000 AXNT20 KNHC 291756 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT WED APR 29 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 1745 UTC. ...THE ITCZ... THE ITCZ AXIS EXTENDS FROM 07N11W TO THE EQUATOR AT 23W THEN CONTINUES S OF THE EQUATOR TO 03S38W. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS OBSERVED WITHIN 120 NM OF A LINE FROM 02N07W TO 02N19W...WITHIN 120 NM OF THE ITCZ AXIS BETWEEN 20W AND 35W...AND ALSO IN A CLUSTER WITHIN 90 NM OF 02N40W. ...DISCUSSION... GULF OF MEXICO... AN UPPER LEVEL TROUGH DISSECTS THE GULF FROM CENTRAL FLORIDA TO THE SW BAY OF CAMPECHE. AN UPPER RIDGE IS COLLAPSING SE OVER THE NW GULF ACCOMPANIED BY DEBRIS CIRRUS COVERING THE AREA N OF 24NW OF 92W. THERE IS STILL SOME EVIDENCE OF A MID LEVEL TROUGH OVER THE CENTRAL WATERS WITH PATCHES OF LOW CLOUDS AND WEAK SHOWERS NOW SPREADING WNW NEAR 25N88W...WITH ANOTHER SMALL CLUSTER OVER THE EXTREME NE YUCATAN PENINSULA. OTHERWISE THE UPPER LEVELS APPEAR QUITE DRY. ELSEWHERE AT THE SURFACE...HIGH PRES LOCATED OVER THE W ATLC HAS A RIDGE EXTENDING W AND DISSECTING THE GULF OF MEXICO FROM NW FLORIDA TO THE BAY OF CAMPECHE. THE ASSOCIATED GRADIENT IS MAINTAINING FRESH E TO SE LOW LEVEL FLOW ACROSS GULF WATERS. CARIBBEAN SEA... AN QUASI STATIONARY UPPER LEVEL ANTICYCLONE OVER S AMERICA IS CURRENTLY ESTIMATED NEAR 08N62W. AN ASSOCIATED UPPER RIDGE EXTENDS NW ACROSS COLOMBIA CRESTING ALONG POINTS 14N91W TO 20N84W TO BEYOND 21N75W. UPPER DEBRIS MOISTURE FROM CONVECTION FLARING ALONG THE E PACIFIC ITCZ...BETWEEN 76W AND 98W...IS STREAMING NE ACROSS THE UPPER RIDGE AND TURNING ENE ACROSS ALL THE E CARIBBEAN ISLANDS BECOMING A NARROW BAND OF MOISTURE ALONG 21N OVER THE CENTRAL N ATLC. AT THE LOW LEVELS...ATLC HIGH PRESSURE N OF AREA IS MAINTAINING FRESH EASTERLY TRADES ACROSS THE CARIBBEAN. TYPICAL OROGRAPHIC SHOWERS ARE NOTED OVER THE LARGER ISLANDS WITH ELEVATED TERRAIN. STREAKS OF TRADE WINDS CUMULUS ACCOMPANIED BY BRIEF SHOWERS ARE NOTED ELSEWHERE. ATLANTIC OCEAN... THE UPPER LEVELS ARE QUITE COMPLICATED BUT BASICALLY AN UPPER TROUGH DOMINATES THE SUBTROPICAL ATLC BETWEEN 80W AND 68W...AND ANOTHER UPPER TROUGH LIES BETWEEN 48W AND 27W. DRY UPPER AIR IS INDICATED OVER THE DISCUSSION AREA W OF 69W AND ALSO ALONG A 240 NM WIDE BAND CENTERED ALONG 32N58W TO 24N41W TO 28N30W. DRY UPPER AIR IS ALSO NOTED S OF 18N BETWEEN 55W AND 25W WITH THE DRY AIR CONTINUING NE WITHIN 300 NM EITHER SIDE OF LINE FROM 12N30W TO OVER INTERIOR AFRICA AT 28N03W. BETWEEN THESE DRY AREAS IS A BAND OF DENSE CIRRUS ADVECTED E ALONG WITHIN AN UPPER WIND MAXIMUM AND CURRENTLY DISPLAYING TRANSVERSE UPPER BANDING...WITH POSSIBLE TURBULENCE...ALL WITHIN 90 NM EITHER SIDE OF LINE 21N55W TO 21N32W TO NEAR 29N11W. SURFACE HIGH PRESSURE CENTERS ALONG 31N ARE MAINTAINING A FAIRLY TIGHT PRESSURE GRADIENT ACROSS MOST OF THE ATLC S OF 32N. A WEAK FRONTAL TROUGH IS SPLITTING THE RIDGE ALONG 33N52W TO 29N68W AND IS ACCOMPANIED BY TOWERING CUMULUS AND LIGHT SHOWERS. SOME SHOWERS HAVE FORMED NEAR 24N67W AND ARE SPREADING W IN THE FRESH NE FLOW. LOCALLY OVERCAST STRATOCUMULUS CLOUDS ARE SPREADING SW OVER THE E ATLC WATERS FROM 19N TO 29N BETWEEN 35W AND 19W. OTHERWISE LOCALLY BROKEN CUMULUS IS OBSERVED RACING ACROSS THE ATLC WATERS IN STRONG TRADES. $$ NELSON