000 AXPZ20 KNHC 172255 AAA TWDEP TROPICAL WEATHER DISCUSSION...UPDATED NWS NATIONAL HURRICANE CENTER MIAMI FL 2255 UTC SUN APR 17 2016 UPDATED TO ADD NEWLY FORMED ITCZ-RELATED CONVECTION 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2230 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...UPDATED THE MONSOON TROUGH IS NOT IDENTIFIABLE. ITCZ AXIS EXTEND FROM 05N96W TO 09N112W TO 05N128W TO 03N140W. SCATTERED STRONG CONVECTION IS WITHIN 60 NM OF THE AXIS BETWEEN 133W-140W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 45 NM OF THE AXIS BETWEEN 130W-133W...AND WITHIN 60 NM N OF THE ITCZ BETWEEN 97W- 100.5W. TROUGH EXTENDS FROM 09N86W TO 06N96W. SCATTERED MODERATE CONVECTION IS WITHIN 60 NM S OF TROUGH. ...DISCUSSION... WEAK HIGH PRES COVERS THE AREA N OF 20N BETWEEN 118W-135W. SEAS OF 8-9 FT IN A NW SWELL ARE CONFINED FROM 05N-23N BETWEEN 108W-120W. THIS AREA OF NW SWELL WILL GRADUALLY SHRINK FROM N TO S WHILE SHIFTING WESTWARD OVER THE NEXT COUPLE OF DAYS. A WEAK INVERTED TROUGH IS NEAR 124W MOVING W 15-20 KT. THE TROUGH IS EXPECTED TO REMAIN WEAK AS IT MOVES THROUGH THE FAR WESTERN PORTION MON AND MON NIGHT. SEAS OF 8 FT IN NW SWELL ARE WITHIN AN AREA DEFINED FROM 08N-12N BETWEEN 120W-128W. THIS AREA WILL EXPAND N AND W BY TUE AFTERNOON AS LONG PERIOD NW SWELL CONTINUES TO INFILTRATE THE WESTERN PORTION OF THE AREA. A RATHER STRONG SPRING TIME COLD FRONT ENTERED THE FAR NW CORNER OF THE DISCUSSION AREA THIS AFTERNOON. THE PARENT GALE CENTER IS N OF THE AREA NEAR 35N139W WITH PRES OF 1005 MB. THIS SYSTEM IS CLEARLY DEFINED ON VISIBLE SATELLITE IMAGERY THIS AFTERNOON. A VERY TIGHT PRES GRADIENT BEHIND THE FRONT...AND BETWEEN THE LOW AND A STRONG 1030 MB HIGH WELL NW OF THE REGION NEAR 34N163W HAS INDUCED NW-N WINDS OF 20-30 KT OVER THE FAR NW CORNER OF THE AREA. SEAS WITH THESE WINDS ARE IN THE 10-14 FT RANGE...WHICH IS HIGHER THAN EARLIER ANTICIPATED. A COUPLE OF SHIP REPORTS JUST W OF THE NW CORNER OF THE AREA REPORTED SIGNIFICANT WAVEHEIGHTS OF 14 FT. S-SW 20-25 KT WINDS ARE WITHIN 180 NM E OF THE FRONT N OF 28N WITH SEAS OF 8-10 FT. SEAS OF 8-9 FT IN NW SWELL ARE ELSEWHERE W OF A LINE FROM 32N132W TO 20N135W TO 09N140W. THE GALE CENTER IS FORECAST TO REACH NEAR 35N137W WITH PRES OF 999 MB BY LATE TONIGHT WITH THE COLD FRONT EXTENDING THROUGH 32N133W TO 25N140W. THE NW-N WINDS BEHIND THE FRONT ARE FORECAST TO DIMINISH SLIGHTLY AT THAT TIME WITH SEAS STILL 10-14 FT IN NW SWELL. S-SW WINDS OF 20-25 KT ARE STILL EXPECTED WITHIN 180 NM E OF THE FRONT N OF 29N WITH SEAS OF 8-10 FT...AND SIMILAR SEAS ELSEWHERE W OF A LINE FROM 32N131W TO 20N133W TO 10140W. BY MON AFTERNOON...THE GALE CENTER IS FORECAST BY THE GLOBAL MODELS TO HAVE UNDERGONE WEAKENING WHILE LIFTING N TO NEAR A POSITION NEAR 36N131W WITH THE FRONT ALSO WEAKENING ALONG A POSITION FROM 32N127W TO 24N133W ...AND STATIONARY TO 21N140W. A POST-FRONTAL TROUGH IS EXPECTED FROM THE LOW TO 32N132W TO 28N140W. WINDS AT THAT TIME ARE FORECAST TO DIMINISH CONSIDERABLY WITH W-NW WINDS OF 15-20 KT OVER THE NW WATERS...HOWEVER LONG PERIOD NW SWELL WILL BE SLOW IN SUBSIDING WITH SEAS TO 11 FT EXPECTED W OF THE WEAKENING FRONT. A STRONG UPPER TROUGH IS SEEN ON WATER VAPOR IMAGERY STRETCHING FROM A LARGE QUASI-STATIONARY UPPER LOW OVER THE CENTRAL ROCKIES SSW OVER FAR NORTHERN MEXICO...AND CONTINUING TO SOUTHERN BAJA CALIFORNIA...AND TO 17N112W TO A BASE NEAR 02N112W. AN UPPER DIFFLUENT FLOW PATTERN E OF THE TROUGH IS SUPPORTING AMPLE DEEP ATMOSPHERIC MOISTURE IN THE FORM OF MULTILAYERED CLOUDS WITH EMBEDDED SCATTERED SHOWERS AND ISOLATED TSTMS FROM WITHIN ABOUT 230 NM EITHER SIDE OF A LINE FROM 08N112W TO 12N105W. NE OF THESE CLOUDS AND PRECIPITATION...EXTENSIVE COVERAGE OF OVERCAST MAINLY MID TO HIGH LEVEL CLOUDS ARE NOTED STREAMING NE TO OVER MUCH OF CENTRAL AND SOUTHEASTERN MEXICO...AND TO THE SW GULF OF MEXICO. THESE CLOUDS ARE SSE OF A SUB-TROPICAL JET STREAM BRANCH THAT LIES ALONG A LINE FROM 12N112W TO 19N109W TO 24N103W. GLOBAL MODEL GUIDANCE SUGGESTS THAT THE UPPER TROUGH WILL SHIFT EASTWARD WHILE DAMPENING OUT THROUGH LATE MON NIGHT. A PIECE OF THE TROUGH IS EXPECTED TO LAG BEHIND TO THE SW OF THE GULF OF TEHUANTEPEC AT THAT TIME. THIS MAY INTRODUCE ADDITIONAL INSTABILITY TO THE EASTERN PART OF THE ITCZ POSSIBLY ENHANCING CONVECTION ALONG IT. GULF OF CALIFORNIA... NW 20-25 KT WINDS N OF 30N ARE FORECAST TO SOON SHIFT SOUTHWARD FROM ABOUT 28N-29.5N THEN DIMINISH TO 15-20 KT TONIGHT AS THE PRES GRADIENT ACROSS THE REGION WEAKENS. $$ AGUIRRE