[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 141805
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST TUE 14 DEC 2004

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN
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...

ITCZ 7N10W 6N20W 6N30W 6N40W 7N50W 7N60W...AND FROM THE COLOMBIA
COAST NEAR 6N77W TO 6N83W. ISOLATED MODERATE TO LOCALLY STRONG
SHOWERS AND THUNDERSTORMS IN CLUSTERS FROM 3N TO 10N BETWEEN 10W
AND 28W. SCATTERED MODERATE TO ISOLATED STRONG SHOWERS AND
THUNDERSTORMS WITHIN 30 TO 60 NM ON EITHER SIDE OF 11N30W 12N35W
13N38W. WIDELY SCATTERED MODERATE TO ISOLATED STRONG SHOWERS AND
THUNDERSTORMS FROM 5N TO 8N BETWEEN 33W AND 38W. ISOLATED
MODERATE SHOWERS ELSEWHERE FROM 2N TO 12N BETWEEN 40W AND 60W.

...DISCUSSION...

THE GULF OF MEXICO...
THE COLDEST AIRMASS OF THE SEASON TO DATE IS MAKING ITS WAY
SOUTHWARD THIS AFTERNOON...BEHIND A SURFACE COLD FRONT NOW
THROUGH 32N70W TO THE SOUTHEASTERN FLORIDA COAST NEAR 27N80W...
INTO THE CENTRAL GULF OF MEXICO NEAR 25N90W...CURVING
SOUTHWESTWARD TO THE MEXICO COAST NEAR 19N96W...AND FINALLY
CURVING NORTHWESTWARD IN MEXICO TO 24N104W AND 31N111W.
COLD AIR STRATIFORM CLOUDS ARE OVER THE GULF WATERS NORTH OF
THE FRONT. OVERCAST MULTILAYERED CLOUDS ARE WITHIN 160 NM TO
THE NORTH OF THE LEADING EDGE OF THE CLOUD LINE...25N82W 24N85W
23N90W 21N95W 18N94W. MIDDLE TO UPPER TROUGH MOVING THROUGH THE
UNITED STATES GULF COAST STATES...IS EXPECTED TO SWING RAPIDLY
SOUTHEASTWARD DURING THE NEXT 24 HOURS THROUGH THE SOUTHEASTERN
UNITED STATES...PUSHING THE COLD FRONT SOUTHWARD THROUGH SOUTH
FLORIDA BY THIS EVENING AND THE REST OF THE GULF OF MEXICO BY
SUNRISE ON WEDNESDAY. A FEW SHOWERS ARE POSSIBLE DURING THE
PASSAGE OF THE FRONT THROUGH THE GULF WATERS...WITH A THICKER
COVERAGE OF RAIN IN THE SOUTHWESTERN GULF. A SURFACE 1043 MB
HIGH PRESSURE CENTER NOW IS IN THE OKLAHOMA PANHANDLE. THE
PRESSURE GRADIENT IS FORECAST TO INCREASE ENOUGH TO WARRANT
A STORM WARNING FOR 14/1800 UTC TODAY.

THE CARIBBEAN SEA...
GENERALLY ZONAL FLOW ALOFT CONTINUES WITH SOME ANTICYCLONIC
CURVATURE TO THE FLOW AS A BROAD FLAT RIDGE AXIS LIES ALONG 68W.
VERY DRY CONDITIONS ARE ASSOCIATED WITH THE ZONAL FLOW IN THE
MIDDLE TO UPPER LEVELS WITH STRONG SUBSIDENCE. ONE SURFACE TROUGH
RUNS FROM 21N65W TO PUERTO RICO TO 16N67W AND 12N71W. ISOLATED
MODERATE SHOWERS AND POSSIBLE THUNDERSTORMS ARE FOUND FROM 11N
TO 21N BETWEEN 64W AND 72W. A SECOND TROUGH IS IN THE
SOUTHEASTERN CORNER OF THE AREA ALONG 14N62W 12N62W 11N63W.
ISOLATED MODERATE SHOWERS FROM THE COAST TO 14N BETWEEN 60W
AND 64W. SCATTERED MODERATE TO ISOLATED STRONG SHOWERS AND
THUNDERSTORMS ALONG THE NICARAGUA COAST IN SURFACE ONSHORE FLOW
AND SOME POSSIBLE LEFT OVER INSTABILITY FROM THE SURFACE TROUGH
DURING THE LAST 24 TO 48 HOURS.

