005
http://mail.yahoo.com
==============================================
List usage info: http://www.zuikoholic.com
List nannies: olympusadmin@xxxxxxxxxx
==============================================
|