000 AXNT20 KNHC 212333 TWDAT TROPICAL WEATHER DISCUSSION... NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT MON APR 21 2008 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN 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 3N5W 3N21W 4N40W 3N52W. A SECOND ITCZ AXIS IS SOUTH OF THE EQUATOR WITH THE MOST CONVECTIVE ACTIVITY. SCATTERED MODERATE/STRONG CONVECTION IS INLAND OVER W AFRICA MOVING OFF THE COAST OF LIBERIA AND SIERRA LEONE. CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE FROM THE ITCZ AXIS TO THE EQUATOR BETWEEN 25W-31W AND WITHIN 90 NM OF THE ITCZ AXIS BETWEEN 34W-45W. ...DISCUSSION... GULF OF MEXICO... AN UPPER LOW IS OVER E NORTH CAROLINA WITH A NARROW UPPER TROUGH EXTENDING OVER THE FAR E GULF AND THE FLORIDA PENINSULA. A SURFACE LOW IS OFF THE CAROLINA COAST WITH A SURFACE TROUGH EXTENDING THROUGH THE W ATLC INTO THE GULF OVER THE FLORIDA KEYS ALONG 25N86W TO 28N91W. SCATTERED SHOWERS AND CLUSTERS OF ISOLATED THUNDERSTORMS ARE WITHIN 60 NM OF THE SURFACE TROUGH. OTHERWISE A BROAD UPPER RIDGE DOMINATES THE GULF ANCHORED IN THE E PACIFIC REGION EXTENDING AN AXIS THROUGH THE BAY OF CAMPECHE TO THE COAST NEAR THE LOUISIANA/TEXAS BORDER. A WEAK 1017 MB HIGH REMAINS N OF THE SURFACE TROUGH NEAR 28N87W. SOUTHERLY SURFACE FLOW OVER THE W GULF IS BANKING SOME LOW LEVEL CLOUDS ALONG THE COAST OF W LOUISIANA AND TEXAS. OTHERWISE THE REMAINDER OF THE GULF IS QUIET THIS AFTERNOON. CARIBBEAN SEA... A BROAD UPPER TROUGH IN THE CENTRAL ATLC DIPS S OVER THE NE CARIBBEAN FROM HISPANIOLA TO OVER THE LEEWARD ISLANDS WHILE THE REMAINDER OF THE CARIBBEAN IS DOMINATED BY UPPER WESTERLY FLOW GENERATED BY THE E/W UPPER RIDGE FROM THE TROPICS. MODERATE EASTERLY TRADE WINDS COVER THE AREA RESULTING FROM THE WEAK PRESSURE GRADIENT OVER THE ATLC WATERS. AFTERNOON SHOWERS/ THUNDERSTORMS HAVE GENERATED OVER JAMAICA AND PORTIONS OF HISPANIOLA AND ARE DRIFTING OVER THE IMMEDIATE COASTAL WATERS. HOWEVER WITH THE STRONG SUBSIDENCE AND DRY AIR THAT DOMINATES THE CARIBBEAN...THIS ACTIVITY WILL DIMINISH LATER THIS EVENING. ATLANTIC OCEAN... A NARROW UPPER TROUGH COVERS THE FAR W ATLC TO OVER FLORIDA WITH THE UPPER LOW OVER E NORTH CAROLINA AND A 1010 MB LOW OFF THE CAROLINA COAST AND A SURFACE TROUGH EXTENDING INTO THE REGION NEAR 32N75W S OVER THE N BAHAMA ISLANDS NEAR 26N78W THEN INTO THE GULF OF MEXICO ACROSS THE FLORIDA KEYS. A SECOND SURFACE TROUGH EXTENDS FROM THE SURFACE LOW ALONG 30N78W TO A DEVELOPING SURFACE LOW ALONG THE COAST OF FLORIDA NEAR DAYTONA BEACH. SECOND UPPER TROUGH IS OVER THE CENTRAL ATLC EXTENDING S TO 17N BETWEEN 53W-68W INCLUDING THE NE CARIBBEAN. A SURFACE TROUGH ASSOCIATED WITH THIS FEATURE EXTENDS FROM 31N52W ALONG 26N56W TO 22N62W. A LARGE UPPER RIDGE IS TO THE E GENERATING ENOUGH UPPER DIFFLUENCE TO ENHANCE SCATTERED SHOWERS/ISOLATED THUNDERSTORMS COVERING THE AREA N OF 22N FROM 51W-58W. JUST TO THE W OF THIS UPPER TROUGH IS A MID LEVEL LOW NEAR 26N61W AND SURFACE REFLECTION IN THE FORM OF A SURFACE TROUGH EXTENDING FROM 28N62W 26N63W TO 24N62W. ISOLATED SHOWERS/THUNDERSTORMS FROM 26N-28N BETWEEN 60W-63W. AN UPPER RIDGE IS OVER THE E/CENTRAL ATLC WITH THE AXIS ALONG 42W WITH A WEAK UPPER TROUGH OVER THE FAR E ATLC EXTENDING FROM THE CANARY ISLANDS THROUGH 25N18W TO 20N26W. A LARGE SURFACE RIDGE DOMINATES THE E ATLC N OF 18N E OF 50W ANCHORED BY A 1024 MB HIGH NEAR 30N30W...THUS FAIR WEATHER SKIES OVER THE AREA E OF 50W. THE TYPICAL E/W UPPER RIDGE AXIS EXTENDS ACROSS THE TROPICS AND INTO THE CARIBBEAN. $$ WALLACE