000 AXNT20 KNHC 212306 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT SAT APR 21 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 7N10W 4N20W 2N35W INLAND OVER SOUTH AMERICA NEAR 3N51W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 6N TO S OF THE EQUATOR BETWEEN 40W-50W AND INTO SOUTH AMERICA. CLUSTERS OF SIMILAR CONVECTION ARE WITHIN 120/150 NM OF THE ITCZ AXIS FROM 20W-35W. ...DISCUSSION... GULF OF MEXICO... BROAD UPPER RIDGE THAT COVERS THE GULF HAS RELAXED E/W OVER THE PAST 24 HOURS AND EXTENDING THE CARIBBEAN INTO THE GULF THROUGH THE YUCATAN CHANNEL TO OVER THE NW GULF COAST NEAR THE LOUISIANA/TEXAS BORDER TO JUST ACROSS FLORIDA. DRY AIR AT THE MID/UPPER LEVELS ARE LIMITING CLOUDS. HOWEVER...LOW LEVEL SEABREEZE SHOWERS ARE MOVING OFF THE W COAST OF FLORIDA S OF TAMPA TO THE MIDDLE FLORIDA KEYS. SURFACE RIDGE HAS BUILT S FROM OVER THE E US INTO THE GULF AND W ATLC ANCHORED BY A 1024 MB HIGH OVER SW NORTH CAROLINA. THIS WILL REMAIN THROUGH THE MID WEEK WITH THE ANCHORED MOVING EASTWARD INTO THE W ATLC. MODERATE EASTERLY WINDS DOMINATE THE ENTIRE AREA WITH RETURN FLOW AROUND THE SURFACE RIDGE IS BUILDING CLOUDS ALONG THE E SLOPES OF THE SIERRA MADRE MOUNTAINS. SCATTERED SHOWERS/THUNDERSTORMS ARE DEVELOPING OVER THE S PORTIONS OF THE MOUNTAINS S OF 21N. CARIBBEAN SEA... DEEP LAYERED TROUGH OVER THE W ATLC DIPS INTO THE N/CENTRAL ATLC FROM OVER PUERTO RICO TO E CUBA DRAPING A COLD FRONT ACROSS THE VIRGIN ISLANDS NEAR 18N65W TO 17N68W WHERE IT CONTINUES AS A SURFACE TROUGH ALONG 14N72W TO 11N77W. SCATTERED SHOWERS/ THUNDERSTORMS ARE WITHIN 120 NM SE OF THE COLD FRONT TO OVER THE VIRGIN/LEEWARD ISLANDS. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE WITHIN 60/90 NM EITHER SIDE OF THE TROUGH. THE UPPER LEVELS HOWEVER ARE DOMINATED BY A BROAD UPPER RIDGE ANCHORED INLAND OVER SOUTH AMERICA. THIS UPPER RIDGE IS PUMPING TROPICAL MOISTURE ACROSS THE S CARIBBEAN ENHANCING THE SHOWERS/ THUNDERSTORMS OVER THE E CARIBBEAN PRIMARILY ASSOCIATED WITH THE FRONT/TROUGH. THE ITCZ AXIS EXTENDS OVER PANAMA GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS INLAND AND ALONG THE IMMEDIATE COASTAL WATERS. ATLANTIC OCEAN... THE DEEP LAYERED TROUGH COVERS THE W ATLC INTO THE CENTRAL ATLC N OF 18N E OF 47W TO JUST E OF FLORIDA WITH THE ASSOCIATED COLD FRONT EXTENDING THROUGH 32N44W SW ALONG 25N52W ACROSS THE VIRGIN ISLANDS INTO THE CARIBBEAN. SCATTERED SHOWERS WITH POSSIBLE ISOLATED THUNDERSTORMS ARE WITHIN 120 EITHER SIDE OF THE FRONT. BROAD UPPER RIDGE COVERS THE E/CENTRAL ATLC FROM 30W-47W. AN UPPER LEVEL TROUGH EXTENDS FROM AN UPPER LOW INLAND OVER MOROCCO ACROSS W AFRICA INTO THE FAR E ATLC TO OVER THE CAPE VERDE ISLANDS COVERING THE AREA N OF 14N E OF 30W. SURFACE HIGH PRESSURE COVERS THE E ATLC N OF 16N FROM AFRICA COAST TO THE CENTRAL ATLC FRONT ANCHORED BY A 1023 MB HIGH JUST SE OF THE AZORES. DRY AIR DOMINATES MUCH OF THE ATLC LIMITING SHOWER ACTIVITY TO THE AREA NEAR THE CENTRAL ATLC FRONT. $$ WALLACE