Scientific Forecaster Discussion
Area forecast discussion for the Florida Keys
National Weather Service Key West Florida
245 PM EDT Sat Sep 20 2014
satellite interrogation on the Continental U.S. Scale showing an upper low off
the California coast...another over old Mexico...and a developing
upper low along the trough near the eastern Seaboard. These systems
are driving a ridge southward through the Mississippi Valley through
the southern Gulf of Mexico where a piece of short wave energy is
kicking up about 400 miles south of New Orleans. There are still
discrete showers and thunderstorms well ahead of the main body of
activity. Winds are out of the south at 5 to 10 knots at the island
terminals...and at the C-man stations south of the island
chain...with near 10 knots north.
the book end lows will continue to pinch the ridge between and pull
the ridge axis southward from the lower Mississippi Valley through
the southern Gulf of Mexico. For US this means the low level
confluence will be just to our west and north. Have elected to keep
middle chance rain south of the island chain...high chance along the
island chain and the Bay and Gulf side waters...with numerous showers
and scattered thunderstorms on the Gulf waters west of Mainland
Monroe County to the Dry Tortugas overnight. Sunday and after have
made slight changes due to a few weak waves moving trough the
westerlies...and the Atlantic ridge nosing across the northern
Caribbean...Cuba...and The Straits. The ridge axis will increase as
the first wave approaches Monday night and Tuesday. Have modified
rain chances slightly Monday night and Tuesday to reflect the passing
of the wave. The second wave will arrive early Saturday and will go
high end chance again.
a weak trough to the northeast will gradually lift away from the
Florida East Coast through Monday. There are a few weak waves
upstream of the region in the tropics that will pass mainly south of
the Keys area through the end of the next week. These waves will
combine with the weak trough near the area to keep scattered rain
and produce periods with surging winds beginning Monday night. At
this time we do not expect any cautionary or advisory statements.
mainly VFR conditions are expected at the Key West and Marathon
terminals through middle afternoon. There is a chance for MVFR or lower
conditions later this afternoon and early this evening...and have
inserted vicinity thunderstorm at both locations on that account. Vicinity
showers has also been maintained through the overnight period. A
light southwest wind will be variable through the overnight period.
on this date in Keys weather history...2005...Hurricane Rita passed
through the Florida Straits...about 40 nautical miles south of Key
West producing storm tide 3 to 5 feet above mean sea level...flooding
many streets along the Lower Keys. The minimum pressure in Key West
as Rita passed was 995.3 mb / 29.39 inches of Mercury...with
sustained winds of 62 miles per hour and gusts up to 76 miles per hour.
Preliminary point temps/pops...
Key West 79 90 80 89 / 50 40 40 40
Marathon 79 91 80 90 / 50 40 40 40
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