000 AXPZ20 KNHC 180955 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC SAT DEC 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 0945 UTC. ...TROPICAL LOWS... .A WELL DEFINED SURFACE LOW PRES CENTERED AT 09.5N 110W IS ESTIMATED AT 1010 MB WITH TROUGH EXTENDING NE TO 14N105W. SOUTHWESTERLY WINDS 15 TO 20 KT ARE NOTED WITHIN ABOUT 90 NM OVER THE SE QUADRANT WITH SEAS TO 8 FT. THE LOW IS EXPECTED TO MOVE TO NEAR 09N113W 1009 MB IN 24 HOURS...AND NEAR 09N116W AT 1008 MB IN 48 HOURS WITH LITTLE CHANGE IN WINDS AND SEAS. .ANOTHER PERSISTENT SURFACE LOW PRES IS CENTERED NEAR 07N89W AND ESTIMATED AT 1011 MB. SHIP REPORTS INDICATE SOUTHWESTERLY WINDS AT 15 TO 20 KT WITHIN ABOUT 180 NM OVER THE SE QUADRANT WITH SEAS TO 8 FT. THE LOW IS EXPECTED TO MEANDER IN THE SAME AREA THROUGH 48 HOURS WITH LITTLE CHANGE IN WIND AN SEAS. ...ITCZ... INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 07N77W TO LOW PRES NEAR 07N89W...TO ANOTHER LOW PRES NEAR 09N110W...WITH AXIS CONTINUING W THROUGH POINTS 07N125W...12N136W AND BEYOND 10N140W. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS MOVING OFF THE COAST OF COLOMBIA OVER THE PACIFIC WATERS N OF 02N TO THE E OF 80W. A LARGE CLUSTER OF MODERATE TO STRONG CONVECTION IS NOTED W OF THE DISCUSSION AREA NEAR 09N142W AND IS NOW SPREADING E INTO THE DISCUSSION AREA WITHIN 90 NM OF 08N140W. ISOLATED MODERATE AND STRONG CONVECTION IS FLARING WITHIN 150 NM OF 10N110W. ...DISCUSSION... UPPER ANTICYCLONES ARE CENTERED AT 13N142W AND 21N130W. AN UPPER TROUGH EXTENDS FROM 32N95W ACROSS OLD MEXICO ALONG 20N104W TO A BASE AT 10N113W. AN UPPER RIDGE EXTENDS W ACROSS THE SW CARIBBEAN AND COSTA RICA TO A CREST AT 10N90W. UPPER MOISTURE IS SPILLING ACROSS THE SUBTROPICAL RIDGE TO THE N OF 30N BETWEEN 140W AND 130W...THEN THE MOISTURE DIVES SE INTO THE UPPER TROUGH AND EVENTUALLY EVAPORATES ALONG 22N BETWEEN 120W AND 110W. MUCH DENSER MOISTURE CONTINUES E ACROSS THE UPPER RIDGE OVER THE ENTIRE SW CONUS. FURTHER S...THE ITCZ IS UNDER THE UPPER RIDGE AND IS SUPPORTING THE CONVECTION PREVIOUSLY MENTIONED NEAR 09N142W...WITH SOME OF THE DEBRIS MOISTURE SPREADING E OVER THE AREA FROM 05N TO 15N BETWEEN 130W AND 140W. UPPER DEBRIS MOISTURE ASSOCIATED WITH THE CONVECTION NEAR 10N109W QUICKLY EVAPORATES IN THE SAME AREA. DEBRIS MOISTURE IS NOTED S OF 10N E OF 83W. OTHERWISE THE UPPER LEVELS ARE VERY DRY OVER THE DISCUSSION AREA. A SURFACE COLD FRONT EXTENDS FROM 32N133W TO 29N140W ACCOMPANIED BY A 20 TO 25 KT WIND SHIFT ALONG THE FRONT WITH SEAS TO 11 FT IN NW SWELL. SEVERAL SECONDARY SURGES WILL PUSH THE NORTHERN SEGMENT OF THE FRONT E TO THE NORTHERN BAJA CALIFORNIA PENINSULA AROUND THE MIDDLE OF NEXT WEEK FOLLOWED BY SEAS TO 14 FT IN NW SWELL...BUT SUBSIDING TO ABOUT 11 FT BEFORE REACHING THE BAJA PENINSULA. A LOW LEVEL TROUGH EXTENDS FROM 09N137W TO 16N130W WITH NE TRADES TO 20 KT WITHIN 240 NM W OF TROUGH. EXPECT THE TROUGH TO CONTINUE SHIFTING W AND MOVING W OF 140W EARLY NEXT WEEK. SOUTHEASTERLY FLOW OVER THE DEEP TROPICS TO THE S OF 05N AND W OF 133W WILL SPREAD N TO ABOUT 10N W OF 125W SUN...WITH SEAS BUILDING TO 8 FT IN THE SAME AREA. GAP WINDS...A WEAK COLD FRONT WILL MOVE SE THROUGH THE WESTERN GULF OF MEXICO TONIGHT WITH 20 TO 25 KT NORTHERLY WINDS SURGING THROUGH THE CHIVELAS PASS AND INTO THE GULF OF TEHUANTEPEC AROUND LATE TONIGHT. GUIDANCE NOW SUGGESTS SOUTHERLY RETURN FLOW WILL QUICKLY BECOME ESTABLISHED OVER THE GULF OF MEXICO ON SUN DIMINISHING THE THE N WINDS IN THE GULF OF TEHUANTEPEC TO LESS THAN 20 KT SUN NIGHT. $$ NELSON