000 AXPZ20 KNHC 182205 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 2205 UTC THU DEC 18 2008 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 2145 UTC. ...ITCZ... INTERTROPICAL CONVERGENCE ZONE IS CENTERED ALONG...5N78W 5N90W 5N100W 7N110W 8N121W 6N131W 5N140W. SCATTERED MODERATE CONVECTION IS WITHIN 120 NM S OF THE AXIS BETWEEN 112W-117W. ...DISCUSSION... UPPER LEVEL PATTERN IS CHARACTERIZED BY AN OMEGA BLOCK FROM THE CENTRAL PACIFIC TO WESTERN N AMERICA...WITH A HIGHLY AMPLIFIED UPPER RIDGE W OF THE AREA 150W...A LONGWAVE UPPER TROUGH FROM THE ROCKIES SW INTO THE AREA THROUGH 32N127W TO 24N133W TO THE DEEP TROPICS TO WEAK UPPER LEVEL LOW NEAR 11N131W. TO THE E OF THE TROUGH...MID/UPPER LEVEL RIDGING EXTENDS FROM THE WESTERN GULF OF MEXICO WSW ALONG 19N103W TO 15N113W TO 12N126W. A SURFACE COLD FRONT ASSOCIATED WITH THE LONGWAVE TROUGH EXTENDS FROM NEAR THE FAR WESTERN TEXAS PANHANDLE SW ACROSS SOUTHERN BAJA CALIFORNIA TO 21N117W WHERE IT BECOMES DIFFUSE TO 20N123W. BEHIND THE FRONT NW-N WINDS OF 20 KT ARE PRESENTLY OCCURRING...BUT ARE FORECAST TO DIMINISH TO NE 20 KT IN ABOUT 24 HOURS AND BECOME CONFINED TO THE AREA N OF 18N BETWEEN 117W-125W IN 48 HOURS AS THE FRONT DISSIPATES. MAIN MARINE IMPACT WILL CONTINUE TO BE NLY SWELLS UP TO 13 FT THAT ARE TRAINING SWD BEHIND THE FRONT TOWARDS THE EQUATORIAL ZONE. WAVEWATCH GUIDANCE SUGGESTS THAT THESE SWELLS WILL SLOWLY DECAY THROUGH THE NEXT 24-30 HOURS AS YET ANOTHER COLD FRONT NOW ENTERING THE NW CORNER OF THE AREA QUICKLY PUSHES TO ALONG 30N135W TO 26N140W IN 24 HOURS THEN FADES TO A FRONTAL TROUGH IN 36-48 HOURS. SW WINDS OF 20-25 KT ARE EXPECTED AHEAD OF THE FRONT...BUT LATEST WAVE GUIDANCE SHOWS SEAS BUILDING TO ABOUT 8 OR 9 FT. STRONG S TO SW FLOW ALOFT GENERALLY BETWEEN 110W AND 130W STREAMING FROM THE ITCZ NE TOWARDS BAJA CALIFORNIA AND NORTHERN MEXICO CONTINUES TO SUPPORT A FAVORABLE UPPER LEVEL ENVIRONMENT ENHANCING CONVECTION WITHIN THIS AREA WHERE CIMSS TPW LOOPS SHOW AMPLE MOISTURE CONVERGING DUE TO PROGRESSIVE EASTERLY FLOW IN THE TROPICAL EPAC...AND NORTHERLY FORCING FROM THE COLD FRONTAL ZONE INTRUDING S INTO THE SUBTROPICS. CONVECTION IS LIKELY TO PERSIST DURING THE NEXT 24 HOURS THERE AS ANOTHER WEAK EASTERLY WAVE ALONG 115W AIDS IN MAINTAINING BROAD LOW LEVEL CONVERGENCE. IN FACT...GFS GUIDANCE CONTINUES TO SUGGEST THE DEVELOPMENT OF A BROAD LOW LEVEL TROUGH OR EVEN SURFACE LOW BETWEEN 118W AND 125W DURING THE NEXT 2 TO 3 DAYS. THIS IS MOST PROBABLY DUE TO OCCUR IN RESPONSE TO SHORT WAVE ENERGY ACROSS THE CENTRAL PACIFIC DIVING INTO THE BACKSIDE OF THE LONGWAVE UPPER TROUGH AND DEVELOPING A VIGOROUS CUTOFF LOW NEAR 22N132W BY 48 HOURS...AND THEN RETROGRADE SW. THIS SCENARIO WILL MAINTAIN VERY ACTIVE ITCZ CONVECTION ACROSS THIS REGION...MODULATING AND EXTENDING NE ACROSS THE EPAC WARM SST RIDGE TO NEAR THE SOUTHERN TIP OF BAJA CALIFORNIA. NE TRADES OF 20-25 KT CONTINUE ACROSS THE W CENTRAL SECTION OF THE AREA FROM 9N-21N W OF 119W AS VERIFIED BY QUIKSCAT DATA FROM NEAR 1400 UTC THIS MORNING. THIS AREA IS FORECAST TO MERGE WITH THE AREA OF N-NE WINDS OF 20-25 KT N OF 18N BETWEEN 117W-125W IN THE NEXT 48 HOURS IN RESPONSE TO A TIGHTENING PRESSURE GRADIENT. MODERATE GAP WINDS OF 20 TO 25 KT CONTINUE ACROSS AND DOWNSTREAM OF THE GULFS OF TEHUANTEPEC...PAPAGAYO...AND PANAMA...AS COOLER AND DRIER MODIFIED AIR HAS MOVED FROM THE SW AND W ATLC...ACROSS THE CARIBBEAN...AND ACROSS CENTRAL AMERICA...ASSOCIATED WITH LINGERING CENTRAL ATLANTIC UPPER TROUGH. SEAS DOWNSTREAM OF THESE GULFS REMAIN JUST UNDER 8 FEET...WITH VERY SLIGHT IMPROVEMENT DURING THE NEXT 24 HOURS. MODERATE S TO SE TRADE WINDS WILL CONTINUE FROM S OF THE ITCZ TO THE EQUATOR...WITH SEAS 6 FT AND LESS IN MERGING LONG PERIOD SWELL FROM BOTH HEMISPHERES. PERSISTENT MODERATE GAP FLOW THROUGH THE GULF OF PANAMA CONTINUES MAINTAIN GOOD CONVERGENCE ALONG THE ITCZ ALONG THE COAST OF COLUMBIA...WITH CONVECTION THERE EXPECTED TO REMAIN ACTIVE DURING THE NEXT 24 HOURS. $$ AGUIRRE