000 AXNT20 KNHC 091754 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT SUN AUG 09 2009 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS OF SOUTH AMERICA...AND 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1730 UTC. ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 21W FROM 08N TO 17N MOVING W 10-15 KT. ASSOCIATED LOW PRES 1010 MB IS LOCATED ALONG THE WAVE AXIS NEAR 13N. LATEST VISIBLE SATELLITE IMAGERY INDICATED A WELL DEFINED LOW/MID LEVEL CYCLONIC CIRCULATION WITH A CLUSTER OF MODERATE TO STRONG CONVECTION FLARING UP NEAR THE LOW LEVEL CIRCULATION...AND AN ADDITIONAL BAND OF SCATTERED MODERATE CONVECTION WITHIN 90 NM EITHER SIDE OF A LINE THROUGH 12N21W TO 09N25W. THERE IS A MEDIUM PROBABILITY OF TROPICAL CYCLONE FORMATION WITH THIS WAVE AND LOW OVER THE NEXT 48 HOURS. REFER TO THE TROPICAL WEATHER OUTLOOK UNDER AWIPS/WMO HEADERS MIATWOAT/ABNT20 KNHC FOR ADDITIONAL DETAILS. TROPICAL WAVE IS TILTED NW TO SE FROM 20N42W TO 06N37W MOVING W NEAR 15 KT. THE AXIS OF THE WAVE IS ORIENTED WITHIN A MAXIMUM OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY. THERE IS NO DEEP CONVECTION ASSOCIATED WITH THE WAVE...HOWEVER SOME TURNING WAS NOTED IN THE FIELD OF STRATOCUMULUS COMPRISING THE NORTHERN EXTENT OF THE WAVE. TROPICAL WAVE IS ALONG 47W/48W S OF 15N MOVING W NEAR 12 KT. WAVE IS ALONG THE TRAILING EDGE OF A MOISTURE MAXIMUM OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY WITH NO ASSOCIATED DEEP CONVECTION. THE WAVE IS OF LOW AMPLITUDE AND MAY BECOME ABSORBED INTO THE LARGER CIRCULATION COMPRISING THE WAVE ABOVE. TROPICAL WAVE IS ALONG 65W S OF 16N MOVING W NEAR 20 KT. THE WAVE IS EMBEDDED WITHIN AN AREA OF MODERATE EASTERLY TRADES OVER THE E CARIBBEAN WHICH IS PARTIALLY MASKING THE WAVE SIGNATURE AND ANY SHOWERS/CONVECTION IS MORE ASSOCIATED WITH THE ITCZ THAN THE WAVE ITSELF. TROPICAL WAVE IS ALONG 86W S OF 20N MOVING W NEAR 17 KT. WAVE REMAINS ALONG THE TRAILING EDGE OF A MOISTURE MAXIMUM OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY AND IS EMBEDDED IN RATHER DRY STABLE AIR WITH NO ASSOCIATED DEEP CONVECTION. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 13N22W 9N35W 10N46W 14N55W 11N64W. A SURFACE TROUGH EXTENDING FROM 18N56W TO 10N55W WITH CLUSTERS OF SCATTERED MODERATE ISOLATED STRONG CONVECTION W OF THE TROUGH AXIS WITHIN 60-75 NM OF LINE FROM 16N56W TO 14N58W...THEN ACROSS THE SOUTHERN WINDWARD ISLANDS NEAR 13N62W. CLUSTERS OF SCATTERED MODERATE TO ISOLATED STRONG CONVECTION ARE WITHIN 120 NM S OF THE ITCZ BETWEEN 35W-43W. ...DISCUSSION... GULF OF MEXICO... AMPLIFIED PATTERN IN PLACE OVER THE CONUS WITH AN UPPER RIDGE/ANTICYCLONE ANCHORED OVER SOUTH CAROLINA WITH AN EXTENSION OF THE RIDGE INTO THE GULF OF MEXICO TO NEAR 22N94W. SURGE OF DRY AIR ALOFT WAS SWEEPING SWD ACROSS THE NW ATLANTIC...FLORIDA AND THE FAR E GULF CAPPING THUNDERSTORM DEVELOPMENT OVER FLORIDA EXCEPT IN AREAS OF SEABREEZE CONVERGENCE. ON THE BACKSIDE OF THE RIDGE AND EAST OF A TROUGH OVER MEXICO SOUTHERLY FLOW ALOFT WAS ADVECTING SIGNIFICANT DEEP LAYERED MOISTURE NWD TOWARD THE TEXAS AND LOUISIANA COASTS. 12Z RAOBS FROM THE AREA INDICATED PRECIPITABLE WATER VALUES OF 2 TO 2.25 INCHES. SCATTERED THUNDERSTORMS WERE POPPING UP OVER THE NW GULF AND THE ADJACENT COASTAL AREAS OF TEXAS AND LOUISIANA WITH DAYTIME HEATING. A MORE CONCENTRATED AREA OF SCATTERED STRONG THUNDERSTORMS WAS OCCURRING OVER THE FAR SW GULF AND ALONG THE COAST OF MEXICO FROM VERACRUZ TO TAMPICO. CARIBBEAN SEA... THE PERIPHERY OF AN UPPER RIDGE OVER THE NW ATLC AND E GULF OF MEXICO WAS RETREATING AWAY FROM THE NW CARIBBEAN. IN ITS WAKE AN UPPER LEVEL TROUGH EXTENDING FROM THE WINDWARD PASSAGE TO JUST OFF THE COAST OF NICARAGUA WAS ADVANCING WESTWARD AT 10-15 KT. VERY DRY AIR ALOFT WAS NOTED WITHIN 120 NM OF THE TROUGH AXIS AND WAS SPREADING WESTWARD OVER PORTIONS OF HONDURAS AND NICARAGUA. AN UPPER LEVEL RIDGE AXIS EXTENDED FROM THE NORTHERN LEEWARD ISLANDS TO 14N76W. DIFFLUENT SOUTH AND SOUTHEASTERLY FLOW OVER THE CARIBBEAN S OF THE RIDGE AXIS WAS AIDING IN THE DEVELOPMENT OF SCATTERED SHOWERS AND THUNDERSTORMS ACROSS THE SOUTHERN WINDWARD ISLANDS AND NEAR THE ABC ISLANDS. THIS ACTIVITY APPEARED TO BE ALIGNED WITH AN EXTENSION OF THE ITCZ FROM THE ATLANTIC. A MORE CONCENTRATED AREA OF SCATTERED STRONG THUNDERSTORMS WAS OCCURRING OVER THE FAR SW CARIBBEAN WITHIN 90 NM OF THE COAST OF PANAMA AND COSTA RICA. ATLANTIC OCEAN... AN UPPER RIDGE/ANTICYCLONE OVER SOUTH CAROLINA GOVERNED THE PATTERN OVER THE FAR NW PORTION OF THE SUBTROPICAL ATLC WITH DRY AIR ALOFT SWEEPING SW ACROSS THE REGION SUPPRESSING THUNDERSTORM ACTIVITY EXCEPT IN AREAS OF SEABREEZE/FAVORED CONVERGENCE. FURTHER E...A NARROW UPPER TROUGH EXTENDED FROM 27N63W ACROSS THE WINDWARD PASSAGE INTO THE WEST-CENTRAL CARIBBEAN. A LARGE AREA OF UPPER LEVEL DIFFLUENT FLOW EXISTED BETWEEN THE RIDGE AND TROUGH AND SUPPORTED THE GENERATION OF SCATTERED SHOWERS AND THUNDERSTORMS WITHIN 60-90 NM S OF A SURFACE TROUGH WHICH EXTENDS FROM 31N62W TO 28N72W. AN UPPER LOW OVER THE CENTRAL ATLC NEAR 32N45W IS BEGINNING TO SHEAR OUT TO THE NE OVER AN AMPLIFIED RIDGE EXTENDING FROM 32N33W TO AN ANTICYCLONE NEAR 22N38W THEN CONTINUING SW TO NEAR 18N55W. A CHANNEL OF MODERATE TO STRONG NORTHERLY WINDS AND DRY AIR ALOFT WAS SWEEPING SWD BETWEEN THE RIDGE AND AN UPPER LEVEL LOW NEAR THE CANARY ISLANDS. THIS FLOW MAY IMPACT THE POTENTIAL DEVELOPMENT OF THE LOW PRESSURE AREA NEAR 13N21W/THE CAPE VERDE ISLANDS. THE REMAINDER OF THE ATLC REMAINS TRANQUIL WITH A BROAD AREA OF SAHARAN DUST COVERING MOST OF THE AREA E OF 75W. $$ COBB