000 AXPZ20 KNHC 190947 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC SUN SEP 19 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 0915 UTC. ...ITCZ... MONSOONAL S TO SW FLOW DOMINATES THE DEEP TROPICS ACROSS THE AREA...WITH A MONSOONAL TROUGH EXTENDING FROM A DEVELOPING LOW NEAR 16N104W 1007 MB TO 12N113W TO 13N121W TO LOW PRES 13N125W 1009 MB TO 10N132W TO 10N140W. SCATTERED TO NUMEROUS MODERATE TO STRONG CONVECTION WAS OCCURRING WITHIN 90 NM EITHER SIDE OF AXIS FROM 105W TO 112W. ELSEWHERE SCATTERED MODERATE CONVECTION WAS OCCURRING WITHIN 120 NM S OF AXIS. ...DISCUSSION... ALOFT... A DEEP LAYERED LOW IN THE NE PACIFIC APPROACHING THE WASHINGTON-OREGON COASTS HAD TROUGH AXIS EXTENDING ACROSS FAR NW PORTION OF AREA. AHEAD OF THE TROUGH A JET STREAM BRANCH STRETCHED FROM 24N140W TO NE OF THE REGION AT 32N130W. WATER VAPOR IMAGERY SHOWED AN ANTICYCLONE GRADUALLY MOVING W NEAR 26N120W WITH A RIDGE AXIS EXTENDING SW ACROSS THE AREA TO 17N150W...AND E-SE FROM THE ANTICYCLONE TO FAR SOUTHERN BAJA CALIFORNIA. IMAGERY ALSO SHOWED AN EXTENSIVE AREA OF MODERATE SUBSIDENCE WITH RESULTANT STABLE ENVIRONMENT N OF 19N SE OF THE UPPER TROUGH...AND S OF THE TROUGH TO THE ITCZ REGION W OF 131W. S OF THE ANTICYCLONE...STRONG UPPER LEVEL EASTERLY WINDS TO 55 KT WERE NOTED ACROSS THE AREA S OF S OF 20N AND E OF 125W. DEEP CONVECTION OCCURRING S OF THE MONSOON TROUGH BETWEEN 102W AND 112W WAS DIVERTING THE FLOW AROUND THESE CB TOWERS AND INDUCING DIVERGENT FLOW ALOFT. A MIDDLE TO UPPER LEVEL WAS NEARLY STATIONARY OVER THE SIERRA MADRE OCCIDENTALES. UPPER LEVEL SPEED DIVERGENCE TO THE S OF THIS TROUGH HAS ALLOWED NOCTURNAL CONVECTION EXITING THE W SLOPES OF THE MOUNTAINS TO EXPLODE DURING THE PAST FEW HOURS WITH A LARGE CLUSTER OF TSTMS ALONG THE COAST OF MEXICO FROM MANZANILLO TO LAS ISLAS TRES MARIAS. SURFACE... DEEP LAYER LOW AND ACCOMPANYING TROUGH MENTIONED ABOVE WAS SUPPORTING A COLD FRONT THAT EXTENDED FROM 30N131W TO 26N140W MOVING E ABOUT 15 KT. THE FRONT WILL WEAKEN TO A FRONTAL TROUGH FROM 30N127W TO 26N140W IN ABOUT 24 HOURS...THEN DISSIPATE ON MON. SW WINDS TO 20 KT WERE INDICATED WITHIN 180 NM E OF THE FRONT N OF 29N...WHILE NW TO N WINDS TO 20 KT WERE W OF THE FRONT N OF 29N. SEAS TO 8 FT IN NW SWELL WERE NOTED WITHIN THESE WIND AREAS ON EITHER SIDE OF THE FRONT...BUT WILL SUBSIDE TO LESS THAN 8 FT BY 48 HOURS. WEAK RIDGING AHEAD OF THE FRONT COMBINING WITH LOWER PRES OVER NW MEXICO AND BAJA CALIFORNIA HAD INCREASED NW TO N WINDS TO 20-25 KT N OF 23N E OF 120W TO THE BAJA CALIFORNIA W COAST PER A RECENT ASCAT PASS. THESE CONDITIONS ARE FORECAST TO CHANGE LITTLE OVER THE NEXT 2 DAYS. SW WINDS ASSOCIATED WITH THE ACTIVE MONSOON TROUGH IS BEING FOCUSED BY A STRING OF EMBEDDED LOWS AS MENTIONED ABOVE UNDER ITCZ. THE LOW NEAR 16N104W APPEARED TO BE GAINING MOMENTUM OVER THE PAST SEVERAL HOURS AS GLOBAL MODELS HAVE BEEN HINTING DURING THE PAST SEVERAL DAYS. THIS WAS NOTED BY CYCLONIC CIRCULATION OF LOW CLOUD LINES TO ITS E...AND BY THE RECENT BURSTS OF NUMEROUS CONVECTION AROUND THE PERIPHERY TO THIS BROAD LOW. THE LOW WAS DRIFTING NW...AND IS FORECAST TO SHIFT NW WITHIN THE E END OF THE MONSOON TROUGH OVER THE NEXT FEW DAYS. TROPICAL CYCLONE FORMATION IS POSSIBLE WITH THIS SYSTEM OVER THE NEXT FEW DAYS. MARINE... FRESH TO STRONG SW WINDS PERSIST S OF THE MONSOON TROUGH AXIS TO ABOUT 08N E OF 125W AND ARE PRODUCING SEAS MAXING OUT TO NEAR 12 FEET BETWEEN 105W AND 110W. THESE WINDS ARE EXPECTED TO INCREASE TO 30 KT BY 24 HOURS ACROSS THIS AREA AS THE LOW BECOMES BETTER ORGANIZED. LARGE SWELLS WILL CONTINUE TO PROPAGATE FROM SW TO NE OVER A BROAD PORTION OF THE AREA THROUGH THE WEEKEND. $$ STRIPLING