000 AXNT20 KNHC 132350 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT SAT OCT 13 2012 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...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL ANALYSIS. BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC. ...SPECIAL FEATURES... TROPICAL STORM RAPHAEL IS CENTERED NEAR 17.9N 63.5W AT 14/0000 UTC OR ABOUT 20 NM WSW OF ST. MARTIN...AND 75 NM E OF ST. CROIX. RAPHAEL IS MOVING N AT 10 KT. MINIMUM CENTRAL PRESSURE IS 1O04 MB. MAXIMUM SUSTAINED WIND SPEED IS 45 KT WITH GUSTS TO 55 KT. SEE THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC. WATCHES AND WARNINGS HAVE BEEN PLACED OVER A GOOD PORTION OF THE EASTERN CARIBBEAN. THE SYSTEM IS SUPPORTING A LARGE AREA OF STRONG CONVECTION FROM 14N-19N BETWEEN 61W-64W IMPACTING MUCH OF THE LEEWARD ISLANDS. SCATTERED MODERATE/STRONG CONVECTION IS ELSEWHERE FROM 12N-24N BETWEEN 57W-65W. HEAVY RAINFALL IS EXPECTED TO CONTINUE WITH FLOODING LIKELY ACROSS THE ISLANDS IMPACTED. ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 18N33W TO 10N33W MOVING WEST NEAR 15 KT. THE WAVE LIES WITHIN A BROAD LOW-AMPLITUDE SURGE OF DEEP LAYER MOISTURE PRESENT IN TOTAL PRECIPITABLE WATER IMAGERY. THE LAST VISIBLE SATELLITE IMAGES OF THE DAY ALSO INDICATED THAT THERE WAS LOW-LEVEL CYCLONIC FLOW AROUND THE WAVE AXIS. DUE TO AN UPPER LEVEL TROUGH JUST WEST OF THE WAVE...CONVECTION IS BEING SHEARED TO THE EAST. SCATTERED MODERATE/STRONG CONVECTION IS FROM 6N-10N BETWEEN 30W-36W...AND FROM 10N-15N BETWEEN 30W-33W. MORE CONVECTION CONTINUES FARTHER E...BUT IS LIKELY MORE TIED TO THE UPPER TROUGH THAN THE WAVE. ...THE ITCZ/THE MONSOON TROUGH... THE MONSOON TROUGH EXTENDS ACROSS W AFRICA TO THE COAST OF GUINEA-BISSAU AT 12N17W CONTINUING TO 10N22W. THE ITCZ BEGINS AT 10N22W AND CONTINUES ALONG 10N30W 8N38W 8N44W. SCATTERED MODERATE/STRONG CONVECTION IS FROM 8N-11N BETWEEN 21W-30N...AND FROM 12N-16N BETWEEN 24W-30W. THIS ACTIVITY IS BEING ENHANCED BY AN UPPER LEVEL TROUGH TO THE WEST. SIMILAR ACTIVITY IS ALSO FROM 8N-11N BETWEEN 44W-54W. ...DISCUSSION... GULF OF MEXICO... FAIR WEATHER DOMINATES THE GULF OF MEXICO TONIGHT DUE TO DRY AIR ALOFT AROUND AN UPPER LEVEL RIDGE EXTENDING FROM CENTRAL MEXICO TO THE GREAT LAKES REGION. THE UPPER RIDGE SUPPORTS A SURFACE RIDGE ANCHORED BY A 1033 MB HIGH CENTERED JUST OFFSHORE OF DELAWARE. THIS PATTERN IS PROVIDING ANTI-CYCLONIC SURFACE FLOW ACROSS THE GULF WITH WIND SPEEDS RANGING FROM 15-20 KT WITH THE STRONGEST WINDS RESIDING IN THE SE GULF. THE RIDGE IS EXPECTED TO MOVE EASTWARD OVER THE NEXT 24 