[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 201139
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT TUE SEP 20 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
1015 UTC.

...SPECIAL FEATURES...

A 1008 MB LOW IS EMBEDDED ALONG THE MONSOON TROUGH AXIS NEAR
11N38W MOVING W AT 5-10 KT. TOTAL PRECIPITABLE WATER IMAGERY
INDICATES THAT LOW-LEVEL MOISTURE IS MAXIMIZED FROM 07N-15N
BETWEEN 31W-41W. SCATTERED MODERATE AND ISOLATED STRONG
CONVECTION IS FROM 09N-13N BETWEEN 35W-42W.  ENVIRONMENTAL
CONDITIONS ARE EXPECTED TO REMAIN CONDUCIVE FOR A TROPICAL
DEPRESSION TO FORM LATER TODAY OR ON WEDNESDAY.

...TROPICAL WAVES...

TROPICAL WAVE IS ANALYZED FROM 10N-18N ALONG 17W MOVING W AT
10-15 KT. VISIBLE METEOSAT-9 SATELLITE IMAGERY INDICATES A BROAD
LOW TO MID-LEVEL CYCLONIC CIRCULATION HAS EMERGED OFF THE COAST
OF W AFRICA. EXAMINING RECENT UPPER AIR TIME SECTION ANALYSES
FROM BAMAKO MALI...THIS WAVE APPEARS TO HAVE PASSED AROUND
18/1200 UTC AND IS POISED TO FULLY PASS DAKAR SENEGAL...AT THE
SURFACE AND ALOFT...THIS MORNING. DEEP CONVECTION REMAINS
LIMITED WITH ISOLATED MODERATE CONVECTION FROM 12N-15N BETWEEN
17W-20W.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 14N18W TO
09N26W TO THE SPECIAL FEATURES 1008 MB LOW NEAR 11N38W TO
09N49W. WIDELY SCATTERED MODERATE CONVECTION IS FROM 04N-07N
BETWEEN 22W-31W...AND FROM 06N-08N BETWEEN 36W-48W.

...DISCUSSION...

GULF OF MEXICO...
WATER VAPOR IMAGERY INDICATES AN UPPER LEVEL SHORTWAVE TROUGH IS
PROGRESSING ACROSS THE OHIO AND LOWER MISSISSIPPI RIVER VALLEYS
THIS MORNING WITH MOSTLY SOUTHWESTERLY FLOW ALOFT ACROSS MUCH OF
THE NORTHERN GULF WATERS. THIS TROUGH SUPPORTS A COLD FRONT
REMAINING NORTH OF THE GULF COAST ACROSS SE TEXAS AND NORTHERN
LOUISIANA HOWEVER...A PRE-FRONTAL TROUGH EXTENDS FROM SOUTHWARD
ALONG 90W TO 27N90W. LOW-LEVEL MOISTURE CONVERGENCE IN THE
VICINITY OF THE TROUGH ALONG WITH MIDDLE TO UPPER LEVEL
DIFFLUENCE IS GENERATING AN AREA OF WIDELY SCATTERED SHOWERS AND
TSTMS N OF 28N BETWEEN 85W-90W. SE OF THE PROGRESSIVE
TROUGHING...AN UPPER LEVEL RIDGE AXIS EXTENDS FROM THE SW GULF
WATERS NE OVER THE FLORIDA PENINSULA AND INTO THE SW NORTH ATLC.
WHILE E-SE FLOW PREVAILS ACROSS THE EASTERN GULF...LOW-TOPPED
ISOLATED SHOWERS ARE OCCURRING N OF 23N E OF 90W...INCLUDING THE
STRAITS OF FLORIDA.

CARIBBEAN SEA...
AN UPPER LEVEL SHORTWAVE TROUGH EXTENDS INTO THE WESTERN
CARIBBEAN FROM THE SW NORTH ATLC WITH AXIS FROM 27N71W TO
17N83W. THIS IS PROVIDING MUCH OF THE CARIBBEAN SEA WITH NORTH
TO GENERALLY WESTERLY UPPER LEVEL FLOW. WATER VAPOR IMAGERY
INDICATES MUCH OF THIS FLOW IS MODERATELY DRY ALOFT WITH VERY
FEW SHOWERS OCCURRING THIS MORNING S OF A LINE FROM THE YUCATAN
CHANNEL NEAR 22N86W TO 12N72W. NORTH OF THIS LINE HOWEVER...A
SURFACE TROUGH IS ANALYZED FROM WESTERN CUBA NEAR 22N84W TO
SOUTH OF JAMAICA NEAR 15N77W. ISOLATED SHOWERS AND TSTMS ARE
PRIMARILY OCCURRING NORTH OF THIS BOUNDARY WHERE LOW-LEVEL
MOISTURE CONVERGENCE IS MAXIMIZED. THIS CONVECTIVE ACTIVITY IS
MOSTLY SOUTH OF CUBA AND N OF 16N BETWEEN 70W-82W. FARTHER
EAST...CONTINUED UPPER LEVEL TROUGHING OVER THE SW NORTH ATLC
EXTENDS SOUTHWARD INTO THE NE CARIBBEAN AND IS PROVIDING FOR THE
ADVECTION OF TROPICAL MOISTURE NORTHWARD ACROSS HISPANIOLA...
PUERTO RICO...AND THE LEEWARD ISLAND. ISOLATED SHOWERS AND TSTMS
ARE OCCURRING N OF 14N E OF 70W. THE UPPER LEVEL TROUGHING AND
SUBSEQUENT UPPER LEVEL DIFFLUENT FLOW EAST OF THE TROUGH AXIS IS
FORECAST TO REMAIN IN PLACE ACROSS THE WESTERN CARIBBEAN THROUGH
THURSDAY MORNING...WITH THE INCREASED POSSIBILITY OF WIDELY
SCATTERED SHOWERS AND ISOLATED TSTMS OVER HISPANIOLA AND PUERTO
RICO THROUGH THE REMAINDER OF THE WEEK.

ATLANTIC OCEAN...
AN UPPER LEVEL RIDGE AXIS EXTENDS FROM THE EASTERN GULF OF
MEXICO OVER THE FLORIDA PENINSULA INTO THE SW NORTH ATLC TO
BEYOND 32N76W. EAST TO SOUTHEASTERLY LOW-LEVEL FLOW HOWEVER
STILL REMAINS CONVERGENT OVER THE FAR W ATLC WITH ISOLATED
SHOWERS AND TSTMS OCCURRING N OF 29N W OF 76W. FARTHER EAST OVER
THE REMAINDER OF THE W ATLC...AN UPPER LEVEL TROUGH AXIS EXTENDS
FROM 32N68W TO EASTERN CUBA NEAR 21N77W AND INTO THE WESTERN
CARIBBEAN SEA. EAST OF THE UPPER LEVEL TROUGH AXIS...MIDDLE TO
UPPER LEVEL TROPICAL MOISTURE CONTINUES TO ADVECT NORTHWARD
BETWEEN 56W-74W. WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS ARE
OCCURRING FROM 17N-29N BETWEEN 58W-75W. 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 1023 MB HIGH CENTERED SE
OF THE AZORES NEAR 36N21W. EMBEDDED WITHIN THE SW PERIPHERY OF
THIS SURFACE RIDGE...A WEAK 1012 MB SURFACE LOW IS CENTERED NEAR
18N53W AND CONTINUES TO DRIFT WESTWARD. SCATTERED SHOWERS AND
TSTMS ARE OCCURRING WITHIN 120 NM OF THE CENTER OF THE LOW.

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

$$
HUFFMAN




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