[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 162348
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST FRI DEC 16 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 2300 UTC.

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

THE ITCZ EXTENDS ACROSS FAR WRN AFRICA TO THE COAST OF LIBERIA
NEAR 7N11W CONTINUING W ALONG 6N25W 7N43W. SCATTERED
MODERATE/STRONG CONVECTION IS WITHIN 45 NM EITHER SIDE OF THE
AXIS BETWEEN 27W-39W.

...DISCUSSION...

THE GULF OF MEXICO...
A COLD FRONT IS SLOWLY MAKING ITS WAY ACROSS THE NW GULF OF
MEXICO FROM THE CENTRAL LOUISIANA COAST NEAR 29N92W ALONG 27N95W
TO THE MEXICAN COAST NEAR 22N98W WHERE IT CONTINUES AS A
STATIONARY FRONT TO THE NW. SCATTERED SHOWERS ARE WITHIN 75 NM
BEHIND NW OF THE FRONT ALONG WITH N-NE WINDS UP TO 20 KTS. THE
REMAINDER OF THE BASIN IS EXPERIENCING MOSTLY FAIR WEATHER WITH
A FEW PATCHES OF LOW CLOUDS AND POSSIBLE ISOLATED SHOWERS
ESPECIALLY IN THE SW CORNER IN THE BAY OF CAMPECHE. ALOFT...SWLY
FLOW COVERS THE AREA AROUND AN UPPER LEVEL RIDGE EXTENDING FROM
THE WRN CARIBBEAN INTO THE W ATLC. THE FRONT IS EXPECTED TO
STALL OVERNIGHT AND DISSIPATE OVER THE NEXT COUPLE OF DAYS AS A
SURFACE RIDGE BUILDS ACROSS THE BASIN.

THE CARIBBEAN SEA...
MUCH OF THE NRN CARIBBEAN IS EXPERIENCING MOSTLY FAIR WEATHER
DUE TO DRY AIR ALOFT AROUND AN UPPER LEVEL RIDGE EXTENDING FROM
NRN COLOMBIA TO CENTRAL CUBA. THIS PATTERN IS ALSO PROVIDING
DIFFLUENCE ALOFT OVER THE SW CARIBBEAN...WHICH COMBINED WITH
SURFACE CONVERGENCE NEAR THE MONSOON TROUGH EXTENDING ACROSS
COSTA RICA AND PANAMA TO NRN COLOMBIA IS HELPING PRODUCE
SCATTERED SHOWERS/THUNDERSTORMS S OF 14N BETWEEN 75W-85W. ACROSS
THE ERN CARIBBEAN...A SHEAR LINE EXTENDS FROM MARTINIQUE NEAR
15N61W TO N OF COLOMBIA ALONG 13N67W 13N75W PRODUCING ISOLATED
SHOWERS WITHIN 45 NM TO EITHER SIDE. NELY WINDS OF 20-25 KTS ARE
TO THE N OF THE AXIS IN THE CENTRAL CARIBBEAN...WITH 15 KT WINDS
ACROSS THE ERN. A FORMING COLD FRONT IS ALSO APPROACHING THE NRN
LEEWARD ISLANDS WHICH IS ALREADY PRODUCING ISOLATED SHOWERS
AHEAD OF IT WHICH WILL LIKELY IMPACT THE ISLANDS SHORTLY. ALSO
EXPECT SHOWER/THUNDERSTORM ACTIVITY TO CONTINUE OVER THE SW
CARIBBEAN FOR THE NEXT SEVERAL DAYS.

THE ATLANTIC OCEAN...
UPPER LEVEL RIDGING COVERS THE WRN ATLC SUPPORTING A 1024 MB
HIGH NEAR 30N72W PROVIDING MOSTLY FAIR WEATHER ACROSS THE WRN
ATLC. A NARROW UPPER LEVEL TROUGH IS ALONG 53W NOW APPEARS TO BE
BECOMING A CUT-OFF UPPER LEVEL LOW NEAR 28N53W. THE UPPER
LOW/TROUGH IS SUPPORTING A 1006 MB SURFACE LOW NEAR 24N52W. A
DISSIPATING FRONT IS AROUND THE LOW CENTER ALONG 26N52W 23N49W
19N53W TO THE LESSER ANTILLES NEAR 15N61W. SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS ARE MAINLY NE OF THE LOW CENTER
FROM 23N-30N BETWEEN 47W-54W. ISOLATED SHOWERS ARE WITHIN 150 NM
S OF THE FRONTAL BOUNDARY. A SECONDARY FORMING COLD FRONT IS NW
OF THE DISSIPATING FRONT EXTENDING FROM THE LOW CENTER AT 24N52W
ALONG 22N51W 19N58W 19N68W. ISOLATED SHOWERS ARE WITHIN 45 NM
AHEAD OF THE FRONT BETWEEN 60W-68W. THE UPPER TROUGH IS ALSO
SUPPORTING A SECOND 1005 MB SURFACE LOW FARTHER E NEAR 27N46W. A
SURFACE TROUGH EXTENDS SWD FROM THE LOW CENTER ALONG 19N47W
11N51W 8N55W. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE E OF
THE TROUGH FROM 10N-31N BETWEEN 39W-46W UNDER THE AREA OF
STRONGEST DIFFLUENCE ALOFT. THE ERN ATLC IS UNDER THE INFLUENCE
OF SURFACE RIDGING ANCHORED BY A 1034 MB HIGH BETWEEN THE AZORES
AND MADEIRA ISLANDS NEAR 36N20W PROVIDING MOSTLY FAIR WEATHER.
ALOFT...AN UPPER LEVEL RIDGE COVERS MUCH OF THE ERN ATLC WITH
AXIS ALONG 38W. HOWEVER...AN UPPER LEVEL LOW DISRUPTS THE UPPER
RIDGE NEAR 22N27W...BUT IS CAUSING LITTLE SIGNIFICANT WEATHER
BESIDES A FEW UPPER LEVEL CLOUDS E OF THE CAPE VERDE ISLANDS.
EXPECT THE FRONTAL SYSTEM IN THE CENTRAL ATLC TO LIFT N AND
GRADUALLY SHIFT E BEFORE BEING SWEPT UP BY THE NEXT FRONTAL
SYSTEM EARLY NEXT WEEK.

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

$$
WALTON





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