000 AXPZ20 KNHC 130341 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 0405 UTC SAT JUN 13 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 0315 UTC. ...ITCZ... AXIS IS CENTERED ALONG 10N84W TO 8N97W TO 11N120W TO 8N132W TO 10N140W. SCATTERED MODERATE TO STRONG CONVECTION EXISTS FROM 5N -9N BETWEEN 85W AND 93W. SCATTERED MODERATE TO STRONG CONVECTION IS NOTED FROM 4N-10N BETWEEN 95W AND 107W. SCATTERED MODERATE CONVECTION IS WITHIN 60 NM OF 13N123W. SCATTERED MODERATE CONVECTION IS FROM 06N TO 10N W OF 129W...WHICH IS BEING ENHANCED BY LOW LEVEL CONVERGENCE NEAR A SURFACE TROUGH EMBEDDED WITHIN THE ITCZ EXTENDING FROM 13N138W TO 08N140W. ...DISCUSSION... A 1011 MB SURFACE LOW IS PRESENT NEAR 17N118W MOVING NE ABOUT 5 KT. A SURFACE TROUGH EXTENDS FROM THE LOW SW TO NEAR 12N125W. THIS FEATURE IS IN AN ENVIRONMENT FEATURING MID/UPPER-LEVEL DRY AIR...RELATIVELY COOL SEA SURFACE TEMPERATURES...AS WELL AS ENHANCED SOUTHWESTERLY SHEAR E OF AN UPPER TROUGH AXIS EXTENDING FROM 19N123W TO 30N122W. WHILE THESE CONDITIONS ARE INHIBITING ORGANIZED DEEP CONVECTION NEAR THE LOW...COOLER MID-LEVEL TEMPERATURES NEAR THE UPPER TROUGH CONTINUE TO SUPPORT SCATTERED MODERATE TO STRONG PULSE CONVECTION WITHIN 150 NM OF THE LOW CENTER. THE TIGHT PRESSURE GRADIENT BETWEEN THE LOW AND THE A SURFACE RIDGE OVER THE N WATERS IS LIKELY SUPPORTING WINDS OF 20 TO 30 KT WITHIN 150 NM IN THE NW SEMICIRCLE OF THE LOW...WITH WINDS TO 20 KT WITHIN 90 NM IN THE SE 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 COULD BE 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. ADDITIONALLY...SUBSIDENCE IN NORTHWESTERLY FLOW ALOFT E OF AN UPPER LEVEL RIDGE OVER THE CENTRAL PACIFIC IS SUPPORTING A 1023 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 10N TO 19N W OF 128W BASED ON THE ASCAT PASS AROUND 12/1830 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 AND EASTWARD TO THE COAST OF MEXICO INCLUDING PORTIONS OF THE GULF OF CALIFORNIA...WHERE NW 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 ADDITIONAL EASTWARD PROGRESS...THESE WINDS CONTINUE INCREASING IN AREAL COVERAGE AND INTENSITY...WITH NW WINDS OF 20 TO 25 KT FROM FROM 21N TO 28N E OF 114W INCLUDING THE GULF OF CALIFORNIA DURING THE NEXT DAY. LATER IN THE WEEKEND...THE STRONGEST WINDS WILL BE FOUND NEAR THE S AND W COASTS OF BAJA CALIFORNIA. ADDITIONALLY...ATMOSPHERIC LIFT E OF THE AFOREMENTIONED UPPER TROUGH IS FORECAST TO SUPPORT WEAK SMALLER SCALE SURFACE LOWS IN THE NORTHERN GULF OF CALIFORNIA DURING THE NEXT COUPLE DAYS...WHICH WILL BE ENHANCED AT NIGHT WHEN NOCTURNAL DRAINAGE FLOW IS MAXIMIZED. UPPER LEVEL JET MAXIMA ROUNDING THE BASE OF THE UPPER LEVEL TROUGH WILL CONTRIBUTE TO ENHANCED DOWNSLOPE FLOW INTO THE NORTHERN GULF OF CALIFORNIA...FURTHER SUSTAINING THE SURFACE LOWS AND CORRESPONDING THREAT FOR SW TO W WINDS OF 20 TO 25 KT ACROSS THE N GULF OF CALIFORNIA. THE HIGH RESOLUTION QUIKSCAT PASS AROUND 12/1300 THU MORNING UTC CONFIRMED THE PRESENCE OF THESE WINDS IN THE N GULF OF CALIFORNIA. HIGHER RESOLUTION GLOBAL AND REGIONAL MODEL GUIDANCE ALSO INDICATES THESE WINDS CONTINUING DURING THE NEXT FEW DAYS. THE UPPER TROUGH IS ALSO 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 FOLLOWED BY NW SWELL TO 6 FT. OTHERWISE...S TO SW SWELL ASSOCIATED WITH WAVE HEIGHTS OF 8 TO 12 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