Area Forecast Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS62 KKEY 210132
AFDKEY

AREA FORECAST DISCUSSION FOR THE FLORIDA KEYS
NATIONAL WEATHER SERVICE KEY WEST FL
930 PM EDT SAT SEP 20 2014

.DISCUSSION...IN THE MID AND UPPER LEVELS...(700-200 MB)...LATEST
AVAILABLE IR IMAGERY OVERLAID AS OF 900 PM OVERLAID WITH MODEL
STREAMLINE ANALYSIS CONTINUE TO DEPICT A UNSEASONABLY DEEP MID
AND UPPER CYCLONIC FLOW PATTERN REMAINS IN PLACE ACROSS THE CENTRAL
AND EASTERN CONUS. A SHORTWAVE...AT 500 MB...IS TRYING TO PINCH OFF
OVER THE GEORGIA SOUTH CAROLINA PIEDMONT. ACROSS THE LOWER
LATITUDES...THE CENTER OF A WESTWARD MIGRATING TUTT (TROPICAL
UPPER TROPOSPHERIC TROUGH) CELL IS MOVE ACROSS THE WESTERN CARIBBEAN
SEA.

AT THE SURFACE AND IN THE LOWER TO MIDDLE LEVELS...AS OF 900
PM...DEVELOPING YET WEAK LOW PRESSURE IS OCCURRING WELL EAST OF
JACKSONVILLE FLORIDA...ALONG A SURFACE FRONTAL BOUNDARY WHICH SNAKES
SOUTHWEST TO ACROSS THE FLORIDA PENINSULA. AT THE SAME TIME...A WEAK
NON-TROPICAL SURFACE LOW IS ALSO OVER THE SOUTHEASTERN GULF OF
MEXICO ABOUT 150 MILES WEST OF KEY WEST. THE 00Z SOUNDING
ILLUSTRATED A MOIST LOWER TO MID TROPOSPHERE...(WITH PWAT RIGHT AT
2.00)...AND GENTLE TO MODERATE NORTHWEST TO NORTHERLY FLOW EXHIBITED
FROM THE SURFACE TO 3000 FEET AGL...WHICH PROMPTLY BECOMES SOUTHWEST
TO WEST AND FRESHENING A BIT ABOVE THAT. YET DESPITE THE PRESENCE OF
DEEP MOISTURE IN THE LOWER TO MID TROPOSPHERE BENEATH AN UNSTABLE
MID AND UPPER CYCLONIC FLOW...MOST OF THE SHOWER AND THUNDERSTORM
ACTIVITY IS PRESENTLY WELL NORTHEAST AND WEST OF THE KEYS...WITH THE
EXCEPTION OF THE AFOREMENTIONED DEEP CUBAN CONVECTION ALONG LAND
BOUNDARIES...WHICH IS ON THE EDGE OF THE OUTERMOST FLORIDA STRAITS.
TEMPERATURES OVER THE ISLANDS ARE NEAR 80 DEGREES...WITH DEWPOINTS
IN THE LOWER TO MID 70S. C-MAN STATIONS ARE RECORDING NORTHWEST TO
NORTH WINDS AT 10 TO 15 KNOTS AND GUSTY...WITH ISLAND SENSORS NEAR
10 MPH.

