000 AXPZ20 KNHC 272117 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 2205 UTC WED MAY 27 2009 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2115 UTC. ...TROPICAL WAVES... A TROPICAL WAVE IS ALONG 78W S OF 16N EXTENDING FROM THE SW CARIBBEAN INTO THE GULF OF PANAMA. THE WAVE IS MOVING WESTWARD AT 15-20 KT...AND WILL MAKE FURTHER PROGRESS INTO THE E PACIFIC REGION DURING THE NEXT DAY. THIS WAVE IS ASSOCIATED WITH A MAXIMUM IN DEEP LAYER MOISTURE BASED ON TOTAL PRECIPITABLE WATER PRODUCT FROM CIMSS. ALSO...CIMSS WAVETRAK PRODUCT INDICATES A MAXIMUM IN LOW LEVEL CYCLONIC CIRCULATION AROUND THE WAVE. THIS WAVE IS ASSOCIATED WITH SCATTERED MODERATE CONVECTION ACROSS WESTERN PORTIONS OF PANAMA AND THE ADJACENT PACIFIC WATERS. THIS CONVECTION IS BEING ENHANCED BY LOW LEVEL CONVERGENCE NEAR THE ITCZ. ...ITCZ... THE ITCZ AXIS EXTENDS ALONG 09N79W TO 08N92W TO 12N101W TO 03N130W TO 04N140W. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS FROM 05N TO 07N BETWEEN 82W AND 86W. SCATTERED MODERATE CONVECTION IS FROM 03N TO 10N BETWEEN 89W AND 95W. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS FROM 05N TO 12N BETWEEN 99W AND 109W. SCATTERED MODERATE CONVECTION IS FROM 04N TO 07N BETWEEN 112W AND 124W. ...DISCUSSION... A SURFACE RIDGE EXTENDS SOUTHWARD INTO THE NORTHERN WATERS FROM A 1023 MB SURFACE HIGH N OF THE AREA NEAR 36N133W. THE SURFACE HIGH AND RIDGE CONTINUE TO DRIVE NE TO E TRADE WINDS OF 15 TO 20 KT FROM 11N TO 15N W OF 137W BASED ON THE QUIKSCAT PASS AROUND 27/1500 UTC. SEAS TO 8 FT LIKELY PERSIST IN THIS AREA AS WELL. DURING THE NEXT TWO DAYS...THE SURFACE HIGH IS FORECAST TO WEAKEN AS IT DRIFTS EASTWARD AND INTERACTS WITH ATMOSPHERIC LIFT ASSOCIATED WITH A MID/UPPER-LEVEL SHORTWAVE TROUGH. THIS TROUGH IS CURRENTLY N OF 28N BETWEEN 126W-132W...WITH INSTABILITY NEAR THE TROUGH SUPPORTING SCATTERED SHOWERS IN THIS AREA. HOWEVER...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 THIS EVENING. A DEEP LAYER TROUGH CURRENTLY NW OF THE DISCUSSION AREA CONTINUES DIGGING SOUTHWARD 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 EARLY FRI...WITH SOUTHERLY WINDS INCREASING TO 20 KT AHEAD OF THE FRONT LATE THU ACROSS THE FAR NW WATERS. 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 10 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 108W AND 111W. COMPUTER MODEL GUIDANCE IS LIKELY UNDER-FORECASTING THESE WIND SPEEDS...BASED ON COMPARISONS WITH RECENT SCATTEROMETER DATA. THE HIGH RESOLUTION QUIKSCAT PASS AROUND 27/1315 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. DURING THE NEXT TWO DAYS...THIS AREA OF WINDS IS FORECAST TO AFFECT LOCATIONS FROM 16N TO 20N E OF 107W. CONVECTION ASSOCIATED WITH THE ITCZ IS BEING ENHANCED BY UPPER LEVEL DIVERGENCE NEAR TWO UPPER LEVEL TROPICAL RIDGES. THE WESTERN RIDGE IS FROM 02N TO 13N W OF 129W. UPPER LEVEL DIVERGENCE ASSOCIATED WITH THIS RIDGE IS SUPPORTING SCATTERED MODERATE CONVECTION FROM 11N TO 13N BETWEEN 125W AND 129W. THE EASTERN RIDGE IS FROM 03N TO 14N E OF 112W. ABUNDANT DEEP LAYER MOISTURE IS EMBEDDED WITHIN THE EASTERN RIDGE AND IS INTERACTING WITH THE TROPICAL WAVE ALONG 78W S OF 16N TO GENERATE CONVECTION OVER PORTIONS OF THE E PACIFIC REGION. $$ COHEN