[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 271202
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 AM EST THU DEC 27 2007

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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 1115 UTC

...THE ITCZ...

FROM NORTHERN COASTAL SIERRA LEONE TO 7N20W 4N30W...CROSSING
THE EQUATOR ALONG 40W TO NORTHEASTERN COASTAL BRAZIL NEAR
3S45W. ISOLATED MODERATE SHOWERS AND POSSIBLE LOCAL
THUNDERSTORMS ARE SOUTH OF 7N EAST OF 50W...AND SOUTH OF 11N
WEST OF 55W IN THE ATLANTIC OCEAN. OVERCAST HIGH CLOUDS ARE
WITHIN 120 NM TO 180 NM ON EITHER SIDE OF 10N43W 16N30W...
AND FROM 13N TO 26N EAST OF 30W.

...DISCUSSION...

THE GULF OF MEXICO...
A MIDDLE TO UPPER LEVEL TROUGH IS DIGGING SOUTHWARD THROUGH
CALIFORNIA INTO THE BAJA PENINSULA/NORTHERN MEXICO/NEW MEXICO.
DRY MIDDLE TO UPPER LEVEL WESTERLY-TO-SOUTHWESTERLY WIND FLOW
CROSSES MEXICO NORTH OF 23N. A BAND OF MOISTURE FROM THE EASTERN
PACIFIC OCEAN IS WITHIN 120 NM TO 180 NM ON EITHER SIDE OF THE
LINE THROUGH 17N109W TO 21N100W IN MEXICO TO THE CENTRAL GULF OF
MEXICO NEAR 26N90W BEYOND 30N83W ALONG THE FLORIDA/GEORGIA
BORDER. MORE DRY AIR IS SOUTHEAST OF THE MOISTURE BAND. A MIDDLE
TO UPPER LEVEL TROUGH PASSES THROUGH LOUISIANA TO DEEP SOUTH
TEXAS. THIS TROUGH SUPPORTS THE COLD FRONT THAT PASSES THROUGH
THE NORTH CENTRAL U.S.A. GULF COAST STATES INTO THE SOUTHWESTERN
CORNER OF THE GULF OF MEXICO. A SURFACE RIDGE COVERS SOUTH
CAROLINA/GEORGIA/FLORIDA. BROKEN TO OVERCAST MULTILAYERED CLOUDS
AND POSSIBLE SHOWERS ARE WITHIN 60 NM ON EITHER SIDE OF THE
FRONT. THE FORECAST IS FOR THIS FRONT TO DISSIPATE DURING THE
NEXT 24 HOURS. A SECOND FRONT WILL FOLLOW THE FIRST ONE...BUT
NOT FOR ANOTHER FEW DAYS...TO BE IN THE WESTERN GULF OF MEXICO
BY 29/0000 UTC.

THE CARIBBEAN SEA...
ONE AREA OF UPPER LEVEL ANTICYCLONIC FLOW/RIDGE EXTENDS AS FAR
TO THE NORTH AS CUBA AND THE BAHAMAS SOUTH OF 24N. MIDDLE TO
UPPER LEVEL DRY AIR/SUBSIDENCE EVERYWHERE. HIGH LEVEL CLOUDS
FROM THE EASTERN PACIFIC OCEAN ITCZ PRECIPITATION HAVE CROSSED
THE AREA OF NORTHWESTERN COLOMBIA/PANAMA/COSTA RICA INTO THE
SOUTHWESTERN CORNER OF THE AREA. THE MIDDLE TO UPPER LEVEL
ANTICYCLONIC FLOW FROM THE WESTERN CARIBBEAN SEA RIDGE COVERS
THE AREA AS FAR TO THE EAST AS 66W. THE ATLANTIC OCEAN-TO-
CARIBBEAN SEA MIDDLE TO UPPER LEVEL TROUGH REACHES BARBADOS.
THE TROUGH IS SURROUNDED BY DRY AIR/SUBSIDENCE. BROAD SURFACE
LOW PRESSURE COVERS THE SOUTHWESTERN CORNER OF THE AREA.
SCATTERED MODERATE SHOWERS TO ISOLATED STRONG THUNDERSTORMS ARE
WITHIN A 15 NM RADIUS OF 9N77W IN THE GULF OF URABA. POSSIBLE
SHOWERS IN BROKEN LOW TO MIDDLE LEVEL CLOUDS FROM 13N TO 20N
BETWEEN 75W AND 83W...AND FROM 17N TO 21N ALONG 85W/86W.

THE ATLANTIC OCEAN...
THE WESTERN ATLANTIC OCEAN DEEP LAYER TROUGH FROM SIX HOURS AGO
STILL EXISTS...BUT IT HAS BEEN PUSHED EASTWARD ABOUT 200 NM BY
THE NEXT MIDDLE TO UPPER LEVEL TROUGH THAT IS PUSHING ITSELF
INTO THE EASTERN U.S.A. THE WESTERN ATLANTIC OCEAN TROUGH STILL
SUPPORTS THE ATLANTIC OCEAN COLD FRONT THAT PASSES THROUGH
32N70W TO 31N71W. A DISSIPATING COLD FRONT CONTINUES FROM 31N71W
TO 29N75W TO 26N79W. SHOWERS ARE POSSIBLE IN LINES OF LOW TO
MIDDLE LEVEL CLOUDS THAT ARE NORTH OF 25N BETWEEN 70W AND 80W.
HIGH CLOUDS ARE NORTH OF 22N BETWEEN 53W AND 65W IN UPPER LEVEL
DIFFLUENT WIND FLOW EAST OF THE FRONT/TROUGH. MIDDLE TO UPPER
LEVEL ANTICYCLONIC WIND FLOW...FROM THE CARIBBEAN SEA RIDGE...
COVERS THE ATLANTIC OCEAN WEST OF 50W. A DEEP LAYER CYCLONIC
CIRCULATION CENTER REMAINS IN THE CENTRAL ATLANTIC OCEAN NEAR
26N38W ON WATER VAPOR IMAGERY...AND A 1012 MB LOW PRESSURE
CENTER IS NEAR 26N39W ON THE 27/0600 UTC SURFACE MAP ANALYSIS.
THE DEEP LAYER TROUGH RUNS FROM THE 26N38W CYCLONIC CENTER TO
21N41W 17N43W 14N54W TO BARBADOS. AN OCCLUDED FRONT EXTENDS FROM
THE 26N41W SURFACE LOW PRESSURE CENTER NORTHEASTWARD TO 32N38W.
A SURFACE TROUGH FROM THE 26N41W LOW PRESSURE CENTER TO 24N37W
AND 19N45W. A SECOND SURFACE TROUGH EXTENDS FROM THE LOW CENTER
TO 24N40W AND 23N45W. THIS SECOND TROUGH EASILY MAY DEVELOP INTO
A COLD FRONT AS IT IS BRINGING A SECOND ROUND OF ENERGY TO THE
ATMOSPHERIC DYNAMICS AROUND THE CYCLONIC CENTER. WIDELY
SCATTERED TO SCATTERED MODERATE SHOWERS AND ISOLATED STRONG
THUNDERSTORMS ARE FROM 21N BEYOND 32N BETWEEN 33W AND 40W.

$$
MT



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