000 AXNT20 KNHC 172348 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT THU SEP 17 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC. ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 20W S OF 17N MOVING W NEAR 12 KT. THE WAVE COINCIDES WITH A DEEP LAYER MOISTURE MAXIMUM ACROSS THE FAR ERN TROPICAL ATLC AS NOTED ON TOTAL PRECIPITABLE WATER IMAGERY. ALSO...CIMSS WAVETRAK MODEL GUIDANCE SHOWS AN AREA OF 850 MB VORTICITY IN THE VICINITY OF THE WAVE AXIS FROM 9N-15N. SCATTERED SHOWERS AND ISOLATED MODERATE CONVECTION IS FROM 7N-17N BETWEEN 17W-22W. TROPICAL WAVE IS ALONG 84W S OF 22N MOVING W NEAR 15 KT. THE WAVE IS FOUND WITHIN A BROAD AREA OF DEEP LAYER MOISTURE AS NOTED ON TPW IMAGERY ACROSS THE WRN CARIBBEAN AND CENTRAL AMERICA. THE LOW-LEVEL CLOUD FIELD SHOWS SOME CYCLONIC TURNING IN THE VICINITY OF THE WAVE AXIS N OF 16N. SCATTERED MODERATE CONVECTION IS WITHIN 150 NM EITHER SIDE OF THE WAVE AXIS. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS MOVING ACROSS ERN HONDURAS AND CENTRAL NICARAGUA FROM 12N-16N BETWEEN 84W-86W. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 10N21W 11N32W 8N38W 7N44W 9N56W 10N62W. WIDELY SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 6N-11N BETWEEN 24W-43W. ...DISCUSSION... GULF OF MEXICO... AS OF 2100 UTC...A COLD FRONT EXTENDS THROUGH ERN LOUISIANA AND INTO THE N/CENTRAL GULF ALONG 29N90W SW TO 24N96W. SCATTERED SHOWERS AND ISOLATED TSTMS ARE ACROSS THE WRN GULF FROM 24N-26N BETWEEN 93W-98W. A PRE-FRONTAL SURFACE TROUGH IS ANALYZED FROM THE FLORIDA BIG BEND REGION NEAR 29N85W TO 24N90W. SCATTERED SHOWERS AND TSTMS ARE WITHIN 60 NM EITHER SIDE OF THE SURFACE TROUGH WITH MOST OF THE ACTIVITY REMAINING N OF 26N OVER THE NE GULF AND INLAND OVER THE NRN FLORIDA PENINSULA AND ERN FLORIDA PANHANDLE. THESE BOUNDARIES ARE SUPPORTED ALOFT BY AN UPPER LEVEL LOW CENTERED OVER NRN LOUISIANA WITH UPPER LEVEL TROUGHING DIPPING ACROSS THE NW GULF TO 23N W OF 88W. WITH MOIST SWLY UPPER LEVEL FLOW PRESENT ACROSS MUCH OF THE NE AND CENTRAL GULF...THE CONVECTION ALONG THE SURFACE TROUGH AND OVER THE NE GULF IS BEING ENHANCED BY UPPER LEVEL DIFFLUENCE BETWEEN THE UPPER LEVEL TROUGHING OVER THE NW GULF AND AN UPPER LEVEL ANTICYCLONIC CIRCULATION CENTERED OVER SRN FLORIDA NEAR 26N81W. CARIBBEAN SEA... WITH THE TROPICAL WAVE ALONG 84W AND AN UPPER LEVEL ANTICYCLONIC CIRCULATION CENTERED OVER THE SRN FLORIDA PENINSULA THAT EXTENDS UPPER LEVEL RIDGING ACROSS THE NW CARIBBEAN...SCATTERED SHOWERS AND ISOLATED TSTMS ARE N OF 17N BETWEEN 80W-87W. AN UPPER LEVEL LOW CONTINUES TO SPIN IN THE CENTRAL CARIBBEAN CENTERED NEAR 15N75W. ISOLATED SHOWERS AND POSSIBLE TSTMS ARE BETWEEN 75W-80W ON THE WRN PERIPHERY OF THE UPPER LOW. MOIST TROPICAL AIR... ATMOSPHERIC INSTABILITY...AND LIFT GENERATED FROM THE UPPER LOW IS PRODUCING SCATTERED SHOWERS AND ISOLATED TSTMS ACROSS THE REMAINDER OF THE CARIBBEAN FROM 62W-75W. ONE AREA OF MOST ACTIVE CONVECTION IS N OF 16N BETWEEN 67W-72W...INCLUDING ERN PUERTO RICO...THE MONA PASSAGE AND HISPANIOLA. ANOTHER AREA OF SCATTERED SHOWERS AND ISOLATED TSTMS IS OBSERVED ON SATELLITE IMAGERY S OF 14N BETWEEN 68W-75W. MODERATE TRADE WINDS REMAIN ACROSS MUCH OF THE BASIN THIS EVENING. ATLANTIC OCEAN... AN UPPER LEVEL SHORTWAVE TROUGH IS ACROSS THE W ATLC NEAR 30N72W AND SUPPORTS A SURFACE TROUGH THAT EXTENDS FROM NEAR 31N71W SW TO THE CENTRAL BAHAMAS NEAR 25N75W. SCATTERED SHOWERS ARE WITHIN 120 NM E OF THE TROUGH AXIS AND EXTENDS ACROSS MUCH OF THE CENTRAL AND NW BAHAMAS FROM 23N-26N BETWEEN 75W-78W. THIS ACTIVITY IS SUPPORTED ALOFT BY UPPER LEVEL DIFFLUENCE AS AN UPPER LEVEL ANTICYCLONIC CIRCULATION IS CENTERED OVER THE SRN FLORIDA PENINSULA AND EXTENDS RIDGING TO ANOTHER UPPER HIGH CENTERED NEAR 28N71W. FARTHER TO THE SE...A 1015 MB SURFACE LOW ...REMNANT OF FRED...IS CENTERED NEAR 25N62W AND EXTENDS A SURFACE TROUGH FROM 22N62W THROUGH THE LOW TO 27N61W. SURFACE CONVERGENCE NEAR THE LOW AND TROUGH ARE SUPPORTING ISOLATED SHOWERS FROM 20N-26N BETWEEN 59W-65W. AN UPPER LEVEL LOW LOCATED SE OF THE AFOREMENTIONED SURFACE LOW IS CENTERED NEAR 20N52W AND CONTINUES TO GENERATE SCATTERED SHOWERS AND TSTMS FROM 19N-23N BETWEEN 50W-55W. THE REMAINDER OF THE CENTRAL AND ERN ATLC IS DOMINATED BY A BROAD SURFACE RIDGE ANCHORED BY A 1026 MB HIGH NEAR 34N45W. NORTH OF THE ITCZ AXIS IN THE TROPICAL CENTRAL ATLC...A 1008 MB LOW IS CENTERED NEAR 13N37W. SCATTERED SHOWERS AND ISOLATED TSTMS ARE DISPLACED NORTH FROM THE ITCZ AXIS REGION FROM 12N-16N BETWEEN 34W-38W. IN THE UPPER LEVELS ACROSS THE TROPICAL ERN ATLC...AN UPPER LEVEL RIDGE EXTENDS FROM W AFRICA ALONG 15N17W TO 8N40W AND CONTINUES TO SUPPORT THE CONVECTION IN THE VICINITY OF THE ITCZ. $$ HUFFMAN