[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 201135
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
705 AM EST THU DEC 20 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 1115 UTC.

...THE ITCZ/THE MONSOON TROUGH...

THE MONSOON TROUGH PASSES THROUGH SOUTHERN COASTAL LIBERIA NEAR
5N8W TO 5N10W. THE ITCZ CONTINUES FROM 5N10W TO 4N15W...CROSSING
THE EQUATOR ALONG 22W...TO 1S26W...REACHING THE EQUATOR ALONG
33W AGAIN...AND CONTINUING ALONG THE EQUATOR TO 40W. CONVECTIVE
PRECIPITATION...SCATTERED STRONG FROM 6N TO 8N BETWEEN 48W AND
61W...SCATTERED MODERATE TO ISOLATED STRONG FROM 2N TO 5N TO THE
EAST OF 15W...AND FROM 6N IN GUYANA TO 11N BETWEEN 54W AND 59W...
ISOLATED MODERATE ELSEWHERE TO THE SOUTH OF 5N TO THE EAST OF
38W.

...DISCUSSION...

THE GULF OF MEXICO...

MIDDLE LEVEL SOUTHWESTERLY WIND FLOW COVERS MUCH OF THE EASTERN
ONE-THIRD OF THE AREA. THE REST OF THE GULF OF MEXICO IS COVERED
BY MIDDLE LEVEL TO UPPER LEVEL WESTERLY-TO-NORTHWESTERLY WIND
FLOW.

HIGH LEVEL MOISTURE HAS REACHED THE GULF OF MEXICO...TO THE WEST
OF A LINE THAT RUNS FROM NORTHEASTERN FLORIDA...INTO THE NORTH
CENTRAL GULF...TO THE WEST CENTRAL GULF WATERS/MEXICO COAST NEAR
23N. A DEEP LAYER TROUGH IS MOVING THROUGH THE AREA STRETCHES
FROM WESTERN MISSOURI...INTO OKLAHOMA AND NORTH CENTRAL TEXAS.

PLEASE READ THE HIGH SEAS FORECAST...MIAHSFAT2...AND THE
OFFSHORE FORECAST...MIAOFFNT4...FOR MORE DETAILS ABOUT
THE GALE WARNING...AT 6 HOURS INTO THE FORECAST PERIOD...
TO THE WEST OF THE 30N92W 23N98W COLD FRONT.
EXPECT 20 TO 30 KNOT WINDS AND SEA HEIGHTS TO 8 FEET
ELSEWHERE TO THE WEST OF THE FRONT.

THE CARIBBEAN SEA...

BROAD MIDDLE LEVEL SOUTHEASTERLY WIND FLOW COVERS THE AREA TO
THE EAST OF 80W...BECOMING SOUTHWESTERLY WIND FLOW TO THE NORTH
OF 18N TO THE WEST OF 80W.

MIDDLE LEVEL TO UPPER LEVEL SOUTHWESTERLY WIND FLOW MOVES FROM
THE SOUTHWESTERN CORNER OF THE AREA...AND FROM COLOMBIA AND
VENEZUELA NORTHWARD...IN ORDER TO BE TO THE SOUTH OF 15N.
COMPARATIVELY DRIER AIR IN SUBSIDENCE...IN WATER VAPOR SATELLITE
IMAGERY...COVERS THE ENTIRE AREA...EXCEPT FOR THE SOUTHWESTERN
CORNER AND THE CONVECTIVE PRECIPITATION.

BROKEN LOW LEVEL TO MIDDLE LEVEL CLOUDS AND POSSIBLE RAINSHOWERS
ARE MOVING SOUTHWESTWARD ACROSS PUERTO RICO...THEY HAVE BEEN
TO THE SOUTH OF 18N BETWEEN 60W AND 65W...FROM 14N TO 18N
BETWEEN 67W AND 75W...MOVING ONSHORE IN NICARAGUA...AND
ELSEWHERE TO THE NORTH OF 15N TO THE WEST OF 80W.

