000
AXNT20 KNHC 201812
TWDAT 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT MON APR 20 2009

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...METEOROLOGICAL ANALYSIS...WEATHER
OBSERVATIONS...AND RADAR.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1730 UTC.

...ITCZ...
THE ITCZ IS CENTERED ALONG 06N10W...CROSSING THE EQUATOR NEAR 
17W AND CONTINUES ALONG 03.5S25W AND INTO NE BRAZIL NEAR 04S38W. 
NO SIGNIFICANT CONVECTION IS NOTED IN THE DISCUSSION AREA. 
ISOLATED SHOWERS ARE NOTED WITHIN 360 NM N OF THE ITCZ EAST OF 
30W. OTHERWISE ISOLATED MODERATE CONVECTION ASSOCIATED WITH THE 
ITCZ IS SOUTH OF THE EQUATOR.

...DISCUSSION...

GULF OF MEXICO...
COLD FRONT ENTERS THE GULF NEAR APALACHICOLA FLORIDA AND EXTENDS 
SW ALONG 25N90W 19N96W IN THE WESTERN BAY OF CAMPECHE. LOW-LEVEL 
CONVERGENCE COUPLED WITH MOIST AND UNSTABLE MIDDLE TO UPPER 
LEVEL SOUTHWEST FLOW ALOFT IS PRODUCING SCATTERED SHOWERS AND 
ISOLATED TSTMS WITHIN 200 NM E OF THE FRONT. THE COLD FRONT 
IS FORECAST TO CONTINUE PUSHING EWD AND BE POSITIONED SE OF THE 
REGION BY MIDDAY TUESDAY. A HIGH PRESSURE RIDGE WILL BUILD IN 
BEHIND THIS FRONT WITH NLY WINDS UP TO 20 KTS WITH A RELATIVELY 
COOLER AND DRIER AIRMASS IN PLACE.

CARIBBEAN SEA... 
A SURFACE RIDGE LOCATED OVER THE W ATLC IS MAINTAINING FRESH ELY 
TRADE WINDS ACROSS THE CARIBBEAN SEA. THE STRONGEST OF THESE 
WINDS...UP TO 25 KTS...ARE ACROSS THE CENTRAL CARIBBEAN AND 
ALONG THE NRN COAST OF COLOMBIA. MAINLY FAIR WEATHER IS OVER THE 
CARIBBEAN WITH DEEP LAYER DRY AIR AND SUBSIDENCE. HOWEVER 
THE TRAILING END OF AN OLD FRONT IS WEST OF HISPANIOLA WITH 
SCATTERED SHOWERS IN THIS AREA EXTENDING WEST TO BETWEEN CUBA 
AND JAMAICA. MOIST SW UPPER FLOW ACROSS THE SE CARIBBEAN COUPLED 
WITH MID-LEVEL INSTABILITY IS GENERATING CLOUDINESS OVER THE 
WINDWARD ISLANDS TO OVER THE TROPICAL ATLC EXTENDING TO 50W.

ATLANTIC OCEAN...
A FRONTAL SYSTEM IS LOCATED IN THE CENTRAL ATLC EXTENDS SW 
THROUGH 32N47.5W TO 24N55W WHERE THE FRONT CONTINUES AS 
STATIONARY TO 20N64W. SCATTERED SHOWERS E OF THE FRONT ARE N OF 
23N BETWEEN 45W AND 50W. W OF THE COLD FRONT...A WEAK 1017 MB 
LOW IS NEAR 28N54W WITH A SURFACE TROUGH EXTENDING SW TO 23N61W. 
THIS FEATURE WILL CONTINUE TO DISSIPATE AS THE UPPER LEVEL 
SUPPORT MOVE OFF TOWARDS THE NE. SUBSIDENCE IN UPPER W TO NW 
FLOW ALOFT ACROSS THE REMAINDER OF THE W ATLC WEST OF THE COLD 
FRONT IS ASSOCIATED WITH A LARGE SCALE TROUGH NEAR THE FRONT AND 
AN UPSTREAM RIDGE WITH AN AXIS NEAR 70W. AT THE SURFACE...A 1026 
MB HIGH IS CENTERED NEAR 30N64W AND IS DRIFTING EAST NORTHEAST.  
GENERALLY FAIR WEATHER CONDITIONS ARE PRESENT WEST OF THE FRONT 
EXCEPT FOR SCATTERED SHOWERS AND AN ISOLATED THUNDERSTORM OVER 
THE NORTHWEST PART OF THE AREA ASSOCIATED WITH THE APPROACHING 
GULF OF MEXICO COLD FRONT. SOME SHOWERS ARE EMBEDDED IN THE 
EASTERLY FLOW SOUTH OF 25N MAINLY WEST OF THE BAHAMAS. ACROSS 
THE E ATLC...SUBSIDENCE ASSOCIATED WITH A SURFACE RIDGE IS 
RESULTING IN GENERALLY FAIR WEATHER CONDITIONS. THIS SURFACE 
RIDGE IS ANCHORED BY A 1033 MB SURFACE HIGH NEAR 34N24W. ACROSS 
THE TROPICAL ATLC...AN UPPER LEVEL HIGH IS CENTERED NEAR 5N45W 
WITH UPPER LEVEL DIVERGENCE ENHANCING CONVECTION ALONG THE ITCZ 
MAINLY SOUTH OF THE EQUATOR.

$$
LL