000 AXPZ20 KNHC 120925 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 UTC Wed Dec 12 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 over the Gulf of Mexico continues to produce a tight pressure gradient across the Isthmus of Tehuantepec, leading to a large area of strong gales across the Gulf of Tehuantepec and downstream to near 14N96W. The large area of gales has generated high seas to around 17 ft. Gale force winds will diminish this morning to less than 30 kt, then rapidly decrease during the afternoon and evening as high pressure over the Gulf of Mexico weakens and shifts east. Large N to NE swell will propagate well away from the source region, with the leading edge of 8 ft seas expected to reach W to 110W and S to 02N today, merging with a large area of 8 ft seas approaching from the northwest. Please refer to the Eastern Pacific High Seas Forecast under AWIPS/WMO headers HSFEP2/FZPN03 KNHC for more specific marine details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 06N77W TO 06N93W. The ITCZ continues from 06N93W TO 05N103W TO 11N126W to beyond 07N140W. Scattered moderate isolated strong convection is noted from 09N to 16N between 119W and 129W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Gulf of Tehuantepec...After the ongoing gale wind event quickly tapers off today, light to gentle winds are expected through Thu night. A cold front forecast to move into the Gulf of Mexico on Thu is expected to initiate another strong gale force wind event Fri through Sun. Broad high pressure NW of the area extends a ridge SE to near the Revillagigedo Islands. The gradient between the high and troughing in the Gulf of California is supporting gentle N to NW winds in Gulf of California. Model guidance suggests that the pressure gradient will begin to tighten tonight, with fresh to strong winds expected over almost all of the Gulf of California Thu through Fri. 6 to 8 ft seas in NW swell across the offshore waters of Baja California will continue over the region through this morning, then subside below 8 ft by this evening. Another push of large NW swell will reach the waters west of Baja California late Thu. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo...A broad and significant plume of NE winds extends across the Papagayo region to near 08.5N90W this evening, where seas are 8-10 ft. Winds will pulse to just below gale force overnight, remain fresh to strong Wed night, then diminish to 10-15 kt Thu. Fresh to strong winds will return Sat and expand in coverage through the weekend. Seas of 8-10 ft can be expected during the periods of the stronger winds. Gulf of Fonseca...Scatterometer data during the past six hours showed 25 kt winds across the coastal waters of El Salvador and Nicaragua, including the Gulf of Fonseca. Fresh to strong NE winds will persist for a few more hours this morning, diminish significantly in the afternoon, then remain light to gentle through Sat night. Gulf of Panama... Fresh N to NE winds spilling across Panama into the Gulf of Panama this morning are expected to continue through tonight, then begin to diminish on Thu. Seas will peak at 6 to 7 ft at times of strongest winds. Elsewhere, gentle to moderate winds will persist on either side of the monsoon trough through the remainder of the week, with seas in the 4-6 ft range. REMAINDER OF THE AREA... NW swell associated with a dissipated front supports 8 to 10 ft seas across most of the area W of 120W. High pressure building northwest of the area and lower pressures near the ITCZ will support fresh to strong NE trade winds from 09N to 25N west of 127W through Thu, with seas in the 9-12 ft range. Wave model guidance suggests a rather large area of 8 ft or greater seas will stretch from about 02N to 15N between 92W and 110W as a result of long-period northwest swell mixing with shorter period northeast swell generated from current the Gulf of Tehuantepec event, and to a lesser extent those from the Gulfs of Papagayo and Fonseca. This area of swell will merge into a larger area of seas associated with northwest swell which will cover most of the forecast area west of 92W today. A surface trough is analyzed along the ITCZ near 128W-129W. Associated winds are moderate to fresh, with seas of 8-10 ft. The trough is east of a pronounced upper-level trough as seen in water vapor. The upper trough will amplify southward, but the surface trough will gradually lose its identity and continue westward over the next couple of days. $$ Mundell