000 AXNT20 KNHC 221753 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT TUE AUG 22 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 1715 UTC. ...SPECIAL FEATURE... TROPICAL DEPRESSION FOUR IS CENTERED NEAR 13.6N 26.1W 0R ABOUT 140 NM SOUTHWEST OF THE SOUTHERN MOST CAPE VERDE ISLANDS AT 22/1500 UTC MOVING WNW AT 15 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1007 MB. MAXIMUM SUSTAINED WIND SPEED IS 30 KT WITH GUSTS TO 40 KT. A 24 HOUR INFRARED SATELLITE LOOPS SHOWS THAT THE DEPRESSION HAS NOT GAINED CONVECTION OR MUCH ORGANIZATION TO IT. ONE POSSIBLE REASON IS BECAUSE OF THE LARGE AMOUNT STABLE AIR AND SAHARAN DUST TO THE N OF THE CYCLONE. SOME OF THE STRATOCUMULUS CLOUDS ARE WRAPPING INTO THE CIRCULATION OF THE DEPRESSION. SCATTERED SHOWERS AND TSTMS ARE MAINLY CONFINED FROM 12N-15N BETWEEN 25W-29W. STRENGTHENING IS FORECAST. FOR MORE DETAILS SEE LATEST NHC FORECAST/ADVISORY UNDER HEADERS MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS. ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 46W S OF 20N MOVING W NEAR 15 KT. THIS WAVE CONTINUES TO BE FAIRLY WELL-DEFINED WITH BROAD LOW-MID CYCLONIC TURNING NOTED ABOUT THE AXIS. A LOW-MID LEVEL SWIRL IS STILL EVIDENT ALONG THE WAVE NEAR 10.5N. DESPITE ITS STRUCTURE...DEEP CONVECTION REMAINS MINIMAL AND CONFINED WITHIN THE ITCZ. FURTHER DEVELOPMENT OF THIS WAVE DOES NOT APPEAR LIKELY AS ITS OVERALL STRUCTURE REMAINS BROAD AND THE NRN EXTENSION OF THE WAVE REMAINS EMBEDDED IN A LARGE AREA OF SAHARAN DUST. TROPICAL WAVE IS NEARING THE LESSER ANTILLES ALONG 60W/61W S OF 20N MOVING W 15-20 KT. AN ILL-DEFINED INVERTED-V SHAPE IS NOTED ON SATELLITE IMAGERY AND HELPED LOCATE THE AXIS. SCATTERED SHOWERS AND TSTMS COVER A LARGE AREA EMBEDDED IN THE ITCZ FROM 10N-14N BETWEEN 53W-72W. A WEAK TROPICAL WAVE IS IN THE WRN CARIBBEAN ALONG 77W/78W S OF 18N MOVING W 15 KT. ONLY A SLIGHT HINT OF LOW CLOUD CURVATURE IS NOTED ON VIS IMAGES ABOUT THE AXIS. THIS WAVE IS EMBEDDED IN A DRY STABLE ENVIRONMENT PRODUCING ONLY ISOLATED SHOWERS IN ITS VICINITY. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 16N16W 9N26W 10N44W 10N60W ACROSS NRN S AMERICA AND PANAMA INTO THE E PAC. BESIDES FOR THE TROPICAL WAVES...SCATTERED MODERATE CONVECTION IS OVER CNTRL AMERICA FROM 8N-11N W OF 82W INTO THE E PAC. ...DISCUSSION... GULF OF MEXICO... AN UPPER TROUGH STRETCHES ACROSS THE AREA FROM AN UPPER LOW JUST S OF THE FL PANHANDLE NEAR 29N86W SW TO ANOTHER UPPER LOW IN THE W GULF NEAR 25N96W ACROSS CNTRL MEXICO. CONSIDERABLE CLOUDINESS COVERS THE MAJORITY OF THE REGION EXCEPT FOR THE NW PORTION WHICH LIES UNDER THE SRN PERIPHERY OF A U.S. MID-UPPER RIDGE. SCATTERED SHOWERS AND ISOLATED TSTMS ARE MOST ORGANIZED NEAR THE UPPER LOW CENTERS FROM 