000 AXPZ20 KNHC 270322 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 0405 UTC WED MAY 27 2009 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. BASED ON 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0300 UTC. ...ITCZ... THE ITCZ AXIS EXTENDS ALONG 05N77W TO 06N90W TO 08N105W TO 03N124W TO 05N140W. SCATTERED MODERATE CONVECTION IS FROM 05N TO 08N BETWEEN 83W AND 88W. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS FROM 03N TO 10N BETWEEN 90W AND 98W. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS FROM 07N TO 11N BETWEEN 101W AND 116W. SCATTERED MODERATE CONVECTION IS FROM 07N TO 09N W OF 138W. .DISCUSSION... A SURFACE RIDGE EXTENDS SOUTHWARD INTO THE NORTHERN WATERS FROM A 1026 MB SURFACE HIGH N OF THE AREA NEAR 36N135W. THE SURFACE HIGH AND RIDGE ARE BEING SUPPORTED BY SUBSIDENCE ASSOCIATED WITH AN UPPER LEVEL RIDGE APPROACHING THE W UNITED STATES. THE SURFACE HIGH AND RIDGE CONTINUE TO DRIVE NE TO E TRADE WINDS UP TO 20 KT FROM 12N TO 20N W OF 130W BASED ON EARLIER SCATTEROMETER DATA. WAVEWATCH OUTPUT INDICATES SEAS TO 8 FT IN THIS REGION. DURING THE NEXT TWO DAYS...THE SURFACE HIGH IS FORECAST TO WEAKEN AS IT DRIFTS SOUTHEASTWARD AND A MID/UPPER-LEVEL SHORTWAVE TROUGH APPROACHES. THIS TROUGH IS CURRENTLY W OF THE SURFACE HIGH...AND IS ALONG 136W N OF 27N. INSTABILITY ASSOCIATED WITH THIS TROUGH IS CURRENTLY SUPPORTING SCATTERED SHOWERS N OF 27N BETWEEN 131W AND 137W...THOUGH DEEP CONVECTION IN THIS REGION IS BEING SUPPRESSED BY SUBSIDENCE ASSOCIATED WITH THE AFOREMENTIONED SURFACE HIGH AND RIDGE. AS THE SURFACE HIGH WEAKENS...ITS ASSOCIATED SURFACE PRESSURE GRADIENT WILL WEAKEN...WITH THE TRADE WINDS DIMINISHING BELOW 20 KT BY LATE TONIGHT. A DEEP LAYER TROUGH CURRENTLY N OF THE DISCUSSION AREA IS FORECAST TO DIG SOUTHWARD DURING THE NEXT TWO DAYS AS AN UPPER LEVEL JET MAXIMUM DIVES SOUTHEASTWARD TOWARD THE TROUGH AXIS. AN ASSOCIATED COLD FRONT WILL ENTER FAR NW PORTIONS OF THE DISCUSSION AREA BY LATE THU INTO EARLY FRI...WITH SOUTHERLY WINDS INCREASING TO 20 KT AHEAD OF THE FRONT. HOWEVER... CONSENSUS AMONG GLOBAL MODELS IS THAT AN UPPER LOW WILL CUT OFF OVER THE SOUTHERN EXTENT OF THE TROUGH BY LATE SATURDAY NW OF THE DISCUSSION AREA. THE FRONT WILL CORRESPONDINGLY WEAKEN BY EARLY IN THE WEEKEND WITH DEEP LOW PRESSURE REMAINING N OF THE AREA...AND WINDS OVER THE NW FORECAST WATERS DIMINISHING. HOWEVER...STRONG WINDS AROUND THE SURFACE LOW N OF THE AREA WILL RESULT IN SEAS OF 8 TO 9 FT IN NW SWELL ENTERING THE NW WATERS THIS WEEKEND. THE SURFACE PRESSURE GRADIENT BETWEEN THE SURFACE RIDGE OVER THE N WATERS AND A SURFACE TROUGH OVER MEXICO IS RESULTING IN NW WINDS OF 20 TO 25 KT FROM 20N TO 23N BETWEEN 107W AND 112W. COMPUTER MODEL GUIDANCE IS LIKELY UNDER-FORECASTING THESE WIND SPEEDS...AS THE HIGH RESOLUTION QUIKSCAT PASS AROUND 26/1345 UTC INDICATED THAT WINDS COULD HAVE LOCALLY REACHED 30 KT IN THIS AREA...HIGHEST NEAR THE COAST OF BAJA CALIFORNIA. THESE WIND SPEEDS WERE AROUND 10 KT HIGHER THAN COMPUTER MODEL OUTPUT AND ARE BEING ENHANCED BY VARIATIONS IN TERRAIN ALONG THE COAST OF MEXICO. THIS AREA OF WINDS IS FORECAST TO CONTINUE TO AFFECT THE FAR EASTERN WATERS DURING THE NEXT FEW DAYS...THOUGH THE AREA IS FORECAST TO SLIDE SOUTHWARD IN CORRESPONDENCE WITH THE MOTION OF THE AFOREMENTIONED SURFACE HIGH. AS FOR CONVECTION...A SURFACE TROUGH EMBEDDED WITHIN THE ITCZ EXTENDS IS DRIFTING W OF THE DISCUSSION AREA...WITH ASSOCIATED LOW LEVEL CONVERGENCE SUPPORTING SCATTERED MODERATE CONVECTION FROM 07N TO 09N W OF 138W. THIS CONVECTION IS ALSO BEING SUPPORTED BY UPPER LEVEL DIVERGENCE ASSOCIATED WITH AN UPPER LEVEL HIGH CENTERED NEAR 06N139W AND AN ASSOCIATED UPPER LEVEL RIDGE AXIS EXTENDING FROM THE UPPER LEVEL HIGH TO 07N123W. ADDITIONALLY...A BROAD UPPER LEVEL RIDGE IS OVER THE E PACIFIC FROM 05N TO 17N E OF 115W. UPPER LEVEL DIVERGENCE AND DEEP LAYER MOISTURE NEAR THIS FEATURE ARE ENHANCING THE CONVECTION ASSOCIATED WITH THE ITCZ...ALONG WITH SCATTERED MODERATE CONVECTION WITHIN 60 NM OF 07N82W AND SCATTERED MODERATE AND ISOLATED STRONG CONVECTION WITHIN 60 NM OF 09N86W. $$ COHEN