000
AXNT20 KNHC 181148
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL  
805 AM EDT THU AUG 18 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 CARIBBEAN SEA TROPICAL WAVE IS ALONG 20N80W 17N80W 12N79W.
WHAT APPEARS TO BE THE MIDDLE LEVEL CYCLONIC CIRCULATION CENTER 
THAT IS ASSOCIATED WITH THE WAVE IS NEAR 16N78W. STRONG 
RAINSHOWERS AND THUNDERSTORMS ARE WITHIN A 15 TO 30 NM RADIUS OF 
THE MIDDLE LEVEL CENTER. ISOLATED MODERATE RAINSHOWERS ARE 
ELSEWHERE FROM 12N TO CUBA BETWEEN 75W IN THE WINDWARD PASSAGE 
AND 82W. THIS SYSTEM CONTINUES TO SHOW SIGNS OF ORGANIZATION. 
SURFACE BAROMETRIC PRESSURES ARE BEGINNING TO FALL IN THE AREA 
OF THE TROPICAL WAVE. IT IS POSSIBLE THAT THIS SYSTEM MAY 
DEVELOP INTO A TROPICAL CYCLONE DURING THE NEXT 48 HOURS... 
BEFORE IT MOVES OVER CENTRAL AMERICA. ANYONE WHO LIVES ALONG
THE COASTS OF HONDURAS...NICARAGUA...BELIZE...AND THE EASTERN 
YUCATAN PENINSULA SHOULD MONITOR THE PROGRESS OF THIS TROPICAL 
WAVE. THE WAVE IS MOVING WESTWARD 15 TO 20 MPH.

...TROPICAL WAVES...

AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 38W FROM 12N TO 19N.
ISOLATED MODERATE RAINSHOWERS AND POSSIBLE THUNDERSTORMS ARE
FROM 12N TO 15N BETWEEN 38W AND 40W. SIGNIFICANT DEVELOPMENT 
INTO A TROPICAL CYCLONE IS NOT LIKELY DURING THE NEXT COUPLE
OF DAYS. CONDITIONS MAY BECOME MORE CONDUCIVE FOR DEVELOPMENT 
AFTER THAT TIME. THIS WAVE IS MOVING WESTWARD 15 TO 20 MPH.

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

THE MONSOON TROUGH PASSES THROUGH 21N17W AT THE AFRICA 
COAST...ON TOP OF THE CAPE VERDE ISLANDS...TO 13N30W 13N37W 
8N46W. SCATTERED MODERATE TO STRONG RAINSHOWERS AND 
THUNDERSTORMS ARE FROM 9N TO 13N BETWEEN AFRICA AND 25W...
AND FROM 5N TO 10N BETWEEN 32W AND 47W. SCATTERED MODERATE 
RAINSHOWERS TO ISOLATED STRONG THUNDERSTORMS ARE FROM 10N
TO 12N BETWEEN 55W AND 60W.

...DISCUSSION...

THE GULF OF MEXICO...

AN UPPER LEVEL TROUGH/SHEAR AXIS EXTENDS FROM SOUTHWESTERN 
FLORIDA INTO THE SOUTH CENTRAL AND SOUTHWESTERN WATERS OF THE 
GULF OF MEXICO. AN UPPER LEVEL CYCLONIC CIRCULATION CENTER IS
IN THE YUCATAN CHANNEL ALONG THE NORTHEASTERN CORNER OF THE 
YUCATAN PENINSULA. RAINSHOWERS ARE POSSIBLE TO THE EAST OF 
87W...AND FROM 24N TO 29N BETWEEN 91W AND 93W. A 1016 MB HIGH 
PRESSURE CENTER IS NEAR 26N93W. THE SURFACE PRESSURE GRADIENT
IS COMPARATIVELY FLAT AND WEAK.

THE CARIBBEAN SEA...

A TROPICAL WAVE IS ALONG 20N80W 17N80W 12N79W. WHAT APPEARS TO 
BE THE MIDDLE LEVEL CYCLONIC CIRCULATION CENTER THAT IS 
ASSOCIATED WITH THE WAVE IS NEAR 16N78W. STRONG RAINSHOWERS AND 
THUNDERSTORMS ARE WITHIN A 15 TO 30 NM RADIUS OF THE MIDDLE 
LEVEL CENTER. ISOLATED MODERATE RAINSHOWERS ARE ELSEWHERE FROM 
12N TO CUBA BETWEEN 75W IN THE WINDWARD PASSAGE AND 82W.
PLEASE REFERENCE THE SPECIAL FEATURES SECTION AT THE BEGINNING 
OF THIS BULLETIN FOR MORE DETAILS ABOUT THIS TROPICAL WAVE.
AN UPPER LEVEL CYCLONIC CIRCULATION CENTER IS IN THE YUCATAN 
CHANNEL ALONG THE NORTHEASTERN CORNER OF THE YUCATAN PENINSULA. 
REMNANT RAINSHOWERS ARE POSSIBLE TO THE NORTH OF 17N TO THE WEST 
OF 85W IN THE NORTHWESTERN CORNER OF THE AREA.
 
THE ATLANTIC OCEAN...
AN UPPER LEVEL TROUGH PASSES THROUGH 32N71W IN THE ATLANTIC 
OCEAN...TO GRAND BAHAMA ISLAND AND THE ABACO ISLANDS IN THE 
BAHAMAS...INTO THE FLORIDA STRAITS. THE SOUTHERN END OF 
A STATIONARY FRONT REACHES 31N78W. ISOLATED MODERATE 
RAINSHOWERS AND POSSIBLE THUNDERSTORMS ARE TO THE NORTHWEST
OF THE LINE THAT PASSES THROUGH BERMUDA TO THE WINDWARD PASSAGE.
AN UPPER LEVEL CYCLONIC CIRCULATION CENTER IS NEAR 23N55W. UPPER 
LEVEL CYCLONIC WIND FLOW COVERS THE ATLANTIC OCEAN TO THE NORTH 
OF 17N BETWEEN 47W AND 72W. ISOLATED MODERATE RAINSHOWERS COVER 
THE AREA FROM 19N TO 32N BETWEEN 53W AND 62W. AN UPPER LEVEL 
TROUGH PASSES THROUGH 35N17W IN THE EASTERN ATLANTIC OCEAN TO 
29N19W. THIS TROUGH SUPPORTS A COLD FRONT THAT IS ALONG 31N/32N
BETWEEN 17W AND 27W FRONTAL BOUNDARY THAT IS TO THE NORTH OF
THE AREA OF THIS BULLETIN. BROAD UPPER LEVEL CYCLONIC WIND FLOW 
COVERS THE AREA FROM THE MONSOON TROUGH TO 20N BETWEEN 26W AND 
50W. BROAD SURFACE ANTICYCLONIC WIND FLOW IS TO THE NORTH OF 20N 
TO THE EAST OF 75W.

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

$$
MT