000 AXPZ20 KNHC 181007 CCA TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC WED MAR 18 2009 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 0900 UTC. ...ITCZ... THE ITCZ AXIS LIES ALONG A LINE FROM 03N79W TO 04.5N90W TO 02N104W THEN SOMEWHAT DIFFUSE TO 02N119W CONTINUING MORE WELL DEFINED TO 08N140W. ISOLATED SHALLOW TO MODERATE CONVECTION WAS WITHIN 60 NM OF AXIS BETWEEN 84W AND 91W...AND BETWEEN 121W AND 127W. SCATTERED TO NUMEROUS MODERATE AND ISOLATED STRONG CONVECTION WAS WITHIN 90 NM OF AXIS W OF 135W. ...DISCUSSION... THE UPPER LEVEL PATTERN ACROSS THE NE PACIFIC FEATURES A ZONALLY-ELONGATED POLAR JET STREAM THAT EXTENDS FROM THE CENTRAL PACIFIC REGION EWD...AND N OF 38N...INTO THE NORTHERN ROCKIES OF THE CONUS. THE CORRESPONDING VERTICAL SHEAR IS ASSOCIATED WITH A STATIONARY FRONT THAT REMAINS WELL N OF THE DISCUSSION AREA. HOWEVER...THE UPPER LEVEL FLOW N OF THE REGION IS FORECAST TO AMPLIFY LATER THIS WEEK...AS A SHORTWAVE TROUGH CURRENTLY OVER THE GULF OF ALASKA DIVES SOUTHEASTWARD. IN RESPONSE...THIS STATIONARY FRONT WILL BE FORCED SOUTHWARD BY FRIDAY...WITH A WEAKENING COLD FRONTAL BOUNDARY EXPECTED TO APPROACH NORTHWEST PORTIONS OF THE DISCUSSION AREA BY SATURDAY. WHILE THE WIND IMPACT FROM THIS SYSTEM WILL BE RELATIVELY MINIMAL THROUGH SATURDAY...A BROAD SPECTRUM OF NORTHWESTERLY SWELL WILL INVADE THE FAR NW AND N WATERS SAT THROUGH SUN...RAISING WAVE HEIGHTS IN EXCESS OF 11 FT...AND BUILD FURTHER THROUGH MONDAY. S OF THIS ZONAL JET LIES A COMPLEX HIGH AMPLITUDE RIDGE-TROUGH RIDGE PATTERN SPANNING FROM 160W TO 70W. A DEEP LAYERED LOW LINGERING N OF THE HAWAIIAN ISLAND CHAIN THE PAST SEVERAL DAYS HAS MOVED OVER THE WRN MOST RIDGE AND WAS ALONG 140W N OF 25N...WITH A SECOND S/W TROUGH DOWNSTREAM ALONG 120W APPROACHING BAJA CALIFORNIA AND COMING INTO PHASE WITH THE HIGH AMPLITUDE TROUGH JUST W OF 120W. A BROAD ZONE OF UPPER LEVEL DIVERGENCE WAS ACTING TO ENHANCE AREAS OF SCATTERED MODERATE TO DEEP CONVECTION BETWEEN 05N AND 15N FROM 120W TO 140W...WHERE NE TO ELY WINDS OF 20-25 KT WERE CONVERGING WITH WEAKER LOW LEVEL ELY FLOW ACROSS THE TROPICAL BELT. THE DEEPEST AND MOST PERSISTENT CONVECTION ACROSS THIS AREA HAS CONTINUED HERE FOR THE PAST TWO DAYS ALONG THE NRN PORTIONS OF A STRONG MOISTURE GRADIENT. THIS AREA WILL LIKELY REMAIN CONVECTIVELY ACTIVE FOR ANOTHER 24-36 HOURS AS THE UPPER LEVEL DYNAMICS AND DIVERGENCE SHIFT EWD. A 1028 MB SURFACE HIGH WAS CENTERED N OF THE AREA NEAR 34N131W...WITH THE ENHANCED SURFACE PRESSURE GRADIENT AT THE SOUTHERN PERIPHERY OF THIS FEATURE ENHANCING NE TO E TRADES ACROSS THE REGION...AND CONTRIBUTING TO THE BROAD LOW LEVEL CONVERGENCE ZONE DISCUSSED ABOVE. OLD NWLY SWELL CONTINUES TO PROPAGATE THROUGH MOST OF THE FORECAST AREA THIS MORNING...WITH HIGHEST SEAS NEAR 11 FT LOCATED WITHIN THIS BAND OF ENHANCED NE TO E TRADES...IN A MIX OF NW AND SW SWELL AND NELY WIND WAVES. AS THE UPPER FLOW N OF THE AREA AMPLIFIES...THE SURFACE HIGH IS EXPECTED TO WEAKEN DURING THE NEXT FEW DAYS. IN RESPONSE...TRADE WINDS WILL SLACKEN...WITH SEAS GRADUALLY SUBSIDING. GAP WINDS... SURFACE HIGH PRESSURE BUILDING SOUTHWARD OVER EASTERN MEXICO IN THE WAKE OF A FRONT OVER THE GULF OF MEXICO IS SUPPORTING A RELATIVELY STRONG SURFACE PRESSURE GRADIENT ACROSS THE ISTHMUS OF TEHUANTEPEC...WITH STRONG N TO NE WINDS FUNNELING INTO THE GULF OF TEHUANTEPEC. COMPUTER MODEL GUIDANCE AND RECENT SCATTEROMETER PASSES INDICATE THAT WINDS IN THIS REGION HAVE DIMINISHED BELOW GALE FORCE...BUT WERE STILL IN THE 20-30 KT RANGE PRIOR TO 06Z. THUS THE GALE WARNING FOR THE GULF OF TEHUANTEPEC HAS EXPIRED. ALSO...TRADE WINDS ACROSS THE CARIBBEAN CONTINUE WITH A PERSISTENT SURFACE LOW OVER NW COLOMBIA. THESE WINDS CONTINUE TO BLEED INTO THE GULFS OF PANAMA AND PAPAGAYO. GAP WINDS OF AROUND 20 KT IN THE GULFS OF TEHUANTEPEC AND PAPAGAYO ARE FORECAST TO CONTINUE PERIODICALLY DURING THE NEXT FEW DAYS...WITH THE STRONGEST WINDS EXPECTED LATE AT NIGHT WHEN DRAINAGE FLOW OFF HIGHER TERRAIN IS MAXIMIZED IN THE PRESENCE OF DEEP LAYER DRY AIR. HOWEVER...WINDS IN THE GULF OF PANAMA ARE EXPECTED TO FLUCTUATE AROUND 20 KT THROUGH 24 HOURS BEFORE DIMINISHING BY 48 HOURS...WHEN THE SURFACE RIDGING OVER THE CARIBBEAN WEAKENS AND THE SURFACE LOW OVER NW COLOMBIA FILLS. $$ STRIPLING