[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 211801
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST MON JAN 21 2008

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN
SECTIONS OF SOUTH AMERICA...AND THE 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 1715 UTC

...THE ITCZ...
FROM 6N10W TO 4N20W 3N30W 2N40W...CROSSING THE EQUATOR AT 49W...
AND CONTINUING INTO NORTHEASTERN BRAZIL NEAR 2S53W. ISOLATED
MODERATE SHOWERS TO POSSIBLE THUNDERSTORMS ARE SOUTH OF 6N
BETWEEN 14W AND 30W. WIDELY SCATTERED MODERATE SHOWERS/ISOLATED
STRONG THUNDERSTORMS SOUTH OF 4N BETWEEN 30W AND 50W. ISOLATED
MODERATE SHOWERS SOUTH OF 3N EAST OF 6W.

...DISCUSSION...

THE GULF OF MEXICO...
BROAD MIDDLE TO UPPER LEVEL SOUTHWESTERLY WIND FLOW MOVES ACROSS
THE OPEN WATERS OF THE GULF OF MEXICO. BROAD ANTICYCLONIC FLOW
EXTENDS FROM THE SURFACE-TO-LOW LEVELS OF THE ATMOSPHERE UNDER
THE HIGHER LEVEL FLOW REGIME. BROKEN TO OVERCAST LOW TO MIDDLE
LEVEL CLOUDS COVER THE AREA. POSSIBLE SHOWERS BUT NO DEEP
CONVECTIVE ACTIVITY AT THIS TIME. THE STRONG PRESSURE GRADIENT
AFTER THE LATEST COLD FRONT IS HELPING TO GENERATE NORTHEAST-
TO-EAST WINDS RANGING FROM 20 KT TO 30 KT AND SEAS RANGING
FROM 8 FT TO 12 FT IN THE STRAITS OF FLORIDA. PLEASE REFER
TO THE MIAHSFAT2 HIGH SEAS FORECAST FOR SPECIFIC DETAILS.

THE CARIBBEAN SEA...
THE SOUTHERN END OF A COLD FRONT EXTENDS FROM THE ATLANTIC OCEAN
TO 23N75W IN THE BAHAMAS TO 22N78W IN CUBA. A TROUGH CONTINUES
FROM 22N78W IN CUBA TO 19N85W IN THE NORTHWESTERN CARIBBEAN
SEA...TO 12N87W IN WESTERN NICARAGUA. MODERATE SHOWERS WITHIN
A 30 NM RADIUS OF 20N85W. OTHER POSSIBLE SHOWERS ARE WEST OF THE
LINE FROM 20N80W IN CUBA...TO THE CAYMAN ISLANDS TO 15N83W BROAD
SURFACE TO LOW LEVEL CYCLONIC FLOW IS SOUTH OF 17N. HIGH LEVEL
SOUTHERLY FLOW MOVES FROM SOUTH AMERICA INTO THE CARIBBEAN
SEA...REACHING 14N AND CURVING TOWARD THE EAST-NORTHEAST.
MIDDLE TO UPPER LEVEL ANTICYCLONIC FLOW COVERS THE AREA FROM
CUBA/HAITI/JAMAICA TO THE NORTHWESTERN CARIBBEAN SEA. MIDDLE
TO UPPER LEVEL DRY AIR/ SUBSIDENCE COVERS THE ENTIRE AREA.
SURFACE EASTERLY WIND FLOW IS LOOSELY RELATED TO LARGE SCALE
ATLANTIC OCEAN ANTICYCLONIC FLOW. A 1029 MB HIGH PRESSURE
CENTER IS NEAR 30N46W. LARGE-SCALE ANTICYCLONIC FLOW FROM THIS
ATLANTIC OCEAN HIGH PRESSURE CENTER REACHES THE CARIBBEAN SEA.
THE ISOBARS ON THE SURFACE MAP DO NOT APPEAR TO SHOW A STRONG
PRESSURE GRADIENT. THAT DOES NOT MEAN THAT A SLIGHT CHANGE IN
THE PRESSURE FIELD IS NOT ABLE TO GENERATE COMPARATIVELY FASTER
WIND SPEEDS ACROSS THE OPEN WATERS OF THE CARIBBEAN SEA.
AN EXAMPLE OF FAST WINDS FROM WHAT DOES NOT APPEAR TO BE SUCH
A STRONG GRADIENT ACCORDING TO THE ISOBARIC ANALYSIS IS FROM 10N
TO 17N BETWEEN 69W AND 82W. WINDS ARE FROM THE NORTHEAST-TO-EAST
FROM 20 KT TO 30 KT AND SEAS RANGE FROM 8 FT TO 12 FT. PLEASE
REFER TO THE MIAHSFAT2 HIGH SEAS FORECAST FOR SPECIFIC DETAILS.
A SURFACE TROUGH IS AT THE END OF AN EASTERN ATLANTIC COLD
FRONT...ALONG 13N50W TO 16N60W IN THE EASTERN CARIBBEAN SEA...
TO SOUTHWESTERN PUERTO RICO AND THE EASTERN DOMINICAN REPUBLIC.
ISOLATED MODERATE SHOWERS COVER THE CARIBBEAN SEA ISLANDS FROM
GUADELOUPE TO ANTIGUA AND BARBUDA/MONTSERRAT/SAINT KITTS AND
NEVIS TO THE U.S.A. AND BRITISH VIRGIN ISLANDS...TO EASTERN/
NORTHEASTERN PUERTO RICO...TO THE EASTERN/NORTHEASTERN DOMINICAN
REPUBLIC. POSSIBLE SHOWERS IN CLUSTERS OF LOW CLOUDS ARE NORTH
OF 11N65W 14N75W 14N80W. SHOWERS ARE POSSIBLE ELSEWHERE FROM 13N
TO 18N EAST OF 80W.

THE ATLANTIC OCEAN...
AN ATLANTIC OCEAN COLD FRONT PASSES THROUGH 32N58W TO 25N70W TO
CUBA NEAR 22N78W. THE FRONT CURRENTLY IS DEFINED BY A
COMPARATIVELY THIN BAND OF LOW CLOUDS. BROKEN TO OVERCAST
MULTILAYERED CLOUDS AND POSSIBLE PRECIPITATION ARE WITHIN 90 NM
ON EITHER SIDE OF 24N80W 29N70W BEYOND BERMUDA. A 1029 MB HIGH
PRESSURE CENTER
IS NEAR 30N46W. THIS HIGH PRESSURE CENTER AND ITS ASSOCIATED
FLUCTUATIONS IN THE PRESSURE GRADIENT ARE PRODUCING 20 KT
TO 30 KT WIND SPEEDS IN THE CENTRAL AND SOUTH CENTRAL ATLANTIC
OCEAN. PLEASE REFER TO THE MIAHSFAT2 HIGH SEAS FORECAST FOR
SPECIFIC FORECAST INFORMATION REGARDING WIND AND SEAS IN THIS
AREA AND NEAR THE FRONTAL BOUNDARIES. A DEEP LAYER CYCLONIC
CIRCULATION CENTER AND TROUGH COVER THE ATLANTIC OCEAN EAST OF
40W NORTH OF 10N. A 1009 MB GALE LOW PRESSURE CENTER IS NEAR
32N29W. A COLD FRONT PASSES THROUGH 30N24W TO 20N26W 15N30W
12N40W. A TROUGH CONTINUES FROM 12N40W TO 13N50W 16N60W IN THE
EASTERN CARIBBEAN SEA...TO SOUTHWESTERN PUERTO RICO AND THE
EASTERN DOMINICAN REPUBLIC.

$$
MT


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