000 AXPZ20 KNHC 091548 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1605 UTC SUN DEC 09 2012 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL ANALYSIS. BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1545 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS W FROM THE COAST OF COLOMBIA AT 08N77W ACROSS THE SOUTHERN COASTS OF PANAMA AND COSTA RICA TO 09N84W...THEN TURNS SW TO 08N88W WHERE LOW LEVEL WINDS INDICATE A TRANSITION TO AN ITCZ. THE ITCZ CONTINUES W ALONG 08N TO 110W...BUT IS INTERRUPTED BY AN EMBEDDED TROUGH THAT EXTENDS FROM 07N100W TO 11N96W...AND ALSO INTERRUPTED A SECOND TROUGH THAT EXTENDS FROM 10N115W TO 14N110W. THE ITCZ BECOMES DEFINED AGAIN AT 12N115W...AND CONTINUES SW TO BEYOND 07N140W. SCATTERED STRONG CONVECTION WITH FREQUENT LIGHTING RECENTLY FLARED ALONG THE MONSOON TROUGH WITHIN 60 NM OF 06N78W...WITH NEW ACTIVITY NOW DEVELOPING AT 04.5N80W. ISOLATED MODERATE TO STRONG CONVECTION FLARES INTERMITTENTLY ALONG THE EASTERNMOST TROUGH THAT IS EMBEDDED WITHIN THE ITCZ...ROUGHLY WITHIN 90 NM OF 09N96W. SIMILAR CONVECTION IS OBSERVED ALONG THE W SEGMENT OF THE ITCZ...WITHIN 45 NM EITHER SIDE OF A LINE FROM 14N108W TO 10N125W AND A SECOND LINE FROM 08N131W TO 09N140W. THE ARRAY OF MODEL GUIDANCE SUGGESTS THAT A SURFACE LOW WILL DEVELOP ALONG THE EASTERNMOST TROUGH EMBEDDED IN THE ITCZ NEAR 100W. SCATTEROMETER DATA AND NIGHT CHANNEL IMAGERY CONFIRMS A NE-SW TROUGH IN CONTRAST TO CLOSED SURFACE LOW. ALTHOUGH A LOW CENTER MAY CLOSE OFF AT LEAST INTERMITTENTLY...A HOSTILE UPPER ENVIRONMENT IS PRESENT TO THE W OF 100W. SINCE THIS TROUGH/LOW PRES IS LIKELY TO GENERATE ONLY NE-E-SE WINDS AT 15-20 KT AND ONLY OVER ITS NORTHERN PERIPHERY WITH SEAS ONLY TO 5-7 FT...IT IS NOT MENTIONED IN THE TEXT HIGH SEAS...BUT WILL BE DEPICTED ON THE MARINE FACSIMILE CHARTS. ...DISCUSSION... ALOFT...A LONGWAVE UPPER RIDGE DOMINATES THE EASTERN N PACIFIC. AN UPPER SHORTWAVE TROUGH DISSECTS N AMERICA CONTINUING INTO THE DISCUSSION AREA ALONG 32N114W TO 26N130W TO A SMALL UPPER CYCLONE AT 24N140W. THE UPPER TROUGH IS MERGING WITH THE REMNANTS OF ANOTHER UPPER TROUGH OVER THE ENTIRE AREA N OF 10N BETWEEN 116-130W. AN UPPER ANTICYCLONE IS OVER THE DEEP TROPICS AT 08N140W WITH A SHORTWAVE RIDGE EXTENDING N TO A CREST AT 23N140W. UPPER DEBRIS MOISTURE...ORIGINATING FROM THE ITCZ RELATED CONVECTION DESCRIBED BETWEEN 131-140W...AND CONVECTION W OF AREA BETWEEN 140-160W...IS ADVECTED NE BUT MOST OF THE MOISTURE REMAINS WITHIN THE ANTICYCLONIC ENVELOPE TO THE S OF 21N W OF 130W. AN UPPER ANTICYCLONE IS QUASI-STATIONARY OVER THE DEEP TROPICAL PACIFIC AT 09N91W WITH AN UPPER RIDGE EXTENDING N-NW TO A GENTLE CREST FROM 25N110W TO BEYOND 32N103W. A DENSE MOISTURE PLUME IS OBSERVED OVER THE NE PORTION OF THE DISCUSSION AREA WITHIN 90 NM OF A LINE FROM 26N130W TO 27N119W TO BEYOND 32N104W. DEBRIS MOISTURE FROM ITCZ CONVECTION AND THE EMBEDDED LOW LEVEL TROUGH EXTENDING FROM 10N115W TO 14N110W...IS ADVECTED N ALONG THE NW PERIPHERY OF THE UPPER RIDGE...ROUGHLY WITHIN 210 NM OF A LINE FROM THE PACIFIC AT 15N108W TO ACROSS NORTHERN MEXICO...THEN TURNING E ACROSS THE NORTHERN GULF OF MEXICO AND ACROSS FLORIDA...EVENTUALLY FEEDING INTO THE CONVECTION FLARING OVER THE