000 AXNT20 KNHC 271755 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT THU AUG 27 2009 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1715 UTC. ...SPECIAL FEATURES... TROPICAL STORM DANNY IS CENTERED NEAR 27.5N 73.1W AT 27/1500 UTC OR ABOUT 280 NM NE OF NASSAU AND ABOUT 480 NM S-SE OF CAPE HATTERAS NORTH CAROLINA MOVING NW OR 310 DEG AT 11 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1006 MB. MAXIMUM SUSTAINED WIND SPEED IS 50 KT WITH GUSTS TO 60 KT. SLOW STRENGTHENING IS POSSIBLE DURING THE NEXT COUPLE OF DAYS...AND THE FORECAST CALLS FOR DANNY TO BECOME A HURRICANE IN ABOUT 48 HOURS BEFORE START TO LOSE TROPICAL CHARACTERISTICS. SCATTERED TO NUMEROUS MODERATE TO STRONG CONVECTION IS FROM 26N-29N BETWEEN 68W-72W. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT5/WTNT25 KNHC FOR MORE DETAILS. INTERESTS FROM THE CAROLINAS NORTHWARD TO NEW ENGLAND SHOULD MONITOR THE PROGRESS OF DANNY. A TROPICAL STORM WATCH MAY BE REQUIRED FOR PORTIONS OF THIS AREA LATER TODAY. ...TROPICAL WAVES... A TROPICAL WAVE IS ALONG 26W S OF 19N MOVING W NEAR 15 KT. THIS WAVE COINCIDES WITH A BROAD AREA OF LOW-LEVEL CYCLONIC CURVATURE NEAR 10.5N26.0W. THE CIMSS WAVETRACK GUIDANCE DEPICTS A MAXIMUM AREA OF 850 MB VORTICITY IN THE VICINITY OF THE WAVE AXIS AND ACROSS THE CAPE VERDE ISLANDS. THE ASSOCIATED SHOWER ACTIVITY HAS BECOME A LITTLE BETTER ORGANIZED DURING THE MORNING HOURS AND ADDITIONAL SLOW DEVELOPMENT OF THIS SYSTEM IS POSSIBLE OVER THE NEXT COUPLE OF DAYS. SATELLITE IMAGERY SHOWS AN AREA OF SCATTERED MODERATE TO ISOLATED STRONG CONVECTION JUST AHEAD OF THE WAVE AXIS FROM 8N-12N BETWEEN 28W-32W. THIS CONVECTION IS BEING ENHANCED BY UPPER LEVEL DIFFLUENCE ON THE SRN PERIPHERY OF AN ERN TROPICAL ATLC UPPER LEVEL ANTICYCLONIC CIRCULATION CENTERED NEAR 19N29W. A SECOND TROPICAL WAVE IS ALONG 46W S OF 20N MOVING W NEAR 15 KT. ONLY A FEW SHOWERS ARE NOTED NEAR THE INTERSECTION OF THE WAVE AXIS AND THE ITCZ. AN UPPER LEVEL LOW IS CENTERED N OF THE THIS FEATURE AND IS HELPING TO INDUCE SCATTERED SHOWERS NEAR THE NORTHERN END OF THIS WAVE. A THIRD TROPICAL WAVE IS ALONG 77W S OF 19N MOVING W NEAR 10 KT. WAVE REMAINS WITHIN AN AREA OF MAXIMUM DEEP LAYER MOISTURE AS OBSERVED ON THE TOTAL PRECIPITABLE WATER IMAGERY...HOWEVER DRY...SUBSIDENT NELY FLOW ALOFT IS OVER THE CENTRAL CARIBBEAN AND THUS INHIBITING ANY DEEP CONVECTION OR SHOWER ACTIVITY. