000 AXNT20 KNHC 261757 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT MON AUG 26 2013 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1715 UTC. ...SPECIAL FEATURES... TROPICAL DEPRESSION FERNAND IS CENTERED NEAR 20.3N 97.7W AT 26/1500 UTC OR ABOUT 45 NM SSW OF TUXPAN MEXICO MOVING NW AT 8 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1007 MB. MAXIMUM SUSTAINED WIND SPEED IS 30 KT WITH GUSTS TO 40 KT. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS FROM 19N-24N BETWEEN 96W-99W...WITH WIDELY SCATTERED MODERATE CONVECTION ELSEWHERE FROM 17N-26N BETWEEN 92W-100W. THE MOST SIGNIFICANT IMPACT FROM FERNAND REMAINS THE LARGE AMOUNTS OF RAINFALL EXPECTED OVER A LARGE PORTION OF EAST-CENTRAL MEXICO DURING THE NEXT 24 TO 48 HOURS. THIS PRECIPITATION IS LIKELY TO CAUSE LIFE-THREATENING FLASH FLOODS AND MUD SLIDES. SEE LATEST NHC INTERMEDIATE PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT1/WTNT31 KNHC AND THE FULL FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS. ...TROPICAL WAVES... TROPICAL WAVE EXTENDS FROM A 1011 MB LOW CENTERED NEAR 08N23W TO ANOTHER 1011 MB LOW CENTERED NEAR 17N20W. WHILE THE WAVE AXIS HAS EMERGED OFF THE WEST AFRICA COAST OVER THE PAST 24 HOURS... THESE LOW-LEVEL CYCLONIC CIRCULATIONS REPRESENT THE SOUTHERN AND NORTHERN VORTICITY CENTERS RESPECTIVELY ALONG THE WAVE AXIS. THE SOUTHERN VORTICITY MAXIMUM CARRIES WITH IT THE MOST CONVECTION WHICH REMAINS EMBEDDED WITHIN THE MONSOON TROUGH AXIS FROM 09N- 12N BETWEEN 19W-27W. AS THE LOW-LEVEL ENERGY CONTINUES TO PROPAGATE WESTWARD AS A WHOLE...THE LOW CENTERS ARE EXPECTED TO ABSORB INTO ONE BROADER CYCLONIC CIRCULATION ALONG THE WAVE AXIS IN THE VICINITY OF 10N30W. BOTH PRIMARY GLOBAL MODELS...THE GFS AND ECMWF BOTH SUGGEST THIS SCENARIO OCCURRING OVER THE NEXT 24 HOURS WITH THE SOUTHERN VORTICITY MAXIMUM CONTINUING WESTWARD AS THE DOMINATE FEATURE WITH THE TROPICAL WAVE ACROSS THE EASTERN TROPICAL ATLC. TROPICAL WAVE EXTENDS FROM 14N41W TO 24N38W MOVING W AT 10-15 KT. THE WAVE REMAINS EMBEDDED WITHIN A MAXIMUM OF TOTAL PRECIPITABLE WATER EXTENDING NORTHWARD FROM THE MONSOON TROUGH REGION FROM 13N-24N BETWEEN 33W-41W AND COINCIDES WITH A 700 MB TROUGH AXIS WITH A RELATIVE VORTICITY MAXIMUM CENTERED IN THE VICINITY OF THE NORTHERN EXTENT OF THE WAVE AXIS NEAR 22N39W. THE WAVE LACKS ANY SIGNIFICANT DEEP CONVECTION AT THIS TIME DUE TO THE PRESENSE OF THE SAHARAN AIR LAYER ACROSS MUCH OF THE CENTRAL AND EASTERN ATLC. TROPICAL WAVE EXTENDS FROM 11N77W TO 20N74W MOVING W AT 15 KT. THE WAVE CONTINUES TO BE EMBEDDED WITHIN BROAD LOW-LEVEL TROUGHING ACROSS THE CENTRAL AND WESTERN CARIBBEAN SEA AS STRONGER EASTERLY TRADES ARE NOTED TO THE EAST OF THE WAVE AXIS BETWEEN 68W-78W. TOTAL PRECIPITABLE WATER IMAGERY INDICATES THE WAVE LIES WITHIN A RELATIVELY MOIST ENVIRONMENT WITH SCATTERED MODERATE CONVECTION OCCURRING FROM 12N-17N BETWEEN 75W-84W. