000 AXPZ20 KNHC 192321 AAA TWDEP TROPICAL WEATHER DISCUSSION...UPDATED NWS NATIONAL HURRICANE CENTER MIAMI FL 2321 UTC SAT MAR 19 2016 UPDATED ITCZ/MONSOON TROUGH SECTION 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 2300 UTC. ...SPECIAL FEATURES... A RATHER STRONG COLD FRONT FOR THIS TIME IN MARCH IS CURRENTLY MOVING SSE THROUGH THE SW GULF OF MEXICO. THE FRONT WILL PASS E OF THE CHIVELA EARLY ON SUN. NWP MODELS DEPICT VERY STRONG HIGH PRES SURGING S ALONG THE SIERRA MADRE ORIENTAL MOUNTAINS OF EASTERN MEXICO IN THE WAKE OF THE FRONT THROUGH MON. THE RESULTING TIGHT PRES GRADIENT OVER SOUTHEASTERN MEXICO IS FORECAST TO INDUCE A GULF OF TEHUANTEPEC GALE WIND EVENT TO BEGIN AROUND 18Z SUN AS N-NE WINDS OF 30-35 KT. THE PRES GRADIENT CONTINUING TO TIGHTEN THROUGH SUN NIGHT AND INTO MON MORNING...ALLOWING FOR A COOLER AIR MASS TO FILTER IN THROUGH THE GAP AND OUT OVER VERY WARM 28-29 DEG CELSIUS SEA SURFACE TEMPERATURES. THIS WILL ALLOWING FOR MIXING OF VERY STRONG WINDS ALOFT DOWN TO THE SURFACE...THUS BOOSTING THE GALE FORCE WINDS QUICKLY UP TO 45 KT WITH SEAS BUILDING FROM 8-10 FT SUN AFTERNOON TO 11-17 FT BY LATE SUN NIGHT. WINDS STAY AT THE RANGE OF 30-45 KT INTO MON AFTERNOON WITH SEAS BUILDING FURTHER TO 12- 19 FT. A LARGE SWATH OF N-NE 20-30 KT WINDS WILL SPREAD S AND SW FROM THE GULF TO ENCOMPASS AN ELSEWHERE AREA WITHIN 90 NM EITHER SIDE OF A LINE FROM 16N95W TO 14N95.5W TO 12N97W LATE SUN NIGHT...AND ELSEWHERE WITHIN 90 NM EITHER SIDE OF A LINE FROM 16N95W TO 15N95W TO 11.5N97W TO 10.5N99W BY MON AFTERNOON. SEAS WITHIN THE ELSEWHERE AREA WILL BE IN THE RANGE OF 9-13 FT LATE SUN NIGHT...AND REACH A HIGHER RANGE OF 10-15 FT BY MON AFTERNOON. THE PARENT HIGH CENTER OF THE TIGHT PRES GRADIENT IS FORECAST BY THE NWP MODELS TO SHIFT EASTWARD AND WEAKEN ALONG THE FAR NORTHERN GULF TUE. THIS WILL ALLOW FOR THE CULPRIT TIGHT PRES GRADIENT TO SLACKEN...AND FOR THE GALE FORCE WINDS TO DROP BELOW GALE FORCE INTENSITY. SEE LATEST NWS HIGH SEAS FORECAST UNDER AWIPS/WMO HEADERS MIAHSFEP2/FZPN03 KNHC FOR MORE DETAILS. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...UPDATED THE ITCZ AXIS EXTENDS FROM 06N84W TO 06N95W TO 06N105W TO 04N118W TO 03N130W TO 04N140W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 60 NM OF THE AXIS BETWEEN 115W-119W AND ALSO BETWEEN 133W-137W. SCATTERED MODERATE CONVECTION IS WITHIN 60 NM OF THE AXIS BETWEEN 84W-92W. IN ADDITION...SCATTERED MODERATE CONVECTION IS NOTED JUST E OF THE ITCZ FROM 04N-07N BETWEEN 82W-84W. ...DISCUSSION... WATER VAPOR IMAGERY SHOWS A LARGE DEEP LAYER CYCLONIC VORTEX WELL TO THE NW OF THE DISCUSSION AREA NEAR 48N148W WITH AN ASSOCIATED TROUGH EXTENDING SEWD TO THE FAR NW PART OF