000 AXNT20 KNHC 211759 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT MON AUG 21 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... A STRONG TROPICAL WAVE HAS MOVED OFF THE AFRICAN COAST...NOW ALONG 21W WITH A WELL DEFINED LOW CENTERED NEAR 12N. AT 12Z...IT WAS ANALYZED AT 1011 MB. THIS WAVE IS PROBABLY THE MOST VIGOROUS IN THE E ATLC SO FAR THIS YEAR. CONVECTION HAS DECREASED SOME FROM THIS MORNING BUT REMAINS WELL ORGANIZED WITH NUMEROUS SHOWERS AND TSTMS IN AN BANDED FEATURE WHICH WRAPS TWO-THIRDS AROUND THE LOW. SCATTERED MODERATE CONVECTION IS ALSO FOUND S OF THE LOW FROM 6N-10N BETWEEN 19W-25W. THIS AREA MAY DEVELOP INTO A TROPICAL DEPRESSION DURING THE NEXT DAY OR TWO AS IT MOVES WNW AT 10-15 KT. ONE OF THE POSSIBLE LIMITING FACTORS FOR FURTHER DEVELOPMENT IS THE LARGE AREA OF DUST TO THE N AND W OF THE LOW...BUT IT IS DIFFICULT TO DETERMINE HOW MUCH OF A FACTOR IT WILL BE. ...TROPICAL WAVES... TROPICAL WAVE IN THE E ATLC HAS BEEN ADJUSTED AHEAD ALONG 41W S OF 19N MOVING W NEAR 20 KT. A 1012 MB LOW IS PLACED ON THE WAVE NEAR 10N. THIS SFC LOW IS VERY BROAD...BUT SFC OBS AND A 09Z QUIKSCAT PASS HAS HELPED LOCATE THE LOW CENTER. THE WAVE ITSELF IS ALSO BROAD...BUT IS HIGH AMPLITUDE WITH CYCLONIC TURNING COVERING A LARGE AREA ABOUT THE AXIS. FURTHER DEVELOPMENT DOES NOT APPEAR LIKELY AT THIS TIME DUE TO ITS VERY BROAD NATURE AND THE LARGE AREA OF SAHARAN DUST THAT SURROUNDS THE NRN EXTENSION OF THE WAVE. TROPICAL WAVE IS ABOUT 400 NM E OF THE WINDWARD ISLANDS ALONG 54W S OF 19N MOVING W 15-20 KT. WELL DEFINED WAVE STRUCTURE WITH AN INVERTED V-SHAPE EVIDENT ON IR AND VIS IMAGES. THIS WAVE ALSO APPEARS TO BE THE LEADING EDGE OF THE SAHARAN DUST. SCATTERED SHOWERS AND TSTMS ARE WITHIN 300 NM EITHER SIDE OF THE AXIS MAINLY S OF 13N. THE WRN EXTENT OF THE MOISTURE IS SPREADING OVER THE WINDWARD ISLANDS. TROPICAL WAVE IS IN THE E CARIBBEAN ALONG 71W S OF 18N MOVING W NEAR 15 KT OVER THE PAST 24 HOURS. LITTLE SIGNATURE IS APPARENT ON SATELLITE IMAGERY AND ONLY ISOLATED SHOWERS ARE NEAR THE WAVE AXIS. TROPICAL WAVE IS IN THE W CARIBBEAN ALONG 86W S OF 18N MOVING W 10-15 KT. THIS WAVE IS MAINLY INLAND OVER CNTRL AMERICA. NO ORGANIZATION TO THE WAVE IS NOTED...BUT IN COMBINATION WITH UPPER DIFFLUENCE...CLUSTERS OF SCATTERED MODERATE CONVECTION ARE IN THE W CARIBBEAN FROM 17N-20N BETWEEN 79W-82W MOVING N. MORE CONVECTION HAS FORMED FARTHER S FROM 11N-14N BETWEEN 81W-85W. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 9N22W 11N39W 9N61W ACROSS NRN S AMERICA AND PANAMA INTO THE E PAC. BESIDES FOR THE TROPICAL WAVES...CLUSTERS OF SCATTERED MODERATE CONVECTION IS OVER N S AMERICA AND PANAMA MOVING INTO THE E PAC W OF 77W FROM 2N-11N. ...DISCUSSION... GULF OF MEXICO... AN UPPER LOW IS SPINNING IN THE SW GULF NEAR 23N94W WITH TROUGHING EXTENDING E TO A SMALL UPPER LOW IN THE CNTRL GULF NEAR 25N86W TO CENTRAL FLORIDA. CONSIDERABLE CLOUDINESS LIES S OF 27N...BUT THERE ARE ONLY SOME