ATLANTIC N OF BERMUDA. IN CONTRAST...THE UPPER LEVELS APPEAR VERY DRY OVER THE DISCUSSION AREA S OF 17N E OF 102W... CONTINUING TO SUPPRESS CONVECTION EXCEPT FOR THE SMALL CLUSTERS PREVIOUSLY MENTIONED NEAR 06N78W AND ALONG THE EASTERNMOST TROUGH EMBEDDED IN THE ITCZ AT 99W. AT THE LOW LEVELS...A 1011 MB SURFACE LOW IS ANALYZED OVER THE NORTHERN GULF OF CALIFORNIA. THE LOW WILL LIFT EASTWARD DRAGGING A COLD FRONT S ACROSS THE EXTREME NE WATERS...INCLUDING THE GULF OF CALIFORNIA THIS AFTERNOON. THIS WILL RESULT IN WINDS BECOMING N-NE 10-15 KT ALONG THE W COAST OF THE BAJA PENINSULA TONIGHT INTO MON. LIGHT AND VARIABLE WINDS CURRENTLY OVER THE NORTHERN GULF OF CALIFORNIA TODAY WILL BECOME NW 20-30 KT BEHIND THE FRONT TONIGHT...THEN DIMINISH TO 15-25 KT WITH THESE CONDITIONS SPREADING S ACROSS THE ENTIRE GULF THROUGH MON NIGHT. EXPECT SEAS MAY BUILD TO 5-8 FT BRIEFLY IN THE NORTHERN GULF WATERS MON IN THE AREAS OF LONG NW FETCH...AND 3-6 FT IN THE SOUTHERN GULF WATERS BY LATE MON NIGHT. THESE NW WINDS SHOULD DIMINISH TO 10-15 KT OVER THE WATERS S OF 29N ON TUE NIGHT...AND BECOME LIGHT AND VARIABLE OVER THE WATERS N OF 29N. OVER THE PACIFIC A SURFACE RIDGE EXTENDS FROM 32N135W TO 16N103W. NORTHEASTERLY 15-20 KT SURFACE WINDS ARE OBSERVED W OF LINE FROM 32N121W TO 08N140W...WITH COMBINED SEAS 6-9 FT IN NE SWELL THAT IS MIXING WITH N SWELL IN THE WATERS N OF 25N E OF 130W. THE SEAS ARE EXPECTED TO INCREASE BRIEFLY TO 9-10 FT OVER THE WATERS N OF 28N W OF 134W TONIGHT. THE GRADIENT WILL RELAX ON MON AND TUE WITH A COLD FRONT EXPECTED TO MOVE INTO THE N CENTRAL WATERS ON TUE NIGHT...PASSING ACROSS THE NORTHERN BAJA PENINSULA ON THU ACCOMPANIED BY A 15-20 KT SW-W-NW WIND SHIFT. SEAS WILL BUILD TO 7-10 FT BEHIND THE FRONT WITH THESE CONDITIONS ARRIVING AT THE NORTHERN BAJA CALIFORNIA PENINSULA ON FRI. WINDS WILL BECOME SOUTHERLY AT 5-10 KT OVER THE NORTHERN GULF OF CALIFORNIA ON WED...INCREASING TO 15-20 KT WED EVENING...BECOMING S-SW AT 20-30 KT LATE WED NIGHT IN ADVANCE OF THE COLD FRONT PASSING ACROSS THE NORTHERN GULF OF CALIFORNIA WATERS LATE THU NIGHT. GAP WINDS... GULF OF TEHUANTEPEC...A COLD FRONT WILL ENTER THE NW GULF OF MEXICO LATE SUN NIGHT. THE ASSOCIATED NORTHERLY WINDS WILL SURGE AT 15-20 KT THROUGH THE CHIVELA PASS TUE NIGHT...GRADUALLY INCREASING WED...REACHING GALE FORCE LATE WED...WITH MINIMAL GALE CONDITIONS EXPECTED TILL A FEW HOURS AFTER SUNRISE ON THU. NOTE THAT MODEL GUIDANCE HAS BEEN FLUCTUATING ON THE STRENGTH OF THIS NEXT TEHUANTEPEC EVENT. THE SEA SURFACE AND MARINE LAYER IN/DOWNSTREAM OF THE GULF OF TEHUANTEPEC REMAINS COOLER THAN THE SURROUNDING AREAS TO THE E AND W. SINCE THE LOW LEVEL WINDS ARE FORECAST TO REMAIN LIGHT AT 5-10 KT FROM THE S-SW THROUGH MON NIGHT...WOULD EXPECT THE COOLER OCEANIC AND ATMOSPHERIC ENVIRONMENT TO MAINTAIN SOMEWHAT. THUS WOULD EXPECT THE MAXIMUM SEA HEIGHTS ON WED TO BE SIGHTLY LESS THAN THE PREVIOUS TEHUANTEPEC EVENTS. GULF OF PAPAGAYO...NE WINDS WILL CONTINUE TO PULSE AT 10-15 KT WITH AN OCCASIONAL SURGE TO 15-20 KT VERIFIED BY LATEST SCATTEROMETER PASSES...IN AND DOWNSTREAM OF THE GULF OF PAPAGAYO THROUGH THE MIDDLE OF NEXT WEEK...WITH GUIDANCE SUGGESTING AN INCREASE TO 20-25 KT BEGINNING LATE WED NIGHT. $$ NELSON