000 AXPZ20 KNHC 101552 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1605 UTC SAT SEP 10 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1545 UTC. ...ITCZ/MONSOON TROUGH... THE SOUTHERN SEGMENT OF THE MONSOON TROUGH EXTENDS W ACROSS COSTA RICA FROM 10N80W TO 09N86W...THEN TURNS WNW OVER THE PACIFIC TO 10N95W...THEN TURNS NW TO NEAR 20N113W...THEN TURNS SW THROUGH AN EMBEDDED 1008 MB SURFACE LOW AT 16N118W WHICH IS SHOWING SIGNS OF STRENGTHENING WHILE DRIFTING NW...CONTINUING SW TO A 1009 MB SURFACE LOW AT 13N130W. THE TROUGH EXTENDS FURTHER SW TO 11N139W WHERE LOW LEVEL WINDS INDICATE THAT THE ITCZ BEGINS. BROKEN TO LOCALLY OVERCAST MULTILAYERED CLOUDS WITH SCATTERED MODERATE ISOLATED STRONG CONVECTION...ACCOMPANIED BY NUMEROUS LIGHTNING STRIKES...IS MOVING OFF THE COAST OF COLOMBIA FROM 02N TO 06N AND IS ALONG AND WITHIN 60 NM OF THE COAST OF CENTRAL AMERICA FROM 81W TO 89W. SIMILAR ACTIVITY IS OBSERVED WITHIN 60 NM OF 19N111W AND WITHIN 90 NM OF 15N120W AND 13N132W AND 08N12W. ...DISCUSSION... AN UPPER ANTICYCLONE IS CENTERED AT 28N141W WITH A RIDGE EXTENDING NE WELL BEYOND 32N137W TO NW CANADA. ANOTHER UPPER ANTICYCLONE IS IS OVER CENTRAL OLD MEXICO AT 21N100W WITH AN UPPER RIDGE EXTENDING W OVER THE PACIFIC TO A CREST AT 20N122W. ALTHOUGH A LONGWAVE RIDGE DOMINATES N AMERICA...TWO SIGNIFICANT SHORTWAVE TROUGHS ARE SHIFTING E THROUGH THE LONGWAVE RIDGE. THE WESTERNMOST TROUGH HAS A DEEP LAYERED CYCLONE OVER SOUTHERN CALIFORNIA WITH AN UPPER TROUGH AMPLIFYING SW TOWARDS TO AN UPPER CYCLONE AT 18N132W WHICH IN TURN HAS AN UPPER TROUGH S TO ANOTHER SMALL UPPER CYCLONE AT 11N140W. THIS DEEPENING UPPER TROUGH HAS EFFECTIVELY SEPARATED THE UPPER RIDGE INTO THE TWO SEGMENTS PREVIOUSLY DESCRIBED. AN ASSOCIATED 1005 MB SURFACE LOW IS OVER SOUTHERN CALIFORNIA WITH A HEAT TROUGH EXTENDING S ACROSS THE BAJA CALIFORNIA. THIS UPPER TROUGH IS FORECAST TO CONTINUE EASTWARD TO ALONG 123W ON SUN. CONVECTION IS ENHANCED OVER CALIFORNIA E OF THE SURFACE LOW WITH THE DEBRIS MOISTURE ADVECTED E ACROSS ARIZONA...NEW MEXICO AND W TEXAS AND INTO THE EASTERN SHORTWAVE TROUGH THAT EXTENDS S OVER THE WESTERN GULF OF MEXICO. THE UPPER LEVELS APPEAR DRY ELSEWHERE W OF OF A LINE FROM 15N130W TO 30N110W. THE UPPER RIDGE EXTENDING W FROM MEXICO IS ROUGHLY IN PHASE WITH THE LOWER LEVEL MONSOON TROUGH AND ENHANCES THE CONVECTION PREVIOUSLY MENTIONED. THE DEBRIS MOISTURE FANS OUT OVER THE TROPICAL PACIFIC S OF 17N E OF 130W AND MERGES WITH THE DEBRIS MOISTURE FROM TROPICAL CYCLONE NATE IN THE BAY OF CAMPECHE AND DEBRIS MOISTURE FROM PREVIOUSLY MENTIONED CONVECTION ASSOCIATED WITH THE MONSOON TROUGH ALONG CENTRAL AMERICA. GULF OF CALIFORNIA...SOUTHERLY WINDS AT 15 TO 20 KT WILL CONTINUE OVER THE WATERS N OF 29N THROUGH EARLY TONIGHT...THEN DIMINISH EARLY SUN. NORTHERLY SWELLS...RESULTING IN COMBINED SEAS OF 8 FT...WILL MOVE INTO THE WATERS N OF 29N BETWEEN 119W AND 128W TODAY... SPREADING S TO ALONG 25N BETWEEN 120W AND 136W BY EARLY NEXT WEEK. CROSS EQUATORIAL SOUTHERLY SWELL...WITH SEAS TO 9 FT... WILL MOVE N OVER THE WATERS S OF 10N BETWEEN 130W AND 93W OVER THE WEEKEND. $$ NELSON