[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 311813
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST WED DEC 31 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 1745 UTC.

...THE ITCZ...

FROM LIBERIA NEAR 7N10W TO 2N30W TO 1N40W INTO EXTREME
NORTHEASTERN BRAZIL NEAR THE EQUATOR ALONG 52W. SCATTERED
MODERATE SHOWERS AND ISOLATED STRONG THUNDERSTORMS FROM
3N TO 4N BETWEEN 36W AND 38W...AND FROM THE COASTAL PLAINS
OF FRENCH GUIANA/SURINAME/GUYANA TO 10N BETWEEN 52W AND 60W.
ISOLATED MODERATE SHOWERS FROM 3N TO 4N BETWEEN 11W AND 22W.

...DISCUSSION...

THE GULF OF MEXICO...
BROAD UPPER LEVEL ANTICYCLONIC FLOW WITH A RIDGE COVERS THE
AREA. A THIN STRIP OF HIGH LEVEL MOISTURE IS MOVING THROUGH
AN AREA SURROUNDED BY MIDDLE TO UPPER LEVEL DRY AIR IN
SUBSIDENCE...FROM 24N TO 27N BETWEEN 80W AND 86W TOUCHING SOUTH
FLORIDA. UPPER LEVEL MOISTURE ALSO NORTH OF THE LINE FROM 20N97W
TO 26N90W TO 28N80W. A DEEP LAYER TROUGH THAT IS MOVING THROUGH
THE EASTERN HALF OF THE U.S.A. IS BECOMING MORE AND MORE
STRETCHED FROM EAST-TO-WEST. THIS TROUGH STILL SUPPORTS A COLD
FRONT THAT RUNS FROM EASTERN LOUISIANA TO EAST TEXAS TO CENTRAL
TEXAS AND THE NORTHERN SECTIONS OF THE TEXAS BIG BEND...AND
BEYOND. SCATTERED MODERATE SHOWERS TO POSSIBLE THUNDERSTORMS
ARE FROM 27N TO 28N BETWEEN 93W AND 95W IN LINES OF SURFACE-TO-
LOW LEVEL CONFLUENT WIND FLOW...ESPECIALLY ALONG 27N/28N BETWEEN
90W AND 97W. OTHER POSSIBLE SHOWERS ARE SOUTH OF 29N EAST OF 90W
IN AREAS OF OTHER SURFACE-TO-LOW LEVEL CONFLUENT WIND FLOW.

THE CARIBBEAN SEA...
UPPER LEVEL ANTICYCLONIC FLOW COVERS THE NORTHWESTERN CORNER OF
THE AREA...NORTH OF 15N IN HONDURAS INTO THE GULF OF MEXICO
WEST OF 79W. SHOWERS ARE POSSIBLE IN CLUSTERS OF LOW
CLOUDS...SOME IN LINES OF SURFACE-TO-LOW LEVEL CONFLUENT WIND
FLOW...THAT ARE SPREAD ACROSS THE AREA...FROM 12N TO 16N BETWEEN
THE ISLANDS AND 65W...FROM 14N TO 18N BETWEEN 68W AND 76W...
SOUTH OF 15N WEST OF 77W...AND NORTHWEST OF 17N76W 16N84W.

THE ATLANTIC OCEAN...
A COLD FRONT PASSES THROUGH 32N46W TO 26N60W TO 24N70W TO 25N80W
AT THE COAST OF FLORIDA NEAR MIAMI. SHOWERS ARE POSSIBLE IN SMALL
CLUSTERS OF BROKEN LOW CLOUDS WITHIN 15 TO 30 NM ON EITHER SIDE
OF THE FRONT. THIS FRONT IS SUPPORTED FROM THE SURFACE INTO THE
UPPER LEVELS OF THE ATMOSPHERE BY A TROUGH THAT PASSES THROUGH
32N46W TO 26N57W. PREDOMINANTLY UPPER LEVEL WESTERLY WIND FLOW
COVERS THE REST OF THE AREA NORTH OF 10N WEST OF 60W.
A SURFACE RIDGE IS ALONG 21N59W TO A 1018 MB HIGH PRESSURE
CENTER NEAR 22N46W TO A SECOND 1018 MB HIGH PRESSURE CENTER
NEAR 25N28W. THE SOUTHERN END OF A MIDDLE TO UPPER LEVEL TROUGH
REACHES SOUTHERN MOROCCO. THIS TROUGH CONTINUES TO SUPPORT
A COLD FRONT THAT PASSES THROUGH 32N13W TO 27N17W. BROAD UPPER
LEVEL ANTICYCLONIC FLOW IS IN BETWEEN THE 32N46W-26N57W TROUGH
AND THE EASTERN ATLANTIC OCEAN TROUGH THAT TOUCHES MOROCCO.
UPPER LEVEL SOUTHWESTERLY WIND FLOW CONTINUES TO BE TO THE SOUTH
OF 14N59W 15N50W 18N30W BEYOND 22N17W ACROSS AFRICA.

$$
MT



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