[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 161147
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 AM EST TUE DEC 16 2008

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS
OF SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST
FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED
ON SATELLITE IMAGERY...METEOROLOGICAL ANALYSIS...WEATHER
OBSERVATIONS...AND RADAR.

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1115 UTC.

...THE ITCZ...
ITCZ IS CENTERED ALONG 7N12W 5N22W 4N32W 6N47W 5N52W. SCATTERED
MODERATE CONVECTION IS WITHIN 60 NM N AND 180 NM S OF THE AXIS
BETWEEN 26W-32W. ISOLATED MODERATE CONVECTION IS WITHIN 90 NM OF
THE AXIS E OF 22W.

...DISCUSSION...

GULF OF MEXICO...
A STRONG COLD FRONT IS DRAPED ACROSS THE NW GULF EXTENDING FROM
SE LOUISIANA TO 28N94W TO NE MEXICO NEAR 24N98W. NW OF THE
FRONT...N TO NE 20-25 KT WINDS ARE ADVECTING MUCH COOLER AND
DRIER CONDITIONS ACROSS THE NW GULF REGION...WITH SURFACE
TEMPERATURES IN THE 30S F ACROSS MUCH OF SE TEXAS AND EVEN THE
20'S F WELL INLAND. THIS MODIFIED CONTINENTAL POLAR AIRMASS IS
BEING ANCHORED BY A 1041 MB SFC HIGH OVER THE CENTRAL PLAINS.
THE FRONT HAS BEEN MAKING SLOWER PROGRESS TO THE SE...AND IS
FORECAST TO BECOME STATIONARY OVER THE NW GULF LATER TODAY...AS
THE SURFACE HIGH TAKES MORE OF AN EASTWARD TRAJECTORY ACROSS THE
NE CONUS. IN THE MEANTIME...MODERATE WESTERLY FLOW ALOFT
CONTINUES ACROSS THE GULF ADVECTING TROPICAL/SUBTROPICAL
MOISTURE FROM THE PACIFIC. HOWEVER...ONLY ISOLATED SHOWERS ARE
EMBEDDED IN THIS MOISTURE PLUME.

CARIBBEAN SEA...
GENERALLY FAIR WEATHER CONDITIONS ARE IN PLACE ACROSS THE ENTIRE
CARIBBEAN. A SURFACE RIDGE OVER THE CENTRAL ATLC IS ENHANCING
MODERATE TO FRESH TRADE WINDS ACROSS THE REGION...STRONGEST IN
THE ATLC PASSAGES AS NOTED IN RECENT SCATTEROMETER PASSES.
WIDESPREAD SUBSIDENCE EXISTS IN WESTERLY AND NORTHWESTERLY ALOFT
ACROSS THE CARIBBEAN...LIMITING THE DEVELOPMENT OF ANY DEEP
CONVECTION. HOWEVER...SCATTERED SHALLOW SHOWERS AND LOW TOPPED
TSTMS ARE MOVING THROUGH PUERTO RICO...HISPANIOLA AND MUCH OF
THE NE CARIBBEAN ON STRONG NLY LOW-LEVEL FLOW TO THE W OF SFC
TROUGHING IN THE SUBTROPICAL CENTRAL ATLC. TYPICAL SHALLOW
ISOLATED SHOWERS ARE POSSIBLE ELSEWHERE...ESPECIALLY OVER
HONDURAS AND NICARAGUA WHERE THE ATMOSPHERE ALOFT IS
SLIGHTLY MORE MOIST IN A DIFFLUENT PATTERN.

ATLANTIC OCEAN...
THE WESTERN ATLC IS EXPERIENCING MAINLY FAIR WEATHER WITH ONLY
SCATTERED HIGH LEVEL CLOUDS STREAMING IN ON NW FLOW AND PATCHY
LOW LEVEL CLOUDS AND EMBEDDED SHOWERS DRIVEN BY STRONG ELY
FLOW...ESPECIALLY NEAR A SFC TROUGH OFF THE NE FLORIDA COAST.
THE PATTERN IS MORE ACTIVE IN THE CENTRAL ATLC AS A 1014 MB SFC
LOW HAS TAKEN SHAPE NEAR 29N55W WITH AN ASSOCIATED TROUGH
EXTENDING SSW TO 18N59W. A FRONTAL BOUNDARY JUST W OF THE LOW
FROM 32N52W TO 25N58W IS SLOWLY RETREATING AND WEAKENING AS THE
SFC LOW/TROUGH SHIFTS W. LOW LEVEL CONVERGENCE ASSOCIATED WITH
THESE FEATURES COUPLED WITH INSTABILITY AND UPPER DIFFLUENCE
ALONG AND E OF AN UPPER TROUGH IS RESULTING IN SCATTERED SHOWERS
AND TSTMS N OF 22N BETWEEN 45W-58W. THE TIGHT PRES PATTERN
BETWEEN THE LOW...FRONT...AND HIGH PRES OVER THE N CENTRAL ATLC
IS PRODUCING GALE FORCE N TO NE WINDS JUST W OF THE FRONT. OVER
THE NEXT COUPLE OF DAYS...STRONG UPPER LEVEL DIVERGENCE
ASSOCIATED WITH AN UPPER LEVEL JET MAXIMUM NEAR THE BASE OF THE
UPPER TROUGH IS FORECAST TO INDUCE SUFFICIENT SURFACE PRESSURE
FALLS TO RESULT IN THE DEEPENING OF THE SURFACE LOW AS IT TRACKS
SW STEERED BY THE E PERIPHERY OF A MID-LEVEL RIDGE. FARTHER
E...A 1030 MB SURFACE HIGH NEAR THE AZORES IS PRODUCING FRESH TO
STRONG NE TO E TRADES. STRONG WLY FLOW ALOFT IS SPREADING
ABUNDANT HIGH LEVEL MOISTURE ACROSS THE DEEP TROPICS AND
ENHANCING ITCZ CONVECTION.

$$
COHEN/CANGIALOSI





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