THE ATLANTIC OCEAN...
A SURFACE COLD FRONT NOW THROUGH 32N70W TO THE SOUTHEASTERN
FLORIDA COAST NEAR 27N80W...INTO THE CENTRAL GULF OF MEXICO NEAR
25N90W. ZONAL FLOW ALOFT TO ABOUT 60W WHERE A SHEARING TROUGH
EXTENDS FROM 32N58W TO 24N61W. SURFACE TROUGH THROUGH 32N61W
27N66W 23N70W TO SOUTHEASTERN CUBA NEAR 20N74W...STILL REMAINING
FROM YESTERDAY. BROKEN TO OVERCAST MULTILAYERED CLOUDS AND
POSSIBLE SHOWERS/THUNDERSTORMS WITHIN 20 TO 40 NM ON EITHER SIDE
OF THE EASILY RECOGNIZABLE CLOUD LINE MARKING THIS FEATURE.
BLOCKING PATTERN COVERS THE ATLC E OF 55W. A MID TO UPPER LEVEL
ANTICYCLONE IS CENTERED NEAR 32N41W WITH A MID TO UPPER LEVEL
TROUGH MOVING WWD BENEATH THE ANTICYCLONE. THE TROUGH EXTENDS
FROM 28N45W TO 13N50W. A WEAK CYCLONIC CIRCULATION WAS INDICATED
AT THE NORTHERN END OF THIS TROUGH. DOWNSTREAM DIVERGENCE ALONG
WITH VERY UNSTABLE AIR IS PRODUCING A LARGE AREA OF OVERCAST
HIGH CLOUDS AND WIDELY SCATTERED MODERATE CONVECTION FROM
10N-13N BETWEEN 32W-44W. OTHERWISE HIGH PRESSURE CONTROLS THE
ATLC BETWEEN 30W AND THE W ATLC COLD FRONT. 999 MB DEEP-LAYERED
CUTOFF LOW IN THE NORTHEASTERN ATLANTIC...NEAR 30N18W WITH A
DISSIPATING COLD FRONT FROM 30N15W THRU THE ERN CANARY ISLANDS
TO 23N20W. VERY COLD AIR ALOFT IS LEADING TO COLD-AIR
INSTABILITY SHOWERS AND A FEW THUNDERSTORMS FROM 26N TO 29N
BETWEEN 18W AND 22W. THE LOW IS EXPECTED TO MOVE
WEST-SOUTHWESTWARD THEN TURN MORE TO THE SOUTH DURING THE NEXT
24 HOURS WHILE SLOWLY FILLING. GENERALLY BROKEN LOW/MIDDLE LEVEL
CLOUDS N OF 20N E OF 45W WITH THE CLOUDS BECOMING MORE SCATTERED
FARTHER INTO THE CENTRAL ATLC. ACTIVE SUBTROPICAL JET EXTENDS
ALONG 14N46W ENEWD INTO NW MAURITANIA TRANSPORTING UPPER LEVEL
MOISTURE INTO AFRICA. SATELLITE DERIVED WINDS INDICATED CORE
SPEEDS WERE NEAR 100 KT. TRANSVERSE BANDING WITHIN THE AREA OF
HIGH CLOUDS IN THE VICINITY OF THE CAPE VERDE ISLANDS SUGGESTS
THE POSSIBILITY OF CLEAR AIR TURBULENCE...THOUGH THE SIGNATURES
HAVE BECOME LESS DEFINED OVER THE PAST SEVERAL HOURS.

$$
MT


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