000 AXPZ20 KNHC 150755 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 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 0600 UTC surface analysis and satellite imagery through 0900 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: Strong high pressure currently building southward along the Sierra Madre Oriental and across the western Gulf of Mexico, behind a late season strong cold front, will create a very tight pressure gradient across SE Mexico. Northerly winds will quickly surge across the Tehuantepec region today, reaching 30-40 kt by early this morning and to 30-45 kt late in the afternoon. These winds are forecast to persist tonight into Mon morning, while slightly diminishing. Minimal gale force winds are expected through Tue morning. Seas as high as 18 to 20 ft are expected tonight into Mon. 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 07N78W to 09N90W to 05N104W. The ITCZ stretches from 08N108W to 07N125W to 07N140W. Scattered moderate convection is within 120 nm S of through between 90W and 104W. Similar convection is within about 150 nm N of the ITCZ axis between 122W and 138W, and from 10N to 12N between 105W and 108W. ...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. Seas in the 8-10 ft range are forecast to subside to 7-9 ft late today. Little change in these marine conditions are expected during the forecast period. Gulf of California: Winds of 20-25 kt are noted across the Gulf of California between 25N and 28N with seas to 8 ft. Winds will diminish considerably late today, and then shift to the S on Mon. Gulf of Tehuantepec: 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 this morning. Please, see Special Features section above for details. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: Fresh gap winds are expected across and downstream of the Gulf of Papagayo area tonight, and will increase to strong Mon through Thu. Elsewhere, 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. REMAINDER OF THE AREA... The pressure gradient between lower pressure in the vicinity of the ITCZ and high pressure of 1029 mb centered just N of the area near 32N133W is producing fresh to strong trade winds north of the ITCZ and west of 125W. The aerial extent of the trades will diminish today as the high pressure continues to move SW and weakens. Large NW swell is propagating southeastward through the forecast waters, with max seas of around 12 ft in the waters N of 15N W of 130W per 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 region W of 108W by tonight. A cold front, currently crossing near 32N140W, 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