000 AXPZ20 KNHC 280953 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC SUN AUG 28 2011 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL ANALYSIS. BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0945 UTC. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH AXIS EXTENDS NW ALONG THE PACIFIC COAST OF CENTRAL AMERICA FROM THE PANAMA AND COLOMBIA BORDER AT 08N77W TO 19N105W...THEN MOVES OFFSHORE CONTINUING W INTO THE 1008 MB LOW PRES AT 19N120W...THEN TURNS ABRUPTLY SW TO 09N140W WHERE LOW LEVEL WINDS SUGGEST THE ITCZ BEGINS. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS OBSERVED N OF 04N E OF 84W WITH NUMEROUS LIGHTNING STRIKES DETECTED. SIMILAR CONVECTION IS NOTED WITHIN 60 NM OF THE COAST OF CENTRAL AMERICA FROM 85W TO 98W AND FROM 105W TO 111W...AND WITHIN THE AREA BOUNDED BY 09N TO 16N BETWEEN 98W AND 115W. ...DISCUSSION... AN UPPER LONG WAVE TOUGH DOMINATES THE NE PACIFIC E OF 160W. AN EMBEDDED SHORTWAVE TROUGH EXTENDS THROUGH A SERIES OF UPPER CYCLONES FROM THE OREGON COAST TO A WELL DEFINED CYCLONE AT 31N144W WITH A TROUGH S TO BASE AT 12N143W. UPPER MOISTURE IS INDICATED WITHIN 420 NM OF THE UPPER CYCLONE AND JUST BRUSHING THE NW CORNER OF THE DISCUSSION AREA AT 32N140W. AN UPPER ANTICYCLONE IS ANCHORED OVER CENTRAL NEW MEXICO WITH AN UPPER RIDGE EXTENDING SW ACROSS THE NORTHERN BAJA CALIFORNIA PENINSULA TO A FAIRLY SHARP CREST AT 24N130W...EFFECTIVELY BLOCKING THE EASTWARD ADVANCE OF THE UPPER TROUGH. INTENSE CONVECTION ACCOMPANIED BY NUMEROUS LIGHTNING STRIKES...WAS ENHANCED ALONG THE SIERRA MADRE OCCIDENTAL. THIS SCATTERED MODERATE ISOLATED STRONG CONVECTION IS CURRENTLY MOVING W OFF THE MEXICAN COAST OUT TO ABOUT 30 NM OVER THE PACIFIC AND THE EASTERN GULF OF CALIFORNIA FROM 20N TO 27N. THE DEBRIS MOISTURE IS SPREADING W ACROSS THE BAJA CALIFORNIA PENINSULA TO OVER THE PACIFIC E OF A LINE FROM 20N108W TO 30N118W. AN UPPER TROUGH DISSECTS THE GULF OF MEXICO FROM NE TO SW...AND CONTINUES W ACROSS CENTRAL OLD MEXICO AND OVER THE E PACIFIC INTO AN ILL DEFINED UPPER CYCLONES AT 20N110W...16N118W AND 21N126W...THEN TURNS SW THROUGH AN UPPER CYCLONE AT 12N135W... WITH THE TROUGH CONTINUING SW TO BEYOND 09N140W. AN UPPER ANTICYCLONE IS OVER THE STRAITS OF THE YUCATAN AT 21N84W WITH A RIDGE EXTENDING SW OVER GUATEMALA. AN UPPER TROUGH IS DIGGING SW ACROSS THE CENTRAL CARIBBEAN WITH EVIDENCE OF AN UPPER CYCLONE DEVELOPING OVER THE PACIFIC NEAR 09N85W. THE UPPER FLOW IS GENERALLY NE OVER THE TROPICS TO THE S OF 20N BETWEEN 95W AND 80W...AND IS ADVECTING DEBRIS MOISTURE S TO ALONG 03N BETWEEN 78W AND 122W. A SURFACE HIGH PRESSURE IS NEAR 32N141W WITH A BROAD RIDGE OVER THE PACIFIC N OF 20N W OF 125W. A 1008 MB SURFACE LOW PRES IS AT 19N120W WITH THE LATEST SCATTEROMETER DATA INDICATING THE GRADIENT IS SUPPORTING NE WINDS 15-20 KT WITHIN 120 NM OVER THE NW QUADRANT. SCATTERED MODERATE CONVECTION HAS BEEN FLARING NEAR THE CENTER BUT IS CURRENTLY ABSENT. THE LOW IS EXPECTED TO DRIFT W TO NEAR 19N121W ON TONIGHT...NEAR 18N122W MON...THEN WEAKEN TO AN OPEN TROUGH MON NIGHT. MONSOONAL SOUTHWESTERLY FLOW AT 20 KT...SEAS 8-11 FT...IS OBSERVED IN THE SCATTEROMETER DATA WITHIN ABOUT 150 NM EITHER SIDE OF A LINE FROM 07N124W TO 15N106W. THE GRADIENT IS EXPECTED TO WEAKEN WITH WINDS BELOW 20 KT AND SEAS LESS THAN 8 FT BY LATE MON NIGHT. REINFORCING SW SWELL WILL REACH THE EQUATOR BETWEEN 120W AND 140W LATE TONIGHT...AND MOVE ACROSS THE EQUATOR BETWEEN 120W AND 90W BY MON NIGHT...REACHING THE CENTRAL AMERICAN COAST BETWEEN 105W AND 85W ON WED. $$ NELSON