000 AXNT20 KNHC 172357 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT SUN AUG 17 2008 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. ...SPECIAL FEATURES... TROPICAL STORM FAY CENTERED NEAR 21.0N 80.3W OR ABOUT 175 NM... 330 KM...SOUTHEAST OF HAVANA CUBA AND ABOUT 230 NM...430 KM... SOUTH-SOUTHEAST OF KEY WEST FLORIDA AT 18/0000 UTC MOVING SLOWLY AND SOMEWHAT ERRATICALLY TOWARD THE WEST-NORTHWEST NEAR 9 KT... 17 KM/HR. A TURN TOWARD THE NORTHWEST IS EXPECTED TONIGHT...WITH A TURN TOWARD THE NORTH EXPECTED MONDAY OR MONDAY NIGHT. ON THE FORECAST TRACK...FAY IS EXPECTED CROSS WESTERN CUBA OVERNIGHT TONIGHT OR MONDAY MORNING...AND MOVE NEAR THE FLORIDA KEYS MONDAY OR MONDAY NIGHT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1001 MB. MAXIMUM SUSTAINED WIND SPEED IS 45 KT WITH HIGHER GUSTS. SLOW STRENGTHENING IS FORECAST DURING THE NEXT COUPLE OF DAYS...AND FAY COULD BE APPROACHING HURRICANE STRENGTH WHEN IT REACHES WESTERN CUBA TONIGHT AND WHEN IT APPROACHES THE FLORIDA KEYS MONDAY OR MONDAY NIGHT. PLEASE SEE THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC AND PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT1/WTNT31 KNHC FOR MORE DETAILS. FAY HAS BECOME A LITTLE BETTER ORGANIZED IN SATELLITE AND RADAR IMAGERY THIS EVENING...WITH INCREASED CURVED BANDS OF CONVECTION NEAR THE CENTER IN THE NORTHEASTERN SEMICIRCLE. FAY IS EXPECTED TO PRODUCE TOTAL RAINFALL ACCUMULATIONS OF 4 TO 8 INCHES OVER MUCH OF CUBA...WITH ISOLATED MAXIMUM AMOUNTS OF 12 INCHES. THESE RAINS COULD PRODUCE LIFE-THREATENING FLASH FLOODS AND MUD SLIDES. RAINFALL ACCUMULATIONS OF 1 TO 3 INCHES ARE POSSIBLE OVER GRAND CAYMAN AND OVER THE CENTRAL BAHAMAS. HEAVY RAIN MAY BEGIN TO AFFECT THE FLORIDA KEYS AND SOUTH FLORIDA TONIGHT AND INTO MONDAY. RAINFALL TOTALS OF 4 TO 6 INCHES...WITH MAXIMUM AMOUNTS OF 10 INCHES ARE POSSIBLE FOR THE FLORIDA KEYS AND SOUTH FLORIDA. ...TROPICAL WAVES... THE TROPICAL WAVE THAT WAS PREVIOUSLY ALONG 35W IS RELOCATED FURTHER EAST ALONG 29W/30W BASED ON LATEST VIS SAT IMAGERY FOR THE DAY AND A QSCAT PASS FROM AROUND 2000 UTC THAT SHOWED A CYCLONIC TURNING ALONG THE WAVE AXIS NEAR 13N. THE WAVE SHOWS UP VERY WELL ON THE TPW PRODUCT WITH A BROAD AREA OF DEEP LAYERED MOISTURE. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS BEHIND THE WAVE AXIS FROM 9N-12N BETWEEN 23W-28W. ISOLATED MODERATE CONVECTION IS ALSO NOTED SPINNING NEAR 13N BETWEEN 28W AND 31W. A TROPICAL WAVE IS APPROACHING THE LESSER ANTILLES AND EXTENDS FROM 21N57W TO 8N60W. THIS WAVE IS MOVING WEST 10-15 KT AND IS INTERACTING WITH AN UPPER-LEVEL TROUGH THAT ENTERS THE NE CARIBBEAN. A NARROW BAND OF MOISTURE IS AHEAD OF THE WAVE AXIS PRODUCING SCATTERED SHOWERS OVER THE WINDWARD ISLANDS AND COASTAL WATERS. ...THE ITCZ... THE ITCZ AXIS IS CENTERED ALONG 15N17W 10N34W 7N45W 7N56W. MOST OF THE CONVECTIVE ACTIVITY IS ASSOCIATED WITH THE TROPICAL WAVE LOCATED NEAR 29W/30W. A CLUSTER OF MODERATE CONVECTION IS NEAR 7N29W...AND NEAR 9N52W. ...DISCUSSION... THE GULF OF MEXICO... AN UPPER-LEVEL HIGH CENTERED NOW OVER W-CENTRAL MEXICO EXTENDS A RIDGE EWD OVER THE