TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL  
805 PM EDT WED AUG 24 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.

...SPECIAL FEATURE...
MAJOR HURRICANE IRENE IS CENTERED NEAR 23.5N 75.0W AT 25/0000 
UTC OR ABOUT 160 NM...295 KM SE OF NASSAU IN THE BAHAMAS...OR 
ABOUT 705 NM...1300 KM S OF CAPE HATTERAS NORTH CAROLINA. MOVING 
NW AT 11 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 954 MB. 
MAXIMUM SUSTAINED WIND SPEED IS 105 KT WITH GUSTS TO 130 KT. 
PLEASE SEE THE LATEST INTERMEDIATE PUBLIC ADVISORY UNDER 
AWIPS/WMO HEADER MIATCPAT4/WTNT34 KNHC AND THE FULL 
FORECAST/ADVISORY UNDER AWIPS/WMO HEADER MIATCMAT4/WTNT24 KNHC 
FOR MORE DETAILS. NUMEROUS STRONG CONVECTION IS WITHIN 150 NM OF 
THE CENTER.  TOTAL PRECIPITABLE WATER IMAGERY INDICATES VERY 
MOIST CONDITIONS AT LEAST 250 NM FROM THE CENTER...WITH DRIER 
AIR IN THE WESTERN SEMICIRCLE PERIPHERY.  HURRICANE FORCE WINDS 
EXTEND OUTWARD UP TO 50 NM FROM THE CENTER AND TROPICAL STORM 
FORCE WINDS EXTEND OUTWARD UP TO 200 NM FROM THE CENTER. IRENE 
IS A MAJOR HURRICANE. SOME ADDITIONAL STRENGTHENING IS FORECAST 
FOR THE NEXT 24 HOURS. 

A 1007 MB LOW IS CENTERED ABOUT 250 NM SW OF THE CAPE VERDE 
ISLANDS NEAR 13N27W WITH SCATTERED MODERATE TO STRONG CONVECTION 
WITHIN 150 NM OF THE CENTER. SHOWER/THUNDERSTORM ACTIVITY HAS 
INCREASED IN ORGANIZATION ENVIRONMENTAL CONDITIONS APPEAR 
GENERALLY CONDUCIVE FOR DEVELOPMENT OF THIS LOW INTO A TROPICAL 
CYCLONE IN THE NEXT TWO DAYS. THIS SYSTEM HAS A HIGH CHANCE OF 
BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES 
WEST-NORTHWESTWARD AT AROUND 10 KT. 

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

THE MONSOON TROUGH IS ANALYZED ACROSS AFRICA ENTERING THE E 
TROPICAL ATLC NEAR 19N16W. THE MONSOON TROUGH CONTINUES TO THE 
1007 MB LOW AT 13N27W TO NEAR 10N35W. THE ITCZ AXIS EXTENDS FROM 
THERE TO 13N48W TO 13N52W. SCATTERED MODERATE TO STRONG 
CONVECTION IS OCCURING WITHIN 150 NM OF THE CENTER OF THE LOW.  
SCATTERED MODERATE CONVECTION IS WITHIN 120 NM N OF THE ITCZ 
AXIS W OF 47W.

...DISCUSSION...

GULF OF MEXICO...
WITH ALMOST NO SURFACE PRESSURE GRADIENT...THE WINDS ACROSS THE 
GULF ARE VERY WEAK THIS EVENING WITH MAX OF 10 KT E IN THE NEAR 
THE U.S. GULF COAST.  ISOLATED SHOWERS AND THUNDERSTORMS ARE 
OCCURRING OVER THE GULF...BUT NO CONCENTRATED OR ORGANIZED 
CONVECTION TO BE FOUND.  IN THE UPPER LEVELS...A LOW IS PRESENT 
OVER THE NE GULF OF MEXICO WITH A TROUGH AXIS EXTENDING SW TO 
THE YUCATAN OF MEXICO.  DURING THE NEXT DAY...THE SURFACE WINDS 
WILL INCREASE TO 10-15 KT AND WILL BACK TO A NORTHEASTERLY 
DIRECTION.  WITH HURRICANE IRENE REMAINING EAST OF THE FLORIDA 
PENINSULA...SUBSIDENCE FROM THE HURRICANE WILL CONTRIBUTE TO 
KEEPING CONVECTION TO A MINIMUM OVER THE GULF.

CARIBBEAN SEA...
RAINBANDS ASSOCIATED WITH HURRICANE IRENE ARE PROVIDING SOME 
PRECIPITATION OVER THE NORTH CENTRAL CARIBBEAN SEA AND OVER 
PUERTO RICO AND HISPANIOLA.  LIKEWISE THE LARGE CIRCULATION OF 
THE HURRICANE HAS CAUSED THE NORMAL TRADEWIND REGIME TO BE 
DISRUPTED.  IN THE NW CARIBBEAN...WEAK NORTHERLY WINDS ARE 
OCCURRING AND IN THE SW AND CENTRAL CARIBBEAN WEAK SW WINDS ARE 
OBSERVED.  A 1500Z ASCAT PASS AND SOME SHIPS INDICATE THAT SW 
WINDS TO 30 KT ARE OCCURRING IN THE WINDWARD PASSAGE.  AS THE 
HURRICANE MOVES TOWARD THE NW AWAY FROM THE CARIBBEAN DURING THE 
NEXT DAY...CONVECTION AND WINDS SHOULD DIMINISH AND CONDITIONS 
RETURN TO MORE TYPICAL SUMMERTIME REGIME BY LATE FRIDAY.  IN THE 
UPPER LEVELS...THE NE OUTFLOW FROM IRENE PREVAILS AND IS 
ADVECTING UPPER LEVEL MOISTURE AND CIRRUS ACROSS THE EASTERN AND 
CENTRAL CARIBBEAN.

ATLANTIC OCEAN...
THE CIRCULATION AROUND MAJOR HURRICANE IRENE IS BECOMING QUITE 
LARGE WITH 20 KT WINDS EXTENDING NEARLY 600 NM ACROSS.  AS THE 
HURRICANE IS CURRENTLY CENTERED OVER THE CENTRAL BAHAMAS...HEAVY 
RAIN WILL CONTINUE OVER THE CENTRAL AND NORTHWESTERN BAHAMAS 
THIS EVENING AND TOMORROW...WHILE THE SOUTHEASTERN BAHAMAS WILL 
SEE DIMINISHING RAINFALL.  A WEAK 1014 MB LOW IS CENTERED NEAR 
23N44W.  THIS LOW REACQUIRED SCATTERED MODERATE CONVECTION 
EARLIER TODAY...BUT IS NEARLY NON-EXISTENT AGAIN THIS EVENING.  
THIS SYSTEM HAS VERY LITTLE CHANCE TO BECOME A TROPICAL CYCLONE. 
MOST OF THE TROPICAL NORTH ATLANTIC HAS WEAK TO MODERATE 
EASTERLY TRADEWINDS UNDER THE INFLUENCE OF A 1027 MB HIGH AT 
35N38W.  IN THE UPPER LEVELS...RIDGING EXTENDS WESTWARD FROM 
WEST AFRICA ALONG 20N TO 45W.  A STRONG UPPER LOW IS CENTERED 
NEAR 24N53W.  SW WINDS ON THE EASTERN SIDE OF THIS UPPER LOW IS 
PROVIDING SUBSTANTIAL VERTICAL SHEAR OVER THIS AFOREMENTIONED 
LOW.