000
AXNT20 KNHC 281651
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SAT APR 28 2007

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL 
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHEASTERN 
SECTIONS OF SOUTH AMERICA...AND THE ATLANTIC OCEAN TO THE 
AFRICAN COAST FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION 
IS BASED ON SATELLITE IMAGERY...METEOROLOGICAL ANALYSIS... 
WEATHER OBSERVATIONS...AND RADAR.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1615 UTC.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 6N8W 3N17W 3N27W 1N42W 2N52W. 
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 75 NM OF 
4N W OF 48W TO INLAND OVER SOUTH AMERICA. SCATTERED MODERATE 
CONVECTION IS WITHIN 120 NM OF THE AXIS FROM 25W-31W. 

...DISCUSSION...

GULF OF MEXICO...
THE SLOW MOVING COLD FRONT IS IN THE W ATLC WHILE DISSIPATING 
AS IT CROSS FLORIDA FROM LAKE OKEECHOBEE TO FT MYERS. THE 
ASSOCIATED SHORTWAVE UPPER TROUGH IS COMPLETELY IN THE W ATLC. A 
SURFACE RIDGE CONTINUES TO BUILD ACROSS THE GULF ANCHORED BY A 
1022 MB HIGH OVER N LOUISIANA/MISSISSIPPI. THE UPPER LEVELS OF 
THE GULF ARE DOMINATED BY AN UPPER RIDGE THAT EXTENDS FROM 
CENTRAL AMERICA/CARIBBEAN. THIS RIDGE CONTINUES TO PUMP TROPICAL 
MOISTURE OVER THE GULF BUT IS PRODUCING ONLY SCATTERED HIGH 
CLOUDS. LOW LEVEL MOISTURE IS BEING USHERED IN ON THE RETURN 
FLOW BEHIND THE PRECEDING FRONT GENERATING SCATTERED SHOWERS 
WITH A POSSIBLE ISOLATED THUNDERSTORM OVER THE NW GULF N OF 25N 
W OF 93W. THE REMAINDER OF THE GULF IS UNDER FAIR SKIES WITH DRY 
AIR IN PLACE...THUS LITTLE CHANCE OF SHOWERS. 

CARIBBEAN SEA...
SHORTWAVE UPPER TROUGH OVER THE W ATLC DIPS INTO THE N CARIBBEAN 
N OF 17N FROM 69W-78W BRINGING DRY AIR TO OVER THE AREA N OF 16N 
W OF 70W. THE REMAINDER OF THE CARIBBEAN IS UNDER A BROAD FLAT 
UPPER RIDGE ANCHORED OVER SOUTH AMERICA GIVING THE AREA MOSTLY 
ZONAL FLOW. THIS RIDGE IS HOWEVER ADVECTING TROPICAL MOISTURE 
ACROSS PANAMA AND COSTA RICA GIVING THAT AREA S OF 12N W OF 80W 
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS. MODERATE/STRONG 
EASTERLY TRADE WINDS ARE BRINGING IN SOME LOW LEVEL MOISTURE 
WITH POSSIBLE ISOLATED SHOWERS ACROSS THE CARIBBEAN E OF 80W 
WHILE THE REMAINDER OF THE AREA IS UNDER MOSTLY FAIR SKIES. 

ATLANTIC...
SHORTWAVE UPPER TROUGH IS OVER THE W ATLC AND EXTENDS S TO JUST 
OVER THE N CARIBBEAN FROM 65W-78W. THE ASSOCIATED COLD FRONT 
ENTERS THE REGION NEAR 32N77W TO 29N79W WHERE IT IS RAPIDLY 
DISSIPATING OVER FLORIDA NEAR LAKE OKEECHOBEE. SCATTERED SHOWERS 
AND POSSIBLE ISOLATED THUNDERSTORMS ARE WITHIN 60 NM OF THE 
FRONT. UPPER RIDGE COVERING THE CARIBBEAN EXTENDS AN AXIS JUST E 
OF THE SHORTWAVE TROUGH WITH ENOUGH DIFFLUENCE TO GENERATE 
SCATTERED SHOWERS WITHIN 120 NM OF A SURFACE TROUGH THAT EXTENDS 
FROM 29N63W TO 22N66W...BUT WITH THE DRY AIR OVER THE ATLC THESE 
SHOWERS DO NOT LOOK TO BE LINGERING. WEAK UPPER TROUGH EXTENDS 
OVER THE CENTRAL ATLC THROUGH 27N43W SW TO 18N52W. THIS IS A 
RATHER BENIGN FEATURE AGAIN PRODUCING ONLY WIDELY ISOLATED 
SHOWERS. THE REMAINDER OF THE ATLC IS DOMINATED BY A BROAD 
SURFACE RIDGE ANCHORED BY A 1030 MB HIGH WELL N OF THE REGION 
AND GIVING THE REMAINDER OF THE ATLC FAIR WEATHER.

$$
WALLACE