000 AXPZ20 KNHC 180343 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 0405 UTC SAT DEC 18 2010 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 0300 UTC. ...ITCZ... INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS ALONG 08N82W TO LOW PRES NEAR 07N89W TO LOW PRES NEAR 10N110W TO 07N125W TO 12N135W TO 10N140W. NO SIGNIFICANT CONVECTION NOTED. ...DISCUSSION... W OF 110W... ZONAL FLOW ALOFT PERSISTS OF 28N BETWEEN AN UPPER RIDGE ALONG 130W N OF 20N...AND AN UPPER LOW WELL N OF THE AREA. A SHORT WAVE TROUGH PIVOTING AROUND THE UPPER LOW IS PUSHING A COLD FRONT INTO THE DISCUSSION AREA...EXTENDING FROM 33N132W TO 30N138W TO 29N140W. A 1934Z ASCAT PASS SHOWED FRESH SW FLOW E OF THE FRONT N OF 29N. THE FRONT WILL REACH FROM 30N130W TO 26N140W BY SAT MORNING...THEN WILL MAKE SLOW PROGRESS SUN INTO MON AS THE UPPER SUPPORT LIFTS OUT...REACHING 20N127W TO 26N140W. LOOKING AHEAD...ANOTHER SHORT WAVE TROUGH WILL PIVOT INTO THE AREA ON MON...GIVING THE STALLING FRONT A REINFORCING SHOT OF COLD AIR AND ADVANCING THE FRONT EASTWARD. MEANWHILE A RELATIVELY WEAK 1019 MB SURFACE HIGH WILL REMAIN IN PLACE NEAR 23N123W. S OF THE RIDGE...A TROUGH ALONG THE ITCZ 15N134W TO 10N135W. GIVEN THE WEAK PRES GRADIENT BETWEEN THE HIGH PRES AND THE LOW PRES AREA...NE TRADE WIND FLOW REMAINS MODEST. FURTHER SOUTH...AN ASCAT PASS FROM 18Z ALONG WITH SHIP AND TOGA-TAO BUOY DATA INDICATED FRESH SE CROSS-EQUATORIAL FLOW WITH 8 FT SE SWELL S OF 06N W OF 130W. MODELS INDICATED THIS WILL PERSIST OVER THE NEXT 48 HOURS BUT DIMINISH IN AREAL COVERAGE. E OF 110W... A WEAK LOW PRES AREA IS NOTED ALONG THE ITCZ...NEAR 07N89W WITH AN ESTIMATED PRES AROUND 1011 MB. THE GFS RUN CONTINUES TO SHOW SW WINDS INCREASING TO 30 KT BY SAT NIGHT...BUT THIS AGAIN MAY BE OVERDONE DUE TO CONVECTIVE FEEDBACK. THE 12Z ECMWF IS LESS AGGRESSIVE WITH THIS LOW SHOWING WINDS TO 20 KT SAT. THE 12Z UKMET INITIALIZED WITH THE LOW...BUT SHOWS IT FILLING THROUGH 24 HOURS. FORECAST WILL REFLECT A BLEND OF THE GFS AND ECMWF...FAVORING THE ECMWF. FURTHER EAST...NORTHERLY GAP WIND FLOW APPEARS TO BE DIMINISHING THROUGH THE GULF OF PANAMA. THE GFS IS INDICATING INCREASED SW FLOW OFF COLOMBIA SAT AS LOW PRES DEVELOPS OVER NW COLOMBIA. FURTHER NORTH...NORTHERLY WINDS WILL INCREASE THROUGH THE GULF OF TEHUANTEPEC SAT NIGHT AS A WEAK COLD FRONT MOVES THROUGH THE SW GULF OF MEXICO THROUGH THE TEHUANTEPEC ISTHMUS. GLOBAL MODELS SHOW FAIRLY MODEST AND SHORT LIVED GAP WIND FLOW THROUGH EARLY SUN WITH WINDS OF 20 TO 25 KT...DIMINISHING SUNDAY. SEA SURFACE TEMPERATURES REMAIN FAIRLY COOL OVER THE GULF OF TEHUANTEPEC DUE TO UPWELLING FOLLOWING A GALE EVENT THAT ENDED ON TUE...SO GAP WIND FLOW MAY NOT EFFICIENTLY MIX TO THE SURFACE WITH THE NEXT ROUND OF WINDS. $$ CHRISTENSEN