000 AXPZ20 KNHC 181601 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 1605 UTC THU DEC 18 2008 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... INTERTROPICAL CONVERGENCE ZONE IS CENTERED ALONG...07N76W TO 06N88W TO 08N101W TO 09N116W TO 06N140W. SCATTERED MODERATE 45 NM EITHER SIDE OF LINE FROM 08N139W TO 08N131W. SCATTERED TO NUMEROUS ISOLATED STRONG WILL PERSIST NEXT 12 HOURS FROM 07N122W TO 06N106W...AND EXTENDS AS FAR N AS 17N ALONG 112W. 05N77W TO 06N94W TO 07N106W TO 10N117W TO 07N127W TO 06N140W. SCATTERED MODERATE FROM 07N TO 11N BETWEEN 109W AND 122W. ...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 150W...A LONGWAVE UPPER TROUGH FROM THE ROCKIES SW INTO THE TROPICS ALONG 08N132W...AND AN UPSTREAM RIDGE ACROSS CENTRAL AMERICA AND THE GULF OF MEXICO. A SURFACE COLD FRONT ASSOCIATED WITH THE LONGWAVE TROUGH EXTENDS FROM A 1004 MB SURFACE LOW IN NW ARIZONA TO THE CENTRAL GULF OF CALIFORNIA AND ACROSS CENTRAL BAJA NEAR 27N113W AND THEN CONTINUES SW AND THEN W INTO THE SUBTROPICAL EPAC TO NEAR 19N133W. NW TO N WINDS OF 25 TO 30 KT IN THE WAKE OF THE COLD FRONT OFFSHORE OF S CALIFORNIA AND THE BAJA ARE SLOWLY ABATING LATE THIS MORNING TO LESS THAN 30 KT AS THE SURFACE LOW CONTINUES TO SLOWLY LIFT NE AWAY FROM THE REGION. NORTHERLY SWELL GENERATED BEHIND THE FRONT CONTINUES TO PROPAGATE S ACROSS THE EQUATORIAL ZONE AND WILL FADE SLIGHTLY E OF 130W DURING THE NEXT 12 HOURS BEFORE ANOTHER PULSE OF LARGE NW SWELL ENTERS THE AREA THIS EVENING THROUGH TONIGHT. SHIP OBSERVATION AND WAVE WATCH GUIDANCE SUGGEST MAX WAVE HEIGHTS WELL OFFSHORE OF THE BAJA HAVE DIMINISHED 12 TO 13 FT THIS MORNING. STRONG S TO SW FLOW ALOFT BETWEEN 130W AND 110W...FROM THE ITCZ NE INTO N MEXICO...CONTINUES TO PRODUCE A FAVORABLE UPPER LEVEL ENVIRONMENT TO ENHANCE CONVECTION ACROSS THIS SAME AREA AND S OF 20N...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 WILL LIKELY PERSIST DURING THE NEXT 24 HOURS THERE AS ANOTHER WEAK EASTERLY WAVE ALONG 112W AIDS IN MAINTAINING BROAD LOW LEVEL CONVERGENCE. IN FACT...GFS GUIDANCE HAS CONTINUED TO SUGGEST THE DEVELOPMENT OF A BROAD LOW LEVEL TROUGH OR EVEN SURFACE LOW BETWEEN 125W AND 120W DURING THE 48 TO 72 HOUR TIME FRAME. THIS IS FORECAST TO OCCUR IN RESPONSE TO SHORT WAVE ENERGY ACROSS THE CENTRAL PACIFIC DIVING INTO THE BACKSIDE OF LONG WAVE EPAC UPPER TROUGH AND DEVELOPING A VIGOROUS CUTOFF LOW NEAR 24N132W BY 48 HOURS...THAT THEN WILL RETROGRADE SW. THIS SCENARIO WILL MAINTAIN VERY ACTIVE ITCZ CONVECTION ACROSS THIS REGION...MODULATING AND EXTENDING NE ACROSS THE EPAC WARM SST RIDGE...TO WITHIN 200 NM OF THE S TIP OF THE BAJA. NORTHEASTERLY TRADE WINDS OF 20 TO 25 KT CONTINUE ACROSS THE W CENTRAL PORTIONS OF THE AREA BASED ON A RECENT SCATTEROMETER PASSES. THIS AREA IS FORECAST TO MERGE WITH AN AREA OF 20-30 KT WINDS IN THE NEXT 48 HOURS IN RESPONSE TO A TIGHTENING PRESSURE GRADIENT. MODERATE GAP WINDS OF 20 TO 25 KT...WITH SMALL AREAS UP TO 30 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. $$ STRIPLING