PATCHES OF DEEP MOISTURE. SCATTERED SHOWERS AND TSTMS ARE NEAR THE UPPER LOW IN THE SW GULF FROM 21N-25N BETWEEN 91W-97W AND ISOLATED SHOWERS LIE E OF 85W S OF 27N. UPPER RIDGING COVERS THE N GULF...ANCHORED BY A STRONG HIGH CENTER OVER N TEXAS. DRY STABLE AIR LIES N OF 27N. AT THE SFC...HIGH PRES RIDGING FROM THE ATLC STRETCHES INTO THE AREA. WINDS ARE LIGHT AND GENERALLY FROM THE SE DRAWING SOME TROPICAL MOISTURE FROM THE CARIBBEAN INTO THE SRN GULF. LITTLE CHANGE IN THE SFC PATTERN IS EXPECTED OVER THE NEXT COUPLE OF DAYS. CARIBBEAN SEA... A BROAD UPPER RIDGE EXTENDS ACROSS THE CARIBBEAN FROM HONDURAS E THRU MUCH OF THE CARIBBEAN ALONG 16N. UPPER DIFFLUENCE BETWEEN THIS HIGH AND THE TROUGHING IN THE GULF...IN ADDITION TO THE NEARBY TROPICAL WAVE IS PRODUCING NUMEROUS SHOWERS AND TSTMS IN THE W CARIBBEAN FROM 15N-20N BETWEEN 79W-82W. THIS ACTIVITY IS MOVING SLOWLY N. MORE PATCHES OF SIMILAR CONVECTION LIES S OF 11N BETWEEN 78W-81W...HIGHLY CONTRIBUTED TO THE ITCZ. ANOTHER TROPICAL WAVE IS IN THE CNTRL CARIBBEAN...HOWEVER THIS ONE REMAINS WEAK PRODUCING ONLY ISOLATED SHOWERS. SCATTERED SHOWERS AND TSTMS ARE BEGINNING TO SPREAD ACROSS THE WINDWARD ISLANDS...CURRENTLY E OF 66W S OF 16N. THIS ACTIVITY IS AHEAD OF THE NEXT TROPICAL WAVE. THE COMBINATION OF THE BUILDING ATLC SFC RIDGE N OF THE AREA AND THE TROPICAL WAVES HAVE INCREASED TRADE WINDS TO 20-25 KT ACROSS A GOOD PORTION OF THE AREA. THESE WINDS WILL LIKELY REMAIN THAT WAY OVER THE NEXT COUPLE OF DAYS AS THE SFC PATTERN CHANGES LITTLE. ATLANTIC OCEAN... SEVERAL UPPER LEVEL LOWS ARE SEEN SPINNING IN WATER VAPOR IMAGERY ACROSS THE WRN AND CNTRL ATLC. THE WRN-MOST IS ABOUT 60 NM E OF DAYTONA BEACH FL. UPPER DIFFLUENCE ON THE S SIDE OF THE LOW IS PRODUCING SCATTERED SHOWERS AND TSTMS ACROSS THE BAHAMAS AND S FLORIDA FROM 22N-27N BETWEEN 76W-81W. ANOTHER UPPER LOW IS ABOUT 250 NM SE OF BERMUDA NEAR 30N61W. DIFFLUENT FLOW ON THE S AND E SIDE OF THE CIRCULATION IS PRODUCING PATCHES OF SHOWERS AND TSTMS. A SFC TROF IS EVIDENT IN QUIKSCAT DATA TO THE S OF THE UPPER LOW ALONG 23N70W 28N65W. SCATTERED SHOWERS AND ISOLATED TSTMS ARE WITHIN 120 NM TO THE E OF THE BOUNDARY. SIMILAR ACTIVITY LIES WITHIN 60 NM OF A LINE ALONG 26N54W 30N59W. ANOTHER UPPER LOW IS NEAR 25N41W. THIS FEATURE IS EMBEDDED IN DRY AIR PRODUCING LITTLE WEATHER. AN UPPER RIDGE EXTENDS FROM THE CARIBBEAN ACROSS HISPANIOLA TO NEAR 24N66W. THE E ATLC IS DOMINATED BY AN UPPER RIDGE WITH A HIGH CENTER NEAR 16N39W...THE RIDGE AXIS STRETCHES NE TO BEYOND 32N17W. DRY STABLE UPPER LEVEL AIR COVERS THE AREA UNDER THIS RIDGE. IN ADDITION TO THE DRY UPPER LEVEL AIR...WIDESPREAD SAHARAN DUST IN THE MID-LEVELS HAS SURGED OUT TO NEAR 55W BETWEEN 11N-25N. BESIDES FOR THE SPECIAL FEATURE...TROPICAL WAVES AND SFC TROUGH MENTIONED...HIGH PRES RIDGING DOMINATES WITH THE SURFACE HIGHS ANALYZED N OF THE REGION. THIS FAIRLY STRONG SFC RIDGE HAS INCREASED TRADE WINDS IN THE TROPICS. $$ CANGIALOSI