THE SURFACE PRESSURE GRADIENT CONTINUES TO BE
COMPARATIVELY WEAK ACROSS THE AREA.

THE MONSOON TROUGH PASSES THROUGH 7N73W IN COLOMBIA...BEYOND
6N80W IN THE EASTERN PACIFIC OCEAN. CONVECTIVE PRECIPITATION...
SCATTERED MODERATE TO STRONG TO THE SOUTH OF 11N FROM THE GULF
OF URABA OF COLOMBIA...ALONG THE PANAMA COAST/IN THE COASTAL
WATERS...TO THE EXTREME SOUTHEASTERN POINT OF NICARAGUA...
ISOLATED MODERATE TO LOCALLY STRONG IN THE EASTERN PACIFIC OCEAN
TO THE WEST OF COLOMBIA AND THE SOUTH OF PANAMA TO THE NORTH
OF 5N TO THE EAST OF 83W.

PLEASE READ THE HIGH SEAS FORECAST...MIAHSFAT2...AND THE
OFFSHORE FORECAST...MIAOFFNT3...FOR MORE DETAILS ABOUT
20 TO 25 KNOT WINDS AND 8 FOOT SEA HEIGHTS IN 6 HOURS...
FROM 11N TO 13N BETWEEN 70W AND 77W.

THE ATLANTIC OCEAN...

A MIDDLE LEVEL TO UPPER LEVEL TROUGH PASSES THROUGH 32N55W
TO 25N54W. THE TROUGH SUPPORTS A COLD FRONT THAT PASSES THROUGH
32N48W TO 27N55W 23N66W AND 23N76W. CONVECTIVE PRECIPITATION...
BROKEN TO OVERCAST LOW LEVEL AND MIDDLE LEVEL CLOUDS AND
POSSIBLE PRECIPITATION COVER THE ATLANTIC OCEAN TO THE SOUTH OF
24N BETWEEN 60W AND 80W...AND ELSEWHERE WITHIN 90 NM ON EITHER
SIDE OF 20N61W 23N58W 27N52W BEYOND 32N45W...AND WITHIN 90 NM
ON EITHER SIDE OF 20N52W 26N46W 30N43W.

A 1020 MB HIGH PRESSURE CENTER IS NEAR 30N76W. BROAD SURFACE
ANTICYCLONIC WIND FLOW COVERS THE ATLANTIC OCEAN TO THE NORTH
OF THE 32N48W 23N76W COLD FRONT.

A MIDDLE LEVEL TO UPPER LEVEL EASTERN ATLANTIC OCEAN TROUGH
PASSES THROUGH 32N20W TO 27N29W 21N33W 14N35W AND 9N38W.
THE TROUGH SUPPORTS A STATIONARY FRONT THAT PASSES THROUGH
32N22W TO 31N24W. A DISSIPATING COLD FRONT CONTINUES FROM
31N24W TO 28N30W AND 26N35W. RAINSHOWERS ARE POSSIBLE FROM
20N TO 27N BETWEEN 20W AND 30W...AND FROM 27N TO 30N BETWEEN
10W AND 20W.

AN EASTERN ATLANTIC OCEAN SURFACE RIDGE PASSES THROUGH 32N13W...
ACROSS THE CANARY ISLANDS...TO 25N25W AND 19N36W.

PLEASE READ THE HIGH SEAS FORECAST...MIAHSFAT2...FOR MORE
DETAILS ABOUT...THE GALE WARNING IN THE CENTRAL ATLANTIC OCEAN...
TO THE NORTH OF 30N WITHIN 180 NM TO THE EAST OF THE FRONT THAT
IS ALONG 31N49W 23N65W 22N78W. A SECOND GALE WARNING IS FORECAST
AT THE 24-HOUR TIME DURING THE FORECAST PERIOD...IN THE WESTERN
ATLANTIC OCEAN...TO THE NORTH OF 30N WITHIN 120 NM TO THE EAST
OF A COLD FRONT THAT WILL BE ALONG 31N79W 29N81W.

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

$$
MT





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