000 AXNT20 KNHC 221105 TWDAT TROPICAL WEATHER DISCUSSION... NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 AM EDT TUE APR 22 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1000 UTC. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 02N09E 02N32W 01N51W. SCATTERED MODERATE CONVECTION WITHIN 120 NM N OF AXIS BETWEEN 27W AND 37W. A SECOND ITCZ AXIS IS SOUTH OF THE EQUATOR ALONG 03S03W 04S12W 04S39W. SCATTERED MODERATE TO ISOLATED STRONG CONVECTION WITHIN 120 NM OF THE SECOND AXIS BETWEEN 01W AND 12W. ...DISCUSSION... GULF OF MEXICO... A MID/UPPER LEVEL RIDGE IS MOVING EAST OVER THE LOWER MISSISSIPPI VALLEY AND NORTHERN GULF OF MEXICO...BEHIND AN UPPER LOW MOVING OFF THE CAROLINA COAST. 1016 MB SURFACE HIGH PRESSURE IS CENTERED NEAR 28N87W. A SURFACE TROUGH ASSOCIATED WITH THE UPPER LOW OFF THE CAROLINAS EXTENDS FROM ACROSS THE BAHAMAS THROUGH THE STRAITS OF FLORIDA AND TO THE SOUTH OF THE SURFACE HIGH ACROSS THE SOUTHEASTERN GULF. SHOWERS WERE ACTIVE ALONG THE TROUGH EARLIER IN THE EVENING BUT HAVE SINCE DISSIPATED. DRY SUBSIDENT AIR PREVAILS OVER THE EASTERN GULF...IN NW FLOW ALOFT BETWEEN THE MID/UPPER RIDGE AND THE UPPER LOW. SHIP AND BUOY OBSERVATIONS SHOW SEAS TO BE 2 FT OR LESS OVERALL. BUOYS OVER THE WESTERN GULF ARE REPORTING MODERATE SE WINDS ON THE WESTERN EDGE OF THE SURFACE HIGH PRES. SATELLITE IMAGERY SHOWS POSSIBLE ADVECTION FOG OR LOW STRATUS OVER THE NW GULF OFF THE TEXAS COAST THIS MORNING. LITTLE CHANGE IS EXPECTED OVER GULF WATERS THROUGH TONIGHT. WINDS WILL GRADUALLY INCREASE OVER THE WESTERN GULF TOMORROW BETWEEN THE HIGH PRES OVER THE EASTERN GULF AND AN AREA OF LOW PRES DEVELOPING OVER THE PLAINS. CARIBBEAN... A MID/UPPER LEVEL TROUGH SHOWING UP ON WATER VAPOR IMAGERY DIGGING THROUGH THE EASTERN CARIBBEAN IS BRINGING DRY SUBSIDENT ACROSS MUCH OF THE CARIBBEAN BASIN E OF 70W. SOME MID AND UPPER LEVEL CLOUDINESS IS EVIDENT IN THE WESTERLY FLOW FOLLOWING THE TROUGH. A FEW SHOWERS OFF THE SOUTHEAST COAST OF CUBA STARTING TO DISSIPATE. THESE WERE THE PRODUCT OF DRAINAGE FLOW CONVERGENCE AT THE SURFACE...AND SLIGHTLY UNSTABLE MID LEVEL AIR MOVING INTO THE AREA WITH THE NW FLOW ALOFT. OTHERWISE...MODERATE TO FRESH TRADES PERSIST ACROSS THE WHOLE BASIN. ATLANTIC OCEAN... A BROAD UPPER TROUGH EXTENDS FROM AN UPPER LOW ALONG THE CAROLINA COAST TO SOUTHEAST FLORIDA. AN ASSOCIATED SURFACE TROUGH EXTENDS FROM THE CAROLINAS TO A WEAK SURFACE LOW 1011 MB OFF THE EAST CENTRAL FLORIDA COAST...THEN ON TO THE FLORIDA KEYS. ANOTHER WEAKER SURFACE TROUGH IS SITUATED FURTHER EAST...AND EXTENDS FROM 31N74W THROUGH THE CENTRAL BAHAMAS...THEN TO CENTRAL CUBA. THESE TROUGHS WILL MAKE SLOW PROGRESS TO THE SE TODAY IN CONCERT WITH THE UPPER SUPPORT. FURTHER EAST...ANOTHER UPPER TROUGH SHOWS UP ON WATER VAPOR AND SATELLITE DERIVED WINDS...FROM NEAR BERMUDA TO 23N52W. UPPER DIVERGENCE TO THE EAST OF THIS TROUGH IS GENERATING SCATTERED SHOWERS GENERALLY N OF 23N E OF THE TROUGH TO 50W. SHIP OBSERVATIONS AND SCATTEROMETER DATA INDICATE A 1012 MB SURFACE LOW IS FORMING NEAR 28N56W. THIS WILL SHIFT TO THE NE AND DEEPEN SLIGHTLY THROUGH 24 HOURS AS THE UPPER TROUGH LIFTS OUT. AN UPPER RIDGE IS CENTERED SOUTH OF THE TROUGH NEAR 9N44W. DIVERGENCE ALOFT ON THE EAST AND SOUTH SIDES OF THE UPPER ANTICYCLONE IS STARTING TO ENHANCE CONVECTION ALONG THE ITCZ...GENERALLY W OF 25W. A 1025 MB SURFACE HIGH IS CENTERED TO THE WEST OF THE CANARY ISLANDS NEAR 30N27W. AN ASCAT PASS FROM 6 HOURS AGO SHOWED GENERALLY MODERATE TRADE WIND FLOW ACROSS THE EASTERN ATLC TO THE SOUTH OF THE SURFACE HIGH. THE EXCEPTION IS ALONG THE AFRICAN COAST TO AS FAR SOUTH AS SENEGAL WHERE SHIP AND SCATTEROMETER DATA SHOW 25 TO 30 KT NORTHERLY FLOW. LITTLE CHANGE IS EXPECTED IN THE TRADE WIND FLOW OVER THE NEXT 48 HOURS. $$ CHRISTENSEN