OFB's on SFC Maps

[Jon Miller]

I've read in past posts that outflow boundaries can be "easily" found on sfc maps - question is -do you look for the same clues as in trying to locate a frontal boundary - ie wind shifts, temp changes , dew point changes etc or are there other things to look for ? And how long to OFB's last ?
Thanks for any help .

Jon Miller
KT8NDO

 

[David Drummond]

Sometimes you can find them on surface obs. I find that easier in places with mesnonets in place. Like Ok, of the Texas South Plains. I find it easier using visible satellite loops and radar loops. Sometimes they are short lived, but usually your looking for something left over from the night before. Sometimes one flowing off some storms can interact with something else and kick off other storms, or even initiate new ones.

 

[Bill Schintler]

RE: OFB identification

An OFB is in effect a frontal boundary that marks the leading edge of a rain-cooled airmass. They show up as a change of wind direction and (usually) speed. A sudden temperature drop usually accompanies the passage of an OFB.

Visible satellite is also an excellent way to determine the position of an OFB, as the following image illustrates:

Source:
http://cimss.ssec.wisc.edu/goes/misc/980529_1859_vis.GIF

They also show up well on weather radar reflectivity and velocity data, especially when the OFB is close to the radar site - 50 miles or less. The following three radar grabs show the reflectivity, velocity, and reflectivity with the OFB position overlaid. Note also the pre-frontal surface obs on the lower-right side of the images, and the post-frontal observation near the center.

Source:
http://upload.wikimedia.org/wikipedia/commons/3/3d/Outflow_bndry.png