000 AXNT20 KNHC 252356 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT SAT AUG 25 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... THE CENTER OF TROPICAL STORM ISAAC AT 26/0000 UTC IS NEAR 21.7N 76.7W. THIS POSITION IS ABOUT 70 NM ENE OF CAMAGUEY CUBA...AND ABOUT 325 NM ESE OF KEY WEST FLORIDA. ISAAC IS MOVING NW AT 17 KT. THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 997 MB. THE MAXIMUM SUSTAINED WIND SPEED IS 50 KT WITH GUSTS TO 60 KT. PLEASE READ THE FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC AND THE PUBLIC ADVISORY...MIATCPAT4/WTNT34 KNHC FOR MORE DETAILS. THE RAIN IMPACTS OF ISAAC SPREAD ACROSS A LARGE AREA FROM THE CARIBBEAN ALL THE WAY INTO THE SE GULF OF MEXICO. CURRENTLY NUMEROUS MODERATE/ISOLATED STRONG CONVECTION IS FROM 15N-21N BETWEEN 69W-74W...INCLUDING MUCH OF HISPANIOLA. SIMILAR ACTIVITY IS N OF CUBA INTO THE FLORIDA STRAITS FROM 22N-25N BETWEEN 76W-81W. ELSEWHERE...SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 18N-26N BETWEEN 67W-85W...INCLUDING PORTIONS OF PUERTO RICO...CUBA...THE BAHAMAS...AND SOUTHERN FLORIDA. TROPICAL WAVE EXTENDS FROM 21N31W TO A 1009 MB SURFACE LOW NEAR 15N32W MOVING WNW NEAR 15 KT. THE WAVE/LOW LIES WITHIN A LARGE SURGE OF DEEP LAYER MOISTURE PRESENT ACROSS MUCH OF THE EASTERN TROPICAL ATLC. BROAD CYCLONIC FLOW IS AROUND THE WAVE/LOW AND THE MONSOON TROUGH AND THE SYSTEM HAS BECOME SLIGHTLY MORE ORGANIZED TODAY. CURRENTLY SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 13N-20N BETWEEN 28W-36W. DEVELOPMENT OF THIS SYSTEM IS POSSIBLE OVER THE NEXT COUPLE OF DAYS. ...THE ITCZ/THE MONSOON TROUGH... THE MONSOON TROUGH EXTENDS ACROSS W AFRICA TO THE COAST OF MAURITANIA AT 20N16W CONTINUING TO A 1009 MB SURFACE LOW CONNECTED TO A TROPICAL WAVE AT 15N32W AND ALONG 10N39W 10N48W. THE ITCZ BEGINS AT 10N48W TO 12N60W. SCATTERED MODERATE CONVECTION IS FROM 8N-10N BETWEEN 38W-44W. ...DISCUSSION... THE GULF OF MEXICO... WEAK SURFACE RIDGING EXTENDS ACROSS THE MAJORITY OF THE GULF OF MEXICO EXTENDING FROM A SURFACE HIGH OVER GEORGIA TO THE SW GULF. A FEW SHOWERS/THUNDERSTORMS CONTINUE OVER THE FAR NW GULF N OF 27N BETWEEN 93W-96W DUE TO INCREASED RETURN FLOW AROUND THE SURFACE RIDGE. THE SE GULF IS ALREADY BEING IMPACTED BY LOW-LEVEL MOISTURE WRAPPING AROUND THE NORTHERN SIDE OF TROPICAL STORM ISAAC WITH STRONG SHOWERS EXTENDING THROUGH THE FLORIDA STRAITS AND PORTIONS OF SOUTH FLORIDA AS WELL AS CUBA. THIS ACTIVITY IS ENHANCED BY DIFFLUENCE ALOFT AROUND AN UPPER LEVEL TROUGH EXTENDING FROM THE FLORIDA PANHANDLE TO THE YUCATAN PENINSULA. THIS UPPER TROUGH WILL PLAY A ROLE IN THE TRACK OF ISAAC ONCE IT APPROACHES THE SE GULF. UPPER LEVEL RIDGING IS TO EITHER SIDE OF THE TROUGH. DRY AIR ALOFT IS SINKING S AROUND THE WEST SIDE OF THE UPPER TROUGH AND CONTINUING INTO THE NW CARIBBEAN. THIS DRY AIR IS HELPING MAINTAIN MOSTLY CLEAR SKIES FOR NOW. AS THE CENTER OF ISAAC MOVES CLOSER TO THE BASIN