000 AXPZ20 KNHC 151606 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 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 1200 UTC surface analysis and satellite imagery through 1515 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 strong late season cold front, has blasted through the Isthmus of Tehuantepec and across the regional Pacific waters to the south this morning. Satellite imagery shows a broad arch cloud shifting southward across the Pacific coastal waters extending to about 200 nm S of Salina Cruz, and indicating the leading edge of strong northerly winds and cooler, drier air. Northerly winds quickly increased to gale force this morning across the Gulf of Tehuantepec and are estimated at 30-40 kt currently this morning, and will reach 30- 45 kt late in the afternoon. These winds are forecast to persist tonight into Mon morning, while gradually diminishing, becoming minimal gale force 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 09N75W TO 07N79W TO 09N88W TO 05N105W. The ITCZ stretches from 9N106W TO 06N120W TO beyond 07N140W. Scattered moderate to strong convection is noted within 90 nm N and 150 nm S of through between 83W and 105W. Similar convection is noted within 210 nm N and 90 nm S of the ITCZ between 105W and 130W. ...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 8-11 ft range this morning 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: NWly winds have slowly gradually diminished this morning through the entire length of the Gulf of California, but continue around 20 kt through central and S portions, where seas are 5-8 ft. Winds and seas will diminish considerably later today and shift S to SW tonight. Then, expect fresh to strong southerly winds across the northern Gulf of California Mon through Tue as a low pressure crosses the area. 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 during the night time hours of Mon through Thu. Gulf of Panama: Moderate to fresh northerly winds are expected across the Gulf of Panama Mon night, and again Wed night. 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 weakening 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 weaken. 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 overnight altimeter data. This swell 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 31.5N140W, 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. Cross equatorial SW swell are forecast to reach the southern forecast waters by Tue morning. Marine guidance suggests seas of 8 ft S of 02N between 105W and 120W by early Tue afternoon, and seas of 8-9 ft S of 03N between 96W and 121W by early Tue evening. $$ Stripling