000
AXNT20 KNHC 182325
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT WED APR 18 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2245 UTC.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 7N9W 4N15W 2N23W CROSSING THE 
EQUATOR NEAR 33W INTO NE SOUTH AMERICA NEAR 2S45W. SCATTERED 
MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 60 NM OF A LINE 
FROM 5.5N16W TO 4N22W. 

...DISCUSSION...

GULF OF MEXICO...
AT 18/2100 UTC...A WEAK BUT FAST MOVING COLD FRONT EXTENDS FROM 
A 1004 MB LOW ALONG THE FLORIDA PANHANDLE COAST NEAR 30N84W W TO 
26N93W WHERE IT CONTINUES TO THE TEXAS COAST NEAR BROWNSVILLE. 
THIS SYSTEM IS ASSOCIATED WITH A SHORTWAVE UPPER TROUGH EMBEDDED 
WITHIN A BROAD UPPER TROUGH THAT COVERS THE E US INTO THE W ATLC 
AND THE GULF N OF 24N E OF 90W. DRY UPPER AIR IS LIMITING 
SHOWERS TO A THIN BAND WITHIN 45 NM OF THE FRONT E OF 86W. ALSO 
AT 18/2100 UTC...AN EQUALLY WEAK SURFACE TROUGH EXTENDS FROM 
NEAR TAMPA FLORIDA TO 23N91W. A BROAD UPPER RIDGE EXTENDS 
FROM THE E PACIFIC REGION OVER MEXICO INTO W TEXAS COVERING THE 
REMAINDER OF THE GULF. LIGHT/MODERATE W TO N WINDS DOMINATE THE 
ENTIRE AREA. THE FRONT WILL MOVE OUT OF THE GULF OVER THE NEXT 
24 TO 36 HOURS AS A RIDGE WILL BUILD S FROM OVER THE E US TO 
ENCOMPASS THE GULF THROUGH THE END OF THE WEEK. 

CARIBBEAN SEA...
BROAD UPPER RIDGE DOMINATES THE ENTIRE AREA ANCHORED INLAND OVER 
SOUTH AMERICA. THE REMNANTS OF A STRONG COLD FRONT EXTENDING 
FROM THE CENTRAL ATLC TO OVER PUERTO RICO AND THE MONA PASSAGE 
GENERATING LOW LEVEL SCATTERED SHOWERS WITH A POSSIBLE ISOLATED 
THUNDERSTORMS N OF 17N TO OVER HISPANIOLA TO THE VIRGIN ISLANDS. 
THE REMAINDER OF THE CARIBBEAN REMAINS CLEAR TO THE DRY AIR IN 
PLACE OVER THE ENTIRE AREA. 

ATLANTIC OCEAN...
THE DEEP LAYERED TROUGH OVER THE E US AND GULF OF MEXICO IS 
MOVING INTO THE NW ATLC N OF 26N E OF 76W. THE UPPER LEVEL RIDGE 
FROM THE CARIBBEAN EXTENDS AN AXIS N ALONG 70W TO 26N COVERING 
THE AREA FROM 65W-75W. THE MOST SIGNIFICANT FEATURE IS A LARGE 
984 MB LOW WELL N OF THE REGION WITH A STRONG COLD FRONT 
ENTERING THE W/CENTRAL ATLC NEAR 32N49W EXTENDING SW ALONG 
24N54W TO 21N60W WHERE IT BECOMES NEAR STATIONARY TO OVER PUERTO 
RICO AND THE MONA PASSAGE. THIS FRONT IS ASSOCIATED WITH A LARGE 
DEEP LAYERED LOW CENTERED WELL N OF THE AREA. DIFFLUENCE TO THE 
E IS ENHANCING SCATTERED SHOWERS AND POSSIBLE ISOLATED 
THUNDERSTORMS WITHIN 250/300 NM E OF THE FRONT N OF THE COLD 
FRONT. DRY AIR AND CLEAR SKIES ARE WITHIN 250/300 NM W OF THE 
FRONT. BROAD DEEP LAYERED TROUGH COVERS THE NE ATLC N OF 25N E 
OF 30W WITH AN OCCLUDED FRONT N OF THE REGION AND A COLD FRONT 
EXTENDING TO THE REGION NEAR 32N22W WITH A SURFACE TROUGH 
ENTERING THE AREA ALONG 27N30W TO 24N40W. SCATTERED SHOWERS ARE 
WITHIN 120 NM SE OF THE SURFACE TROUGH. THIS FRONT BISECTS AN 
AREA OF HIGHER PRESSURE WITH A 1019 MB HIGH N OF THE SURFACE 
TROUGH NEAR 27N40W AND A 1018 MB HIGH S OF THE SURFACE TROUGH 
NEAR 20N36W. AN UPPER TROUGH IS OVER THE E TROPICAL ATLC 
EXTENDING FROM 21N29W S THROUGH AN UPPER LOW NEAR 11N36W TO 
6N39W ENHANCING AN UPPER RIDGE TO THE E THAT COVERS THE AREA S 
OF 24N TO INLAND OVER AFRICA. 

$$
WALLACE