000 AXPZ20 KNHC 160314 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 UTC Mon Apr 16 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 shifted southward along the Sierra Madre Oriental and across the western Gulf of Mexico, behind a strong late season cold front, and has initiated an increasing plume of gale force winds across the Gulf of Tehuantepec. Satellite imagery shows a broad arch cloud shifting southward across the Pacific coastal waters extending to about 300 nm S and SW of Salina Cruz, and indicating the leading edge of strong northerly winds and cooler, drier air. Northerly winds are estimated at 35-45 kt by this evening, and an altimeter pass just indicates seas around 16 ft near 13.5N95.5W. These winds are forecast to persist tonight into Mon morning, then gradually diminish, becoming minimal gale force Tue morning and to only 25 kt by noon time Tue. Seas downwind of the gulf are expected to build as high as 18 to 20 ft 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 09N to 15N between 93W and 105W by early Mon morning. 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 09N92W to 08N100W. The ITCZ stretches from 08N100W to 07N120W to 08N140W. Scattered moderate convection is from 07N to 12N between 90W and 102W. Scattered moderate to isolated strong convection is from 10N to 13N between 102W and 108W. Similar convection is within 60 nm N of the ITCZ axis between 113W and 117W. Scattered moderate convection is within 120 nm S of axis between 120W and 123W, and 120 nm N of ITCZ axis between 132W and 136W. ...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 continue tonight based on altimeter data. The new cold front will sweep across Baja California Norte Monday night and act to freshen wind across the north half of the peninsula through Tue. Gulf of California: Winds will shift S to SW tonight, then, become fresh to strong across the northern Gulf of California Mon through Tue as a low pressure moves across the area. Gulf of Tehuantepec: A strong late season Gulf of Tehuantepec gap wind event has been induced by a strong cold front moving across the Gulf of Mexico. 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... A cold front has entered the NW forecast waters and extends from 30N130W to 28N140W. A 120 nm wide band of mainly low clouds is associated with the front forecast to sweep SE across the N waters tonight and Mon. Fresh to locally strong N to NE winds will follow the front which is forecast to weaken over NE waters Mon. A strong high pressure of 1039 mb follows the front and will bring some increase in winds N of 20N W of 135W tonight. Large NW swell is propagating southeastward through the forecast waters, with max seas of around 12 ft in the far western waters N of the ITCZ. 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 tonight into Mon morning. Cross equatorial SW swell are forecast to reach the southern forecast waters by Tue morning. Marine guidance suggests that seas of 8-9 ft could dominate the waters S of 07N between 96W and 120W by early Tue evening. $$ GR