000 AXNT20 KNHC 270557 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 AM 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0515 UTC. ...SPECIAL FEATURES... TROPICAL STORM DANNY IS CENTERED NEAR 26.0N 71.6W AT 27/0300 UTC OR ABOUT 320 NM ENE OF NASSAU AND ABOUT 585 NM SSE OF CAPE HATTERAS NORTH CAROLINA MOVING NW AT 9 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1006 MB. MAXIMUM SUSTAINED WIND SPEED IS 45 KT WITH GUSTS TO 55 KT. SCATTERED MODERATE TO STRONG CONVECTION IS FROM 25N-28N BETWEEN 67W-71W. SEE LATEST NHC FORECAST/ ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT5/WTNT25 KNHC FOR MORE DETAILS. ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 21W S OF 19N MOVING W NEAR 15 KT. THIS WAVE COINCIDES WITH A BROAD AREA OF LOW-LEVEL CYCLONIC CURVATURE AND CIMSS WAVETRAK GUIDANCE DEPICTS A MAXIMUM AREA OF 850 MB VORTICITY IN THE VICINITY OF THE WAVE AXIS. AN AREA OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WEST OF THE WAVE AXIS FROM 8N-13N BETWEEN 23W-29W AND IS POSSIBLY MORE ASSOCIATED WITH THE ITCZ AND UPPER LEVEL DIFFLUENCE ACROSS THE ERN TROPICAL ATLC. TROPICAL WAVE IS ALONG 44W S OF 21N MOVING W NEAR 20 KT. THE WAVE CONTINUES TO MOVE BENEATH AN VERY DRY AIR MASS ALOFT AS AN UPPER LEVEL RIDGE EXTENDS TO 40W ACROSS THE TROPICAL ATLC. STRONG SUBSIDENCE IS NOTED ON WATER VAPOR IMAGERY. HOWEVER...AN UPPER LEVEL LOW IS CENTERED NW OF THE WAVE AXIS AND IS STRETCHING THE WAVE SLIGHTLY NWD WITH POSSIBLE SHOWERS FROM 18N-23N BETWEEN 40W-47W. OTHER POSSIBLE SHOWERS ARE MOST EMBEDDED WITHIN THE ITCZ AXIS FROM 10N-14N BETWEEN 42W-46W. TROPICAL WAVE IS ALONG 75W S OF 20N MOVING W NEAR 12 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 13N17W 11N20W 11N23W 15N33W 12N43W 11N45W 8N61W. CLUSTERS OF SCATTERED MODERATE CONVECTION ARE ALONG THE W AFRICA COAST FROM 7N-13N BETWEEN 12W-15W. ASIDE FROM THE AREA OF CONVECTION ASSOCIATED WITH THE TROPICAL WAVE ALONG 21W... SCATTERED MODERATE CONVECTION IS FROM 11N-13N BETWEEN 33W-39W. ELSEWHERE...SCATTERED SHOWERS ARE WITHIN 200 NM NORTH OF THE AXIS BETWEEN 42W-54W. ...DISCUSSION... GULF OF MEXICO... A SURFACE TROUGH IS ANALYZED ACROSS THE ERN GULF AND EXTENDS FROM 28N85W TO THE TIP OF THE NE YUCATAN PENINSULA NEAR 22N87W. THIS SURFACE TROUGH IS SUPPORTED BY AN UPPER LEVEL LOW CENTERED OVER SW MISSISSIPPI. THE SURFACE TROUGH ALONG WITH MIDDLE TO UPPER LEVEL DIFFLUENCE SE OF THE UPPER LOW IS GENERATING SCATTERED SHOWERS AND A FEW ISOLATED TSTMS ACROSS MUCH OF THE ERN GULF N OF 23N AND E OF 89W. 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...MOIST SWLY FLOW EXTENDS FROM E/CENTRAL MEXICO TO THE NE GULF AND NRN FLORIDA WITH POSSIBLE SCATTERED SHOWERS WITHIN 90 NM EITHER SIDE OF A LINE FROM TAMPICO MEXICO THROUGH 25N90W TO THE BIG BEND REGION OF FLORIDA. A WEAK RIDGE OF HIGH PRESSURE IS FORECAST TO REMAIN ACROSS THE NRN GULF WATERS AHEAD OF THE NEXT FRONTAL BOUNDARY THAT IS EXPECTED TO STALL ALONG THE LOUISIANA AND TEXAS GULF COAST BY EARLY SUNDAY. CARIBBEAN SEA... AN UPPER LEVEL RIDGE IS ACROSS THE NW CARIBBEAN ANCHORED OVER THE YUCATAN CHANNEL WHILE UPPER LEVEL TROUGHING COVERS THE CENTRAL CARIBBEAN ANCHORED BY AN UPPER LOW CENTERED NEAR 16N74W. THE UPPER DIVERGENT FLOW ACROSS THE FAR WRN CARIBBEAN AND PORTIONS OF CENTRAL AMERICA ARE GENERATING SCATTERED SHOWERS AND ISOLATED TSTMS IMMEDIATELY SOUTH OF CUBA FROM 20N-23N BETWEEN 77W-84W AND SCATTERED SHOWERS OVER CENTRAL AMERICA AND THE YUCATAN PENINSULA. THE REMAINDER OF THE CARIBBEAN IS UNDER DRY STABLE AIR AND MOSTLY CLEAR SKIES. ATLANTIC OCEAN... THE PRIMARY CONCERN FOR THE ATLC IS TROPICAL STORM DANNY LOCATED OVER PORTIONS OF THE SW NORTH ATLC. THE UPPER LEVEL LOW OVER THE CENTRAL CARIBBEAN EXTENDS UPPER LEVEL TROUGHING N TO NEAR T.S. DANNY WHILE UPPER RIDGING IS LOCATED TO THE E AND W OF THE SYSTEM. THE CONVECTION PRIMARILY ASSOCIATED WITH DANNY IS LOCATED IN THE NW QUADRANT OF AN UPPER LEVEL ANTICYCLONE CENTERED NEAR 24N61W. SCATTERED MODERATE TO STRONG CONVECTION IS FROM 25N-28N BETWEEN 67W-71W. THE REMAINDER OF THE SW NORTH ATLC IS UNDER NE TO ELY SURFACE FLOW WITH ISOLATED SHOWERS FROM 23N-29N MOVING WWD ACROSS THE BAHAMAS AND INLAND ACROSS THE FLORIDA PENINSULA. AN UPPER LEVEL LOW IS CENTERED OVER THE CENTRAL ATLC NEAR 28N49W. UPPER LEVEL DIFFLUENCE LOCATED E OF THE UPPER LOW IS GENERATING SCATTERED SHOWERS FROM 24N-32N BETWEEN 40W-47W. FARTHER TO THE EAST...A WEAKENING UPPER LEVEL TROUGH WITH AXIS N OF 20N ALONG 37W IS PRODUCING POSSIBLE SCATTERED SHOWERS FROM 22N-32N BETWEEN 28W-35W. ELSEWHERE ACROSS THE CENTRAL AND ERN ATLC...A SURFACE RIDGE REMAINS IN PLACE AND IS ANCHORED BY A 1025 MB HIGH CENTERED N OF THE DISCUSSION AREA NEAR 35N32W. $$ HUFFMAN