000 AXPZ20 KNHC 101543 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1248 UTC Mon Apr 10 2017 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 1500 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning...strong high pressure building southwestward over the Gulf will increase the pressure gradient over the Isthmus of Tehuantepec early on Wednesday through Thursday afternoon. Winds are expected to pulse to minimal gale force on Wed morning and Thu morning, when nocturnal drainage flow augments the winds. The high pressure ridge will shift east on Thursday and allow the winds to quickly subside. Seas in the Gulf of Tehuantepec will peak around 12 ft on Wednesday morning and around 13 ft Thursday morning. Northeast Pacific Gale Warning...Low pressure north of the discussion waters will drag a cold front into the northern portion tonight. Winds ahead of the front north of 30N are at gale force. The gale is expected to continue through late tonight. Associated seas will build to around 12 ft later today and tonight. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A surface trough axis extends from 04N89W to 05N93W to 1010 mb low pressure near 04N97W to 02N103W. The intertropical convergence zone axis extends from 04N106W to 06N119W, then resumes from 05N120W to 04N124W to 04N130W to 02N136W. Scattered moderate and isolated strong convection is present from 02N to 06N between 87W and 98W. Scattered moderate convection is found within 90 nm either side of a line from 04N124W to 03N140W and from 05N to 07N between 109W and 114W. A surface trough bisects the ITCZ from 06N119W to 08N119W to 10N118W. Scattered moderate and isolated strong convection is observed from 05N to 10N between 115W and 122W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A ridge extends SW into the area from 30N128W to the Revillagigedo Islands. Northwest winds are moderate to fresh W of the Baja California Peninsula where seas are 8-10 ft. Seas will subside to less than 8 ft by early Tue as winds decrease to mainly moderate speeds as the local pressure gradient relaxes. A pulse of fresh NW swell will move back into the area as seas build to 7-10 ft Tue afternoon through Thursday. The pressure gradient will tighten and support fresh to strong NW winds Wed through Fri, helping to keep seas up. In the Gulf of California, moderate NW flow prevails along with 2-4 ft seas. Winds will become light and variable across the northern half of the Gulf tonight through the end of the week, with similar conditions spreading to the southern half of the Gulf by Wednesday evening. Seas will subside to 2 ft or less as the winds decrease. A Gulf of Tehuantepec gap wind event is slated for Wednesday morning through Thursday afternoon. See the special features section for more details. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... In the Gulf of Papagayo, fresh to locally strong nocturnal drainage winds are expected all week. Winds will be a little stronger Wednesday through Friday, when seas peak between 8 and 9 ft. In the Gulf of Panama, moderate to fresh nocturnal northerly flow is expected during the overnight hours this week. Seas will run between 5 and 7 ft. Elsewhere, light to gentle winds, and combined seas of 3 to 6 ft are expected to prevail. REMAINDER OF THE AREA... Long-period 6-9 ft NW swell will decay through tonight from NW to SE, however, a new set of NW swell are beginning to cross 30N140W ahead of an approaching cold front. The front will pass to the SE of 30N140W this evening. Winds just ahead of the front and N of 29.5N will briefly become fresh to strong until around midnight tonight. The front will extend from 30N133W to 28N140W by late Tue morning, then will weaken as it approaches 120W through Thu. A reinforcing front will arrive over the northern waters Wed night, ushering in another and larger set of NW swell. Seas will build to 12 ft near 30N and W of 125W late Wed night and early Thu. The front and the associated swell will decay as they head east from 125W by early Fri. Elsewhere, recent satellite-derived wind data indicated fresh to locally strong trades SW of a ridge axis that extends from 1023 mb high pressure centered near 30N128W to 18N110W. Specifically, this area of enhanced trades and 8 to 9 ft seas is located from 06N to 18N west of 130W. Otherwise, mainly moderate to fresh trades and combined seas of 8 to 10 ft will prevail across the waters N of the ITCZ to 20N and W of 120W through the end of the week. $$ cam