000 AXPZ20 KNHC 300953 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC SUN DEC 30 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0945 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS NW FROM THE COLOMBIAN COAST AT 07N77W TO ALONG THE PACIFIC COAST OF COSTA RICA TO 08N84W...THEN TURNS W ALONG 08N TO 100W WHERE LOW LEVEL WINDS INDICATE A TRANSITION TO AN ITCZ. THE ITCZ THEN CONTINUES W TO 08N110W...TURNS NW TO 09N121W...THEN SW TO BEYOND 06N140W. SCATTERED MODERATE ISOLATED STRONG CONVECTION...ACCOMPANIED BY OCCASIONAL LIGHTNING...IS NOTED WITHIN 90 NM OF 07N79W AND 09.5N98W...AND WITHIN 30 NM OF 05N85W. SIMILAR CONVECTION IS OBSERVED WITH 60 NM EITHER SIDE OF A LINE FROM 11N105W TO 10N119W. ISOLATED MODERATE TO STRONG CONVECTION CONTINUES TO FLARE WITHIN 150 NM EITHER SIDE OF A LINE FROM 13.5N114W TO 09N127W. THE ITCZ CONTINUES TO STRETCH N TO NEAR 09N121W. RECENT NIGHT CHANNEL SATELLITE IMAGERY AND SCATTEROMETER DATA INDICATE THAT THE SURFACE LOW HAS NOT DEVELOPED IN THAT AREA...BUT A WEAK INVERTED TROUGH CONTINUES NE FROM THE ITCZ AT 09N12W TO NEAR 15N116W. THE NORTHERN EXTREME OF THIS TROUGH WILL MERGE WITH THE SOUTHERN EXTENT OF A FRONTAL TROUGH AS IT PASSES THROUGH THE GULF OF CALIFORNIA TONIGHT. THIS TROUGH WILL THEN PERSIST FOR A COUPLE OF DAYS ACCOMPANIED BY A NE-E-SE 10-15 KT WIND SHIFT ALONG THE TROUGH AXIS. ...DISCUSSION... ALOFT...A VIGOROUS UPPER TROUGH EXTENDS ACROSS THE DISCUSSION AREA FROM 32N120W TO A BASE OVER THE DEEP TROPICS AT 09N137W. AN UPPER RIDGE AXIS IS OVER THE FAR NW PORTION WITH UPPER MOISTURE SPILLING ACROSS THE RIDGE AXIS OVER THE AREA N OF 26N W OF 136W. OTHERWISE VERY DRY UPPER AIR IS INDICATED W OF THE TROUGH AXIS. UPPER LEVEL ANTICYCLONES ARE CENTERED OVER COLOMBIA AT 07N72W AND OVER THE NW CARIBBEAN AT 18N82W. AN UPPER RIDGE EXTENDS NW THROUGH THESE ANTICYCLONES ACROSS OLD MEXICO AND NEW MEXICO EVENTUALLY CRESTING WELL N OF THE AREA OVER THE DAKOTAS. BROAD ANTICYCLONIC UPPER WESTERLY FLOW IS OBSERVED OVER THE DEEP TROPICS S OF 07N BETWEEN 118-133W AND COMBINES WITH THE LARGE UPPER TROUGH AND RIDGE PATTERN PREVIOUSLY DESCRIBED TO SET UP AN AREA OF WEAK UPPER DIFFLUENCE SUPPORTING THE ITCZ CONVECTION BETWEEN 110-130W. THE RESULTANT UPPER DEBRIS MOISTURE IS ADVECTED NE ALONG THE PERIPHERY OF THE RIDGE BETWEEN 106-120W... THEN THE MOISTURE FANS OUT AS IT CONTINUES NE ACROSS NORTHERN OLD MEXICO. SOME OF THE MOISTURE SPREADS N ACROSS ARIZONA AND NEW MEXICO...WHILE SOME OF THE MOISTURE TURNS E INTO A NARROW PLUME STREAMING E ACROSS THE NORTHERN GULF OF MEXICO. AN UPPER CYCLONE HAS FORMED OVER THE DEEP TROPICAL PACIFIC NEAR 06N95W WITH AN UPPER TROUGH EXTENDING E TO 05N77W. WEAK