000 AXPZ20 KNHC 040956 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC MON MAY 04 2009 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0915 UTC. ...ITCZ... ITCZ AXIS IS ALONG 07N78W TO 08N99W TO 03N120W TO 05N140W. SCATTERED MODERATE ISOLATED STRONG IS CONFIRMED BY LIGHTNING DATA WITHIN SCATTERED MODERATE ISOLATED STRONG WITHIN 180 NM EITHER SIDE OF LINE FROM 07N83W TO 06N100W AND ALSO WITHIN 90 NM EITHER SIDE OF LINE FROM 07N104W TO 04N122W TO 04N129W TO 09N140W...AND A SEPARATE CLUSTER WITHIN 90 NM OF 09N128W. ...DISCUSSION... ALOFT...AN UPPER CYCLONE HAS NEARLY CUT OFF FROM ITS PARENT TROUGH NEAR 17N133W...BUT THERE IS STILL EVIDENCE OF A CYCLONIC SHEAR AXIS EXTENDING N FROM THE CYCLONE ALONG 24N130W TO 27N120W...AND WELL DEFINED BY A BAND OF DRY UPPER AIR WITHIN 90 NM OF THE SHEAR AXIS. DRY UPPER AIR IS NOTED OVER THE W SEMICIRCLE OF THE CYCLONE AND NOW ROTATING AROUND THE SE QUADRANT VERY NEAR THE CENTER. AN UPPER ANTICYCLONE NEAR HAWAII HAS A RIDGE EXTENDING E INTO THE DISCUSSION AREA TO A SHARP CREST NEAR 25N137W. A QUASI STATIONARY UPPER ANTICYCLONE IS CENTERED AT 12N120W WITH ITS ENVELOPE OF ANTICYCLONIC FLOW DOMINATING THE UPPER LEVELS FROM 05N TO 25N BETWEEN 112W AND 128W. THE CYCLONIC SHEAR AXIS IS SLOWLY ERODING THE TOP OF THE RIDGE BETWEEN 130W AND 118W. UPPER DIFFLUENCE S OF THE RIDGE AND BETWEEN THE RIDGE AND THE CUTOFF CYCLONE HAS BEEN ENHANCING CONVECTION ALONG THE ITCZ BETWEEN 112W AND 135W...WITH THE DEBRIS MOISTURE ADVECTED NE WITHIN 240 NM EITHER SIDE OF LINE FROM 09N130W TO 18N126W WITH THE MOISTURE FANS OUT COVERING THE AREA FROM 18N TO 24N BETWEEN 114W AND 133W. A SERIES OF UPPER TROUGHS ARE OVER THE THE EASTERN CONUS AND THE WESTERN ATLANTIC WITH TWO UPPER TROUGHS MERGING OVER THE SOUTHERN GULF OF MEXICO...THEN CONTINUING SW ACROSS CENTRAL AMERICA ALONG 20N98W INTO A MID TO UPPER CYCLONE OVER THE PACIFIC NEAR 09N106W...WITH THE UPPER TROUGH CONTINUING S ACROSS THE EQUATOR AT 105W. A STATIONARY UPPER RIDGE EXTENDS NW OFF COLOMBIA ACROSS CENTRAL AMERICA CRESTING OVER THE YUCATAN PENINSULA. UPPER DIFFLUENCE E OF THE UPPER CYCLONE AT 09N106W IS ENHANCING CONVECTION OVER ITS E SEMICIRCLE. UPPER DIFFLUENCE UNDER THE RIDGE HAS ENHANCED CONVECTION ALONG THE PACIFIC ITCZ TO THE E OF 100W...AND ALSO ENHANCED A FEW CLUSTERS OVER INTERIOR CENTRAL AMERICA. THE COMBINED UPPER DEBRIS MOISTURE IS CONCENTRATED TO THE NE OF A LINE FROM 00N82W TO 07N105W AND EXTENDING NE ACROSS ALL OF CENTRAL AMERICA AND THE W CARIBBEAN EVENTUALLY EVAPORATING OVER THE N CENTRAL CARIBBEAN ALONG 18N. AT THE SURFACE...A 1024 MB HIGH PRES IS QUASI STATIONARY NEAR 26N133W WITH A RIDGE EXTENDING SW TO BEYOND 26N140W...AND A RIDGE EXTENDING SE TO NEAR 12N113W. THE RIDGE IS BLOCKING THE SOUTHEAST PROGRESSION OF A SERIES OF COLD FRONTS TO N OF 30N...HOWEVER NW SWELLS TO 12 FT WILL SPREAD SE INTO THE EXTREME NW PORTION IN 24 HOURS. TO THE E OF THE SURFACE RIDGE... NORTHERLY WINDS AT 20 KT ARE OBSERVED ALONG THE PACIFIC COAST OF THE BAJA PENINSULA AND EXPECTED TO CHANGE LITTLE TODAY AND TUE...BUT INCREASE TO 20 TO 25 KT WED WITH SEAS BUILDING TO 13 FT IN NW SWELL NEAR 30N118W WED NIGHT. EASTERLY TRADES S OF THE RIDGE AND N OF THE ITCZ ARE MOSTLY IN THE 15 TO 20 KT RANGE AND NOT EXPECTED TO CHANGE MUCH FOR A COUPLE OF DAYS. $$ NELSON