26N-30N BETWEEN 83W-88W AND FROM 19N-26N W OF 92W. AT THE SFC...WEAK RIDGING FROM THE ATLC STRETCHES INTO THE AREA PRODUCING LIGHT S-SE WINDS IN THE E GULF AND MAINLY E WINDS IN THE W GULF. THE SE FLOW IN THE E GULF IS DRAWING TROPICAL MOISTURE FROM THE NW CARIBBEAN INTO THE EXTREME SRN PORTION OF THE AREA. THIS MOISTURE WILL CONTINUE TO PUSH N-NW INTO THE REGION OVER THE NEXT DAY OR SO. CARIBBEAN SEA... THERE ARE TWO MAIN AREAS OF UNSETTLED WEATHER IN THE CARIBBEAN. SCATTERED SHOWERS AND TSTMS ARE IN THE NW CARIBBEAN FROM 17N-23N BETWEEN 81W-88W. THIS ACTIVITY IS PRODUCED MOSTLY BY UPPER DIFFLUENCE IN THE REGION. SHIP AND BUOY OBS IN THE AREA SHOW ISOLATED WINDS TO 30 KT IN THE DEEP CONVECTION. OVER THE PAST SEVERAL HOURS...THE LARGE MASS OF CONVECTION HAS GENERALLY WEAKENED WITH A NEW BURST JUST S OF CUBA. THIS AREA OF WEATHER HAS BEEN MOVING N IN THE CARIBBEAN OVER THE PAST COUPLE OF DAYS BUT IS SHOWING NO SIGNS OF ORGANIZING AND SFC PRESSURES ARE RISING. THE OTHER AREA OF UNSETTLED WEATHER IS IN THE ERN CARIBBEAN ASSOCIATED WITH A TROPICAL WAVE AND THE ITCZ. SCATTERED SHOWERS AND TSTMS ARE E OF 72W S OF 15N. UPPER CONFLUENCE IS PRODUCING UPPER SUBSIDENCE BETWEEN THESE TWO AREAS. A TROPICAL WAVE IS EMBEDDED IN THIS DRY ENVIRONMENT PRODUCING LITTLE WEATHER. TIGHTENED PRES GRAD BETWEEN THE BUILDING ATLC RIDGE AND LOWER PRES OVER S AMERICA AND TROPICAL WAVES IS PRODUCING MODERATE TO STRONG TRADES E OF 78W. THESE WINDS ARE LIKELY TO REMAIN THAT WAY OVER THE NEXT COUPLE OF DAYS. ATLANTIC OCEAN... AN UPPER TROUGH EXTENDS ACROSS A PORTION OF THE W ATLC FROM AN UPPER LOW 550 NM SE OF BERMUDA NEAR 29N54W SW TO 26N72W. A SMALL WEAK SFC REFLECTION AS A TROF IS EMBEDDED IN THE UPPER TROUGHING ALONG 24N73W 29N69W. SCATTERED SHOWERS ARE WITHIN 120 NM E OF THE SFC BOUNDARY. SIMILAR ACTIVITY IS OVER THE BAHAMAS FROM 24N-27N BETWEEN 75W-78W AND FARTHER NE FROM 26N-31N BETWEEN 54W-60W. WEAK UPPER RIDGING EXTENDS FROM THE CARIBBEAN ACROSS E CUBA TO THE CENTRAL BAHAMAS NEAR 23N72W. THE REMAINDER OF THE ATLC IS DOMINATED BY MOSTLY BENIGN FEATURES WHICH INCLUDE AN UPPER TROUGH EXTENDING FROM THE E ATLC NEAR 32N19W THRU AN UPPER LOW NEAR 29N27W TO THE TROPICAL ATLC NEAR 20N50W. DRY STABLE UPPER LEVEL AIR IS IN PLACE ACROSS A GOOD PORTION OF THE E AND CNTRL ATLC TO THE N OF A T.D. FOUR. IN ADDITION TO THE STABLE UPPER LEVEL AIR...SAHARAN DUST IS WIDESPREAD IN THE MID-LEVELS SPREADING TO 65W FROM 11N-25N ACCORDING TO THE MILKY LOOK ON VIS IMAGES AND THE CIMSS SAL TRACKING PRODUCT. THE DUST MIGHT BE LESS DENSE NEAR THE DEPRESSION WITH ANOTHER SURGE TO ITS E. AT THE SFC..BESIDES FOR T.D. 4 AND THE WAVES A BROAD SURFACE RIDGE DOMINATES THE ATLC WITH THE ANALYZED HIGH CENTERS N OF THE DISCUSSION AREA. $$ CANGIALOSI