UPPER DIFFLUENCE IS INDUCED BETWEEN THIS TROUGH AND THE UPPER RIDGE DESCRIBED TO THE N OVER CENTRAL AMERICA...AND IS SUPPORTING THE CLUSTERS OF CONVECTION ALONG THE MONSOON TROUGH AS PREVIOUSLY DESCRIBED. THE SURROUNDING UPPER LEVELS ARE DRY AND THE DEBRIS MOISTURE SEEMS TO QUICKLY EVAPORATE NEAR THE DECAYING CELLS. LOW LEVELS...A SURFACE RIDGE EXTENDS SE ACROSS THE AREA FROM 32N140W TO TO 22N109W. A COLD FRONT IS WEAKENING AS IT MOVES ACROSS THE NORTHERN BAJA PENINSULA. EXPECT THE FRONT TO CONTINUE TO WEAKEN AS IT MOVES ACROSS THE GULF OF CALIFORNIA TONIGHT. ANTICYCLONIC 10-15 KT WINDS ARE OBSERVED ACROSS THE SUB-TROPICS...EXCEPT FOR A SMALL AREA OF NW 15-20 KT WINDS IN THE WAKE OF THE FRONT NEAR 29N124W. SEAS ARE 7-12 FT IN MIXING N...NE...AND NW SWELL. THE NE TRADES S OF THE SURFACE RIDGE FROM 08-22N BETWEEN 127-140W CONTINUE AT 20-25 KT WITH SEAS 9-12 FT IN MIXED NE AND NW SWELL. ELSEWHERE W OF LINE FROM 26N115W TO 15N115W TO 07N140W SURFACE WINDS ARE N TO NE AT 10-20 KT WITH SEAS 8-10 FT PRIMARILY DUE TO MIXING LONG PERIOD NE AND NW SWELL. A SURFACE HIGH WILL SHIFT S INTO THE AREA NEAR 30N130W LATE MON MAINTAINING THE NE TRADES IN THE AREA FROM 08-20N W OF 130W WITH SEAS 9-12 FT IN MIXED NE AND NW SWELL. LARGE LONG PERIOD NW SWELL WILL PROPAGATE INTO THE FAR NW PACIFIC WATERS TONIGHT DRIVING SEAS UP TO 13 FT. THESE NW SWELLS WILL CONTINUE EASTWARD BUT GRADUALLY SUBSIDE WITH SEAS OF 7-10 FT REACHING THE NORTHERN BAJA PENINSULA LATE TUE NIGHT...AND REACHING THE SOUTHERN BAJA PENINSULA LATE WED NIGHT. A COLD FRONT WILL ENTER THE WATERS NEAR 30N140W TUE NIGHT ACCOMPANIED BY A 20-25 KT SW-NW WIND SHIFT WITH SOUTHERLY GALE WINDS PRECEDING THE FRONT OVER THE WATERS N OF 31N. GULF OF TEHUANTEPEC...THE WESTERN PORTION OF A SWATH OF RECENT HIGH RESOLUTION ASCAT WINDS DETECT N-NW 35 KT WINDS OVER THE EASTERN WATERS OF THE GULF OF TEHUANTEPEC. EXPECT STRONG N FLOW W OF RECENT ASCAT SWATH...THUS A MINIMAL STORM FORCE WARNING IS IN EFFECT THROUGH MID MORNING TODAY WITH GALE FORCE CONTINUING THROUGH SUNRISE MON...WITH THE NORTHERLY WINDS DIMINISHING BELOW 20 KT LATE MON. GULF OF PAPAGAYO...NE-E 15-25 KT SURGES ARE EXPECTED TO CONTINUE AND GRADUALLY SPREAD AS FAR W AS 94W BY TONIGHT WHERE THE ASSOCIATED NE SWELLS WILL THEN MIX WITH SW CROSS EQUATORIAL SWELL AS WELL AS N SWELL PROPAGATING S FROM THE STRONG TEHUANTEPEC EVENT. GULF OF CALIFORNIA...LIGHT AND VARIABLE WINDS INDICATED EXCEPT A 15-20 KT SW-W-NW WIND SHIFT IS EXPECTED OVER THE NORTHERN WATERS AS THE WEAKENING COLD FRONT PASSES TODAY-TONIGHT. NW WINDS AT 10-15 KT EXPECTED MOST WATERS BY MON NIGHT AND INCREASING TO 20-25 KT ACROSS THE GULF WATERS N OF 25N LATE TUE. $$ NELSON