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 10N15W 12N23W 10N35W 12N44W 11N48W 10N61W. OUTSIDE OF THE CONVECTION ASSOCIATED WITH THE TROPICAL WAVES...SCATTERED MODERATE CONVECTION IS ALONG THE W AFRICA COAST FROM 8N-13N BETWEEN 13W-17W. ISOLATED TO SCATTERED MODERATE CONVECTION IS WITHIN 90 NM N OF AXIS BETWEEN 48W AND 53W. ...DISCUSSION... GULF OF MEXICO... AS OF 1500...A SURFACE TROUGH IS ANALYZED ACROSS THE ERN GULF EXTENDING FROM 29N84W TO NEAR 25N86W. AN AREA OF SHOWERS WITH EMBEDDED TSTMS IS MAINLY E OF THE TROUGH AXIS COVERING N OF 26N AND E OF 85W. SIMILAR CONVECTION IS ALSO NOTED N OF 28N BETWEEN 86W AND 89W. THIS SURFACE TROUGH IS SUPPORTED BY AN UPPER LEVEL LOW CENTERED OVER ERN LOUISIANA. AN UPPER LEVEL RIDGE COVERS THE REMAINDER OF THE GULF ANCHORED BY AN UPPER LEVEL ANTICYCLONE CENTERED OVER THE YUCATAN CHANNEL. BETWEEN THESE TWO UPPER LEVEL FEATURES...A BAND OF MID/UPPER LEVEL MOISTURE IS OBSERVED UNDER A PREVAILING SWLY FLOW ALOFT AND EXTENDS FROM E/CENTRAL MEXICO TO THE NE GULF AND NRN FLORIDA. AT THE SURFACE...A WEAK RIDGE OF HIGH PRESSURE IS FORECAST TO REMAIN ACROSS THE NORTHERN GULF WATERS AHEAD OF THE NEXT FRONTAL BOUNDARY THAT IS EXPECTED TO MOVE INTO THE N GULF SUN NIGHT. A WEAK SFC TROUGH IS OVER THE SW PORTION OF THE GULF WITH ISOLATED SHOWERS. CARIBBEAN SEA... AN UPPER-LEVEL ANTICYCLONE CENTERED OVER THE YUCATAN CHANNEL DOMINATES THE WESTERN CARIBBEAN AND MUCH OF CENTRAL AMERICA WHILE UPPER LEVEL TROUGHING COVERS THE CENTRAL CARIBBEAN WITH AN EMBEDDED UPPER-LEVEL LOW SITUATED NEAR 15N75W. THIS WEATHER PATTERN ALOFT IS HELPING TO INDUCE SOME SHOWER ACTIVITY OVER THE NW CARIBBEAN AND CENTRAL AMERICA. THE EASTERN CARIBBEAN IS UNDER THE INFLUENCE OF ANOTHER RIDGE THAT IS PRODUCING MODERATE TO STRONG SUBSIDENCE AND THE IMPLIED DRY AIR MASS. AS A RESULT... ONLY SHALLOW TRADE WIND SHOWERS ARE NOTED ACROSS THE AREA. ATLANTIC OCEAN... ALL THE ATTENTION REMAINS FOCUSED ON TROPICAL STORM DANNY MOVING SOMEWHAT ERRATICALLY TOWARD THE NORTHWEST OVER PORTIONS OF THE SW NORTH ATLC. THE LOW-LEVEL CENTER OF DANNY REMAINS EXPOSED BUT NOW IT IS CLOSER TO THE DEEP CONVECTION MAINLY LOCATED TO THE EAST. SEE SPECIAL FEATURES FOR MORE DETAILS. AN UPPER-LEVEL TROUGH EXTENDS NWD TO NEAR DANNY FROM THE UPPER- LEVEL LOW LOCATED OVER THE CENTRAL CARIBBEAN WHILE UPPER RIDGING IS LOCATED TO THE E AND W OF THE TROPICAL CYCLONE. THE REMAINDER OF THE SW NORTH ATLC IS UNDER THE INFLUENCE OF THE RIDGE ANCHORED OVER THE YUCATAN CHANNEL. AN UPPER LEVEL LOW IS SPINNING OVER THE CENTRAL ATLC NEAR 28N48W GENERATING ISOLATED TO SCATTERED SHOWERS. A WEAK SFC TROUGH IS ANALYZED IN THIS AREA ALONG 50W/51W. FARTHER TO THE EAST...A WEAKENING UPPER LEVEL TROUGH WITH AXIS N OF 23N ALONG 37W IS PRODUCING A BAND OF CLOUDINESS WITH ISOLATED SHOWERS. AT THE SURFACE...THE AZORES-BERMUDA HIGH LOCATED NEAR 42N28W DOMINATES MOST OF THE E AND CENTRAL ATLANTIC. $$ GR/MH