000
AXNT20 KNHC 271804
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL  
205 PM EDT SAT AUG 27 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1145 UTC.

...SPECIAL FEATURE...

HURRICANE IRENE IS CENTERED NEAR 35.5N 76.3W AT 27/1800 UTC OR 
ABOUT 40 WNW OF CAPE HATTERAS NORTH CAROLINA...AND 80 NM S OF 
NORFOLK VIRGINIA MOVING N-NE AT 13 KT. ESTIMATED MINIMUM CENTRAL 
PRESSURE IS 950 MB. MAXIMUM SUSTAINED WIND SPEED IS 74 KT WITH 
GUSTS TO 95 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. STRONG BANDS OF HEAVY SHOWERS AND 
THUNDERSTORMS ARE MOSTLY INLAND AND OVER THE COASTAL WATERS OF 
NORTH CAROLINA AND NORTHWARD. IRENE IS FORECAST TO GRADUALLY 
WEAKEN AS IT MOVES ALONG THE EAST COAST OF THE UNITED STATES DUE 
TO LAND INTERACTION...DRY AIR ENTRAINMENT...AND INCREASING 
SOUTHWESTERLY SHEAR.

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

THE MONSOON TROUGH IS ANALYZED ACROSS AFRICA. IT BARELY ENTERS 
THE E TROPICAL ATLC THROUGH THE COAST OF GUINEA-BISSAU NEAR 
12N16W. SCATTERED MODERATE TO STRONG CONVECTION IS FROM 3N-14N E 
OF 23W. A 1011 MB LOW...REMNANTS OF T.D. TEN...IS CENTERED NEAR 
18N35W. A SURFACE TROUGH EXTENDS ALONG THE LOW CENTER FROM 
22N32W 18N35W 12N40W 10N47W WITH SCATTERED WEAK SHOWERS 70 NM W 
OF THE LOW AND WITHIN 170 NM S OF THE TROUGH AXIS W OF 36W. 
ANOTHER SURFACE TROUGH IS IN THE W TROPICAL ATLC ALONG 58W FROM 
12N-16N MOVING TOWARD THE LESSER ANTILLES WITH SCATTERED 
SHOWERS/THUNDERSTORMS W OF THE TROUGH TO OVER THE LESSER 
ANTILLES.

...DISCUSSION...

GULF OF MEXICO...
DRY SUBSIDENT AIR IN THE MID AND UPPER LEVELS OF THE ATMOSPHERE 
IS KEEPING MOST OF THE GULF UNDER FAIR WEATHER CONDITIONS THIS 
AFTERNOON. EXCEPT FOR THE NE CORNER OF THE GULF...THE ENTIRE 
GULF OF MEXICO HAS LIGHT AND VARIABLE WINDS. ONLY A FEW ISOLATED 
SHOWERS ARE OBSERVED OVER THE FAR WRN BASIN OFF THE COAST OF 
TAMPICO AND OVER THE BAY OF CAMPECHE NEAR THE COASTAL WATERS OF 
VERACRUZ MEXICO. WATER VAPOR IMAGERY SHOWS AN UPPER LEVEL 
LONGWAVE/TROUGH EXTENDING ACROSS THE NRN GULF COAST STATES. THIS 
SYSTEM SUPPORTS A SLOW MOVING COLD FRONT ACROSS THE S AND SE 
CONUS. THIS FRONT IS EXPECTED TO DROP INTO THE FAR N GULF WATERS 
LATER THIS AFTERNOON...THEN BECOME STATIONARY AND DISSIPATE 
THROUGH LATE MON.

CARIBBEAN SEA...
AN UPPER TROUGH OVER THE CENTRAL ATLC EXTENDS ITS AXIS S OVER 
THE E AND CENTRAL CARIBBEAN. DEEP LAYER MOISTURE REMAINS ACROSS 
MOST OF THE CARIBBEAN BASIN E OF 77W. THESE CONDITIONS COMBINED 
WITH THE UPPER TROUGH FLOW ALOFT ARE GENERATING CLUSTERS OF 
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS OVER THE CENTRAL 
AND ERN CARIBBEAN BETWEEN 63W-77W. THE MONSOON TROUGH EXTENDS 
FROM SOUTHERN NICARAGUA TO CENTRAL COLOMBIA GENERATING SIMILAR 
CONVECTION NEAR THE COASTAL WATERS OF COSTA RICA...PANAMA AND 
COLOMBIA. THE REMAINDER OF THE DISCUSSION AREA IS UNDER MOSTLY 
CLEAR SKIES THIS AFTERNOON EXCEPT A FEW ISOLATED SHOWERS NEAR 
THE COAST OF BELIZE. A WEAK PRESSURE PATTERN WILL PREVAIL 
THROUGH SUNDAY...AS WEAK SURFACE TROUGH CURRENTLY OVER THE W 
TROPICAL ATLC MOVES INTO THE E CARIBBEAN.

ATLANTIC OCEAN...
THE PRIMARY FOCUS THIS MORNING CONTINUES TO BE HURRICANE IRENE. 
FOR MORE INFORMATION ON IRENE...SEE SPECIAL FEATURES ABOVE. THE 
BROAD CYCLONIC WIND FIELD FROM IRENE IS DRAWING DEEP MOISTURE 
FROM THE N CENTRAL CARIBBEAN WATERS SUPPORTING LINES OF 
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS MOVING OVER THE 
COASTAL WATERS OF CENTRAL BAHAMAS...AND NE OF THE ISLANDS N OF 
26N BETWEEN 70W-74W. TO THE EAST OF THIS AREA OF CONVECTION...A 
WELL DEFINED 1008 MB LOW IS CENTERED NEAR 28N64W SUPPORTED BY A 
LARGE ELONGATED CYCLONIC CIRCULATION SE OF THE LOW CENTER. 
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ARE FROM 22N-32N 
BETWEEN 60W-67W. THE SAME UPPER LEVEL FEATURE ALSO SUPPORTS A 
SURFACE TROUGH THAT IS TO THE SE OF THE SURFACE LOW EXTENDING 
FROM 25N56W TO 20N55W GENERATING SCATTERED WEAK ISOLATED SHOWERS 
WITHIN 20 NM ON EITHER SIDE OF THE TROUGH AXIS. THE REMAINDER OF 
THE ATLC BASIN IS DOMINATED BY A LARGE SURFACE RIDGE ANCHORED N 
OF THE DISCUSSION AREA. CENTRAL ATLC SURFACE RIDGE WILL BUILD 
WESTWARD IN THE WAKE OF IRENE MONDAY THROUGH WEDNESDAY.
 
ADDITIONAL INFORMATION PLEASE VISIT
HTTP://WWW.HURRICANES.GOV/MARINE

$$

GARCIA