000 AXNT20 KNHC 190001 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT MON AUG 18 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 2345 UTC. ...SPECIAL FEATURES... T.S. FAY HEADED NORTHWARD TOWARD THE SOUTHWEST FLORIDA COAST. AT 19/0000 UTC...THE CENTER OF TROPICAL STORM FAY IS CENTERED NEAR 25.0N 81.9W OR ABOUT 90 NM...170 KM...SOUTH OF NAPLES FLORIDA MOVING TOWARD THE NORTH NEAR 8 KT. THIS GENERAL MOTION IS EXPECTED TO CONTINUE TONIGHT AND TUESDAY. ON THE FORECAST TRACK...THE CENTER OF FAY WILL CROSS THE SOUTHWESTERN COAST OF FLORIDA ON TUESDAY. ESTIMATED MINIMUM CENTRAL PRESSURE IS 998 MB. MAXIMUM SUSTAINED WIND SPEED IS 50 KT WITH HIGHER GUSTS. STRENGTHENING IS EXPECTED TONIGHT AND TUESDAY...AND FAY IS FORECAST TO BE AT OR NEAR HURRICANE STRENGTH AS IT APPROACHES THE SOUTHWESTERN COAST OF FLORIDA. PLEASE SEE THE LATEST NHC THE FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC AND PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT1/ WTNT31 KNHC FOR MORE DETAILS. SATELLITE...RADAR...AND AIRCRAFT DATA INDICATE THAT FAY HAS BECOME BETTER ORGANIZED THIS EVENING. THE CONVECTIVE BANDING HAS INCREASED AROUND THE CENTER...AND THE RADIUS OF MAXIMUM WINDS HAS CONTRACTED TO ABOUT 30 N MI. IN ADDITION...THE CENTRAL PRESSURE HAS FALLEN TO 998 MB. FAY IS EXPECTED TO PRODUCE ADDITIONAL RAINFALL ACCUMULATIONS OF 3 TO 5 INCHES OVER THE CENTRAL PORTION OF CUBA...WITH STORM TOTAL AMOUNTS OF 20 INCHES BEING POSSIBLE. THESE RAINS COULD CAUSE LIFE THREATENING FLASH-FLOODS AND MUDSLIDES. RAINFALL ACCUMULATIONS OF 4 TO 8 INCHES...WITH MAXIMUM STORM TOTAL AMOUNTS OF 10 INCHES...ARE POSSIBLE FOR THE FLORIDA KEYS AND THE CENTRAL AND SOUTHERN FLORIDA PENINSULA. RAINFALL ACCUMULATIONS OF 3 TO 5 INCHES ARE POSSIBLE IN THE NORTHWESTERN BAHAMAS. ...TROPICAL WAVES... A TROPICAL WAVE IS IN THE E TROPICAL ATLC ALONG 35W S OF 17N. A 1010 MB LOW IS ANALYZED ALONG THE WAVE AXIS NEAR 13N. SCATTERED SHOWERS AND TSTMS ARE WITHIN 90 NM N SEMICIRCLE OF THE LOW CENTER. SOME BANDING FEATURE IS NOTED ON SATELLITE IMAGERY. THIS SYSTEM HAS CONTINUED TO BECOME BETTER ORGANIZED THIS EVENING AND ADDITIONAL DEVELOPMENT INTO A POSSIBLE TROPICAL CYCLONE CAN BE EXPECTED DURING THE NEXT 48 HOURS AS IT MOVES WESTWARD OR WEST-NORTHWESTWARD AT ABOUT 15 MPH. ANOTHER AREA OF CLOUDINESS WITH MODERATE CONVECTION IS WITHIN 530 NM SE OF THE ABOVE MENTIONED SFC LOW. THE CLOUD PATTERN IS ALSO EXHIBITING CYCLONIC CIRCULATION AS OBSERVED ON RECENT SATELLITE IMAGERY. WILL WAIT FOR MORE SHIP...SCATTEROMETER