Area Forecast Discussion
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000
FXUS62 KKEY 301503
AFDKEY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KEY WEST FL
1103 AM EDT SUN AUG 30 2015

.DISCUSSION...
THE AREA BETWEEN SOUTHERN FLORIDA AND THE NORTHWESTERN CARIBBEAN SEA
IS THE SCENE OF WIDESPREAD CLOUDINESS...SHOWERS...AND THUNDERSTORMS
THIS MORNING. KEY WEST DOPPLER RADAR SCANS INDICATE NUMEROUS...
QUICK-DEVELOPING...AND FAST-MOVING SHOWERS AND SQUALLS...WITH
SCATTERED STRONG THUNDERSTORMS AS WELL. CELL MOVEMENTS ARE COMPLEX...
WITH STORM MOTIONS NORTHWESTWARD ACROSS MOST OF THE KEYS FROM OCEAN
REEF TO KEY WEST AND ADJACENT WATERS...AND WESTWARD OR SOUTHWESTWARD
OVER THE EXTREME SOUTHEASTERN GULF OF MEXICO AND LOWER STRAITS OF
FLORIDA. THESE STORM MOTIONS ARE CONSISTENT WITH THE LOWER-
TROPOSPHERIC FLOW THROUGH A SHARP EASTERLY WAVE...THE AXIS OF WHICH
EXTENDS FROM ABOUT LAKE OKEECHOBEE TO THE YUCATAN CHANNEL. THE WAVE
EMERGED FROM THE REMNANTS OF TROPICAL CYCLONE ERIKA YESTERDAY...AND
DECELERATED AS IT PIVOTED NORTHWESTWARD ALONG THE SOUTHWESTERN FLANK
OF A ROBUST DEEP LAYER MEAN SUBTROPICAL ANTICYCLONE CENTERED BETWEEN
BERMUDA AND THE BAHAMAS. THE SYSTEM IS ASSOCIATED WITH A LARGE PLUME
OF DEEP TROPICAL MOISTURE AS EVIDENCED BY DATA COLLECTED THIS MORNING
FROM THE KEY WEST MORNING RADIOSONDE BALLOON...AS WELL AS ANIMATIONS
OF TOTAL PRECIPITABLE WATER /MIMIC TPW/ FROM THE UNIVERSITY OF
WISCONSIN CIMSS GROUP.

AT THE SURFACE...A WELL-DEFINED TROUGH OF LOW PRESSURE IS ASSOCIATED
WITH THIS SYSTEM...WITH THE AXIS ALIGNED WITH THE LOWER-TROPOSPHERIC
LAYER MEAN POSITION....AND RUNNING FROM ABOUT MAINLAND MONROE
COUNTY...TO DRY TORTUGAS...AND SOUTHWESTWARD TO THE YUCATAN CHANNEL.
AN ASSOCIATED DEEP AREA OF MOISTURE CONVERGENCE AND ASCENT OVER THE
FLORIDA KEYS AND FAVORABLE OUTFLOW ALOFT IS FACILITATING PERSISTENT
DEEP CUMULUS CONVECTION ACROSS THE SERVICE AREA...WITH SOAKING
TROPICAL RAINS AFFECTING MANY KEYS ISLAND COMMUNITIES THIS MORNING.
IN ADDITION...UPSCALE GROWTH WITH DEEP CUMULUS CONVECTION BETWEEN
THE LOWER KEYS AND DRY TORTUGAS IS LEADING TO MESOSCALE CONVECTIVE
SYSTEM DEVELOPMENT...AND THIS MAY BUILD SOUTHWARD OR SOUTHEASTWARD
INTO THE 850MB FLOW DURING THE AFTERNOON...IN CLOSE PROXIMITY TO THE
LOWER KEYS. IF THE MCS DOES BUILD ACROSS PORTIONS OF THE LOWER
KEYS...SOME HIGHER RAINFALL RATES AND INCREASED STREET FLOODING
POTENTIAL WILL OCCUR -- SOMETHING TO MONITOR FOR NOW.

FORECAST REASONING HAS CHANGED LITTLE FROM THE MORNING PACKAGE. IN
SHORT...CLOUDY...WET...AND SQUALLY WEATHER IS EXPECTED THIS
AFTERNOON AND PART OF TONIGHT...WITH RAPID IMPROVEMENT THEREAFTER. A
FEW TWEAKS HAVE BEEN MADE TO THE DIGITAL AND DERIVED PRODUCTS.
&&

.MARINE...
A SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR ALL ZONES...AND SMALL
CRAFT ARE ADVISED TO REMAIN IN PORT THIS AFTERNOON...ESPECIALLY GIVEN
THE COVERAGE OF STRONG SQUALLS AND THUNDERSTORMS. THE REMNANTS OF
ERIKA WILL RESULT IN FRESH TO STRONG BREEZES THIS AFTERNOON AND
TONIGHT. WINDS AND SEAS WILL BE HIGHER IN AND NEAR SHOWERS...
SQUALLS...AND THUNDERSTORMS. BREEZES WILL RELAX AND SEAS WILL
SUBSIDE MONDAY AND MONDAY NIGHT...FOLLOWED BY A RETURN TO LIGHT
EASTERLY BREEZES TUESDAY THROUGH THURSDAY.
&&

.AVIATION...
SHOWERS AND THUNDERSTORMS WILL DEVELOP NEAR THE KEY WEST AND
MARATHON TERMINALS TODAY AND AFFECT THEM DURING PERIODS OF ONE HOUR
AT THE TIME. THESE WILL CAUSE MVFR/IFR CONDITIONS WITH LOW CIGS AND
REDUCTION OF VISIBILITY TO BELOW 2 MILES. WINDS WILL BE GENERALLY
EAST TO SOUTHEAST AT 10 TO 15 KNOTS WITH GUSTS UP TO 25 TO 30 KNOTS.
&&

.KEY WATCHES/WARNINGS/ADVISORIES...
FL...NONE.
GM...SMALL CRAFT ADVISORY IN EFFECT FOR GMZ031-GMZ032-GMZ033-
     GMZ034-GMZ035-GMZ042-GMZ043-GMZ044-GMZ052-GMZ053-GMZ054-
     GMZ055-GMZ072-GMZ073-GMZ074-GMZ075.
&&

$$

PUBLIC/MARINE.........KASPER
WARNINGS/AVIATION.....KN
DATA COLLECTION.......FLING
COORDINATOR...........RIZZO

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