TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL  
805 PM EDT WED AUG 17 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 2330 UTC.

...SPECIAL FEATURE...
AN ACTIVE TROPICAL WAVE IS MOVING THROUGH THE CENTRAL CARIBBEAN 
EXTENDING S OF JAMAICA WITH AXIS FROM 18N77W TO 12N78W MOVING W 
15-20 KT. SATELLITE IMAGERY INDICATES A CLEAR MID-LEVEL 
CIRCULATION AROUND THE AXIS...BUT A WELL-DEFINED SURFACE 
CIRCULATION HAS NOT FORMED AT THIS TIME. ENHANCED DEEP LAYER 
MOISTURE ACCOMPANIES THIS WAVE...ALONG WITH SCATTERED HEAVY 
SHOWERS AND THUNDERSTORMS FROM 13N-19N BETWEEN 74W-80W. THE 
SYSTEM CONTINUES TO SHOW SIGNS OF ORGANIZATION AND ENVIRONMENTAL 
CONDITIONS APPEAR CONDUCIVE FOR A TROPICAL DEPRESSION TO FORM 
DURING THE NEXT DAY OR TWO. INTERESTS ALONG THE COAST OF THE 
WESTERN CARIBBEAN SEA SHOULD MONITOR THE PROGRESS OF THIS 
DISTURBANCE. THIS SYSTEM HAS A HIGH CHANCE OF BECOMING A 
TROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES GENERALLY 
WESTWARD.

...TROPICAL WAVES...

WELL DEFINED TROPICAL WAVE IS ACROSS THE CENTRAL TROPICAL ATLC 
ALONG 19N33W TO THE MONSOON TROUGH NEAR 13N34W MOVING W 15-20 
KT. SATELLITE IMAGERY SHOWS LOW-LEVEL CYCLONIC FLOW AROUND THE 
WAVE AXIS CONCENTRATED AT THE INTERSECTION WITH THE MONSOON 
TROUGH. THIS CYCLONIC FLOW WAS ALSO EVIDENT IN EARLIER ASCAT 
DATA. THE WAVE IS EMBEDDED WITHIN A SURGE OF DEEP LAYER MOISTURE 
ON TOTAL PRECIPITABLE WATER IMAGERY. ISOLATED MODERATE TO STRONG 
CONVECTION IS W OF THE WAVE AXIS FROM 12N-15N BETWEEN 36W-39W.

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

THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 20N16W SW 
ACROSS THE CAPE VERDE ISLANDS ALONG 16N24W TO S OF A TROPICAL 
WAVE NEAR 13N34W TO 8N45W. THE EXTENSION OF THE MONSOON TROUGH 
HAS DISRUPTED THE CONFLUENCE ALONG THE ITCZ AND THEREFORE WAS 
NOT ANALYZED ON THE 1800 UTC SURFACE ANALYSIS. HOWEVER...AN AREA 
OF SCATTERED SHOWERS AND THUNDERSTORMS IS FROM 6N-15N BETWEEN 
47W-57W ASSOCIATED WITH AN AREA OF ENHANCED MOISTURE EVIDENT IN 
TOTAL PRECIPITABLE WATER IMAGERY.

...DISCUSSION...

THE GULF OF MEXICO...
THE LONGWAVE UPPER LEVEL TROUGH IS NOW OVER THE WEST ATLC. IN 
ITS WAVE...UPPER LEVEL NE FLOW COVERS THE DISCUSSION AREA THIS 
EVENING...PROVIDING DRY AIR ALOFT AND SUPPRESSING DEEP 
CONVECTION ACROSS THE AREA. HOWEVER...AT SURFACE...A WEAK 
STATIONARY FRONT LINGERS OVER THE NE GULF...ANALYZED FROM 28N83W 
TO 27N86W TO 29N90W. NO CONVECTION IS IN THE VICINITY OF THE 
FRONT AS THE IT CONTINUES TO WEAKEN IN THE NEXT 24 HOURS. THE 
REMAINDER OF THE BASIN IS UNDER THE INFLUENCE OF A WEAK SURFACE 
RIDGE AROUND A 1017 MB HIGH IN THE NW GULF NEAR 27N94W. THIS 
FEATURE IS EXPECTED TO REMAIN OVER THE WRN HALF OF THE BASIN 
DURING THE NEXT 24 HOURS.

THE CARIBBEAN SEA...
AN UPPER LEVEL INVERTED TROUGH MOVES ACROSS THE FAR NW CARIBBEAN 
GENERATING WIDELY SCATTERED SHOWERS N OF 18N W OF 82W. AN ACTIVE 
TROPICAL WAVE IS S OF JAMAICA SUPPORTING SCATTERED HEAVY SHOWERS 
AND THUNDERSTORMS FROM 13N-19N BETWEEN 74W-80W. SEE SPECIAL 
FEATURES SECTION ABOVE FOR MORE DETAILS. SCATTER SHOWERS ARE OFF 
THE IMMEDIATE COAST OF PANAMA AND COSTA RICA ASSOCIATED WITH THE 
MONSOON TROUGH EXTENDING ACROSS THESE TWO COUNTRIES. MOSTLY FAIR 
WEATHER CONDITIONS ARE OBSERVED ELSEWHERE WITH A FEW ISOLATED 
SHOWERS EMBEDDED WITHIN THE TRADE WIND FLOW. EXPECT THE TROPICAL 
WAVE TO MOVE WWD INTO THE WEST CARIBBEAN BRINGING SIGNIFICANT 
CONVECTION TO CENTRAL AMERICA THROUGH THE WEEKEND.

THE ATLANTIC OCEAN...
A LONGWAVE UPPER LEVEL TROUGH MOVES ACROSS THE WEST ATLC 
GENERATING A LARGE AREA OF SCATTERED SHOWERS AND ISOLATED 
THUNDERSTORMS N OF 27N BETWEEN 65W-75W. THE UPPER TROUGH ALSO 
SUPPORTS A FRONTAL BOUNDARY ALONG 32N75W TO THE COAST OF FLORIDA 
NEAR 29N81W. AN UPPER LEVEL LOW IS CENTERED NEAR 23N57W WITHOUT 
ANY CONVECTION. THE REMAINDER OF THE BASIN IS DOMINATED BY 
SURFACE RIDGING AROUND A 1025 MB HIGH NEAR 32N58W AND A 1024 MB 
HIGH NEAR 33N34W PROVIDING MOSTLY FAIR WEATHER ELSEWHERE ACROSS 
THE DISCUSSION AREA. SATELLITE IMAGERY CONTINUES TO SHOW TWO 
AREAS OF AFRICAN DUST. THE FIRST IS E OF 45W WITH CLEARING 
AROUND THE TROPICAL WAVE ALONG 34W. THE SECOND AREA IS N OF THE 
CARIBBEAN BETWEEN 60W-74W.