000 AXPZ20 KNHC 150220 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 UTC Sun Apr 15 2018 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 0300 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: Strong high pressure will build southward along the Sierra Madre Oriental and across the western Gulf of Mexico through tonight, behind a late season cold front, and create a very tight pressure gradient across SE Mexico. Northerly winds at 20-25 kt will quickly surge across the Tehuantepec region around midnight, building seas to around 9 ft. Then, winds are expected to rapidly increase to 30-40 kt by early Sun morning, and to 30-45 kt late in the afternoon. This event is expected to continue into early next week, while gradually diminishing. Seas as high as 18 to 20 ft are expected Sun night into Mon, before slowly subsiding early next week. In addition, an extensive swath of large N to NE swell generated by these northerly winds will propagate well to the SW of the Tehuantepec area, covering roughly the waters from 08N to 14N between 93W and 105W by early Mon morning. Climatologically speaking, the final winter season gale force wind event typically occurs across the Gulf of Tehunatepec in late March or early April. Please refer to the East Pacific High Seas Forecast under AWIPS/WMO headers HSFEP2/FZPN03 KNHC for more details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A surface trough extends from 10N85W to 09N100W to 08N105W. The ITCZ continues from 08N105W to 07N120W to 08N130W to 07N140W. A cluster of moderate to isolated strong convection is noted from 07N to 10N between 131W and 136W. Scattered moderate convection is from 10N to 12N between 105W and 108W, and within 120 nm N of the ITCZ axis between 115W and 118W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Moderate to fresh NW to N winds and large NW swell prevail west of Baja California Norte. An early altimeter pass indicated a broad area of seas 9-10 ft offshore of Punta Eugenia. Seas there will gradually subside to 8-9 ft on Sun. Fresh to strong NW winds will continue to blow across most of the Gulf of California tonight before winds diminishing considerably late Sun, and then shift to the S on Mon. The most recent altimeter pass indicated seas of up 10 ft near 24N. A late season Gulf of Tehuantepec gap wind event will be induced by a strong cold front moving across the Gulf of Mexico starting early on Sun. Please, see Special Features section above for details. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Light to gentle winds are expected through the forecast period, with a weak surface through extending along 08-09N yielding light S to SW winds to its south. Seas in the 3 to 5 ft range will continue over most of the area. Fresh gap winds are expected tonight across and downstream of the Gulf of Papagayo area, and will increase to strong Mon through Thu. REMAINDER OF THE AREA... The pressure gradient between lower pressure in the vicinity of the ITCZ and high pressure of 1030 mb centered N of the area near 34N135W is producing fresh to strong trade winds north of the ITCZ and west of 125W. The aerial extent of the trades will diminish tonight as the high pressure moves SW and weakens some. Large NW swell is propagating southeastward through the forecast waters, with max seas of around 13 ft in the NW waters based on the most recent altimeter data. This swell event will continue to propagate SE across the forecast waters, mixing with waves generating in the Tehuantepec area by early Mon. Seas of 8 ft or greater will cover much of the forecast waters W of 108W by tonight. A cold front will sweep into the NW waters today. Fresh to locally strong N to NE winds will follow the front which is forecast to weaken over northern waters on Mon. $$ GR