TONIGHT CONDITIONS ACROSS THE SE GULF WILL BEGIN TO DETERIORATE AND WILL CONTINUE THROUGH SUNDAY NIGHT AND INTO MONDAY EVENTUALLY SPREADING NORTHWARD. INTERESTS IN THE EASTERN GULF OF MEXICO SHOULD CONTINUE TO MONITOR THE PROGRESS OF TROPICAL STORM ISAAC. THE CARIBBEAN SEA... TROPICAL STORM ISAAC IS DOMINATING THE CARIBBEAN PRODUCING WIDESPREAD SHOWERS/THUNDERSTORMS ACROSS MUCH OF THE NORTHERN CARIBBEAN ISLANDS ESPECIALLY HISPANIOLA AND PORTIONS OF CUBA. REPORTS FROM HAITI ALREADY ARE INDICATING LARGE AREAS OF DAMAGE AND FLOODING. REPORTS FROM CUBA ARE ALSO INDICATING COASTAL FLOODING IS IN PORTIONS OF BARACOA...GIBARA...AND BANES. FLOODING AND MUDSLIDES ARE LIKELY ACROSS BOTH HAITI AND PORTIONS OF CUBA AS RAINFALL CONTINUES. THE ENTIRE CIRCULATION AROUND ISAAC IS LARGE AND FAIRLY ELONGATED WITH A SURFACE TROUGH EXTENDING FROM SW CUBA NEAR 20N77W THROUGH A WEAK SPOT LOW AT 19N81W TO 19N87W. SOME STRONGER SHOWERS/THUNDERSTORMS HAVE RECENTLY POPPED UP NEAR THE CENTER OF ISAAC AND ACROSS EASTERN CUBA TO JAMAICA. DUE TO THE LARGE CIRCULATION...MUCH OF THE NORTHERN CARIBBEAN WITH CONTINUE TO SEE WIND AND RAIN AS THE STORM CONTINUES TOWARDS THE GULF OF MEXICO. THE NW AND SW CARIBBEAN ARE THE ONLY AREAS STILL UNDER MOSTLY FAIR CONDITIONS DUE TO DRY AIR ALOFT SINKING INTO THE BASIN FROM THE CENTRAL GULF OF MEXICO. SOME STRONG SHOWERS/THUNDERSTORMS HAVE ALSO FORMED OVER COSTA RICA LIKELY INFLUENCED BY THE MONSOON TROUGH EXTENDING FROM THE E PACIFIC TROUGH COSTA RICA AND PANAMA TO NORTHERN COLUMBIA. ALL INTERESTS IN THE NORTHERN CARIBBEAN SHOULD CONTINUE TO MONITOR ISAAC. THE ATLANTIC OCEAN... THE COMBINATION OF LOW-LEVEL MOISTURE BEING DRAWN ACROSS THE BAHAMAS DUE TO TROPICAL STORM ISAAC AND DIFFLUENCE ALOFT AROUND AN UPPER TROUGH OVER THE EASTERN GULF OF MEXICO IS HELPING PRODUCE SCATTERED SHOWERS/THUNDERSTORMS ACROSS MUCH OF THE BAHAMAS AND SOUTH FLORIDA S OF 26N W OF 67W. UPPER LEVEL RIDGING...OUTFLOW FROM ISAAC COVERS THE MAJORITY OF THE WEST ATLC. AN UPPER LEVEL LOW IS TO THE EAST NEAR 20N57W WITH AN ELONGATED AXIS EXTENDING TO THE NW. IT IS HELPING PRODUCE ISOLATED SHOWERS/THUNDERSTORMS FROM 20N-23N BETWEEN 58W-62W...AS WELL AS FROM 23N-31N BETWEEN 54W-59W. SOME OF THIS ACTIVITY IS ALSO INFLUENCED FROM A SURFACE TROUGH EXTENDING FROM 26N56W TO 20N52W. THIS SURFACE TROUGH IS THE REMNANTS OF JOYCE WHICH DISSIPATED A FEW DAYS AGO. THE REMAINDER OF THE ATLC IS DOMINATED BY BROAD SURFACE RIDGING AROUND A PAIR OF HIGH CENTERS N OF THE AREA. THE RIDGE IS SUPPORTED BY A BROAD UPPER LEVEL RIDGE CENTERED NEAR 31N46W WITH A SECOND UPPER RIDGE CENTERED OVER WEST AFRICA. THE LAST VISIBLE SATELLITE IMAGES ALONG WITH GOES-R ENHANCEMENT IMAGERY INDICATE AN AREA OF DUST EXTENDS BETWEEN THE TROPICAL WAVE IN THE TROPICAL ATLC AND THE SURFACE TROUGH IN THE CENTRAL ATLC. SOME DUST ALSO IS EMERGING OFF THE COAST OF AFRICA BEHIND THE WAVE. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ WALTON