Area Forecast Discussion
Issued by NWS
FXUS62 KKEY 291852
Area Forecast Discussion
National Weather Service Key West FL
252 PM EDT FRI JUL 29 2016
.DISCUSSION...In the Middle and upper levels (700-200 mb), latest
available ir imagery overlaid with model streamline analysis as of
200 pm detail the axis of a deep and warm core positively tilted
middle and upper level ridge oriented across the Western Atlantic
from about 34 North 65 West southwestwards to across Central Florida.
Upstream of the Keys, the axis of a TUTT (Tropical Upper Tropospheric
Trough) is located from 27 North 63 West south southwestward to
across Hispaniola into the Southern Caribbean Sea, and migrating
At the surface and in the lower to middle levels (Surface to 700
mb), latest IR imagery overlaid with available marine and land
surface observations and analysis as of 200 pm detail a typically
weak surface ridge across Central Florida to north of the Bahamas.
Across the tropics, there are two waves across the Eastern Atlantic
well east of 50 West. Another two tropical waves west of 50 degrees
are at a low latitude, with the first approaching Barbados. The next
inverted trough upstream of the Keys is north of Hispaniola attm.
Finally, the axis of a departing inverted trough/weak wave now well
west of the Keys over the SE Gulf of Mexico.
.CURRENTLY...As of 200 pm, skies are mostly sunny across the Keys
Island Chain and all adjoining waters with just a tinge of Saharan
dust evident in the visible, and this is obvious when looking at the
milks blue sky this afternoon. Radar detects no showers in the CWA
and just isolated showers and storms along boundaries in South
Florida. Its torrid with temperatures near 90 and dewpoints around
80. C-man stations along the Florida Reef are light to gentle and
southeast at 5 to 10 knots.
.SHORT TERM...Tonight thru Sunday afternoon, Typical uncomfortable
conditions will be the rule as we enter the hottest month of the year
this week. Middle and Upper level easterlies will transport the TUTT
now at the longitude of Hispaniola across South Florida and the Keys
for the second half of the weekend, following deep middle and upper
drying. At the surface and in the lower levels, the next tropical
wave at the longitude of the Dominican Republic will move across
Saturday night through late Sunday afternoon. This feature in tandem
with typical ridging north across the peninsula to the north will
allow medium to good chances for heavy fast moving showers thru this
time. Coverage of showers and thunderstorms may increase as details
become more clear, so keep in mind that rain chances may increase as
we get closer to Saturday.
Sunday night thru Monday Night. Then after the aforementioned wave
moves by to the west, ridging to the north will allow for some mid
level drying, however, overall, given forecast soundings illustration
of deep east winds from surface to 500 mb, will be holding on to a
low chance for showers and isolated storms given towering
cumulus/cumulus cloud line formation over the islands. Across the
tropics, a wave attm that is approaching 50W at lower latitudes is
forecast to continue to move rather fast (at 20 to 25) knots across
the Caribbean Sea, reaching the Western Caribbean on Monday and
Tuesday, where conditions will be more favorable for this wave to
develop (towards the Yucatan).
.LONG TERM...Tuesday thru Friday, Middle and Upper level ridging is
progged to remain locked from the Southern Mississippi Valley to the
Western Atlantic. Surface ridging looks to remain north acorss
Central Florida. The next tropical wave/trough that is upstream of
the Keys is progged to move across Tuesday through Wednesday night.
As such will continue to carry middle of the road chances for showers
for this period, then back to climo behind this wave. This of course
will be dictated by the behavior of the next waves, and there are
indications that middle and upper levels decelerate late next week.
.MARINE...Light to gentle southeast breezes thru Saturday, becoming
gentle to moderate Saturday night ahead of the next wave, then
moderate across the waters late Saturday night thru Sunday night,
except moderate to fresh across the Florida Straits, where a
cautionary statement is probable for that time, with the possibility
of SCA conditions. A second trough/wave is progged to move across
again Monday night thru Tuesday, so SCEC conditions will be possible
again, especially across the Straits. Nevertheless, mariners should
pay close attention because fast moving showers during this time will
also be capable of deliver wind gusts over 30 knots as well.
Light southeasterly breezes today will back this evening out of the
east, with cloud coverage remaining FEW at around 2,000 feet. Rain
chances will remain slight through at least 30/18z, resulting in VFR
conditions at both the EYW and MTH terminals.
Month to date, 3.68 inches of rain has fallen at the Key West
International Airport, which is 0.37 inches above normal. The yearly
rainfall total in Key West now stands at 16.47 inches, which is 1.58
inches below normal. Rainfall records in Key West date back to 1871.
.PRELIMINARY POINT TEMPS/POPS...
Key West 82 90 80 89 / 20 20 40 50
Marathon 82 93 80 92 / 20 20 40 50
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