AND SATELLITE DATA BEFORE PLACING ANOTHER SFC LOW OUT THERE. CLUSTERS OF SCATTERED MODERATE CONVECTION ARE FROM 11N-14.5N BETWEEN 31W-38W RELATED TO THE TROPICAL WAVE/LOW. A TROPICAL WAVE HAS ENTERED THE EASTERN CARIBBEAN. ITS AXIS REMAINS TILTED FROM 21N59W TO 11N63W. A WEAK INVERTED-V SIGNATURE IS NOTED ON SAT IMAGERY WITH A SMALL AREA OF SHOWERS MOVING WWD AHEAD OF THE WAVE AXIS. THIS SHOWER ACTIVITY IS APPROACHING THE ABC ISLANDS. WAVE REMAINS DISTORTED DUE TO AN UPPER LOW TO THE N OF THE WAVE LINE. SCATTERED SHALLOW SHOWERS ARE MOVING THROUGH THE LEEWARD ISLANDS. ...THE ITCZ... THE ITCZ IS CENTERED ALONG 14N16W 10N25W 12N33W 10N45W 8N60W. OUTSIDE OF THE CONVECTION ASSOCIATED WITH THE TROPICAL WAVE...SCATTERED MODERATE CONVECTION IS WITHIN FROM 8N-10N EAST OF 18W TO THE AFRICAN COAST. SIMILAR CONVECTION IS FROM 6N-10N BETWEEN 25W-31W...AND FROM 7N-11N BETWEEN 56W-58W. ...DISCUSSION... GULF OF MEXICO... ALL THE ATTENTION REMAINS FOCUSED ON TROPICAL STORM FAY THAT MADE LANDFALL OVER KEY WEST FLORIDA AT 3 PM EDT. AT THAT TIME... THE WINDS WENT CALM INDICATING THE PRESENCE OF THE STORM CENTER. SEE SPECIAL FEATURES ABOVE. A BROAD UPPER TROUGH OVER THE ERN U.S. DIGS INTO THE NE PORTION OF THE GULF AND EXTENDS TO AN UPPER-LEVEL LOW THAT CONTINUES TO SPIN BETWEEN WESTERN CUBA AND THE YUCATAN PENINSULA. THE REMAINDER OF THE GULF REGION IS UNDER THE INFLUENCE OF A RIDGE ANCHORED ON AN UPPER-LEVEL HIGH NOW LOCATED OVER THE SOUTHERN BAJA PENINSULA. T.S. FAY IS ENTERING THE AREA BETWEEN THE UPPER-LEVEL TROUGH PREVIOUSLY MENTIONED AND A SUBTROPICAL RIDGE OVER THE W ATLC THAT COVERS THE STATE OF FLORIDA AND THE E GULF. DOPPLER RADAR SHOWS THE SPIRAL BANDS ASSOCIATED WITH THE CYCLONIC CIRCULATION OF FAY OVER SOUTH FLORIDA AND THE KEYS. THE OUTER BAND IS REACHING THE AREA OF LAKE OKEECHOBEE. MAXIMUM RAINFALL AMOUNTS SO FAR HAVE BEEN FROM 1 TO 3 INCHES ACROSS PARTS OF MIAMI-DADE COUNTY, ESPECIALLY WHERE THE SPIRAL BANDS HAVE PERSISTED FOR A FEW HOURS. SCATTERED SHOWERS AND TSTMS ARE ALSO ACROSS THE N GULF STATE ASSOCIATED WITH A FRONTAL BOUNDARY THAT REMAINS NEARLY STATIONARY OVER THAT REGION. A WEAK 1014 MB HIGH IS LOCATED NEAR 27N89W AT 2100 UTC. CONDITIONS OVER THE FAR ERN GULF...INCLUDING THE FLORIDA PENINSULA WILL CONTINUE TO DETERIORATE AS T.S. FAY MOVES TOWARD THE NORTH TONIGHT AND TUE. ACCORDING TO THE OFFICIAL FORECAST TRACK...A SECOND LANDFALL IS EXPECTED ALONG THE WEST COAST OF FLORIDA TOMORROW. CARIBBEAN SEA... T.S. FAY CONTINUES TO MOVE AWAY FROM THE