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Land effect Showers?
Posted: Mon May 17, 2004 11:01 am
by smerby
There has been a cool phenomenon along the southeast Florida coast over the last several days. Thanks to a persistent Bermuda high, an ESE steering flow across the Bahamas has caused a daily plume of showers from Grand Bahama all the way to the southeast coast of Florida. I might as well call this the GBP (Grand Bahama Plume), what the hey. Grand Bahama island is oriented E-W and convection from day time heating feeds a string of showers and t-showers that can extend all the way to the Florida coast. Depending on the steering flow wind direction, this plume affects different parts of the southeast Florida coast. A steering flow direction of 120 degrees caused the plume to reach as far north as Melbourne on Saturday, then it shifted farther south across Palm Beach county on Sunday as the wind direction shifted to 100-090 degrees. With little to no shear and the right amount of moisture, this plume has been almost solid at times from the western tip of Grand Bahama, all the way to the FL coast. Almost like lake effect snow, the sun shines either side of the plume, but in it, showers are persistent and heavy at times. The drier the feed of air across Grand Bahama, the more the GBP is broken and sometimes dies out before reachimg the FL coast.
Smerby
http://www.accuweather.com
Posted: Mon May 17, 2004 11:12 am
by Stephanie
During the March 24 - 28, I was vacationing in Ft. Lauderdale and we had cool temps and rain and a strong onshore flow. It was very unusual for that to occur from what I read. Was that the same phenomenon, or was it different?
Posted: Mon May 17, 2004 11:15 am
by wx247
Wow smerby!!! That was a very interesting read. That was something I was not aware of. I will have to look into that further in my spare time.
Posted: Mon May 17, 2004 9:10 pm
by vbhoutex
Smerby, is this a newly noticed phnomenon or something that seems to have been around for a while. Or is is just an anamoly at this time?
Posted: Wed May 19, 2004 11:56 am
by Aquawind
They mentioned this in the NWS Discussion Today.
000
FXUS62 KTBW 191328
AFDTBW
WEST CENTRAL AND SOUTHWEST FLORIDA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAMPA BAY AREA - RUSKIN FL
928 AM EDT WED MAY 19 2004
.DISCUSSION...TBW 88D DOWN TO REPAIR A PAINT CHIP ON THE DOME.
WE HOPE TO HAVE THE RADAR BACK UP BY 1 PM. OTHER AREA 88D'S DEPICTING
SHOWERS EAST OF LAKE OKEECHOBEE. THESE SHOWERS ARE ALONG A CLOUD
STREAMER ORIGINATING IN THE BAHAMAS. INTERESTING TO NOTE...WE ALREADY
HAVE OUTFLOW BOUNDARIES PROPAGATING AWAY FROM THESE SHOWERS...THE
MOST PRONOUNCED OF WHICH IS MOVING NORTHWEST THROUGH SOUTHEAST POLK
COUNTY AT THIS TIME.
Posted: Wed May 19, 2004 10:57 pm
by smerby
Hi David,
This phenomenon has been around for a while and it is more likely to happen when a deep easterly flow sets up, seems earlier than normal this year with the Bermuda high in control. I think the strength of the flow, lack of directional shear, and moisture through the lower 10,000 feet determines how solid and long the plume will be. We have seen long lake effect snow plumes straight as an arrow and they usually set up when winds line up from bottom up and there is ample moisture. Forecasting these Bahama plumes seems tougher than lake effect snow because they oscillate within a small area up and down the coast.
Take care
Smerby
http://www.accuweather.com
Posted: Sat May 22, 2004 6:03 pm
by Rainband
Nice discussion Smerby.
WELCOME!!! to S2K:wink: