000 AXNT20 KNHC 050557 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 AM EDT SAT SEP 05 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0500 UTC. ...SPECIAL FEATURES... TROPICAL WAVE IS W OF THE CAPE VERDE ISLANDS ALONG 28W S OF 20N MOVING W AT 20 KT. A 1012 MB LOW IS EMBEDDED ON THE WAVE AXIS NEAR 14N28W. SATELLITE IMAGERY AND SATELLITE DERIVED WINDS INDICATE LOW-LEVEL CYCLONIC FLOW IN THE VICINITY OF THE WAVE AXIS CONCENTRATED AROUND THE LOW PRESSURE CENTER NEAR 14N. THE WAVE ALSO COINCIDES WITH A DEEP LAYER MOISTURE MAXIMUM OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY. SCATTERED MODERATE CONVECTION IS FROM 7N-9N BETWEEN 29W-32W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 14N-18N BETWEEN 28W-30W. THIS SYSTEM HAS A MEDIUM CHANCE...30 TO 50 PERCENT...OF BECOMING A TROPICAL CYCLONE IN THE NEXT 48 HRS. ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 38W S OF 20N MOVING W NEAR 13 KT. A 1012 MB LOW IS ALONG THE WAVE AXIS NEAR 13N38W. SATELLITE IMAGERY AND SATELLITE DERIVED WINDS INDICATE LOW-LEVEL CYCLONIC FLOW IN THE VICINITY OF THE WAVE AXIS CONCENTRATED AROUND THE LOW PRESSURE CENTER NEAR 13N. THE WAVE COINCIDES WITH A DEEP LAYER MOISTURE MAXIMUM OBSERVED TOTAL PRECIPITABLE WATER IMAGERY. SATELLITE IMAGERY ALSO SHOWS SAHARAN DUST TO THE W OF THE WAVE AXIS WHICH IS LIMITING DEEP CONVECTION TO A SMALL AREA. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 15N-16N BETWEEN 38W-40W. TROPICAL WAVE IS ALONG 56W S OF 17N MOVING W NEAR 13 KT. THE WAVE REMAINS RELATIVELY LOW-AMPLITUDE WITH LITTLE ASSOCIATED DEEP CONVECTION DUE TO DRY SAHARAN DUST TO THE E OF THE WAVE AXIS. THE WAVE COINCIDES WITH A NARROW DEEP LAYER MOISTURE MAXIMUM OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY. WHILE NO DEEP CONVECTION IS PRESENT...ISOLATED SHOWERS ARE FROM 11N-12N BETWEEN 55W-56W. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 19N19W 15N27W 12N33W 11N40W 8N50W 8N62W. A LARGE CLUSTER OF SCATTERED MODERATE/STRONG CONVECTION IS APPROACHING THE AFRICAN COAST FROM 14N-18N BETWEEN 12W-16W. ISOLATED MODERATE CONVECTION IS FROM 6N-9N BETWEEN 43W-49W. ...DISCUSSION... GULF OF MEXICO... AS OF 0300 UTC...A SURFACE TROUGH EXTENDS ACROSS CENTRAL FLORIDA FROM NEAR 28N81W TO THE CENTRAL GULF NEAR 26N89W. THE TROUGH IS SUPPORTED BY AN UPPER LEVEL SHORTWAVE TROUGH THAT EXTENDS FROM THE W FLORIDA PANHANDLE NEAR 31N86W TO THE YUCATAN PENINSULA NEAR 20N87W CONTINUING TO CENTRAL AMERICA. UPPER LEVEL DIFFLUENCE BETWEEN THIS UPPER TROUGH AND A LARGE UPPER LEVEL RIDGE IN THE NW ATLC CENTERED NEAR 35N62W...ALONG WITH LOW-LEVEL CONVERGENCE NEAR THE SURFACE TROUGH ARE SUPPORTING ISOLATED SHOWERS/THUNDERSTORMS ACROSS THE YUCATAN CHANNEL TO NRN FLORIDA FROM 22N-32N E OF 85W. A FEW ISOLATED SHOWERS ARE IN THE