CARIBBEAN SEA BUT A FEEDER BAND PERSISTS OVER CENTRAL CUBA WHERE RAINFALL AMOUNTS GREATER THAN 6 INCHES HAVE BEEN REPORTED...PARTICULARLY OVER THE MOUNTAINOUS TERRAIN OF THE MUNICIPALITY OF PLACETA CUBA. SEE SPECIAL FEATURES ABOVE FOR MORE DETAILS ON T.S. FAY. A BROAD UPPER HIGH IS CENTERED NE OF THE BAHAMA ISLANDS AND EXTENDS A RIDGE THROUGH ERN CUBA AND JAMAICA INTO THE CENTRAL CARIBBEAN . THIS DIFFLUENT PATTERN ALOFT IS SUPPORTING THE CONVECTION ASSOCIATED WITH T.S. FAY ACROSS CENTRAL CUBA AND THE N CENTRAL CARIBBEAN SEA. AN UPPER LOW IN THE W/CENTRAL ATLC EXTENDS WEAK UPPER TROUGHING OVER THE NE CARIBBEAN WITH AXIS CROSSING THE VIRGIN ISLANDS. MOST OF THE BASIN IS DOMINATED BY MODERATE TO STRONG SUBSIDENCE AND DRY STABLE AIR DUE TO THE INFLUENCE OF THE ABOVE MENTIONED RIDGE. THE ITCZ AXIS EXTENDS FROM COLOMBIA INTO THE ERN PACIFIC REGION NEAR THE PANAMA/COSTA RICA BORDER GENERATING SCATTERED SHOWERS AND ISOLATED TSTMS OVER THE FAR SW CARIBBEAN S OF 10N BETWEEN COLOMBIA AND COSTA RICA. SCATTERED SHOWERS AND ISOLATED TSTMS ARE ALSO SEEN OVER PARTS OF HONDURAS AND NICARAGUA. UPPER DIFFLUENCE IS SUPPORTING THIS ACTIVITY. A SFC TROUGH IS ANALYZED FROM WESTERN CUBA TO THE GULF OF HONDURAS. AN EARLIER QSCAT PASS SHOWED SLY WINDS OF 20-25 KT WITHIN 200 NM E OF THE TROUGH AXIS AND N OF 19N. THESE WINDS ARE PART OF THE FAY'S CIRCULATION AND ARE EXPECTED TO DIMINISH LATE TONIGHT THROUGH TUE. A TROPICAL WAVE IS OVER THE E CARIBBEAN. SEA ABOVE. ATLANTIC OCEAN... THE FRONTAL BOUNDARY OVER THE SE U.S. EXTENDS FROM THE W ATLC N OF THE REGION...AND ALONG WITH T.S. FAY IS GENERATING SCATTERED SHOWERS AND THUNDERSTORMS OVER THE W ATLC W OF 72W AND ACROSS THE NW BAHAMAS. AN UPPER HIGH CENTERED NEAR 26N71W IS PROVIDING AMPLE UPPER DIFFLUENCE TO SUSTAIN THIS CONVECTIVE ACTIVITY. A LARGE UPPER LOW IS LOCATED IN THE W/CENTRAL ATLC NEAR 24N62W EXTENDING UPPER TROUGHING OVER THE NE CARIBBEAN. A SURFACE TROUGH IS TO THE E OF THE UPPER LOW EXTENDING FROM 31N56W TO 24N58W GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS WITHIN 150 NM EAST OF THE SURFACE TROUGH. AN UPPER HIGH IS TO THE E NEAR 31N48W. ANOTHER UPPER-LEVEL LOW IS CENTERED NEAR 25N40W WITH A WEAKER SECOND ONE JUST S OF THE MADEIRA ISLANDS. MODERATE SUBSIDENCE AND SOMEWHAT DRY STABLE AIR COVERS THE ATLC BETWEEN 40W-60W AND N OF THE ITCZ TO 24N GIVING THE AREA MOSTLY FAIR WEATHER CONDITIONS. AT THE SURFACE...A RIDGE ANCHORED BY A SERIES OF HIGHS N OF THE REGION COVERS MOST OF THE FORECAST AREA...BUT MAINLY E OF 50W. $$ GR