[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 132351
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT THU OCT 13 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...
TROPICAL WAVE IS IN THE ERN TRPCL ATLC ALONG 11N27W TO 5N32W
MOVING W 10-15 KT. THE WAVE REMAINS LOW AMPLITUDE...BUT DOES
COINCIDE WITH A SLIGHT SURGE OF DEEP LAYER MOISTURE EVIDENT IN
TOTAL PRECIPITABLE WATER. SCATTERED MODERATE/STRONG CONVECTION
IS FROM 6N-11N BETWEEN 25W-32W.

TROPICAL WAVE IS IN THE CENTRAL TRPCL ATLC ALONG 13N43W TO 6N48W
MOVING W NEAR 15 KT. THE WAVE IS EMBEDDED WITHIN A RIDGE OF
ENHANCED DEEP LAYER MOISTURE EVIDENT IN TOTAL PRECIPITABLE WATER
IMAGERY. THE WAVE ALSO IS WELL-DEFINED IN MODEL STREAMLINE
ANALYSIS. CURRENTLY THE WAVE IS UNDER THE INFLUENCE OF AN UPPER
LEVEL TROUGH WHICH IS SHEARING CONVECTION TO THE NE. CURRENTLY
SCATTERED MODERATE CONVECTION IS WITHIN 100 NM EITHER SIDE OF
THE AXIS AS WELL AS NE OF THE AXIS FROM 14N-19N BETWEEN 38W-44W.


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

THE MONSOON TROUGH EXTENDS JUST SLIGHTLY OFF THE AFRICAN COAST
ALONG 16N16W TO 14N19W. THE ITCZ PICKS UP ON THE W SIDE OF THE
ERN-MOST TROPICAL WAVE ALONG 7N34W 8N45W CONTINUING ON THE OTHER
SIDE OF THE WRN-MOST TROPICAL WAVE ALONG 8N49W 7N60W. ALL DEEP
CONVECTION IS DESCRIBED IN ASSOCIATION WITH THE TROPICAL WAVES.
ALTHOUGH...SCATTERED MODERATE/STRONG CONVECTION IS NEAR THE END
OF THE ITCZ INLAND OVER VENEZUELA.

...DISCUSSION...

THE GULF OF MEXICO...
MAINLY WLY-NWLY FLOW ALOFT COVERS THE GULF OF MEXICO BETWEEN AN
UPPER LEVEL RIDGE TO THE S OVER THE NW CARIBBEAN AND AN UPPER
LEVEL TROUGH TO THE N OVER THE ERN CONUS. THIS UPPER TROUGH
SUPPORTS A COLD FRONT EXTENDING FROM NEAR MOBILE ALABAMA TO
BROWNSVILLE TEXAS ALONG 30N88W TO 26N98W. MOSTLY DRY AIR ALOFT
COVERS THE BASIN WHICH IS LIMITING MOST OF THE
SHOWER/THUNDERSTORM ACTIVITY ALONG THE FRONTAL BOUNDARY.
ISOLATED SHOWERS ARE NOTED ALONG THE AXIS WITH MORE SCATTERED
ACTIVITY S OF BROWNSVILLE AND AHEAD OF THE FRONT OVER THE
FLORIDA PANHANDLE AND GEORGIA. A SURFACE TROUGH IS AHEAD OF THE
FRONT EXTENDING FROM NE FLORIDA NEAR 31N81W TO 25N86W. A FEW
ISOLATED SHOWERS ARE ALONG THE TROUGH AXIS. THE SE GULF IS LADEN
WITH DEEP LAYER MOISTURE ASSOCIATED WITH THE MONSOON TROUGH
WHICH HAS BEEN SITUATED N OF ITS TYPICAL POSITION. IT CURRENTLY
EXTENDS ACROSS SRN MEXICO AND NRN CENTRAL AMERICA INTO THE WRN
CARIBBEAN. WIDESPREAD SHOWERS/THUNDERSTORMS ARE ACROSS THIS AREA
INCLUDING THE YUCATAN PENINSULA...CUBA AND REACHING THE FLORIDA
STRAITS. THIS LARGE AREA OF MOISTURE IS EXPECTED TO REMAIN
MOSTLY STATIONARY AND GRADUALLY LIFT N AND COVER THE SRN GULF.
THE COLD FRONT IS EXPECTED TO CONTINUE TO PUSH SE AS HIGH
PRESSURE WILL BUILD OVER THE NW GULF. THIS WILL INCREASE THE
PRESSURE GRADIENT AND WINDS OVER THE BASIN.

