000 AXPZ20 KNHC 180939 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC TUE MAY 18 2010 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0730 UTC. ...TROPICAL WAVES... TROPICAL WAVE WAS FROM 10N86W TO 03N88W MOVING W AT 10-15 KT. NO SIGNIFICANT CONVECTION WAS DIRECTLY ASSOCIATED WITH THE WAVE AT 0730 UTC...BUT THE WAVE IS MOVING UNDER FAVORABLE ANTICYCLONIC FLOW ALOFT AND IS EMBEDDED IN A MOISTURE MAXIMUM ALONG THE ITCZ WHICH SHOULD ALLOW FOR SOME NEAR TERM CONVECTIVE ENHANCEMENT. TROPICAL WAVE WAS FROM 13N115W TO 06N117W WITH EMBEDDED 1011 MB LOW PRES NEAR 09N116W MOVING W AROUND 5-10 KT. SCATTERED MODERATE CONVECTION IS FOCUSED PRIMARILY E OF THE WAVE TO 103W WITHIN 90 NM OF THE ITCZ. THE 0530 UTC ASCAT PASS SHOWS THE LOW LEVEL CENTER HAS BECOME MORE ELONGATED. 30-40 KT SOUTHERLY FLOW ALOFT CURRENTLY RESIDES OVER THE LOW AND WAVE...BUT IT IS EXPECTED TO DIMINISH AS UPPER LEVEL RIDGING BUILDS OVER THE SYSTEM TOMORROW. THIS SHOULD ALLOW FOR A MORE FAVORABLE ENVIRONMENT FOR DEEP CONVECTION. ...ITCZ... THE INTERTROPICAL CONVERGENCE ZONE AXIS WAS ALONG A LINE FROM 03N78W TO 07N94W TO 06N103W TO 09N114W TO 06N140W. SCATTERED MODERATE CONVECTION WAS WITHIN 90 NM S OF THE ITCZ AXIS BETWEEN 103W AND 117W AS WELL AS WITHIN 150 NM N OF THE ITCZ AXIS BETWEEN 110W AND 113W. SCATTERED MODERATE WITH ISOLATED STRONG CONVECTION WAS WITHIN 90 NM N OF THE ITCZ AXIS BETWEEN 124W AND 126W. ...DISCUSSION... DEEP LAYERED TROUGHING OVER NE WATERS AND INTO THE SW U.S. AND NW MEXICO IS BEGINNING TO WEAKEN. THE ASSOCIATED SURFACE COLD FRONT FROM 30N125W TO 28N130W TO 26N140W WAS DISSIPATING AT 0600 UTC. THE FORECAST CALLS FOR THE 120 KT UPPER JET ON THE W SIDE OF THE TROUGH TO WEAKEN AND BECOME MORE ZONAL OVER THE NEXT FEW DAYS AS THE TROUGH TURNS NEGATIVE TILT AND PUSHES NE INTO ROCKIES. THIS MORE ZONAL FLOW ALOFT WILL QUICKLY CARRY THE NEXT SYSTEM EASTWARD FROM THE CENTRAL PACIFIC...WITH ITS COLD FRONT EXPECTED TO GRAZE NW WATERS OVERNIGHT WED NIGHT AS IT WEAKENS. THIS COLD FRONT WILL SHOVE THE DOWNSTREAM RIDGE CURRENTLY BUILDING BEHIND THE DISSIPATING COLD FRONT OVER NE WATERS EASTWARD TOWARD THE COAST. THE TIGHTENING PRES GRADIENT BETWEEN THIS RIDGE AND TROUGHING OVER THE SOUTHERN PLAINS AND NE MEXICO WILL ALLOW NW TO N WINDS TO INCREASE ALONG THE W COAST OF BAJA CALIFORNIA. SHIP DGDD REPORTED 20 KT WINDS AS ITS TREKKED ALONG THE COAST FROM 25N-27N SINCE 1800 UTC AND WINDS ARE EXPECTED TO CONSISTENTLY REACH 25 KT WED WITH SEAS BUILDING TO 8 FT IN NW SWELL. RIDGING WILL BUILD OVER NW WATERS TODAY AND CONTINUE FURTHER ON WED AS A 1029 MB HIGH MOVES IN BEHIND THE SECOND COLD FRONT. LOOK FOR TRADE WINDS TO EXPAND BOTH N AND E OVER THE NEXT FEW DAYS AS A RESULT OF THE INCREASED PRES GRADIENT BETWEEN THE BUILDING SUBTROPICAL HIGH AND THE ITCZ TO THE S. AN UPPER LEVEL ANTICYCLONE IS CENTERED NEAR 12N100W WITH A BROAD RIDGE AXIS EXTENDING FROM SE TO THE NW COAST OF COSTA RICA. SCATTERED MODERATE CONVECTION CAN BE FOUND WITHIN 60 NM OF THE COAST JUST N OF THE RIDGE FROM 10N TO 14N. THE RIDGE ALSO EXTENDS SW OF THE ANTICYCLONE CENTER TOWARD 08N110W...JUST E OF THE DIFFLUENT REAR RIGHT QUADRANT OF A BRANCH OF THE SOUTHERN STREAM UPPER JET THAT LIES FROM CENTRAL MEXICO NEAR 23N102W TO 10N118W. THE DIFFLUENCE IS SUPPORTING CONVECTION ALONG THE ITCZ E OF THE AFOREMENTIONED LOW AND TROPICAL WAVE EMBEDDED IN THE ITCZ NEAR 116W. THE PRIMARY SOUTHERN STREAM JET EXTENDS FROM CENTRAL MEXICO TO 19N115W AND THEN ALONG 19N TO 140W WITH CORE WINDS OF 60-80 KT. BOTH THE PRIMARY JET AND ITS BRANCH FARTHER E ARE ADVECTING CONVECTIVE DEBRIS FROM THE ITCZ TO THE NE OVER CENTRAL MEXICO. CROSS-EQUATORIAL LONG-PERIOD SW SWELL UP TO 9 FT IS PROPAGATING INTO SOUTHERN WATERS PRIMARILY BETWEEN 110W AND 132W THIS MORNING AND WILL EXPAND DURING THE NEXT FEW DAYS. S TO SW SWELL IN THE 17-20 SECOND RANGE WILL REACH THE ENTIRE LENGTH OF COAST WITHIN FORECAST WATERS DURING THE NEXT 24-48 HOURS...BUT SEAS ABOVE 8 FT WILL BE RESTRICTED TO S OF 12N W OF 92W. $$ SCHAUER