HOURS WITH SURFACE RIDGING REMAINING ACROSS THE GULF UNTIL A WEAK COLD FRONT MOVES INTO THE BASIN EARLY MONDAY FOLLOWED BY A STRONGER FRONT LATER IN THE WEEK. CARIBBEAN SEA... TROPICAL STORM RAPHAEL CONTINUES TO IMPACT THE EASTERN CARIBBEAN BRINGING GUSTY WINDS AND HEAVY RAINFALL TO MUCH OF THE LEEWARD ISLANDS. SEE SPECIAL FEATURES ABOVE FOR MORE DETAILS. THE NW CARIBBEAN IS EXPERIENCING FAIR CONDITIONS DUE TO DRY AIR AND SUBSIDENCE ALOFT SINKING SOUTHWARD FROM THE GULF OF MEXICO. HOWEVER...A NARROW UPPER TROUGH EXTENDS FROM CENTRAL CUBA TO HONDURAS PROVIDING AN AREA OF DIFFLUENCE AND MOISTURE ALOFT...WHICH SUPPORTING A FEW SHOWERS/THUNDERSTORMS FROM HONDURAS AND NICARAGUA TO JAMAICA AND EASTERN CUBA. SHOWERS/THUNDERSTORMS ARE ALSO ACROSS COSTA RICA AND PANAMA ASSOCIATED WITH THE MONSOON TROUGH THAT EXTENDS FROM COSTA RICA TO NORTHERN COLOMBIA. THE CENTRAL CARIBBEAN IS ALSO EXPERIENCING FAIR WEATHER DUE TO MODERATE DRY AIR ALOFT AROUND THE WEST SIDE OF AN UPPER LEVEL RIDGE COVERING NORTHERN SOUTH AMERICA AND THE CENTRAL CARIBBEAN. AN UPPER LEVEL TROUGH IS STILL PROVIDING SHEAR ACROSS T.S. RAPHAEL IN THE EASTERN CARIBBEAN. RAPHAEL IS EXPECTING TO CONTINUE IMPACTING THE NE CARIBBEAN FOR AT LEAST THE NEXT 24 HOURS. ATLANTIC OCEAN... A SURFACE TROUGH IS IN THE WEST ATLC ALONG 28N71W TO 23N74W...WHICH IS THE REMNANTS OF TROPICAL DEPRESSION PATTY THAT DISSIPATED EARLIER TODAY. ISOLATED SHOWERS/THUNDERSTORMS REMAIN WITHIN 200 NM EITHER SIDE OF THE AXIS. AN ASCAT PASS FROM EARLIER TODAY ALSO INDICATES THAT STRONG N-NE WINDS UP TO 30 KT REMAIN TO THE NORTH OF THE TROUGH. ALOFT...AN UPPER LEVEL TROUGH IS ALONG 72W PROVIDING MOIST AND DIFFLUENT FLOW TO THE EAST OF THE AXIS SUPPORTING SHOWERS AND ISOLATED THUNDERSTORMS NORTH OF 25N BETWEEN 60W-67W. AN UPPER LEVEL RIDGE IS FARTHER EAST ALONG 56W DRAWING MOISTURE NORTH AND EASTWARD FROM TROPICAL STORM RAPHAEL IN THE CARIBBEAN. SHOWERS AND POSSIBLE THUNDERSTORMS ARE SOUTH OF 26N BETWEEN 57W-65W AND EXTEND INTO STRONGER ACTIVITY TIED TO THE STORM. SEE SPECIAL FEATURES FOR MORE DETAILS ON RAPHAEL. A LARGE UPPER LEVEL RIDGE DOMINATES THE MAJORITY OF THE NE ATLC SUPPORTING A SURFACE RIDGE ANCHORED BY A 1026 MB HIGH NEAR 34N35W. HOWEVER...A LARGE UPPER LEVEL LOW IS ACROSS THE TROPICAL ATLC CENTERED NEAR 23N33W IS SUPPORTING A SURFACE TROUGH ALONG 28N35W TO 20N39W. SCATTERED SHOWERS/POSSIBLE THUNDERSTORMS ARE EAST OF THE TROUGH FROM 20N-24N BETWEEN 34W-38W. THE UPPER LOW/TROUGH IS ALSO ENHANCING CONVECTION NEAR THE ITCZ REGION. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ WALTON