[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 210559
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT WED SEP 21 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0515 UTC.

...SPECIAL FEATURES...

TROPICAL STORM OPHELIA IS CENTERED 12.2N 40.1W AT 21/0300 UTC OR
1375 NM E-SE OF THE NORTHERN LEEWARD ISLANDS MOVING W AT 8 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 1006 MB. MAXIMUM SUSTAINED
WIND SPEED IS 35 KT WITH GUSTS TO 45 KT. SCATTERED MODERATE AND
ISOLATED STRONG CONVECTION IS FROM 08N-11N BETWEEN 39W-46W...AND
FROM 12N-16N BETWEEN 37W-40W. SEE LATEST NHC FORECAST/ADVISORY
UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS.

...TROPICAL WAVES...

TROPICAL WAVE IS ANALYZED FROM 10N-18N ALONG 21W MOVING W AT
10-15 KT. SHORTWAVE INFRARED SATELLITE IMAGERY AND LOW-LEVEL
STREAMLINE ANALYSIS INDICATES A BROAD CYCLONIC CIRCULATION IN
THE VICINITY OF THE WAVE AXIS BETWEEN 18W-24W. NO DEEP
CONVECTION IS NOTED WITH THE WAVE.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM NEAR 09N24W TO 08N28W TO NEAR
TROPICAL STORM OPHELIA THEN TO 09N50W. WIDELY SCATTERED MODERATE
CONVECTION IS FROM 04N-11N BETWEEN 25W-32W.

...DISCUSSION...

GULF OF MEXICO...
WATER VAPOR IMAGERY INDICATES AN UPPER LEVEL LONGWAVE TROUGH IS
LOCATED OVER THE CENTRAL CONUS PROVIDING THE NORTHWESTERN HALF
OF THE GULF WITH MOSTLY SOUTHWESTERLY FLOW ALOFT. SE OF THE
TROUGHING...AN UPPER LEVEL RIDGE AXIS EXTENDS FROM THE YUCATAN
PENINSULA NE OVER THE SOUTHERN FLORIDA PENINSULA AND INTO THE SW
NORTH ATLC. WITH NO STRONGLY INFLUENTIAL UPPER LEVEL FEATURES
ACROSS THE GULF THIS EVENING...A RELATIVELY WEAK PRESSURE
GRADIENT EXISTS. THE NORTHERN EXTENT OF A SURFACE TROUGH EXTENDS
FROM THE NW CARIBBEAN SEA THROUGH THE YUCATAN CHANNEL INTO THE
SE GULF TO 24N89W. WEAK CYCLONIC WIND FLOW IN THE VICINITY OF
THE SURFACE TROUGH IS PROVIDING LIMITED ISOLATED SHOWERS AND
TSTMS S OF 24N BETWEEN 83W-90W. ELSEWHERE...SATELLITE IMAGERY
AND MOSAIC DOPPLER RADAR INDICATE THAT ISOLATED LOW-TOPPED
SHOWERS ARE OCCURRING E OF 84W...INCLUDING THE STRAITS OF
FLORIDA.

CARIBBEAN SEA...
AN UPPER LEVEL LOW IS CENTERED IN THE WESTERN CARIBBEAN NEAR
16N78W AND IS PROVIDING MUCH OF THE CARIBBEAN SEA W OF 78W WITH
NORTHERLY FLOW ALOFT AND GENERALLY WEST-SOUTHWESTERLY FLOW ALOFT
E OF 78W. WATER VAPOR IMAGERY INDICATES MUCH OF THIS FLOW IS
MODERATELY DRY ALOFT WITH VERY FEW SHOWERS OCCURRING THIS
EVENING S OF A LINE FROM THE YUCATAN CHANNEL NEAR 22N86W TO
14N70W. NORTH OF THIS LINE HOWEVER...A SURFACE TROUGH IS
ANALYZED FROM THE YUCATAN CHANNEL NEAR 22N86W TO 17N81W. WIDELY
SCATTERED SHOWERS AND TSTMS ARE PRIMARILY OCCURRING NORTH OF
THIS BOUNDARY WHERE LOW-LEVEL MOISTURE CONVERGENCE IS MAXIMIZED.
THIS CONVECTIVE ACTIVITY IS MOSTLY N OF 16N BETWEEN 69W-85W.
FARTHER EAST...AN UPPER LEVEL RIDGE IS ALONG 61W OVER THE FAR
EASTERN CARIBBEAN WITH ISOLATED SHOWERS AND TSTMS OCCURRING E OF
65W. AS THE UPPER LEVEL LOW AND SUBSEQUENT MIDDLE TO UPPER LEVEL
DIFFLUENT FLOW EAST OF THE TROUGH AXIS IS FORECAST TO REMAIN IN
PLACE ACROSS THE WESTERN CARIBBEAN THROUGH THURSDAY...THE
INCREASED POSSIBILITY OF WIDELY SCATTERED SHOWERS AND ISOLATED
TSTMS OVER HISPANIOLA AND CUBA IS EXPECTED THROUGH THE REMAINDER
OF THE WEEK.

ATLANTIC OCEAN...
AN UPPER LEVEL RIDGE AXIS EXTENDS FROM THE SE GULF OF MEXICO
OVER THE SOUTHERN FLORIDA PENINSULA INTO THE SW NORTH ATLC TO
BEYOND 32N74W. SOUTHEASTERLY LOW-LEVEL FLOW PREVAILS OVER A
LARGE PORTION OF THE W ATLC WITH ISOLATED SHOWERS AND TSTMS
OCCURRING W OF 72W. FARTHER EAST OVER THE REMAINDER OF THE W
ATLC...AN UPPER LEVEL LOW IS CENTERED NEAR 24N72W WITH TROUGH
AXIS EXTENDING FROM 32N65W THROUGH THE LOW AND INTO THE WESTERN
CARIBBEAN SEA. EAST OF THE UPPER LEVEL TROUGH AXIS...MIDDLE TO
UPPER LEVEL TROPICAL MOISTURE CONTINUES TO ADVECT NORTHWARD
BETWEEN 64W-73W. WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS ARE
OCCURRING FROM 19N-28N BETWEEN 63W-76W. THE REMAINDER OF THE
CENTRAL AND EASTERN ATLC IS UNDER THE INFLUENCE OF A SURFACE
RIDGE N OF 20N E OF 55W ANCHORED BY A 1025 MB HIGH CENTERED NEAR
31N44W. EMBEDDED WITHIN THE SW PERIPHERY OF THIS SURFACE
RIDGE...A WEAK SURFACE TROUGH IS ANALYZED FROM 15N-19N ALONG 57W
AND CONTINUES TO DRIFT WESTWARD. SCATTERED SHOWERS AND TSTMS ARE
OCCURRING FROM 15N-18N BETWEEN 56W-59W.

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

$$
HUFFMAN




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