WESTERN HALF OF THE GULF REGION AND THE YUCATAN PENINSULA WHILE A MID/UPPER-LEVEL TROUGH IS OVER THE SE CONUS AND THE NE CORNER OF THE GULF. THIS PATTERN SHOULD ALLOW T.S. FAY TO TURN MORE NORTHWARD AFTER 24 HR...BUT THERE REMAINS SIGNIFICANT DISAGREEMENT BETWEEN THE COMPUTER MODELS ON HOW MUCH OF A TURN WILL OCCUR. SEE SPECIAL FEATURES. THIS UPPER-LEVEL TROUGH SUPPORTS A STATIONARY FRONTAL BOUNDARY THAT LIES OVER THE N GULF STATES AND EXTENDS FROM S GEORGIA TO SE LOUISIANA TO S TEXAS. PREFRONTAL ACTIVITY IS PRODUCING SCATTERED SHOWERS WITH EMBEDDED TSTMS OVER THE GULF N OF 25N. AN OUTER RAINBAND FROM T.S. FAY IS CURRENTLY AFFECTING SOUTH FLORIDA...THE KEYS AND THE SE PORTION OF THE GULF. WEATHER CONDITIONS ARE EXPECTED TO DETERIORATE OVER THE SE GULF TOMORROW AFTERNOON AS FAY EMERGES FROM WESTERN CUBA. AT THE SURFACE...A RIDGE ANCHORED ON A WEAK 1016 MB HIGH SITUATED NEAR 27N88W DOMINATES THE AREA PRODUCING SLY RETURN FLOW OF 10 TO 15 KT OVER THE WESTERN HALF OF THE GULF. NELY WINDS ASSOCIATED WITH THE CYCLONIC CIRCULATION OF FAY ARE ALREADY BLOWING OVER THE SE GULF AS NOTED ON SFC OBSERVATIONS AND AN EARLIER ASCAT PASS. THE CARIBBEAN SEA... MAIN FEATURE IN THE CARIBBEAN SEA IS T.S. FAY LOCATED SOUTH OF CENTRAL CUBA. NEW WATCHES AND WARNINGS WERE ISSUED AT 2100 UTC. RAIN BANDS ASSOCIATED WITH FAY ARE AFFECTING E-CENTRAL CUBA...THE BAHAMAS...SOUTH FLORIDA AND THE KEYS AND THE SE PORTION OF THE GULF OF MEXICO WITH A FEEDER BAND BETWEEN HAITI AND JAMAICA. SEE SPECIAL FEATURES ABOVE. ELONGATED UPPER LOW IS OVER WESTERN TIP OF CUBA EXTENDING AN UPPER TROUGH SW THROUGH THE FAR NW CARIBBEAN O THE N COAST OF HONDURAS NEAR ROATAN ISLAND. THIS LOW IS FORECAST BY THE COMPUTER MODELS TO MOVE AS AN INVERTED TROUGH OVER THE YUCATAN PENINSULA LATE MONDAY INTO TUE. FAY REMAINS ON THE SOUTH SIDE OF A LOW/MID-LEVEL RIDGE ANCHORED ON A HIGH CURRENTLY OVER THE SOUTH-CENTRAL BAHAMAS. THIS RIDGE COVERS THE CENTRAL CARIBBEAN WHILE AN UPPER-LEVEL TROUGH THAT EXTENDS FROM AN UPPER LOW NEAR 26N61W ENTERS THE NE CARIBBEAN. SCATTERED MODERATE CONVECTION IS SEEN OVER COSTA RICA AND PANAMA LIKELY DUE TO THE CLOSE PROXIMITY OF THE ITCZ. ACCORDING TO THE OFFICIAL FORECAST TRACK...FAY IS EXPECTED CROSS WESTERN CUBA OVERNIGHT TONIGHT OR MONDAY MORNING. THE ATLANTIC OCEAN... AS PREVIOUSLY MENTIONED...THERE IS SOME SHOWER AND TSTM ACTIVITY OVER THE W ATLC W OF 70W AND THE BAHAMAS ASSOCIATED WITH THE OUTER RAINBANDS OF T.S. FAY. FURTHER EAST...SCATTERED SHOWERS AND ISOLATED TSTMS ARE SPINNING AROUND AN UPPER-LEVEL LOW LOCATED NEAR 26N61W. UPPER DIFFLUENCE BETWEEN THIS UPPER LOW AN AN UPPER-LEVEL HIGH TO THE E LOCATED NEAR 26N46 IS SUPPORTING A CLUSTER OF MODERATE CONVECTION THAT COVERS FROM 23N-28N BETWEEN 52W-54W. A SFC TROUGH IS ANALYZED IN THAT AREA AND RUNS FROM 30N52W TO 23N56W. THIS TROUGH...24 HOURS AGO WAS PART OF THE TROPICAL WAVE THAT IS NOW APPROACHING THE LESSER ANTILLES. ANOTHER UPPER LEVEL LOW IS W OF THE CANARY ISLANDS NEAR 28N20W. AT THE SURFACE...A 1024 MB HIGH CENTERED OVER THE CENTRAL ATLANTIC NEAR 35N44W EXTENDS A RIDGE W TOWARDS BERMUDA AND THE W ATLC. $$ GR