000 AXPZ20 KNHC 181623 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 1605 UTC WED NOV 18 2015 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 1530 UTC. ...SPECIAL FEATURES... THE DEVELOPING LOW PRES SYSTEM EMBEDDED IN THE MONSOON TROUGH NEAR 13.0N107.2W THIS MORNING HAS GAINED SUFFICIENT ORGANIZATION AND CONVECTION TO BE CLASSIFIED AS A TROPICAL CYCLONE...AND BECOMES TROPICAL DEPRESSION TWENTY-ONE-E. SATELLITE IMAGERY THIS MORNING SHOWS SCATTERED STRONG CONVECTION OCCURRING WITHIN 240 NM NW SEMICIRCLE AND 60 NM ACROSS THE S QUADRANT...WHILE LOW CLOUDS AND OVERNIGHT SCATTEROMETER DATA SUGGEST THAT THE SURFACE CIRCULATION IS EMBEDDED WITHIN THE SE PORTION OF THIS LARGE CLUSTER OF CONVECTION. AN UPPER LEVEL ANTICYCLONE CENTERED ACROSS THE ISTHMUS OF TEHUANTEPEC HAS BEEN IMPARTING SOUTHERLY WIND SHEAR ACROSS THE SYSTEM OVERNIGHT...BUT THE LATEST BURST OF CONVECTION HAS DISRUPTED THE SHEAR AND OUTFLOW HAS IMPROVED. THE UPPER LEVEL HIGH TO THE EAST OF THE DEPRESSION IS EXPECTED TO HELP STEER IT SLOWLY NORTHWESTWARD FOR THE NEXT COUPLE OF DAYS BEFORE AN UPPER LEVEL TROUGH APPROACHES FROM THE W AND STEERS THE SYSTEM MORE NORTHERLY. SOME SLOW AND GRADUAL STRENGTHENING IS EXPECTED DURING THE NEXT 48 HOURS AS THE DEPRESSION REMAINS OVER VERY WARM WATERS AND WITHIN A VERY MOIST ENVIRONMENT. PLEASE SEE LATEST FORECAST ISSUED BY THE NATIONAL HURRICANE CENTER UNDER AWIPS/WMO HEADERS MIATCMEP1/WTPZ21 KNHC FOR MORE DETAILS. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH AXIS EXTENDS FROM LOW PRES 1006 MB IN SW CARIBBEAN NEAR 11.5N81.5W TO 09N90W TO LOW PRES 1005 MB NEAR 13.5N107.5W TO 11N117W TO LOW PRES 1007 MB NEAR 11.5N126W TO 08N130W...WHERE IT TRANSITIONS TO ITCZ...CONTINUING ON TO 07.5N140W. SCATTERED MODERATE TO STRONG CONVECTION IS OBSERVED WITHIN 330 NM S OF THE TROUGH E OF 106W...AND WITHIN 120 NM EITHER SIDE OF TROUGH BETWEEN 114W AND 130W. ...DISCUSSION... N OF 15N E OF 120W...A TIGHT PRESSURE GRADIENT BETWEEN 1032 MB HIGH PRES CENTERED NEAR 35N135W AND LOWER PRESSURE OVER N CENTRAL MEXICO AND ALONG THE MONSOON TROUGH IS ALLOWING FOR FRESH TO STRONG NORTHWESTERLY WINDS TO BLOW THROUGH THE ENTIRE LENGTH OF THE GULF OF CALIFORNIA AND TURNING NORTHERLY TO BEYOND 20N...INCLUDING THE PACIFIC WATERS OFF THE BAJA CALIFORNIA PENINSULA. ALTIMETER SATELLITE DATA FROM THE PAST SEVERAL HOURS CONTINUES INDICATED 10 TO 14 FT SEAS OFF BAJA CALIFORNIA DUE IN PART TO NW SWELL PROPAGATING THROUGH THE REGION. THE PRES GRADIENT WILL BEGIN TO RELAX TODAY AS THE LOW PRES OVER N CENTRAL MEXICO LIFTS NE ALLOWING WINDS AND SEAS TO GRADUALLY DIMINISH THROUGH EARLY THU ACROSS THE REGION. W OF 120W...OVERNIGHT SCATTEROMETER DATA SHOWED STRONG TRADE WINDS OVER MUCH OF THE AREA N OF 13N AND TO THE SOUTH OF THE 1032 MB HIGH PRES CENTERED NEAR 35N135W. VARIOUS ALTIMETER DATA CONTINUE TO SHOW SEAS AS HIGH AS 14 FT IN THE AREA OF THE STRONG TRADE WINDS...HELPED IN PART PRIMARILY BY LONG PERIOD NW SWELL PREVAILING ACROSS MUCH OF THE REGION. THIS IS PRODUCING AN UNUSUALLY LARGE AREA OF CONFUSED SEAS 10 FT AND GREATER... ROUGHLY FROM 10N TO 27.5N AND W OF 115W. THE RIDGE WILL GRADUALLY WEAKEN THROUGH THE REMAINDER OF THE WEEK AND ALLOW THE TRADE WINDS TO DIMINISH ACCORDINGLY. WINDS AND SEAS WILL SUBSIDE...BUT REMAIN 8 FT OR GREATER ACROSS MUCH OF THE AREA THROUGH LATE IN THE WEEK. GULF OF TEHUANTEPEC...LIGHT AND VARIABLE WINDS ARE EXPECTED THROUGH TODAY. HIGH PRES WILL THEN BUILD IN BEHIND A COLD FRONT IN THE WESTERN GULF OF MEXICO N OF THE AREA WHICH WILL INDUCE ANOTHER ROUND OF FRESH TO NEAR GALE FORCE NORTHERLY WINDS IN THE GULF OF TEHUANTEPEC LATE TONIGHT THROUGH AT LEAST THU AFTERNOON...LIKELY CONTINUING FOR SEVERAL DAYS INTO THE UPCOMING WEEKEND. CONDITIONS WILL APPROACH GALE FORCE...HOWEVER CURRENT MODEL GUIDANCE REMAINS BELOW GALE FORCE THROUGH THE NEXT 48 HOURS. LOOKING AHEAD...ANOTHER ROUND OF STRONG GAP WINDS CAN BE EXPECTED BY LATE SAT POSSIBLY REACHING GALE FORCE BY LATE SUN. $$ STRIPLING