.FORECAST...OVERNIGHT...THE SURFACE TO 900 MB SURFACE TROUGH THAT
WAS OVER THE PENINSULA THIS AFTERNOON...(RESPONSIBLE FOR HEAVY
RAIN...WINDS...AND LIGHTNING IN SOUTH FLORIDA)...HAD MANAGED TO MOVE
ACROSS THE KEYS LATER THIS AFTERNOON...AND IS NOW JUST SOUTH OF THE
KEYS ATTM. HENCE...THIS IS ALLOWING WINDS TO BECOME NORTHWEST TO
NORTHERLY FROM THE SURFACE TO 900 MB. AGAIN...THIS WAS LIKELY DUE TO
THE ABOVE DEEPENING SURFACE LOW NOW NORTHEAST OF JACKSONVILLE...AND
THE WEAK LOW PRESSURE WELL WEST OF THE KEYS. SO THEREFORE...HIGHER
CONCENTRATIONS OF SHOWERS AND STORMS SHOULD REMAIN AWAY FROM THE
KEYS. LATEST AVAILABLE MODEL FORECAST SOUNDINGS DO ILLUSTRATE AN
UNFAVORABLE 0-6 KM AVERAGE STORM MOTION VECTOR...MEANING ACTIVITY IN
THE STRAITS WILL EVENTUALLY MOVE NORTHEAST TO EAST...THUS REMAINING
IN THE STRAITS. SO HAVE ALREADY TRIMMED BACK POPS TO ISOLATED
EVERYWHERE IN AN EARLIER UPDATE...EXCEPT ACROSS THE FLORIDA STRAITS.

&&

.AVIATION...
VFR CONDITIONS WILL PREVAIL AT EYW AND MTH TONIGHT AND SUNDAY. MVFR
OR LOWER CONDITIONS ARE CONCEIVABLE AT EYW SUNDAY AFTERNOON. THIS
POSSIBILITY IS NOT GREAT ENOUGH TO INCLUDE IN THE EYW TERMINAL
FORECAST. SUSTAINED NORTHWEST TO NORTH WINDS NEAR 15 KNOTS FROM JUST
OFF THE SURFACE TO ABOUT 3000 FEET WILL VEER TO SOUTHEAST AND
DECREASE TO 5 TO 10 KNOTS AFTER MIDNIGHT TONIGHT.

&&

.CLIMATE...
ON THIS DATE IN FLORIDA KEYS WEATHER HISTORY...IN 2005...HURRICANE
RITA RAPIDLY INTENSIFIED AS IT PROGRESSED TO THE WEST-NORTHWEST
THROUGH THE FLORIDA STRAITS. STORM TIDES THROUGHOUT THE ENTIRE
ISLAND CHAIN WERE 3 TO 5 FEET ABOVE MEAN SEA LEVEL. NUMEROUS STREETS
IN THE LOWER KEYS WERE COMPLETELY IMPASSIBLE DUE TO STORM SURGE
FLOODING. TROPICAL STORM FORCE WINDS WERE MEASURED THROUGHOUT THE
FLORIDA KEYS. THE LOWEST PRESSURE AND HIGHEST WINDS WERE RECORDED AT
SAND KEY LIGHT...JUST BEFORE THE STATION FAILED. THEY WERE 29.19
INCHES OF MERCURY AND SUSTAINED EAST WINDS OF 73 MILES PER HOUR...
WITH A PEAK WIND GUST OF 92 MILES PER HOUR RESPECTIVELY. THERE WERE
NO FATALITIES IN THE FLORIDA KEYS...ALTHOUGH THERE WAS ONE SERIOUS
INJURY IN KEY WEST DUE TO WAVE OVER WASH AS STORM SURGE WAS BUILDING.

&&

&&

.MARINE...OVERNIGHT AND SATURDAY...A NEARBY TROUGH WILL KEEP LIGHT
AND VARIABLE WINDS...TENDING MOSTLY SOUTHWESTERLY FOR THE OVERNIGHT
AND SATURDAY...BUT OF COURSE WINDS AND SEAS WILL BE HIGHER IN AND
AROUND SHOWERS AND THUNDERSTORMS ESPECIALLY.


&&

.KEY WATCHES/WARNINGS/ADVISORIES...
FL...NONE.
GM...NONE.
&&

$$

PUBLIC/MARINE/GRIDS.............DAF
AVIATION/NOWCASTS/CLIMATE.......BS
DATA COLLECTION/UPPER AIR.......BF

VISIT US ON THE WEB AT WEATHER.GOV/KEY

FOLLOW US ON FACEBOOK AND TWITTER AT...

WWW.FACEBOOK.COM/NWSKEYWEST
WWW.TWITTER.COM/NWSKEYWEST












USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.