000 AXNT20 KNHC 200548 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0515 UTC. ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 26W S OF 18N MOVING W NEAR 12 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 ARE LOCATED E OF THE WAVE FROM 14N-19N BETWEEN 21W-26W. TROPICAL WAVE IS ALONG 42W FROM 7N-16N 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 LIMITING PRECIPITATION TO A FEW ISOLATED SHOWERS FROM 14N-17N BETWEEN 38W-43W. TROPICAL WAVE IS ALONG 64W S OF 12N MOVING W NEAR 15 KT. AN AREA OF DEEP LAYER MOISTURE IS MOVING ACROSS INTERIOR EASTERN VENEZUELA AND PORTIONS OF THE SE CARIBBEAN. STRONG SUBSIDENCE ALOFT OVER THE EASTERN CARIBBEAN IS INHIBITING ANY DEEP CONVECTION ASSOCIATED WITH THE WAVE. ...ITCZ... ITCZ AXIS IS CENTERED ALONG 9N13W 11N25W 12N28W 12N33W 9N40W 8N44W 7N60W. A 1011 MB SURFACE LOW IS EMBEDDED WITHIN THE AXIS CENTERED NEAR 12N35W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 10N-15N BETWEEN 30W-35W. ELSEWHERE...CLUSTERS OF ISOLATED MODERATE CONVECTION IS FROM 4N-8N BETWEEN 11W-25W. ...DISCUSSION... GULF OF MEXICO... A 1025 MB SURFACE HIGH CENTERED OVER EASTERN GEORGIA NEAR 34N83W EXTENDS A SURFACE RIDGE OVER FLORIDA...THE ENTIRE GULF OF MEXICO AND EASTERN MEXICO. NE WINDS UP TO 25 KT DOMINATE OVER THE EASTERN GULF AS DEPICTED BY AN EARLIER QUIKSCAT PASS AROUND 20/ 0000 UTC...THEN GRADUALLY DIMINISHING TO E-SE 10-15 KT OVER THE NW GULF AS HINTS OF RETURN FLOW IS BEGINNING ACROSS THE SOUTHERN U.S. PLAINS. THIS SURFACE HIGH IS SUPPORTED ALOFT BY A STABLE DRY AND COOLER 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 OVER THE GULF AND FLORIDA PENINSULA. 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 THROUGH THE WINDWARD PASSAGE AND CONTINUES ALONG 19N80W TO THE NE HONDURAS COAST NEAR 16N85W. 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 1006 MB LOW CENTERED NEAR 13N81W IS PRODUCING NUMEROUS SHOWERS AND SCATTERED STRONG TSTMS FROM THE ITCZ AXIS ALONG 7N TO 16N BETWEEN 76W-87W...INCLUDING PORTIONS OF NICARAGUA...COSTA RICA AND WESTERN 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 16N E OF 69W. ATLANTIC OCEAN... A STATIONARY FRONT ENTERS THE DISCUSSION AREA NEAR 31N65W AND EXTENDS S-SW TO THE WINDWARD PASSAGE NEAR 20N73W. SCATTERED SHOWERS AND TSTMS ARE OCCURRING WITHIN 150 NM EITHER SIDE OF THE FRONT. THIS FRONT IS SUPPORTED ALOFT BY A SHARP UPPER LEVEL TROUGH W OF 63W WITH AXIS ALONG 32N73W TO THE NW BAHAMAS AND YUCATAN CHANNEL. A WEAKNESS IN THE SUBTROPICAL RIDGE IS ANALYZED AS A SURFACE TROUGH THAT EXTENDS FROM 21N54W TO 31N51W. LOW- LEVEL CONVERGENCE NEAR THE SURFACE TROUGH IS GENERATING ISOLATED SHOWERS N OF 20N BETWEEN 52W-60W. FARTHER EAST...AN ELONGATED UPPER LEVEL LOW IS CENTERED NEAR 23N46W. THE UPPER LOW STRETCHES NE TO 28N37W AND SW TOWARDS THE LESSER ANTILLES AND OVER THE EASTERN CARIBBEAN SEA NEAR 13N67W. 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 41W-51W. ELSEWHERE ACROSS THE REMAINDER OF THE EASTERN ATLC...A SURFACE RIDGE EXTENDS SE FROM A 1023 MB HIGH CENTERED NEAR 36N41W TO THE W AFRICA COAST NEAR WESTERN SAHARA. $$ HUFFMAN