000 AXPZ20 KNHC 122126 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 2205 UTC FRI JUN 12 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 2100 UTC. ...ITCZ... AXIS IS CENTERED ALONG 09N84W TO 08N102W TO 12N118W TO 08N132W TO 08N140W. SCATTERED MODERATE TO STRONG CONVECTION IS FROM 03N TO 10N BETWEEN 81W AND 103W. SCATTERED MODERATE CONVECTION IS FROM 11N TO 15N BETWEEN 95W AND 101W. SCATTERED MODERATE CONVECTION IS WITHIN 60 NM OF 12N113W. SCATTERED MODERATE CONVECTION IS FROM 04N TO 11N W OF 127W. ...DISCUSSION... N OF 20N... SUBSIDENCE IN NORTHWESTERLY FLOW ALOFT E OF AN UPPER LEVEL RIDGE OVER THE CENTRAL PACIFIC IS SUPPORTING A 1022 MB SURFACE HIGH NEAR 29N148W...WITH A SURFACE RIDGE EXTENDING EASTWARD ACROSS THE NORTHERN WATERS. THE PRESSURE GRADIENT AT THE SOUTHERN PERIPHERY OF THIS RIDGE IS DRIVING NORTHEASTERLY TRADE WINDS OF 15 TO 20 KT GENERALLY IN AN AREA FROM 09N TO 20N W OF 128W BASED ON THE QUIKSCAT PASS AROUND 12/1800 UTC. THE UPPER LEVEL RIDGE IS SLOWLY TRANSLATING EASTWARD...RESULTING IN THE SURFACE HIGH DRIFTING EASTWARD ALONG WITH THE ATTENDANT SURFACE RIDGE. WITH THIS PERSISTENT RIDGING...THE AFOREMENTIONED AREA OF TRADE WINDS IS FORECAST TO CONTINUE OVER THE SAME GEOGRAPHIC AREA AND WITH THE SAME INTENSITY. HOWEVER...A STRENGTHENING SURFACE TROUGH OVER MEXICO IS STEEPENING THE PRESSURE GRADIENT OFF THE S AND W COASTS OF BAJA CALIFORNIA... WHERE NW TO N WINDS OF 20 KT ARE OCCURRING. THE HIGH RESOLUTION QUIKSCAT PASS AROUND 12/1300 UTC INDICATED NW WINDS OF 20 KT FROM 22N TO 27N WITHIN 120 NM OF THE COAST OF BAJA CALIFORNIA. ALSO...AT 12/1800 UTC...THE SHIP WITH IDENTIFIER V7FE9 WAS REPORTING N WINDS OF 18 KT NEAR 23N112W. AS THE SURFACE RIDGE MAKES FURTHER EASTWARD PROGRESS...THESE WINDS WILL EXPAND IN AREAL COVERAGE AND INTENSITY...WITH NW WINDS TO 20 KT EXTENDING EASTWARD TO THE COAST OF MEXICO FROM 22N TO 27N INCLUDING THE GULF OF CALIFORNIA. ADDITIONALLY...A 1013 MB SURFACE LOW IS PRESENT NEAR 17N118W...WITH A SURFACE TROUGH EXTENDING SOUTHWESTWARD TO 10N126W. THIS FEATURE IS IN AN ENVIRONMENT FEATURING MID/UPPER-LEVEL DRY AREA...RELATIVELY COOL SEA SURFACE TEMPERATURES...AS WELL AS ENHANCED SOUTHWESTERLY SHEAR E OF AN UPPER TROUGH AXIS EXTENDING FROM 19N124W TO 30N124W. WHILE THESE CONDITIONS ARE INHIBITING ORGANIZED DEEP CONVECTION NEAR THE LOW...COOLER MID-LEVEL TEMPERATURES NEAR THE UPPER TROUGH CONTINUE TO SUPPORT SCATTERED MODERATE CONVECTION WITHIN 60 NM OF THE LOW CENTER. THE TIGHT PRESSURE GRADIENT BETWEEN THE LOW AND THE AFOREMENTIONED RIDGE IS SUPPORTING WINDS OF 20 TO 25 KT WITHIN 180 NM IN THE NORTHERN SEMICIRCLE OF THE LOW...WITH WINDS TO 20 KT WITHIN 120 NM IN THE SOUTHERN SEMICIRCLE OF THE LOW. GLOBAL MODELS ARE LIKELY UNDER-INITIALIZING THE STRENGTH OF THE LOW LEVEL WIND FIELD AROUND THE LOW BASED ON RECENT SCATTEROMETER DATA. THIS UNDER-INITIALIZATION IS LIKELY DUE TO THE ENHANCED CONVECTION ACTUALLY OCCURRING NEAR THE LOW. HOWEVER...DURING THE NEXT TWO DAYS...THE LOW WILL LIKELY GRADUALLY WEAKEN AS DEEP LAYER DRY AIR CONTINUES TO BE ENTRAINED INTO THE SYSTEM THUS CAPPING DEEP CONVECTION...WHILE IT REMAINS OVER RELATIVELY COOL WATERS. IN RESPONSE...THE WIND FIELD WILL LIKELY CONTRACT AND DIMINISH TO BELOW 20 KT IN A COUPLE DAYS. THE AFOREMENTIONED UPPER TROUGH IS FORECAST TO EJECT A SHORTWAVE TROUGH EASTWARD OVER THE SW UNITED STATES AND NORTHERN MEXICO THIS WEEKEND BEFORE AMPLIFYING EARLY NEXT WEEK AS AN UPPER LEVEL JET MAXIMUM DIVES SOUTHEASTWARD TOWARD THE TROUGH AXIS. AN ASSOCIATED WEAK COLD FRONT WILL ENTER THE FAR N WATERS ON MONDAY ALONG WITH NW SWELL TO 6 FT. OTHERWISE...S TO SW SWELL ASSOCIATED WITH WAVE HEIGHTS OF 8 TO 11 FT WILL CONTINUE TO OVERTAKE THE SOUTHERN PORTION OF THE DISCUSSION AREA THIS WEEKEND. HOWEVER...MAXIMUM SEAS ARE FORECAST TO DIMINISH AS THESE WAVES DEPART THEIR SOURCE OF GENERATION FROM PREVIOUS SOUTHERN HEMISPHERIC STORMS. THESE WAVES WILL IMPACT THE COAST OF CENTRAL AMERICA AND S MEXICO FOR SAT AND SUN RESULTING IN LARGE AND DANGEROUS BREAKING SURF CONDITIONS ARE ALONG THESE COASTS. $$ COHEN