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM 12N20W TO 08N25W TO 13N33W TO 11N42W TO A 1012 MB LOW NEAR 10N52W TO 08N57W. SCATTERED MODERATE CONVECTION IS FROM 09N-13N BETWEEN 19W-28W...FROM 05N- 08N BETWEEN 27W-30W...AND FROM 08N-13N BETWEEN 35W-58W. ...DISCUSSION... GULF OF MEXICO... WATER VAPOR IMAGERY INDICATES AN UPPER LEVEL TROUGH AXIS EXTENDS FROM OVER THE SW NORTH ATLC NEAR 29N77W TO OVER THE CENTRAL FLORIDA PENINSULA TO OVER PORTIONS OF THE NE GULF NEAR 28N85W. THIS TROUGHING ALOFT SUPPORTS A STATIONARY FRONT DRAPED ACROSS THE NORTHERN GULF WATERS ALONG 29N FROM THE BIG BEND OF FLORIDA TO THE MISSISSIPPI RIVER DELTA REGION AND ALONG THE TEXAS AND LOUISIANA COAST. E OF 90W...MOST OF THE MIDDLE TO UPPER LEVEL DYNAMICS ARE WELL SOUTH OF THE FRONT WITH THE UPPER LEVEL TROUGH GENERATING WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS FROM 23N- 26N BETWEEN 80W-83W...AND FROM 24N-28N BETWEEN 83W-88W. W OF 90W...LOW-LEVEL MOISTURE CONVERGENCE ALONG AND SOUTH OF THE FRONT IS GENERATING SCATTERED SHOWERS AND TSTMS N OF 27N W OF 92W. SLIGHTLY FARTHER SOUTH...AN UPPER LEVEL ANTICYCLONIC CIRCULATION IS CENTERED IN THE WESTERN GULF NEAR 25N97W AND CONTINUES TO PROVIDE A DIFFLUENT ENVIRONMENT ALOFT FOR CONVECTION ASSOCIATED WITH TROPICAL DEPRESSION FERNAND AS IT CONTINUES TO WEAKEN OVER INLAND EAST-CENTRAL MEXICO THIS AFTERNOON. SCATTERED SHOWERS AND TSTMS ARE OCCURRING FROM 17N- 26N BETWEEN 92W-100W. FURTHER ENHANCING THIS CONVECTION IS WEAK SURFACE TROUGHING PARALLELING THE SE TEXAS AND EASTERN MEXICO COAST FROM TUXPAN NORTHWARD TO MATAGORDA BAY. WITH A SURFACE RIDGE ANCHORED TO THE NORTH OVER THE SE CONUS...E-SE WINDS ARE FORECAST TO PERSIST THROUGH LATE WEDNESDAY WHEN THE SURFACE RIDGING WILL SLOWLY SHIFT SOUTHWARD INTO THE GULF BY LATE THURSDAY INTO FRIDAY. CARIBBEAN SEA... UPPER LEVEL NORTHEASTERLY FLOW IS OVER MUCH OF THE NW CARIBBEAN AND CENTRAL AMERICA BETWEEN AN ANTICYCLONE CENTERED OVER THE NW GULF OF MEXICO NEAR 25N97W AND AN UPPER LEVEL LOW CENTERED OVER THE SW CARIBBEAN NEAR 10N81W. WATER VAPOR IMAGERY INDICATES MUCH OF THE NW CARIBBEAN REMAINS DRY AND STABLE ALOFT WITH GENERALLY CLEAR SKIES THIS AFTERNOON. HOWEVER...AS FLOW ALOFT TRANSITIONS TO CYCLONIC ALONG A TROUGH AXIS EXTENDING FROM THE UPPER LEVEL LOW TO OVER JAMAICA NEAR 18N78W...MOISTURE AND CONVECTION INCREASE ACROSS THE CENTRAL AND SW CARIBBEAN IN THE VICINITY OF A TROPICAL WAVE ALONG 76W. SCATTERED SHOWERS AND TSTMS ARE CONCENTRATED WEST OF THE WAVE AXIS FROM 12N-16N BETWEEN 79W-84W WITH