000 AXNT20 KNHC 061744 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT THU APR 06 2006 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...WEATHER OBSERVATIONS... RADAR...AND METEOROLOGICAL ANALYSIS. BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1615 UTC. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 10N10W 3N24W 2N40W...THE EQUATOR AT 45W 1S52W. SCATTERED MODERATE TO STRONG CONVECTION FROM 1N TO 7N BETWEEN 8W AND 14W. SCATTERED SHOWERS AND TSTMS ELSEWHERE WITHIN 90 EITHER SIDE OF THE ITCZ AXIS. ...DISCUSSION... GULF OF MEXICO... HIGH AMPLITUDE MIDDLE TO UPPER LEVEL RIDGE DOMINATES THE PATTERN ALOFT OVER THE GULF EXTENDING FROM A ANTICYCLONE OVER THE BAY OF CAMPECHE NWD OVER THE MISSISSIPPI VALLEY OF THE UNITED STATES. AN UPSTREAM TROUGH IS OBSERVED ADVANCING EWD OVER THE WESTERN TO CENTRAL UNITED STATES BUT NEARLY ALL OF THE ASSOCIATED DYNAMICS/LIFT ARE CONFINED N OF THE AREA. ATTENDANT COLD FRONT IS PUSHING SWD DOWN THE E SLOPES OF THE ROCKIES AND SIERRA MADRE MOUNTAINS AND IS EXPECTED TO MOVE INTO THE NW GULF FRI NIGHT INTO EARLY SAT. STILL...THE FRONT WILL INITIALLY LACK APPRECIABLE MOISTURE AND SHOWER/TSTMS ACTIVITY IS EXPECTED TO BE LIMITED OVER THE W GULF. SOME LOW LEVEL MOISTURE POOLING ALONG THE BOUNDARY AS IT REACHES THE EXTREME E GULF AND FLORIDA MAY PRODUCE SOME SHOWERS/TSTMS LATE SAT OR SUN. ELSEWHERE AT THE SURFACE...STRONG LOW PRES OVER THE CENTRAL U.S. IS PRODUCING MODERATE RETURN FLOW OVER THE W GULF WITH LIGHT AND VARIABLE WINDS OVER THE E GULF WATERS. CARIBBEAN SEA... MIDDLE TO UPPER LEVEL TROUGH OVER THE W ATLC TRAILS SWD OVER CUBA INTO THE W CARIBBEAN. CONFLUENT FLOW INTO THE BASE OF THE TROUGH IS PRODUCING STRONG SUBSIDENCE AND VERY DRY/STABLE CONDITIONS ALOFT GENERALLY W OF A LINE FROM COSTA RICA TO HISPANIOLA. E OF THE SAME LINE...A 60-110 KT SUBTROPICAL JET EXTENDS FROM JUST S OF HISPANIOLA NEWD OVER THE LEEWARD ISLANDS AND INTO THE CENTRAL ATLC. DIFFLUENCE ALONG THE JET AXIS IS PRODUCING A CANOPY OF HIGH CLOUDINESS ACROSS MUCH OF THE E CARIBBEAN AND LESSER ANTILLES. AT THE LOWER LEVELS...THE REMNANTS OF AN OLD FRONTAL BOUNDARY EXTENDING FROM THE NE CARIBBEAN INTO THE CENTRAL ATLC IS PRODUCING SCATTERED SHOWERS AND A FEW TSTMS N OF 15N E OF 65W INCLUDING THE LEEWARD ISLANDS N OF DOMINICA...THE VIRGIN ISLANDS...AND PUERTO RICO. THE TROUGH AND ASSOCIATED MOISTURE IS EXPECTED TO REMAIN QUASI-STATIONARY OVER THE NEXT DAY OR TWO WHILE THE UPPER TROUGH ADVANCES SLOWLY EWD. THIS COMBINATION WILL KEEP UNSETTLED CONDITIONS ACROSS THE NE CARIBBEAN WITH SCATTERED SHOWERS/TSTMS EXPECTED TO CONTINUE THROUGH FRI. AT THE SURFACE...THE ATLANTIC SUBTROPICAL RIDGE REMAINS QUITE WEAK WITH TRADES RUNNING BELOW NORMAL THROUGHOUT THE CARIBBEAN. THE SUBTROPICAL RIDGE WILL REBUILD OVER THE ATLC LATE FRI AND SAT WITH GRADUALLY INCREASING TRADES. ATLANTIC... AN UPPER LEVEL TROUGH-RIDGE-TROUGH PATTERN PREVAILS OVER THE ATLANTIC WITH A TROUGH OVER THE W ATLC FROM THE CANADIAN MARITIMES SWD TO CUBA....RIDGE OVER THE CENTRAL ATLC ROUGHLY ALONG 50W...AND A TROUGH OVER THE E ATLC FROM THE AZORES SWD TO JUST NW OF THE CAPE VERDE ISLANDS. THE BULK OF THE ACTIVE WEATHER REMAINS FOCUSED OVER THE CENTRAL ATLC WHERE DIFFLUENT FLOW ALOFT E OF THE W ATLC TROUGH IS SPARKING A LINE OF SCATTERED SHOWERS/TSTMS ALONG A WEAKENING COLD FRONT FROM 32N60W 28N63W. ACTIVITY BECOMES MORE ISOLATED ALONG THE REMAINDER OF THE WEAKENING FRONTAL BOUNDARY TO 27N72W. A SECOND AREA OF SCATTERED SHOWERS/TSTMS IS LOCATED FURTHER S ALONG AN OLD REMNANT FRONTAL TROUGH EXTENDING FROM THE NE CARIBBEAN TO 22N45W IN THE ATLANTIC. THE STRONGEST AND MOST NUMEROUS OF THIS ACTIVITY IS LOCATED 150-450 NM N OF PUERTO RICO FROM 21N-24N BETWEEN 62W-65W. THE OVERALL PATTERN WILL ADVANCE EWD DURING THE NEXT 24 HOUR WITH THE BEST CHANCE OF SHOWERS/TSTMS BEING N OF 18N BETWEEN 45W AND 55W BY FRI EVENING. ELSEWHERE OVER THE ATLANTIC WATERS...CONFLUENT FLOW AND SUBSIDENCE IS OBSERVED IN WATER VAPOR IMAGERY OVER THE W ATLC W OF A LINE FROM HISPANIOLA TO BERMUDA AND E ATLANTIC E OF A 45W. A WEAK FRONTAL BOUNDARY DROPPING SWD INTO THE E ATLC LATER TODAY AND TONIGHT MAY PRODUCE A FEW ISOLATED SHOWERS. OTHERWISE...GENERALLY TRANQUIL CONDITIONS ARE EXPECTED TO CONTINUE. FINALLY...VISIBLE SATELLITE IMAGERY SHOWS A LOW-LEVEL TROUGH MOVING WESTWARD ALONG 45W GENERALLY S OF 15N. HOWEVER...THE FEATURE IS EMBEDDED WITHIN A LARGE AREA OF DRY/STABLE AIR AND DUST ASSOCIATED WITH A SAL. AS SUCH...IT IS ONLY ABLE TO PRODUCE CONVECTION WITHIN THE ITCZ. $$ RHOME