THE AREA. THE TROUGH SUPPORTS A COLD FRONT THAT IS FAST APPROACHING THE NW CORNER OF THE AREA AS SEEN IN THE LATEST VIS IMAGERY.REMNANTS FROM A PREVIOUS SHORTWAVE TROUGH ARE ANALYZED AS A STATIONARY FRONT THAT EXTENDS FROM A WEAK 1014 MB LOW AT 32N135W SW TO 26N140W. THE STATIONARY FRONT IS FORECAST TO WEAKEN THROUGH EARLY SUN AS THE AFOREMENTIONED COLD FRONT MERGES WITH IT. S-SW WINDS OF 20-25 KT WITH SEAS OF 10-12 FT IN NW SWELL WITHIN 60 NM E OF THE STATIONARY FRONT ARE FORECAST TO SHIFT N OF THE AREA TONIGHT. LATEST NWP MODELS CONTINUE TO SUGGEST THAT A MAJORITY OF WINDS GREATER THAN THE 20 KT THRESHOLD FOR HIGH SEAS INCLUSION TO REMAIN N OF 30N AND THE PRIMARY IMPACT ACROSS THE DISCUSSION WATERS BEING THE NEW PULSE OF NORTHWESTERLY SWELL THAT ACCOMPANIES THE FRONT. EXISTING NW SWELL OF 8-12 FT ASSOCIATED WITH THE STATIONARY FRONT WILL PROPAGATE SSE AND GRADUALLY BEGIN TO SUBSIDE THROUGH SUN...HOWEVER THE APPROACHING COLD FRONT WILL ONCE AGAIN BUILD SEAS INTO A 12-17 FT RANGE NW OF A LINE FROM 32N133W TO 15N140W BY EARLY SUN EVENING. THESE SEAS ARE ONLY FORECAST TO SUBSIDE SLIGHTLY EARLY ON MON AS THEY SPREAD SE...THEN SUBSIDE FURTHER ON MON AFTERNOON. SEAS OF 8-11 FT PRIMARILY IN A NW SWELL ARE FORECAST TO SPREAD SSE TO A LINE FROM NEAR 32N120W TO 18N129W TO 07N119W TO 02N125W TO 02N140W BY EARLY MON EVENING. THE SOUTHERN PORTION OF AN UPPER TROUGH STRETCHES SW FROM THE CENTRAL U.S. TO NW MEXICO AND TO JUST E OF BAJA CALIFORNIA SUR. A JET STREAM BRANCH TO THE SE OF THIS TROUGH IS ADVECTING BROKEN CIRRUS...IN TRANSVERSE BANDING FORMATION...NEWD TOWARDS CENTRAL MEXICO AND THE GULF OF MEXICO. THE CLOUDS ARE NOTED FROM 13N-19N E OF ABOUT 110W AS SEEN IN SATELLITE IMAGERY. WATER VAPOR IMAGERY DEPICTS MODERATE TO STRONG SUBSIDENCE BRINGING VERY STABLE ATMOSPHERIC CONDITIONS N OF 17N E OF 140W...EXCEPT IN THE IMMEDIATE VICINITY OF THE ABOVE MENTIONED STATIONARY FRONT WHERE BROKEN TO OVERCAST MID/UPPER CLOUDS WITH POSSIBLE WIDELY SCATTERED TO ISOLATED SHOWERS EXIST. ELSEWHERE AT THE SURFACE...A 1021 MB HIGH IS ANALYZED AT 28.5N126W WITH A RIDGE AXIS EXTENDING SE TO NEAR 16N116. THE OVERALL PRES GRADIENT BETWEEN THE RIDGE AND LOWER PRES TO THE S WITHIN THE ITCZ REGION IS SUPPORTING MODERATE TO OCCASIONAL FRESH NE TRADES FROM 07N-17N W OF 118W WITH SEAS THERE IN THE RANGE OF 6-8 FT. THESE WINDS ARE EXPECTED TO VARY LITTLE OVER THE NEXT 48 HOURS...HOWEVER THE SEAS WILL SIGNIFICANTLY BUILD AS THE ABOVE MENTIONED NW SWELL PROPAGATES SSE THROUGH WESTERN HALF OF THE AREA. OTHER GAP WINDS... A GULF OF PAPAGAYO GAP WIND EVENT WITH 20-25 KT NE WINDS IS SUGGESTED BY THE LATEST NWP MODELS TO BRIEFLY TAKE PLACE MON MORNING WITH SEAS OF ABOUT 6-7 FT. $$ AGUIRRE