[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 111142
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
705 AM EST SUN DEC 11 2011

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 1100 UTC.

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

THE MONSOON TROUGH EXTENDS ACROSS AFRICA TO THE COAST OF
GUINEA-BISSAU NEAR 11N15W CONTINUING SW TO 7N20W. THE ITCZ
CONTINUES FROM 7N20W ALONG 3N28W 3N48W. ISOLATED MODERATE
CONVECTION IS WITHIN NM N OF THE AXIS BETWEEN 20W-37W.

...DISCUSSION...

GULF OF MEXICO...
MAINLY NELY SURFACE FLOW COVERS THE GULF OF MEXICO THIS MORNING
AROUND AN ELONGATED SURFACE RIDGE WITH AXIS EXTENDING FROM NEW
ENGLAND TO TEXAS. DUE TO THE TIGHT PRESSURE GRADIENT ACROSS THE
BASIN...WINDY CONDITIONS PERSIST UP TO 20 KTS...SLIGHTLY
DECREASED FROM OVERNIGHT. RADAR IMAGERY INDICATES SCATTERED
SHOWERS CONTINUE ACROSS THE NW GULF FROM THE COAST OF LOUISIANA
TO SRN TEXAS. ISOLATED SHOWERS ARE ALSO ACROSS S FLORIDA AND
POSSIBLE IN THE CENTRAL GULF WHERE WIDESPREAD LOW-LEVEL CLOUDS
ARE PRESENT. ALOFT...MOIST WSWLY FLOW DOMINATES AROUND A BROAD
UPPER LEVEL TROUGH COVERING THE FAR ERN CONUS. THE STRONG NELY
SURFACE WINDS ARE ALREADY DIMINISHING AND WILL CONTINUE TO DROP
TO 15 KTS OVER THE NEXT 24 HOURS AS THE SURFACE RIDGE MOVES OFF
TO THE E. ISOLATED SHOWERS WILL ALSO LIKELY REMAIN ACROSS THE
BASIN.

CARIBBEAN SEA...
DRY AIR ALOFT AROUND A BROAD UPPER RIDGE OVER THE CARIBBEAN IS
KEEPING MUCH OF THE BASIN UNDER CLEAR SKIES AND FAIR CONDITIONS.
HOWEVER...DUE TO A SHORTWAVE UPPER LEVEL TROUGH EXTENDING FROM
GUATEMALA INTO THE E PACIFIC...UPPER LEVEL DIFFLUENCE IS PRESENT
OVER THE AREA JUST E OF CENTRAL AMERICA. THIS ALONG WITH AREAS
OF WIND SPEED CONVERGENCE IS HELPING PRODUCE SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS N OF HONDURAS FROM 16N-19N
BETWEEN 85W-88W...AND E OF NICARAGUA S OF 16N BETWEEN 74W-83W.
SOME OF THIS ACTIVITY IS ALSO INFLUENCED BY LOW LEVEL CYCLONIC
FLOW AROUND THE MONSOON TROUGH EXTENDING ACROSS PANAMA TO NRN
COLOMBIA. A SHEAR LINE REMAINS IN THE NE CARIBBEAN ALONG 16N E
OF 69W SUPPORTING ISOLATED SHOWERS WITHIN 30 NM OF THE AXIS. 15
KT ENE WINDS ARE NOTED N OF THE AXIS WHILE 5-10 KT WINDS ARE TO
THE S. EXPECT SHOWERS/THUNDERSTORMS TO REMAIN ACROSS THE FAR WRN
CARIBBEAN AS WELL AS THE NE PORTION OF THE BASIN AS A SURFACE
TROUGH IN THE CENTRAL ATLC DRIFTS WWD.

ATLANTIC OCEAN...
A WEAK COLD FRONT IS IN THE W ATLC ENTERING THE DISCUSSION AREA
NEAR 32N72W TO 30N76W. ISOLATED
SHOWERS ARE WITHIN 75 NM EITHER SIDE OF THE AXIS. THE FRONT IS
SUPPORTED BY A BROAD UPPER LEVEL TROUGH OVER THE FAR ERN CONUS.
AN UPPER LEVEL RIDGE IS TO THE E CENTERED NEAR 34N48W PROVIDING
FAIR WEATHER ACROSS THE REMAINDER OF THE W ATLC. AN UPPER LEVEL
LOW TO THE S OF THE UPPER RIDGE NEAR 23N55W SUPPORTS A SURFACE
TROUGH ALONG 25N61W TO 19N58W. GALE FORCE WINDS
ARE NOTED E OF THE AXIS NEAR 26N54W AND EXPECTED TO CONTINUE
THROUGH 1800 UTC. MOST OF THE SHOWER ACTIVITY IS ALSO E OF THE
AXIS UNDER THE AREA OF DIFFLUENCE ALOFT AROUND THE UPPER LOW
WITH SCATTERED SHOWERS/ISOLATED THUNDERSTORMS FROM 18N-23N
BETWEEN 44W-55W...AND FROM 23N-28N BETWEEN 51W-58W. A SHEAR AXIS
IS TO THE S  OF THE SURFACE TROUGH ALONG 16N W OF 59W CONTINUING
INTO THE NE CARIBBEAN. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS
ARE WITHIN 150 NM N OF THE AXIS. SURFACE RIDGING DOMINATES THE
ERN ATLC AROUND A 1033 MB HIGH NEAR 36N38W SUPPORTED BY BROAD
UPPER RIDGING COVERING THE NRN ATLC. A NARROW UPPER LEVEL TROUGH
EXTENDS FROM THE CANARY ISLANDS TO E OF THE UPPER LEVEL LOW IN
THE CENTRAL ATLC. MAINLY WLY FLOW ALOFT COVERS THE TROPICAL
ATLC. EXPECT THE SURFACE TROUGH IN THE CENTRAL ATLC TO DRIFT WWD
OVER THE NEXT SEVERAL DAYS.

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

$$
WALTON






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