[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 091808
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST SUN DEC 09 2012

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...WEATHER OBSERVATIONS...RADAR...AND
METEOROLOGICAL ANALYSIS.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 1745 UTC.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH PASSES THROUGH COASTAL SIERRA LEONE NEAR
8N13W AND QUICKLY TRANSITIONS TO THE ITCZ NEAR 7N16W. THE ITCZ
CONTINUES THROUGH 4N30W TO 6N41W WHERE IT BECOMES DIFFUSE ACROSS
THE REMAINDER OF THE DEEP TROPICAL ATLC. SCATTERED MODERATE
ISOLATED STRONG CONVECTION WAS NOTED FROM 3N-6N BETWEEN 20W AND
30W...AND FROM 4N-8N BETWEEN 30W AND 38W. ADDITIONAL CLUSTERS OF
CONVECTION WERE NOTED FROM 7N-15N BETWEEN 48W AND 56W IN
ASSOCIATION WITH A SURFACE TROUGH AND ITS INTERACTION WITH AN
UPPER LEVEL TROUGH.

...DISCUSSION...

THE GULF OF MEXICO...
BROAD UPPER LEVEL WEST-SOUTHWESTERLY WINDS COVERS THE GULF OF
MEXICO AND FLORIDA ALONG THE PERIPHERY OF A LARGE UPPER LEVEL
ANTICYCLONE OVER THE NW CARIBBEAN. DRY AIR ALOFT OVER CENTRAL
AMERICA AND THE SW HALF OF THE GULF WAS WORKING ITS WAY NE
ACROSS THE W-CENTRAL GULF. AT THE SURFACE...A WEAK RIDGE
PERSISTED OVER THE GULF WITH LIGHT E TO SE WINDS OF AROUND 10
KT E OF 90W TURNING MORE TO THE SOUTH AND INCREASING TO 15-20 KT
OVER THE GULF N OF 28N W OF 90W WHICH EXTENDED TO THE UPPER
TEXAS AND LOUISIANA COASTS. VISIBLE SATELLITE IMAGERY REVEALED
MOSTLY CLEAR SKIES WITH STREETS OF LOW CLOUDS STREAMING NORTH
OVER THE NW GULF WITHIN THE AREA OF THE STRONGEST LOW LEVEL
FLOW. A COLD FRONT IS SLATED TO MOVE OFF THE TEXAS COAST AROUND
12 UTC MONDAY WITH WINDS SHIFTING TO THE NORTH AND INCREASING TO
20-25 KT LATE MON NW OF THE FRONT.

THE CARIBBEAN SEA...
AN EXTENSIVE UPPER LEVEL ANTICYCLONE AND RIDGE COVERS THE WESTERN
TWO-THIRDS OF THE CARIBBEAN WITH DRY AIR ALOFT IN ITS WAKE. THE
ONLY EXCEPTION IS A PATCH OF DEEP LAYERED MOISTURE ASSOCIATED
WITH CONVECTION OVER THE AREA FROM 16N-20N BETWEEN JAMAICA AND
82W. FURTHER EAST...A FAIRLY SHARP MID-TO UPPER LEVEL TROUGH
EXTENDS FROM THE ATLANTIC OCEAN ACROSS THE NE LEEWARD ISLANDS TO
A BASE OVER EXTREME NORTHERN VENEZUELA NEAR 12N70W. UPPER LEVEL
DIFLUENT FLOW WAS AIDING IN MAINTAINING SOME CONVECTION AND
RESIDUAL MID TO UPPER LEVEL MOISTURE ACROSS THE EXTREME SE
CARIBBEAN AND THE WINDWARD ISLANDS S OF 15N. AT THE SURFACE...
A WEAK SURFACE TROUGH IS ALONG 84W/85W FROM 14N IN EASTERN
HONDURAS TO 20N. SCATTERED MODERATE TO STRONG CONVECTION WAS
NOTED WITHIN 90 NM OF 18N80.5W OR CENTERED ABOUT 125 NM WSW OF
JAMAICA. OTHER CLUSTERS OF STRONG CONVECTION WERE NOTED
WITHIN 90 NM N OF THE COAST OF PANAMA AND WITHIN 45-60 NM OF
13.5N67W. ELSEWHERE ACROSS THE BASIN...LOW TOPPED SHOWERS
WERE POSSIBLE IN LOW CLOUDS STREAMING ACROSS THE CARIBBEAN.
1336 AND 1516 UTC ASCAT PASSES INDICATED AN AREA OF 20-25 KT
WINDS FROM 12N TO 17N BETWEEN 65W AND 78W. THIS AREA WAS
REFLECTED IN THE HIGH SEAS FORECAST...MIAHSFAT2...AND THE
OFFSHORE WATERS FORECAST...MIAOFFNT3.

THE ATLANTIC OCEAN...
A MID-TO UPPER LEVEL TROUGH EXTENDED THROUGH 32N38W TO 21N55W
AND INTO THE CARIBBEAN SEA VIA THE NE LEEWARD ISLANDS. BROAD
WEST-NORTHWESTERLY FLOW SPANNED THE ATLANTIC W OF THE TROUGH AXIS
TO THE E COAST OF FLORIDA WITH SOME OF THIS FLOW ASSOCIATED WITH
THE PERIPHERY OF A LARGE ANTICYCLONE OVER THE NW CARIBBEAN. A
SHORTWAVE TROUGH WAS SKIRTING THE FAR NORTHERN PORTION OF THE
AREA ALONG 70W AND IS EXPECTED TO REMAIN N OF THE AREA IN
GENERALLY ZONAL FLOW ALOFT.

AT THE SURFACE....A WEAK SURFACE TROUGH EXTENDED FROM 32N80W TO
THE COAST OF FLORIDA NEAR CAPE CANAVERAL WHERE A 1017 MB SPOT LOW
WAS NOTED ALONG THE TROUGH. THIS TROUGH WAS PRODUCING MAINLY LOW
CLOUDS AND ISOLATED SHOWERS OVER THE AREA. 1027 HIGH PRESSURE N
OF THE AREA NEAR 34N53W GOVERNED THE WEATHER OVER THE
SUBTROPICAL ATLC N OF 20N BETWEEN 50W AND THE BAHAMAS. FURTHER
EAST...A SURFACE TROUGH EXTENDS THROUGH 32N33W 27N37W TO 26N43W.
A DISSIPATING STATIONARY FRONT EXTENDS FROM 32N26W TO 23N33W
WHERE IT TRANSITIONS TO A SHEAR LINE THROUGH 18N40W TO 15N49W. A
SURFACE RIDGE PASSES THROUGH THE MADEIRA ARCHIPELAGO TO 24N26W
AND 16N34W. WIDELY SCATTERED MODERATE CONVECTION WITHIN BROADER
STRATIFORM PRECIPITATION WAS POSSIBLE FROM 28N TO 32N BETWEEN
24W AND 28W. AS NOTED ABOVE A SURFACE TROUGH IS ALONG 14N53W TO
8N57W. CLUSTERS OF SCATTERED MODERATE CONVECTION WERE NOTED FROM
7N-15N BETWEEN 48W AND 56W.

FOR ADDITIONAL INFORMATION PLEASE VISIT
HTTP://WWW.HURRICANES.GOV/MARINE

$$
COBB





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