000 AXNT20 KNHC 272323 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT WED MAY 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC. ...TROPICAL WAVES... A TROPICAL WAVE IS ALONG 79W FROM 05N TO 16N AND HAS BEEN MOVING W AT 17 KT THE PAST 24 HOURS. CURRENTLY THERE IS SOME CYCLONIC ROTATION ALONG THE WAVE AXIS OVER THE PACIFIC WATERS. THE WAVE WAS PREVIOUSLY UNDER THE W PERIPHERY OF AN UPPER RIDGE THAT ENHANCED CONVECTION ALONG THE PACIFIC COAST OF COLOMBIA. THE WAVE HAS MOVED W OF THESE FAVORABLE CONDITIONS AND CONVECTION HAS DECREASED CONSIDERABLY LATE THIS AFTERNOON. ...THE ITCZ... THE ITCZ AXIS IS CENTERED ALONG 05N09W TO 06N14W CROSSING THE EQUATOR AT 38W TO THE SOUTH AMERICAN COAST AT 02S46W. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS NOTED FROM 01S TO 07N BETWEEN 03W AND 32W. ...DISCUSSION... GULF OF MEXICO... ALOFT...A SHORTWAVE RIDGE ORIGINATING OVER THE TROPICAL E PACIFIC IS CRESTING OVER THE GULF OF MEXICO ALONG POINTS 28N96W 26N96W 22N82W. CONVECTION IS ENHANCED ALONG THE RIDGE CREST... ROUGHLY WITHIN 90 NM OF 27N86W...AND MOVING E AND DIMINISHING WITH TIME. AN UPPER SHORTWAVE TROUGH IS SWINGING E ACROSS CENTRAL TEXAS WITH AN ASSOCIATED COLD FRONT APPROACHING THE TEXAS COAST. A PREFRONTAL TROUGH IGNITED A LARGE CLUSTER OF CONVECTION ALONG THE E CENTRAL TEXAS COAST WITH AN OUTFLOW BOUNDARY RACING SE ACROSS THE NW GULF WATERS DEFINED BY A LINE OF TOWERING CUMULUS. THE REMAINDER OF THE UPPER LEVELS APPEAR QUITE DRY. AGRICULTURE SMOKE IS NOTED OVER THE EASTERN BAY OF CAMPECHE AND SPREADING N TO ALONG 24N BETWEEN 94W AND 87W. CARIBBEAN SEA... AN UPPER RIDGE DOMINATES THE WESTERN CARIBBEAN WHILE AN UPPER TROUGH IS SWINGING E THROUGH THE AREA BETWEEN 75W AND 70W. CONVECTION IS ENHANCED ALONG THE E COAST OF CENTRAL AMERICA FROM HONDURAS TO COSTA RICA...WITH THE DEBRIS MOISTURE SPREADING E OVER THE AREA TO THE S OF 15N AND W OF 76W. SOME UPPER MOISTURE...ORIGINATING FROM A CLUSTER OF CONVECTION THAT FLARED JUST S OF JAMAICA...IS STREAMING E ALONG 17N TO NEAR 70W WHERE IT MERGES WITH DEBRIS MOISTURE FROM CONVECTION OVER INTERIOR HISPANIOLA. THE COMBINED MOISTURE PLUME CONTINUES E ACROSS THE CARIBBEAN TO N OF 15N E OF 65W. THE UPPER LEVELS ARE DRY S OF 15N E OF 75W. ATLC HIGH PRESSURE IS MAINTAINING FRESH E TRADES ACROSS THE LOW LEVELS WITH SHOWERS ENHANCED OVER THE SW CARIBBEAN. ATLANTIC OCEAN... AN UPPER ANTICYCLONE IS CENTERED NEAR 27N64W WITH A RIDGE EXTENDING N TO WELL BEYOND 32N67W. IMMEDIATELY TO THE W OF THIS RIDGE IS A SMALL UPPER CYCLONE OVER SE GEORGIA AT 31N81W...WITH A TROUGH EXTENDING S AND SE ALONG THE E COAST OF FLORIDA AND ACROSS THE SE BAHAMAS TO 21N72W. AFTERNOON SEABREEZE CONVECTION IS ENHANCED WITHIN 120 NM OF THIS TROUGH...WITH THE OVERALL AREA OF CONVECTION SHIFTING E ACROSS THE BAHAMAS AND OVER THE SW ATLC TO THE S OF 27N W OF 68W. DEBRIS MOISTURE FROM THIS CONVECTION IS ADVECTED N UNDER THE UPPER RIDGE WELL TO THE N OF 32N...BUT SOME OF THE MOISTURE IS NOW SPILLING SE ACROSS TE RIDGE BACK INTO THE AREA TO THE N OF 27N BETWEEN 58W AND 68W. A TROPICAL UPPER ANTICYCLONE IS AT 05N16W WITH A RIDGE EXTENDING NW AND CRESTING ALONG POINTS 14N45W TO 26N29W TO 31N19W. DEBRIS MOISTURE IS NOTED ALONG THE PERIPHERY OF THIS RIDGE. AN UPPER TROUGH DOMINATES THE CENTRAL ATLC BETWEEN THESE LARGE ANTICYCLONES...ROUGHLY ALONG 32N42W TO 20N48W. A FEW CONVECTIVE CLUSTERS ARE ENHANCED ALONG THIS TROUGH...BUT THE MOST PART VERY DRY AIR IS INDICATED TO THE N OF 18N BETWEEN 58W AND 40W. AN ASSOCIATED SURFACE COLD FRONT IS APPROACHING THE AREA FROM 32N44W TO TO 30N54W ACCOMPANIED BY OVERCAST MULTILAYERED CLOUDS WITHIN 120 NM NW AND N OF THE LEADING EDGE. $$ NELSON