[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 172340
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST THU NOV 17 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 2315 UTC.

...TROPICAL WAVES...

A TROPICAL WAVE EXTENDS FROM 18N49W TO 11N50W MOVING WNW AT
10-15 KT. THE WAVE IS EMBEDDED WITHIN A BROAD SURGE OF DEEP
LAYER MOISTURE EVIDENT IN TOTAL PRECIPITABLE WATER IMAGERY. AN
UPPER LEVEL TROUGH EXTENDING ALONG 56W IS PLACING DIFFLUENCE
ALOFT OVER THE AREA BETWEEN 41W-53W...INCLUDING THE WAVE. THIS
MAKES IT DIFFICULT TO DISCERN WHETHER CONVECTION NEAR THE WAVE
IS ASSOCIATED DIRECTLY WITH THE WAVE OR THE UPPER LEVEL PATTERN.
REGARDLESS OF THE INFLUENCE...SCATTERED MODERATE/ISOLATED
CONVECTION IS FROM 14N-20N BETWEEN 44W-54W.

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

THE MONSOON TROUGH EXTENDS ACROSS W AFRICA ENTERING OVER ATLC
WATERS NEAR 11N15W TO 6N19W. THE ITCZ CONTINUES FROM 6N19W ALONG
3N32W 6N45 PICKING UP ON THE OTHER SIDE OF THE TROPICAL WAVE
ALONG 8N52W TO 10N61W. SCATTERED MODERATE/STRONG CONVECTION IS
FROM 5N-8N BETWEEN 15W-17W. SIMILAR ACTIVITY IS FROM 6N-9N
BETWEEN 36W-41W...AND N OF 8N BETWEEN 40W-49W. THIS LAST AREA OF
CONVECTION LEADS INTO MORE WIDESPREAD ACTIVITY ASSOCIATED WITH
AN UPPER LEVEL TROUGH OVER THE CENTRAL ATLC.

...DISCUSSION...

THE GULF OF MEXICO...
A WEAK AND FAST MOVING COLD FRONT IS ACROSS THE GULF MEXICO THIS
EVENING EXTENDING FROM NEAR FORT MYERS FLORIDA AT 26N82W ALONG
23N90W 20N97W...AS OF 2100 UTC. ISOLATED SHOWERS ARE ALONG THE
FRONT AXIS WITH SCATTERED SHOWERS/THUNDERSTORMS IN THE SRN BAY
OF CAMPECHE AND ACROSS THE YUCATAN PENINSULA. SURFACE RIDGING IS
BUILDING IN BEHIND THE FRONT AROUND A 1032 MB HIGH OVER SRN
OKLAHOMA. THIS PRESSURE GRADIENT IS SUPPORTING 20-25 KT N-NE
WINDS BEHIND THE FRONT. ALOFT...MAINLY WSWLY FLOW ALOFT COVERS
THE BASIN ACCOMPANIED BY DRY AIR WHICH IS HELPING INHIBIT SHOWER
ACTIVITY ALONG THE FRONTAL BOUNDARY AND KEEPING CONDITIONS FAIR
ELSEWHERE. EXPECT THE FRONT TO CONTINUE TO PUSH SE OUT OF THE
BASIN WITHIN THE NEXT 12-24 HOURS WITH SURFACE RIDGING BUILDING
IN BEHIND IT.

THE CARIBBEAN SEA...
DRY AIR AND SUBSIDENCE COVER MUCH OF THE CARIBBEAN THIS EVENING
AROUND AN UPPER LEVEL RIDGE CENTERED N OF ERN CUBA HELPING
MAINTAIN MOSTLY FAIR CONDITIONS BASIN-WIDE. A FEW ISOLATED
SHOWERS ARE NOTED OVER PORTIONS OF PUERTO
RICO...HISPANIOLA...JAMAICA...AND ERN CUBA. SIMILAR ACTIVITY IS
IN THE NW CARIBBEAN FROM 13N-20N BETWEEN 80W-84W. SCATTERED
SHOWERS/THUNDERSTORMS ARE ALSO OVER PANAMA...AND COSTA RICA
ASSOCIATED WITH THE MONSOON TROUGH THAT EXTENDS ACROSS PANAMA TO
NRN COLOMBIA. AT THE SURFACE...TRADEWIND FLOW OF 10-15 KTS
COVERS MUCH OF THE BASIN. EXPECT SHOWER ACTIVITY TO REMAIN NEAR
THE MONSOON TROUGH AND ACROSS CENTRAL AMERICA WITH FAIR
CONDITIONS ELSEWHERE. THE FRONT CURRENTLY IN THE GULF OF MEXICO
IS EXPECTED TO DISSIPATE BEFORE REACHING THE NW CARIBBEAN.

THE ATLANTIC OCEAN...
A BROAD UPPER LEVEL TROUGH EXTENDS DOWN THE ERN UNITED STATES
SEABOARD SUPPORTING A COLD FRONT THAT ENTERS THE DISCUSSION AREA
NEAR 32N78W TO NRN FLORIDA NEAR 29N81W AND INTO THE GULF OF
MEXICO. POSSIBLE ISOLATED SHOWERS ARE ALONG THE FRONT AXIS. THE
REMAINDER OF THE W ATLC IS EXPERIENCING MOSTLY FAIR WEATHER DUE
TO DRY AIR ALOFT AROUND AN UPPER LEVEL RIDGE EXTENDING FROM ERN
CUBA TO NEAR 33N61W. FARTHER E...A SHARP UPPER TROUGH EXTENDS
ALONG 55W. UPPER LEVEL DIFFLUENCE AROUND THE E SIDE OF THE
TROUGH IS HELPING SUPPORT A BROAD AREA OF SHOWERS/THUNDERSTORMS
FROM N OF THE ITCZ TO 30N BETWEEN 40W-55W. SOME OF THE ACTIVITY
IS ALSO ENHANCED BY A TROPICAL WAVE NEAR 50W...AND A SURFACE
TROUGH ALONG 29N49W TO 22N52W. IT APPEARS THAT A SURFACE LOW MAY
BE FORMING ALONG THE SURFACE TROUGH AXIS. THE ERN ATLC IS
COVERED BY AN UPPER LEVEL RIDGE WITH AXIS ALONG 38W SUPPORTING A
1026 MB HIGH NEAR 35N41W. A BROAD UPPER LEVEL TROUGH IS ACROSS
THE FAR ERN ATLC WITH AXIS EXTENDING OVER NW AFRICA CAUSING NO
SIGNIFICANT WEATHER WITHIN THE DISCUSSION AREA. EXPECT THE AREA
OF DISTURBED WEATHER IN THE CENTRAL ATLC TO BE THE MAIN FOCUS
FOR THE NEXT SEVERAL DAYS AS SHOWER/POSSIBLE THUNDERSTORM
ACTIVITY CONTINUES.

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

$$
WALTON




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