ISOLATED SHOWERS AND TSTMS OCCURRING ELSEWHERE FROM 09N-18N BETWEEN 68W-85W. A PORTION OF THIS CONVECTION REMAINS FOCUSED ALONG THE MONSOON TROUGH AXIS ANALYZED ALONG 10N FROM NORTHERN COLOMBIA WESTWARD ACROSS COSTA RICA AND INTO THE EAST PACIFIC REGION. FINALLY...MOIST SOUTHERN FLOW ALOFT DOMINATES ACROSS THE EASTERN CARIBBEAN BETWEEN THE AFOREMENTIONED TROUGH AXIS AND AN UPPER LEVEL ANTICYCLONE CENTERED OVER THE SW NORTH ATLC NEAR 19N63W. WHILE NO SIGNIFICANT DEEP CONVECTION IS OCCURRING EAST OF THE TROPICAL WAVE...A SURFACE TROUGH...MOST LIKELY RESIDUAL ENERGY LEFT BEHIND BY THE TROPICAL WAVE...IS ANALYZED FROM 15N65W TO 22N63W AND CONTINUES TO GENERATE WIDELY SCATTERED LOW- TOPPED SHOWERS AND TSTMS N OF 13N BETWEEN 60W-72W. HISPANIOLA... MOIST SOUTHWESTERLY FLOW ALOFT IS OVER HISPANIOLA THIS AFTERNOON AND IS PROVIDING FOR AN OVERALL DIFFLUENT ATMOSPHERE FOR THE ISLAND. MOVING WESTWARD BENEATH THIS FLOW IS SURFACE TROUGH ANALYZED FROM 15N65W TO 22N63W. LOW-LEVEL MOISTURE IS FOCUSED ON BOTH SIDES OF THE SURFACE TROUGH BETWEEN 60W-70W WHICH IS ALREADY PROVIDING THE ISLAND WITH ISOLATED SHOWERS E OF 71W. MOISTURE AND PRECIPTATION IS EXPECTED TO INCREASE AS THE SURFACE TROUGH MOVES WEST OVER THE NEXT 24 TO 48 HOURS. PEAK DAYTIME HEATING AND INSTABILITY WILL LIKELY GENERATE MORE INTENSE SHOWERS AND TSTMS WITH ANY ACTIVITY DIMINISHING BEYOND THE LATE EVENING HOURS. ATLANTIC OCEAN... A MIDDLE TO UPPER LEVEL TROUGH AXIS EXTENDS INTO THE DISCUSSION AREA NEAR 32N68W IN THE SW NORTH ATLC AND CONTINUES SOUTHWESTWARD TO A BASE OVER THE CENTRAL FLORIDA PENINSULA NEAR 27N81W. THIS TROUGHING ALOFT SUPPORTS A STATIONARY FRONT ANALYZED FROM 32N65W TO 30N73W TO THE FLORIDA PENINSULA NEAR 29N81W. WATER VAPOR IMAGERY INDICATES THAT THE UPPER LEVEL DYNAMICS ARE MORE CONCENTRATED FARTHER SOUTH OVER THE FLORIDA STRAITS AND ARE GENERATING SCATTERED SHOWERS AND TSTMS FROM 23N- 27N BETWEEN 75W-83W. TO THE NORTHEAST CLOSER TO THE STATIONARY FRONT...LOW-LEVEL MOISTURE CONVERGENCE ALONG AND SOUTH OF THE BOUNDARY CONTINUES TO PRODUCE ISOLATED SHOWERS AND TSTMS WITHIN 240 NM SOUTHEAST OF THE FRONT E OF 75W. A PRE-FRONTAL SURFACE TROUGH FROM 34N60W TO 26N70W IS ALSO PROVIDING FOCUS FOR THE ONGOING CONVECTION. TO THE SOUTHEAST...A SURFACE TROUGH EXTENDS FROM THE NE CARIBBEAN SEA NEAR 15N65W TO 22N63W WITH LOW-LEVEL MOISTURE CONVERGENCE AND INSTABILITY GENERATING WIDELY SCATTERED LOW-TOPPED SHOWERS FROM 15N-23N BETWEEN 60W-70W. ASIDE FROM THE TROPICAL WAVE ALONG 40W...THE REMAINDER OF THE CENTRAL AND EASTERN ATLC IS UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED BY A 1029 MB HIGH CENTERED NORTH OF THE AZORES NEAR 44N25W. 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