097
FXUS62 KKEY 161508
AFDKEY
AREA FORECAST DISCUSSION FOR THE FLORIDA KEYS
NATIONAL WEATHER SERVICE KEY WEST FL
1108 AM EDT WED OCT 16 2013
.DISCUSSION...
SKIES THIS MORNING ARE SUNNY OVER THE LOWER FLORIDA KEYS AND MOST OF
THE UPPER KEYS. HOWEVER...SCATTERED ALTOCUMULUS CLOUDS HAVE OVERSPREAD
SOME AREAS BETWEEN ABOUT THE SEVEN MILE BRIDGE AND ISLAMORADA. THE
CLOUD DECKS CLEARLY ARE MOVING FROM SOUTH TO NORTH...WHICH SEEMS TO
CONFIRM THE PRESENCE OF A VERY SHALLOW LAYER OF WEAK ISENTROPIC LIFT
BETWEEN 5000-8000 FEET AS INFERRED BY KEY WEST MORNING RAWINSONDE
DATA. THIS FEATURE APPARENTLY WENT UNDIAGNOSED BY ALL AVAILABLE
NUMERICAL WEATHER PREDICTION MODELS. ANALYSIS OF SATELLITE IMAGERY
SUGGESTS THAT THE ISENTROPIC LAYER IS ASSOCIATED WITH THE WEST-
NORTHWESTWARD EXTENSION OF A WEAK...SHALLOW TROUGH FROM THE BAHAMAS.
FURTHER SUBJECTIVE ANALYSIS OF SATELLITE VISIBLE IMAGES THIS MORNING
REVEALS A SLIGHT CYCLONIC TURNING IN THE SHALLOW CONVECTION-
YIELDING CLOUDS NEAR THE CAY SAL BANK...INDICATIVE OF AN AREA OF
ENHANCED CYCLONIC VORTICITY WITHIN THE TROUGH. MESOSCALE FEATURES
ALWAYS MAKE IT INTERESTING HERE.
ON THE LARGE SCALE...THE DEEP RIDGE WHICH HAS INFLUENCED LOCAL
WEATHER FOR THE LAST SEVERAL DAYS GRADUALLY IS SHIFTING EASTWARD.
NEVERTHELESS...IT LOOKS LIKE WE WILL HAVE ANOTHER DAY WITH
NORTHEASTERLY LOW-LEVEL FLOW...ALBEIT A BIT WEAKER THAN RECENT DAYS.
THE LOCAL WRF MODEL INDICATES A CLUSTER OF SEA-BREEZE SHOWERS
DEVELOPING AGAIN THIS AFTERNOON OVER THE EVERGLADES AND MOVING
SOUTHWESTWARD OVER PORTIONS OF FLORIDA BAY/GULF OF MEXICO/LOW-MID
FLORIDA KEYS...AND THE MORNING RUN OF THIS MODEL YESTERDAY VERIFIED
VERY WELL DURING THE EVENING. WE THEREFORE ARE CONSIDERING UPDATING
FORECASTS TO INCLUDE A LATE-DAY SLIGHT RAIN CHANCE...AT LEAST OVER
THE LOWER/MIDDLE KEYS ZONES. CURRENT AIR TEMPERATURES IN MOST ISLAND
COMMUNITIES ARE IN THE LOWER 80S WITH DEWPOINTS NOW NEAR 70F. SO...WE
DO HAVE A LITTLE EXTRA THETA-E IN THE BOUNDARY LAYER AS COMPARED WITH
THE LAST FEW DAYS. A FINAL WILD CARD WOULD BE THE AFTERNOON
DEVELOPMENT OF A LOWER KEYS CONVERGENCE ZONE/CUMULUS CLOUD LINE.
HOWEVER...DIFFERENTIAL HEATING ON THE ISLAND SCALE MAY NOT BE
SUFFICIENT TO OVERCOME LARGER SCALE SUBSIDENCE/DRY AIR ENTRAINMENT.
&&
.MARINE...
LIGHT TO GENTLE MAINLY NORTHEAST BREEZES WILL PREVAIL MOST AREAS THIS
AFTERNOON. WINDS OVER FLORIDA BAY LIKELY WILL TURN OUT OF THE EAST OR
EAST-SOUTHEAST AS A BAY BREEZE COMMENCES LATE. ISOLATED SHOWERS WILL
DEVELOP EARLY...MAINLY NEAR THE CAY SAL BANK...AND LATER OVER
NORTHERN FLORIDA BAY AND THE GULF WATERS IN THE VICINITY OF CAPE
SABLE. A FEW SHOWERS WILL BE POSSIBLE NEAR THE LOWER KEYS IF A CLOUD
LINE DEVELOPS.
&&
.AVIATION...
VFR CONDITIONS WILL PREVAIL AT BOTH THE KEY WEST AND MARATHON ISLAND
TERMINALS. A FEW CLOUDS MAY IMPACT THE TERMINALS AOA FL020-030 WITH
SOME SCATTERED CLOUDS AOA 6000-8000 FEET ABOVE MARATHON IN
ASSOCIATION WITH A WEAK DISTURBANCE.
&&
.KEY WATCHES/WARNINGS/ADVISORIES...
FL...NONE.
GM...NONE.
&&
$$
PUBLIC/MARINE.........KASPER
AVIATION/NOWCASTS.....FUTTERMAN
DATA COLLECTION.......VICKERY
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