[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 311745
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST SAT DEC 31 2011

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
1715 UTC.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 05N03W TO
04N15W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM
04N15W TO 01N35W TO 02N44W TO 01N50W. ISOLATED MODERATE
CONVECTION IS FROM 02N-06N BETWEEN 09W-15W...AND FROM 03N-06N
BETWEEN 22W-31W.

...DISCUSSION...

GULF OF MEXICO...
WATER VAPOR IMAGERY INDICATES MOSTLY WEST-SOUTHWESTERLY UPPER
LEVEL FLOW OVER THE GULF THIS AFTERNOON AS AN UPPER LEVEL
SHORTWAVE TROUGH CONTINUES MOVING E-NE OF THE REGION OVER
NORTHERN FLORIDA INTO THE SW NORTH ATLC. AT THE SURFACE...A
RIDGE ANCHORED BY A PAIR OF 1022 MB HIGHS CENTERED NEAR 27N81W
AND 27N89W IS FOR THE TIME BEING KEEPING A FRONTAL BOUNDARY
ANALYZED FROM THE SE CONUS TO THE LOUISIANA AND TEXAS COASTAL
PLAIN AT BAY WITH MOSTLY S TO SW WINDS OVER THE NW AND
NORTH-CENTRAL GULF. ELSEWHERE...A SURFACE TROUGH IS ANALYZED
OVER THE SW GULF FROM 22N91W. WITH VERY LITTLE LOW TO MIDDLE
LEVEL MOISTURE TO WORK WITH...ISOLATED SHOWERS REMAIN POSSIBLE E
OF 92W ON THE MOIST SOUTHERLY RETURN FLOW. THE NEXT COLD FRONT
IS FORECAST TO ENTER THE NW GULF WATERS EARLY SUNDAY INTRODUCING
STRONG NORTH-NORTHEASTERLY WINDS BASIN-WIDE INTO EARLY NEXT
WEEK. THEREAFTER A STRONG RIDGE WILL REMAIN IN PLACE OVER THE SE
CONUS AND NORTHERN GULF THROUGH THE REMAINDER OF THE UPCOMING
WEEK AHEAD.

CARIBBEAN SEA...
BROAD UPPER LEVEL RIDGING IS ACROSS THE CARIBBEAN WITH WATER
VAPOR IMAGERY INDICATING DRY AIR AND SUBSIDENCE EXTENDING
BETWEEN THE TROPICAL NORTH ATLC ALONG 45W TO CENTRAL AMERICA AND
SOUTHERN MEXICO ALONG 90W. WITH A STABLE ATMOSPHERE ALOFT...THE
BASIN REMAINS TRANQUIL CONVECTIVELY...HOWEVER...AT THE
SURFACE...A MODEST PRESSURE GRADIENT BETWEEN A SURFACE RIDGE
OVER THE WESTERN AND CENTRAL ATLC AND LOWER PRESSURE OVER
NORTHERN SOUTH AMERICA IS PRODUCING STRONG E-NE TRADES IN THE
RANGE OF 20 TO 30 KT. THESE CONDITIONS ARE EXPECTED TO PERSIST
THROUGH EARLY MONDAY OF NEXT WEEK AS A COLD FRONT AND FRONTAL
TROUGH ENTER THE SW NORTH ATLC AND NW CARIBBEAN RELAXING THE
PRESSURE GRADIENT AND DIMINISHING THE TRADES. WEST OF THE
ANTICIPATED COLD FRONT...STRONG N-NE WINDS ARE EXPECTED.

ATLANTIC OCEAN...
WATER VAPOR IMAGERY SHOWS AN UPPER LEVEL SHORTWAVE TROUGH
PROGRESSING OVER THE NW PORTION OF THE SW NORTH ATLC WITH AXIS
FROM 35N77W TO 30N80W THAT SUPPORTS A WEAK SURFACE TROUGH
ANALYZED FROM THE NW BAHAMAS NEAR 27N77W TO 32N77W. ISOLATED
SHOWERS ARE NOTED ON SATELLITE IMAGERY EAST OF THE AXIS FROM
28N-32N BETWEEN 74W-78W. TO THE SE...THE SURFACE WEAKNESS WITHIN
THE SUBTROPICAL RIDGE CONTINUES AS ANOTHER SURFACE TROUGH
EXTENDS FROM 20N73W TO 25N71W. ISOLATED SHOWERS ARE OCCURRING
WITHIN 90 NM EITHER SIDE OF THE BOUNDARY. EAST OF 68W TO THE
AFRICAN COAST...ACROSS THE REMAINDER OF THE CENTRAL AND EASTERN
ATLC...AN EXPANSIVE AND RELATIVELY STRONG 1039 MB HIGH IS
CENTERED SE OF THE AZORES NEAR 35N22W. THE INFLUENCE OF THE
RIDGE EXPANDS SOUTHWARD TO 10N AND EXHIBITS AN AXIS EXTENDING
FROM THE HIGH W-SW ALONG 32N45W TO 28N67W. WITH SUCH A STRONG
HIGH PRESSURE SYSTEM IN PLACE...A STRONG PRESSURE GRADIENT
EXISTS WITH GENERALLY MODERATE TO STRONG E-NE TRADES. EARLY
MORNING ASCAT PASSES FROM 31/1028 UTC AND 31/1208 UTC INDICATED
THESE STRONG TRADES WITH POSSIBLE INTERMEDIATE GALE FORCE NE
WINDS IN THE AREA FROM 13N-23N E OF 30W...WHICH INCLUDES THE
WATERS SURROUNDING THE CAPE VERDE ISLANDS.

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

$$
HUFFMAN





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