000 AXNT20 KNHC 042356 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT MON AUG 04 2014 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 2345 UTC. ...SPECIAL FEATURE... THE CENTER OF HURRICANE BERTHA IS NEAR 29.4N 73.6W AT 04/2100 UTC ...OR ABOUT 486 NM WSW OF BERMUDA. BERTHA IS MOVING NORTHWARD...OR 360 DEGREES...AT 16 KT. THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 998 MB. THE MAXIMUM SUSTAINED WIND SPEED IS 65 KT WITH GUSTS TO 80 KT. A CLUSTER OF MODERATE CONVECTION IS FROM 27N-30N BETWEEN 72W-74W WITH RAINBANDS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION ELSEWHERE FROM 24N-30N BETWEEN 69W-76W. ISOLATED TSTMS ARE IN THE RAINBANDS OF THE SW QUADRANT OF BERTHA. PLEASE READ THE LATEST NHC INTERMEDIATE PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT3/WTNT33 KNHC AND THE FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT3/WTNT23 KNHC FOR MORE DETAILS. ...TROPICAL WAVES... TROPICAL WAVE IS JUST EAST OF THE CAPE VERDE ISLANDS WITH AXIS EXTENDING FROM 16N21W TO 9N21W MOVING W AT 10 KT. THE NORTHERN WAVE ENVIRONMENT N OF 13N CONTINUES TO BE AFFECTED BY THE DRY SAHARAN AIR LAYER WHICH IS INHIBITING CONVECTION IN THAT REGION. ISOLATED SHOWERS ARE ELSEWHERE FROM 9N-13N E OF 25W. TROPICAL WAVE IS ABOUT 200 NM E OF THE LESSER ANTILLES WITH AXIS EXTENDING FROM 21N56W TO 11N57W MOVING W AT 20 KT. DRY SAHARAN AIR CONTINUES TO AFFECT MOST OF THE WAVE ENVIRONMENT WHICH ALONG STRONG DEEP LAYER ENVIRONMENTAL SHEAR INHIBIT CONVECTION AT THE TIME. TROPICAL WAVE IS OVER CARIBBEAN WATERS WITH AXIS EXTENDING FROM 18N66W TO 10N67W MOVING W AT 15 KT. NO DEEP CONVECTION IS ASSOCIATED WITH THE WAVE DUE TO DRY AIR SUBSIDENCE FROM THE MIDDLE AND UPPER LEVELS. ISOLATED SHOWERS ARE POSSIBLE FOR COASTAL WATERS OF PUERTO RICO. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE WEST AFRICAN COAST NEAR 14N16W TO 9N24W TO 8N37W. THE INTERTROPICAL CONVERGENCE ZONE AXIS BEGINS NEAR 7N37W AND CONTINUES ALONG 6N46W TO 7N52W. IN ADDITION TO THE CONVECTION ASSOCIATED WITH THE TROPICAL WAVE...WIDELY SCATTERED SHOWERS ARE FROM 5N-10N BETWEEN 23W-30W. SCATTERED MODERATE CONVECTION IS FROM 4N-7N BETWEEN 42W-49W. ...DISCUSSION... GULF OF MEXICO... THE WIND PATTERN IN THE MIDDLE TO UPPER LEVELS IS LEAVING A COL OR AREA OF LOW PRESSURE NEAR THE CENTRAL GULF...THUS SUPPORTING A 1014 MB LOW NEAR 26N91W WITH SCATTERED HEAVY SHOWERS AND TSTMS FROM 23N-27N BETWEEN 88W-94W. A WEAKNESS IN THE SW PERIPHERY OF A MIDDLE LEVEL RIDGE ANCHORED NEAR 32N64W IS SUPPORTING A SURFACE TROUGH ACROSS THE FLORIDA PENINSULA WHICH