THE CARIBBEAN SEA...
DEEP LAYER MOISTURE COVERS THE NW CARIBBEAN ASSOCIATED WITH THE
MONSOON TROUGH THAT CONTINUES TO SIT N OF ITS USUAL LOCATION. IT
CURRENTLY RUNS THROUGH SRN MEXICO ACROSS NRN GUATEMALA AND
BELIZE TO A 1007 MB LOW NEAR 17N87W CONTINUING ESE TO NEAR
14N73W. WIDESPREAD SHOWERS/THUNDERSTORMS ARE ACROSS THIS AREA
FROM 16N-22N BETWEEN 81W-87W...AS WELL AS OVER LAND INCLUDING
NRN NICARAGUA...HONDURAS...GUATEMALA...BELIZE...THE YUCATAN
PENINSULA...CUBA...AND JAMAICA. MANY OF THESE AREAS HAVE ALREADY
RECEIVED SIGNIFICANT RAINFALL OVER THE PAST COUPLE OF DAYS AND
FLOODING IS POSSIBLE. A LARGE CLUSTER OF STRONG
SHOWERS/THUNDERSTORMS IS ALSO OVER THE SW CARIBBEAN FROM 9N-13N
BETWEEN 78W-82W...AS WELL AS ACROSS COSTA RICA AND PANAMA.
ALOFT...AN UPPER LEVEL RIDGE EXTENDS FROM HONDURAS ACROSS WRN
CUBA. TO THE E...A NARROW UPPER LEVEL TROUGH IS ALONG 75W. UPPER
LEVEL DIFFLUENCE AROUND THE ERN SIDE OF THE TROUGH IS SUPPORTING
A FEW CLUSTERS OF SHOWERS/THUNDERSTORMS OVER HISPANIOLA WITH
SCATTERED SHOWERS BETWEEN 64W-75W. FAIR CONDITIONS ARE ACROSS
THE FAR ERN CARIBBEAN INCLUDING THE LESSER ANTILLES DUE TO DRY
AIR ALOFT SINKING INTO THE BASIN AROUND AN UPPER LEVEL RIDGE
ALONG 66W. EXPECT MOIST CONDITIONS TO REMAIN ACROSS THE WRN
CARIBBEAN BRINGING CONTINUED STRONG SHOWERS AND THUNDERSTORMS TO
THAT AREA.

THE ATLANTIC OCEAN...

A BROAD UPPER LEVEL TROUGH OVER THE ERN CONUS EXTENDS OVER THE
FAR WRN ATLC. AN UPPER LEVEL RIDGE IS TO THE E ALONG 66W. AT THE
SURFACE...A 1007 MB LOW LIES UNDERNEATH THE AREA OF DIFFLUENCE
ALOFT CENTERED NE OF THE BAHAMAS NEAR 27N73W. THE SWLY FLOW
ALOFT IS SHEARING THE SHOWERS/THUNDERSTORMS AWAY FROM THE LOW
CENTER FROM 24N-30N BETWEEN 66W-72W. A FEW SHOWERS/THUNDERSTORMS
ARE ALSO N OF HISPANIOLA AND PUERTO RICO. THE LOW IS EXPECTED TO
MOVE NNE AT AROUND 15 KTS OVER THE NEXT COUPLE OF DAYS. THE
UPPER RIDGE SUPPORTS A SURFACE RIDGE AROUND A 1029 MB HIGH WELL
N OF THE DISCUSSION AREA. A NARROW UPPER LEVEL TROUGH IS ALONG
33N40W TO E OF THE WINDWARD ISLANDS NEAR 11N58W. THIS UPPER
TROUGH SUPPORTS A STATIONARY FRONT THAT ENTERS THE AREA ALONG
31N38W TO 29N46W. ISOLATED SHOWERS ARE ALONG THE BOUNDARY. A
SURFACE TROUGH IS TO THE S ALONG 28N41W TO 21N47W. SCATTERED
SHOWERS ARE WITHIN 90 NM EITHER SIDE OF THE AXIS. THE UPPER
TROUGH IS ALSO SHEARING MOISTURE FROM THE ITCZ AND A TROPICAL
WAVE TOWARDS THE NE WHICH IS SUPPORTING UPPER LEVEL CLOUDS AND
POSSIBLE ISOLATED SHOWERS WITHIN A LARGE SWATH FROM NEAR 14N43W
TO 32N30W. AN UPPER LEVEL RIDGE COVERS THE FAR ERN ATLC CENTERED
NEAR 10N29W SUPPORTING A SURFACE RIDGE AROUND A 1021 MB HIGH
NEAR 35N20W PROVIDING FAIR WEATHER ACROSS THIS PORTION OF THE
BASIN.

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

$$
WALTON





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