NW GULF N OF 27N W OF 90W. THIS ACTIVITY IS ENHANCED BY UPPER LEVEL DIFFLUENCE BETWEEN AN UPPER LEVEL RIDGE THAT COVERS THE WRN GULF W OF 92W AND A LARGE UPPER LEVEL TROUGH OVER THE ERN CONUS. EXPECT SHOWERS/THUNDERSTORMS TO PERSIST NEAR THE SURFACE TROUGH AS IT DRIFTS NW AND DISSIPATES MON AND TUE. CARIBBEAN SEA... ISOLATED SHOWERS/THUNDERSTORMS ARE ACROSS THE FAR NW CARIBBEAN N OF 20N BETWEEN 81W-86W IN ASSOCIATION WITH UPPER LEVEL DIFFLUENT FLOW BETWEEN AN UPPER LEVEL TROUGH OVER THE CENTRAL GULF EXTENDING TO S GUATEMALA NEAR 14N90W AND A LARGE UPPER LEVEL RIDGE OVER THE NW ATLC CENTERED NEAR 35N62W. NUMEROUS SHOWERS/THUNDERSTORMS AREA OFF THE COAST OF NICARAGUA AND HONDURAS FROM 12N-15N BETWEEN 79W-84W. ISOLATED SHOWERS ARE ALSO OFF THE COASTS OF COSTA RICA AND NRN COLOMBIA. THESE SHOWERS/THUNDERSTORMS ARE ALL ASSOCIATED WITH MOIST SWLY FLOW ALOFT ALONG WITH UPPER LEVEL DIFFLUENCE BETWEEN THE UPPER LEVEL TROUGH OVER THE NW CARIBBEAN AND AN UPPER LEVEL HIGH DOMINATING THE REMAINDER OF THE CARIBBEAN CENTERED NEAR 13N71W. SCATTERED SHOWERS/THUNDERSTORMS ARE ACROSS HISPANIOLA AND PUERTO RICO FROM 17N-19N BETWEEN 64W-73W DUE TO SURFACE CONVERGENCE NEAR A SURFACE TROUGH...REMNANTS OF ERIKA...THAT EXTENDS FROM 15N70W THROUGH THE MONA PASSAGE TO 21N65W. MODERATE TO FRESH TRADEWINDS ARE ACROSS MUCH OF THE BASIN. OVER THE NEXT 24 HR...EXPECT THE SURFACE TROUGH TO DRIFT NWD OUT OF THE AREA AND A TROPICAL WAVE ALONG 56W WILL REACH THE LESSER ANTILLES AND CONTINUE TO TRACK ACROSS THE ERN CARIBBEAN. ATLANTIC OCEAN... A SURFACE TROUGH EXTENDS ACROSS CENTRAL FLORIDA FROM 28N81W CONTINUING TO 32N76W AND OUT OF THE DISCUSSION AREA. ISOLATED SHOWERS/THUNDERSTORMS ARE WITHIN 150 NM NW OF THE TROUGH AXIS AFFECTING MUCH OF FLORIDA AND THE ADJACENT COASTAL WATERS. THE SHOWERS/THUNDERSTORMS ARE ALSO ENHANCED BY UPPER LEVEL DIFFLUENT FLOW BETWEEN AN UPPER LEVEL TROUGH OVER THE CENTRAL GULF AND A LARGE UPPER LEVEL RIDGE OVER THE NW ATLC CENTERED NEAR 35N62W. A SMALL UPPER LEVEL LOW CENTERED NEAR 25N62W INTRUDES INTO THE SRN EXTENT OF THE UPPER RIDGE. THIS UPPER LEVEL LOW SUPPORTS A SURFACE TROUGH EXTENDING FROM 26N63W TO 31N60W. ISOLATED SHOWERS ARE WITHIN 100 NM EITHER SIDE OF THE TROUGH AXIS. ANOTHER SURFACE TROUGH...REMNANTS OF ERIKA...EXTENDS FROM THE MONA PASSAGE NEAR 19N68W TO 21N65W. ISOLATED SHOWERS ASSOCIATED WITH THE TROUGH ARE FROM 18N-20N BETWEEN 57W-64W. ELSEWHERE ACROSS THE ATLC...A BROAD SURFACE RIDGE DOMINATES ANCHORED BY A 1025 MB HIGH NEAR 31N53W. IN THE UPPER LEVELS...AN UPPER LEVEL HIGH IS CENTERED E OF THE LESSER ANTILLES NEAR 17N55W. AN UPPER LEVEL TROUGH EXTENDS FROM AN UPPER LEVEL LOW NEAR 33N33W TO 19N47W. AN UPPER LEVEL RIDGE DOMINATES THE ERN ATLC CENTERED ALONG THE COAST OF AFRICA NEAR 18N16W. $$ WALTON