000 AXNT20 KNHC 201120 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 AM EDT TUE OCT 20 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1015 UTC. ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 27W S OF 18N MOVING W NEAR 10 KT. THE WAVE COINCIDES WITH A DEEP LAYER MOISTURE MAXIMUM ACROSS THE EASTERN TROPICAL ATLC AS OBSERVED IN TOTAL PRECIPITABLE WATER IMAGERY. GLOBAL MODEL GUIDANCE FIELDS OF 850 MB RELATIVE VORTICITY AND 700 MB STREAMLINES ALSO DEPICT CYCLONIC TURNING IN THE VICINITY OF THE WAVE AXIS BETWEEN 23W-29W. SCATTERED SHOWERS AND ISOLATED MODERATE CONVECTION ARE LOCATED E OF THE WAVE FROM 13N-18N BETWEEN 22W-27W. TROPICAL WAVE IS ALONG 44W FROM 8N-13N MOVING W NEAR 15 KT. THE WAVE APPEARS TO BE MOVING BENEATH A HIGHLY SHEARED ENVIRONMENT AS ENERGY IS BEING STRETCHED NORTHWESTWARD ACROSS THE CENTRAL ATLC. THIS SHEAR IS INHIBITING ANY DEEP CONVECTION...HOWEVER...A FEW ISOLATED SHOWERS ARE FROM 13N-18N BETWEEN 40W-44W. TROPICAL WAVE IS ALONG 65W S OF 11N MOVING W NEAR 12 KT. THIS WAVE HAS BECOME INCREASINGLY DIFFICULT TO TRACK AS A MAJORITY OF THE WAVE IS INTERACTING WITH PORTIONS OF INTERIOR VENEZUELA. STRONG SUBSIDENCE ALOFT OVER THE EASTERN CARIBBEAN AND NORTH CENTRAL VENEZUELA IS INHIBITING ANY DEEP CONVECTION ASSOCIATED WITH THE WAVE. ...ITCZ... ITCZ AXIS IS CENTERED ALONG 9N13W 9N25W 11N29W 12N33W 11N36W 10N42W 9N45W 8N61W. A 1009 MB SURFACE LOW IS EMBEDDED WITHIN THE AXIS CENTERED NEAR 13N35W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 10N-16N BETWEEN 31W-35W. ELSEWHERE...CLUSTERS OF ISOLATED MODERATE CONVECTION ARE FROM 3N-7N BETWEEN 13W-21W. ...DISCUSSION... GULF OF MEXICO... A 1026 MB SURFACE HIGH CENTERED OVER CENTRAL GEORGIA NEAR 33N84W EXTENDS A SURFACE RIDGE OVER FLORIDA...THE ENTIRE GULF OF MEXICO AND EASTERN MEXICO. NE WINDS UP TO 25 KT ARE OBSERVED OVER THE EASTERN GULF GRADUALLY DIMINISHING TO E-SE WINDS OF 10-15 KT OVER THE NW GULF AS RETURN FLOW IS W OF 93W TO ACROSS THE SOUTHERN U.S. PLAINS. THIS SURFACE HIGH IS SUPPORTED ALOFT BY A STABLE AND RELATIVELY DRY AIRMASS ON THE BACKSIDE OF UPPER LEVEL TROUGHING OVER THE WESTERN ATLC...FLORIDA PENINSULA AND EASTERN GULF E OF 85W. NWLY WINDS ALOFT AND VERY STRONG SUBSIDENCE ARE NOTED ON WATER VAPOR IMAGERY OVER THE GULF AND FLORIDA PENINSULA THIS MORNING. THE SURFACE RIDGE IS FORECAST TO SHIFT GRADUALLY EASTWARD REMAINING MOSTLY OVER MUCH OF THE GULF THROUGH MID-WEEK WITH