000 AXPZ20 KNHC 200249 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 0405 UTC SUN MAR 20 2016 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0230 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 LATE TONIGHT INTO EARLY 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 WITH N-NE WINDS OF 30-35 KT WITH A PRE-GALE ONSET OF 20-25 KT EXPECTED NEAR 09Z SUN AND INCREASING TO 20-30 KT BETWEEN 12Z-15Z WITH SEAS BUILDING TO 10 FT. THE PRES GRADIENT WILL CONTINUE 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 11-18 FT BY LATE SUN NIGHT. WINDS STAY AT THE RANGE OF 30-45 KT INTO MON AFTERNOON WITH SEAS BUILDING FURTHER TO 13- 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 9-14 FT LATE SUN NIGHT...AND REACH A HIGHER RANGE OF 10-15 FT BY MON AFTERNOON. THE CULPRIT 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 RESULTANT 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... THE ITCZ AXIS EXTENDS FROM 05N93W TO 06N110W TO 04N120W TO 02N128W TO 04N140W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 60 NM S OF THE AXIS BETWEEN 114W-119W...AND WITHIN 60 NM OF THE AXIS BETWEEN 130W-136W. IN ADDITION...SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS NOTED JUST E OF THE ITCZ FROM 03N-06N BETWEEN 86W-90W. ...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 HAS RECENTLY MOVED INTO THE FAR NW CORNER OF THE AREA AS SEEN IN LAST AVAILABLE VIS IMAGERY. THE COLD FRONT FROM THE PAST FEW DAYS IS CURRENTLY ANALYZED AS A WEAKENING COLD FRONT THAT EXTENDS FROM A WEAK 1018 MB LOW N OF THE AREA AT 35N132W TO 32N133W AND SW TO 25N138W WHERE IT BECOMES A DISSIPATING STATIONARY FRONT TO SW OF THE AREA AT 24N140W. THE COLD FRONT OVER THE FAR NW PART OF THE AREA WILL QUICKLY MERGE WITH THE WEAKENING COLD FRONT NEAR 12Z ON SUN. LATEST WAVEWATCH GUIDANCE SUGGESTS THAT A NEW PULSE OF NW SWELL WILL FOLLOW IN THE WAKE OF THE MERGED FRONT. EXISTING NW SWELL OF 9-12 FT ASSOCIATED WITH THE WEAKENING COLD FRONT WILL PROPAGATE SSE...AND GRADUALLY BEGIN TO SUBSIDE THROUGH SUN...HOWEVER THE NEW NW SWELL TRAIN WILL ONCE AGAIN BUILD SEAS INTO THE 12-17 FT RANGE NW OF A LINE FROM 32N133W TO 25N140W 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 14N-19N E OF 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 29N126W 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 THE 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