000 AXPZ20 KNHC 211001 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC SUN OCT 21 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 ACROSS SW NICARAGUA TO THE NW COAST AT 12N87W...THEN WIGGLES WESTWARD THROUGH 12N98W AND 12N112W TO 08N120W WHERE LOW LEVEL WINDS INDICATE A TRANSITION TO AN ITCZ...WHICH THEN TURNS NW TO NEAR 10N130W WHERE IT IS BRIEFLY INTERRUPTED BY A SURFACE TROUGH. THE ITCZ RESUMES SW OF THE TROUGH EXTENDING SW TO BEYOND 09N140W. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS NOTED WITHIN 60 NM OF CENTRAL AMERICAN COAST FROM COLOMBIA AT 06N78W TO COSTA RICA AT 10N86W...AND ELSEWHERE N OF 10N TO THE E OF 101W...AND ALSO WITHIN 90 NM EITHER SIDE OF A LINE FROM 08N101W TO 10N108W TO 10N115W. ...DISCUSSION... AN UPPER LEVEL RIDGE EXTENDS FROM W TO E ALONG 30N FROM 140W TO 126W. AN UPPER CYCLONE IS CENTERED AT 29N119W AND IS MOVING NE WITH TIME TRAILING AN UPPER TROUGH SW THROUGH 25N130W INTO A SECOND UPPER CYCLONE FILLING W OF THE AREA AT 20N147W. THIN UPPER MOISTURE IS OBSERVED OVER THE N SEMICIRCLE OF THE EASTERN CYCLONE...AND IS SPREADING NE ACROSS THE EXTREME NW PORTION OF THE BAJA PENINSULA THIS MORNING. EXPECT THE UPPER CYCLONE TO MOVE OVER SOUTHERN CALIFORNIA LATER TODAY THEN FILL AS IT CONTINUES ACROSS ARIZONA TONIGHT AS A NEW UPPER SHORTWAVE MOVES ACROSS THE NORTHERN PORTION OF THE AREA DRAGGING A WEAK COLD FRONT INTO THE N-CENTRAL WATERS ACCOMPANIED BY A GRADUAL 10-15 KT W-NW-NE WIND SHIFT...AND SEAS BUILDING TO 8 FT W OF THE DECAYING FRONT ON TUE NIGHT. AN UPPER ANTICYCLONE IS QUASI-STATIONARY OVER W-CENTRAL OLD MEXICO AT 21N103W WITH A RIDGE EXTENDING NNE TO A CREST OVER CENTRAL TEXAS. AN UPPER RIDGE ALSO EXTENDS W...AND HAS AMPLIFIED AND IS NOW CRESTING AT 12N140W. UPPER DIFFLUENCE UNDER THIS TROPICAL RIDGE IS ENHANCING CONVECTION ALONG THE EASTERN PORTION OF THE MONSOON TROUGH AS PREVIOUSLY DESCRIBED WITH THE DEBRIS MOISTURE FANNING OUT OVER THE DEEP TROPICS FROM 08N-15N BETWEEN 83W-104W...WITH SOME OF THE MOISTURE NOW RETURNING N OVER OLD MEXICO TO THE E OF 105W. THE DEBRIS MOISTURE FROM THE CONVECTION BETWEEN 108W-122W EVAPORATES NEAR THE CLUSTERS. A DENSE TROPICAL PLUME HAS DEVELOPED ALONG THE W PERIPHERY OF THIS TROPICAL RIDGE..ROUGHLY WITHIN 240 NM OF A LINE FROM 12N140W TO 20N128W TO 23N118W. THIS MOISTURE WILL LIKELY PASS OVER THE BAJA PENINSULA ON MON. A BROAD SURFACE RIDGE IS BUILDING FROM 32N140W TO 20N110W. BROKEN TO LOCALLY OVERCAST STRATOCUMULUS IS OBSERVED TO THE W OF A LINE FROM 28N114W TO 20N140W. SEAS OF 3-5 FT IN NW SWELL ARE EXPECTED ALONG THE ENTIRE PACIFIC COAST OF THE BAJA CALIFORNIA PENINSULA THROUGH LATE MON...THEN GUIDANCE SUGGESTS NW WINDS WILL INCREASE TO 15-20 KT OVER THE WATERS N OF 28N...WITH SEAS BUILDING 4-6 FT ON MON NIGHT. BY LATE TUE...THE NW WINDS WILL INCREASE TO 20-25 KT...SEAS BUILD TO 5-8 FT...ALONG WESTERN BAJA TO THE N OF 27.5N. NW WINDS 15-20 KT WILL SPREAD S ALONG BAJA TO NEAR 24N LATE WED...WITH SEAS AT 5-7 FT IN NW SWELL. NW WINDS OF 5-10 KT AND SEAS OF 2 FT OR LESS EXPECTED ACROSS THE ENTIRE GULF OF CALIFORNIA THROUGH LATE TUE. GUIDANCE THEN INDICATES NW WINDS WILL INCREASE TO 15-20 KT...SEAS BUILDING TO 3-4 FT...OVER THE GULF WATERS TO THE S OF 24.5N BEGINNING TUE NIGHT. BY WED NIGHT...NW WINDS AT 15-20 KT FORECAST ACROSS THE GULF OF CALIFORNIA S OF 30N WITH SEAS BUILDING 3-6 FT IN WATERS SUBJECT TO NORTHERLY FETCH BY MIDDAY THU. GAP WINDS...A NORTHERLY SURGE AT 20-25 KT HAS BEGUN IN THE GULF OF TEHUANTEPEC AND IS EXPECTED TO CONTINUE TO PULSE THROUGH WED NIGHT...WITH THE STRONGEST DRAINAGE FLOW OCCURRING LATE EACH NIGHT TILL JUST AFTER SUNRISE EACH MORNING. THE GFS GUIDANCE CONTINUES TO SUGGEST THIS NORTHERLY FLOW WILL HELP TRIGGER LOW PRESSURE DEVELOPMENT WITHIN THE MONSOON TROUGH ROUGHLY NEAR 11N100W ON MON NIGHT. ALTHOUGH THERE IS A HINT OF THE LOW PRESSURE DEVELOPMENT IN ABOUT SAME AREA ALONG THE MONSOON TROUGH AXIS IN OTHER MODEL GUIDANCE...THE GFS IS STILL BY FAR THE MOST AGGRESSIVE...THUS THE GFS SOLUTION IS TONED DOWN CONSIDERABLY USING A BLEND OF OTHER MODEL GUIDANCE IN THE EXPERIMENTAL GRIDDED FIELDS. $$ NELSON