Ticker for June 16, 2008

                
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June 16, 2008      June 16, 2008      June 16, 2008      June 16, 2008



Buckin' The Trend

Last night's storms (and the night before, and the night before, etc.)
brought powerful straight-line winds and certainly earned their
warnings. If you were watching closely, you surely noticed that these
storms didn't have that classic southwest-to-northeast motion that
we've all come to know and, uh, recognize.

Nope, these storms were traversing from the northwest.

Why so? Well, contrary to popular opinion (and popular storm behavior,
and behavior of popular storms) severe local storms don't *have* to
come out of the southwest. Last night's action (and the night before,
etc.) took place in what we like to call northwesterly flow. And, we
like to call it that because that's pretty much what it is: mid- and
upper-level winds out of the northwest.

Take a look at last night's map at 500 mb (roughly "halfway up the
atmosphere" at about 18,00 feet):


(Image courtesy of NOAA's Storm Prediction Center)

See the winds out of the west-northwest? These winds are representative
of what we like to call the "steering winds". And, we like to call them
that because that's pretty much what they are: they are the winds that
steer storms.

Typically, a high-end springtime severe weather setup will have
southwesterly flow at mid and upper levels. It just works out that the
combination of ingredients that support high-end severe weather
typically comes into play with southwesterly flow.

But, severe weather can be supported in other regimes as well. Nocturnal
summertime events can, and often do, occur in northwesterly flow.
And that's exactly what happened last night (and the night before, etc.).