[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 092347
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST FRI MAR 09 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 2315 UTC.

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

THE MONSOON TROUGH EXTENDS SW FROM THE AFRICAN COAST AT 09N13W
TO 02N19W WHERE LOW LEVEL WINDS INDICATE A TRANSITION TO AN ITCZ
WHICH IN TURN CONTINUES SW CROSSING THE EQUATOR AT 23W TO
03S30W...THEN THE ITCZ TURNS W TO THE COAST OF S AMERICA AT
03S42W. LOCALLY BROKEN LOW AND MID LEVEL CLOUDS...WITH A FEW
TSTMS...ARE OBSERVED SE OF THE ITCZ AND NW OF A LINE FROM 01N11W
TO 08S35W. CONVECTION IS ACTIVE ALONG THE MONSOON TROUGH AS IT
CONTINUES E ALONG 08N ACROSS AFRICA BETWEEN 10W AND 06E.

...DISCUSSION...

THE GULF OF MEXICO...
AN UPPER ANTICYCLONE OVER THE E PACIFIC NEAR 10N100W RIDGES NE
ACROSS THE SE GULF OF MEXICO...THE FLORIDA STRAITS AND ACROSS
THE NW BAHAMAS. AN UPPER SHORTWAVE TROUGH HAS MOVED OVER THE NW
GULF WITH THE ASSOCIATED SURFACE COLD FRONT CURRENTLY EXTENDING
FROM THE FLORIDA PANHANDLE TO A FRONTAL WAVE DEVELOPING AT
28N94W...WITH THE COLD FRONT THEN CONTINUING S ALONG 96W TURNING
W AND INLAND MEXICO AT 22N97W. BROKEN TO OVERCAST LOW CLOUDS...
WITH WIDESPREAD LIGHT RAIN...ARE OBSERVED TO THE N OF THE
SURFACE FRONT...WITH PATCHY FOG REPORTED THROUGHOUT THE TEXAS
COASTAL BEND AREA OCCASIONALLY REDUCING VISIBILITY BELOW 3 SM.
NORTHERLY WINDS HAVE DIMINISHED TO 20 TO 25 KT N OF THE FRONT.
LIGHTNING DATA IS DETECTING TSTMS ALONG THE FRONTAL BOUNDARY
OFFSHORE THE TEXAS COAST. DENSE UPPER MOISTURE IS INDICATED N OF
27N WHILE THE REMAINDER OF THE GULF IS MOSTLY CLEAR EXCEPT FOR
SMALL AREAS OF CUMULUS. THE COLD FRONT IS EXPECTED TO SOON STALL
AND DRIFT NW WHILE DISSIPATING ON THE NEXT COUPLE OF DAYS.

THE CARIBBEAN SEA...
A POSITIVE TILT UPPER TROUGH HAS ITS MEAN AXIS EXTENDING FROM
HISPANIOLA TO PANAMA...AND IS ACCOMPANIED BY VERY DRY AIR ALOFT.
HOWEVER...DENSE UPPER MOISTURE ORIGINATING FROM CONVECTION OVER
S AMERICA IS ADVECTED NE ACROSS THE SE CARIBBEAN...TO THE SE OF
OF A LINE FROM THE VIRGIN ISLANDS TO THE NW VENEZUELA. LOCALLY
BROKEN LOW LEVEL CLOUDS...WITH BRIEF SHOWERS...ARE RACING
WESTWARD ACROSS THE CARIBBEAN IN EASTERLY 15 TO 20 KT TRADES...
WITH THE EXCEPTION OF AN AREA OF CLEAR SKIES OBSERVED WITHIN 120
NM OF THE NW COLOMBIAN COAST WHERE LOW LEVEL WINDS ARE NE TO E
AT 25 TO 30 KT.

THE ATLANTIC OCEAN...
AN UPPER RIDGE IS ORIENTATED SW TO NE FROM THE FLORIDA STRAITS
TO BEYOND BERMUDA. DENSE UPPER MOISTURE IS OBSERVED W OF THIS
RIDGE AXIS...AND IS PROGRESSING E WITH TIME. AN UPPER CYCLONE IS
CENTERED NEAR 33N62W WITH AN UPPER TROUGH EXTENDING SW THROUGH
ANOTHER UPPER CYCLONE AT 27N66W...WITH THE TROUGH CONTINUING SW
ACROSS HISPANIOLA TO THE SW CARIBBEAN. THE UPPER LEVELS APPEAR
VERY DRY E OF THE PREVIOUSLY MENTIONED UPPER RIDGE...AND THIS
DOWNSTREAM TROUGH. AT THE LOW LEVELS A RIDGE EXTENDS FROM 32N60W
TO CENTRAL FLORIDA WITH LOCALLY BROKEN TRADE WIND CUMULUS MOVING
FROM SE TO NW THROUGH THE RIDGE.

UPPER DIFFLUENCE E OF THE UPPER TROUGH IS ENHANCING CONVECTION
UNDER A BROAD UPPER RIDGE THAT COVERS THE DISCUSSION AREA
BETWEEN 40W AND 60W...IN THE AREA FROM 23N TO 30N BETWEEN 50W
AND 63W WITH A LOW LEVEL TROUGH INDUCED FROM 23N63W TO 29N62W.
LIGHTNING DATA DETECTS TSTMS FIRING OFF WITHIN 150 NM E OF THIS
LOW LEVEL TROUGH. A SURFACE COLD FRONT ENTERS THE AREA AT 32N27N
BUT IMMEDIATELY WEAKENS TO A SHEAR AXIS AS IT CONTINUES W
GRADUALLY DISSIPATING ALONG 24N BETWEEN 40W AND 50W.

A SLIGHTLY NEGATIVE TILT UPPER TROUGH EXTENDS FROM 32N30W TO A
BASE AT 22N29W WHILE A SECOND UPPER TROUGH IS OVER AFRICA TO THE
N OF 16N. A NARROW UPPER RIDGE IS SQUEEZED BETWEEN THESE TROUGHS
AND IS ACCOMPANIED BY UPPER MOISTURE WHICH IS NOW MOVING OVER
THE W AFRICAN COAST TO THE N OF 10N.

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

$$
NELSON





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