IS ENHANCING SCATTERED HEAVY SHOWERS AND TSTMS. THESE SHOWERS AND TSTMS ACTIVITY EXTEND WITHIN 280 NM FROM THE WESTERN COAST OF FLORIDA TO THE EASTERN GULF WATERS. AN INVERTED MIDDLE TO UPPER LEVEL TROUGH OVER THE S-SW GULF SUPPORT A SURFACE TROUGH OVER THE YUCATAN PENINSULA FROM 22N87W TO 16N90W AS WELL AS ISOLATED HEAVY SHOWERS AND TSTMS THAT EXTEND WITHIN 60 NM FROM THE NORTHERN AND WESTERN PENINSULA COASTLINE. OTHERWISE...VARIABLE WINDS OF 5-10 KT DOMINATE ACROSS THE BASIN. THE AREA OF LOW PRESSURE AND ASSOCIATED RAIN OVER THE FLORIDA PENINSULA IS FORECAST TO MOVE NE TOWARDS ATLC WATERS TUE MORNING. HIGH PRESSURE WILL THEN BUILD ACROSS THE GULF THROUGH THURSDAY. CARIBBEAN SEA... MODERATE DEEP LAYER MOISTURE IS OVER THE WESTERN AND SW CARIBBEAN SEA WHICH ALONG MIDDLE TO UPPER LEVEL DIFFLUENT FLOW SUPPORT SCATTERED SHOWERS AND TSTMS N OF 15N BETWEEN 79W-84W. IN THE SW CARIBBEAN SEA...REMNANT SHOWERS ASSOCIATED WITH A FORMER AREA OF LOW PRESSURE ARE S OF 14N. A TROPICAL WAVE IS MOVING OVER THE EASTERN CARIBBEAN WITH NO CONVECTION ASSOCIATED WITH IT. SEE THE TROPICAL WAVES SECTION ABOVE FOR MORE DETAILS. DRY AIR SUBSIDENCE FROM ALOFT IS ACROSS THE REMAINDER BASIN...THUS SUPPORTING CLEAR SKIES AND FAIR WEATHER. TRADES OF 10-15 KT DOMINATE ACROSS THE BASIN WITH HIGHER WINDS UP TO 20 KT ALONG THE COAST OF COLOMBIA AND COASTAL WATERS OF SOUTHERN HISPANIOLA. TRADES ARE EXPECTED TO INCREASE 20-25 KT OVER THE CENTRAL BASIN TUE DUE TO THE PASSAGE OF THE TROPICAL WAVE. A SECOND TROPICAL WAVE IS EXPECTED TO ENTER THE EASTERN CARIBBEAN LATE TONIGHT. ...HISPANIOLA... FAIR WEATHER AND CLEAR SKIES ARE ACROSS THE ISLAND SUPPORTED BY DEEP LAYER DRY AIR. THESE CONDITIONS ARE EXPECTED TO PERSIST THROUGH TUE AFTERNOON WHEN DAYTIME HEATING WILL SUPPORT SOME SHOWERS. ATLANTIC OCEAN... THE HIGHLIGHT IN THE ATLC IS HURRICANE BERTHA DISCUSSED IN THE SPECIAL FEATURES SECTION. A WEAKNESS IN THE SW PERIPHERY OF A MIDDLE LEVEL RIDGE ANCHORED NEAR 32N64W IS SUPPORTING A SURFACE TROUGH ACROSS THE FLORIDA PENINSULA WHICH IS ENHANCING SCATTERED HEAVY SHOWERS AND TSTMS. THESE SHOWERS AND TSTMS ACTIVITY EXTEND WITHIN 130 NM FROM THE EASTERN COAST OF FLORIDA TO THE SW N ATLC WATERS. SIMILAR CONVECTION IS IN THE STRAITS OF FLORIDA AND CUBA NORTHERN COASTAL WATERS. SHOWER ACTIVITY WILL CONTINUE OVER THE SW N ATLC WATERS THROUGH WED AFTERNOON. OTHERWISE...BESIDES THE TROPICAL WAVES ALREADY DISCUSSED...SURFACE RIDGING ANCHORED BY SEVERAL HIGH PRESSURE CENTERS N OF 30N DOMINATES ELSEWHERE. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ NR