SE SURFACE RETURN FLOW TO BE WELL DEVELOPED ACROSS THE WESTERN GULF BY WEDNESDAY AHEAD OF THE NEXT COLD FRONT TO ENTER THE NW GULF WATERS LATE THURSDAY. CARIBBEAN SEA... AN UPPER LEVEL TROUGH IS OVER THE WESTERN ATLC AND GULF OF MEXICO DIPPING SOUTH THROUGH THE YUCATAN CHANNEL AND INTO THE NW CARIBBEAN. THIS UPPER LEVEL TROUGHING SUPPORTS A STATIONARY FRONT THAT EXTENDS INTO THE CARIBBEAN SEA OVER WESTERN HISPANIOLA NEAR 20N72W AND CONTINUES ALONG 18N80W TO THE NE HONDURAS COAST NEAR 15N84W. LOW-LEVEL CONVERGENCE IN THE VICINITY OF THE FRONTAL BOUNDARY COUPLED WITH UPPER LEVEL DIFFLUENCE E OF THE UPPER LEVEL TROUGH ARE GENERATING SCATTERED SHOWERS AND ISOLATED TSTMS WITHIN 150 NM EITHER SIDE OF THE FRONTAL BOUNDARY. TO THE SOUTH OVER THE SW CARIBBEAN...A 1010 MB LOW CENTERED NEAR 13N81W IS PRODUCING NUMEROUS SHOWERS AND SCATTERED TSTMS FROM THE ITCZ AXIS ALONG 8N TO 16N BETWEEN 75W-86W...INCLUDING PORTIONS OF NICARAGUA...COSTA RICA AND PANAMA. AN UPPER LEVEL RIDGE IS POSITIONED ACROSS THE SW CARIBBEAN W OF 70W AND IS ENHANCING THIS CONVECTION. E OF 70W...UPPER LEVEL TROUGHING AND GENERALLY DRY STABLE AIR ALOFT ARE NOTED ON WATER VAPOR IMAGERY WITH ELY TRADE WINDS UP TO 20 KT. A FEW ISOLATED LOW-LEVEL SHOWERS ARE OCCURRING OVER THE NE CARIBBEAN N OF 15N E OF 70W. ATLANTIC OCEAN... A STATIONARY FRONT ENTERS THE DISCUSSION AREA NEAR 31N64W AND EXTENDS S-SW TO NW HISPANIOLA NEAR 20N72W. SCATTERED SHOWERS AND ISOLATED TSTMS ARE OCCURRING WITHIN 120 NM EITHER SIDE OF THE FRONT AND OVER THE AREA FROM 21N-25N BETWEEN 71W-78W. THIS FRONT IS SUPPORTED ALOFT BY A SHARP UPPER LEVEL TROUGH W OF 65W WITH AXIS ALONG 32N70W TO THE NW BAHAMAS AND YUCATAN CHANNEL. A WEAKNESS IN THE SUBTROPICAL RIDGE IS ANALYZED AS A SURFACE TROUGH THAT EXTENDS FROM 21N53W TO 29N51W. LOW-LEVEL CONVERGENCE NEAR THE SURFACE TROUGH IS GENERATING ISOLATED SHOWERS N OF 21N BETWEEN 52W-60W. FARTHER EAST...AN ELONGATED UPPER LEVEL LOW IS CENTERED NEAR 21N50W. THE UPPER LOW STRETCHES NE TO 28N38W AND SW TOWARDS THE LESSER ANTILLES AND OVER THE EASTERN CARIBBEAN SEA NEAR 13N66W. MID-LEVEL LIFT AND UPPER LEVEL DIFFLUENCE IN ASSOCIATION WITH THE UPPER LOW ARE GENERATING SCATTERED SHOWERS AND TSTMS COVERING AN AREA FROM 18N-28N BETWEEN 40W-52W. ELSEWHERE ACROSS THE REMAINDER OF THE EASTERN ATLC...A SURFACE RIDGE EXTENDS SE FROM A 1024 MB HIGH CENTERED NEAR 36N39W TO THE W AFRICA COAST NEAR WESTERN SAHARA. $$ HUFFMAN