000 AXPZ20 KNHC 300242 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 UTC Sat Dec 30 2017 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 0215 UTC. ..SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: After a brief pause of the N to NE gale force winds across the Gulf of Tehuantepec from late morning yesterday into the early afternoon hours as was noted in an Ascat pass, these winds have once again increased to gale force range. Seas with these winds are in the range of 10 to 14 ft. Ship with caller ID "LAQ07" reported combined waveheights of 13 ft near 15N96W at 00Z last night. The tight pressure gradient over southeastern Mexico will slacken through Saturday as high pressure over northeastern Mexico and the far western Gulf of Mexico slides eastward. The net result of this will be for the gale force winds to diminish winds below gale force at 15Z on Saturday morning. In addition, winds to the N of the area will veer Saturday which will further diminish winds funneling southward through the Isthmus of Tehuantepec and out across the Gulf of Tehuantepec. By Sunday, winds will diminish to 15-20 kt. Refer to the latest high seas forecast issued under AWIPS/WMO headers HSFEP2/FZPN03 for more details. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A surface trough extends from NW Colombia southwestward to a 1011 mb low at 06N79W and continues to 06N86W to 07N91W, where latest scatterometer data indicates that it transitions to the ITCZ and continues to 07N102W to 08N110W and 09N116W where it is briefly interrupted by a trough that is along a position from 17N128W to 13N129W to 09N130W. The ITCZ then resumes at 09N131W to beyond 09N140W. Scattered moderate convection is noted within 30 nm of the axis between 101.5W and 105W, and also between 112W and 115W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Gulf of Tehuantepec: Please refer to the special features section above for details on Gulf of Tehuantepec Gale event. Beyond 48 hours, a strong cold front will push into the Gulf of Mexico late on Sunday. The front will reach the Bay of Campeche Monday, with strong high pressure in its wake expected to induce the next gale force gap wind event over the Gulf of Tehuantepec, possibly as a strong gale. Elsewhere, tranquil marine conditions are expected with light to gentle winds prevailing over the forecast waters. Seas in the range of 3 to 5 ft will continue over the offshore waters, while seas in the 1 to 3 ft range will prevail in the Gulf of California. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... NE winds will pulse to fresh to strong over the Gulf of Papagayo through Wednesday of next week. Light to gentle NE to E winds will prevail elsewhere N of 09N, with gentle to moderate S to SW winds expected S of 09N except for light and variable along and near the surface trough. REMAINDER OF THE AREA... A weakening surface trough is analyzed along a position from 17N128W to 13N129W to 09N130W. The strong E winds observed yesterday and through a portion of Friday morning near the northern portion have diminished to fresh winds. Seas of 6 to 8 ft due to mixed NE and NW swells are evident from 16N to 19N between 120W and 130W. These seas will subside to 6 to 7 ft by early Saturday afternoon. Isolated showers are possible within 120 nm either side of the trough from 14N to 17N. Elsewhere, a broad and persistent upper trough is situated N of about 09N and between 109W and 120W. The trough energy in combination with abundant available moisture over this portion of the area is resulting scattered showers and isolated thunderstorms from 10N to 19N between 110W and 120W. Scattered showers and patches of rain are seen from 19N to 26N between 110W and 118W mainly due to divergence aloft on the SE sector of an upper level cyclonic circulation near 25N120W. These features will slowly move eastward through Sunday, with upper level moisture, in the form of mid to broken high clouds, continuing to stream eastward from the moisture area towards much of Baja California and central Mexico. Broad ridging dominates the waters north of 20N with gentle to moderate trades farther S, and seas 5 to 7 ft throughout the region. Little change is expected through Sunday. Beyond 48 hours, deepening low pressure will approach the northwest portion of the forecast area Sunday. The pressure gradient between this deepening low and high pressure to the W of the forecast area will bring strong to near gale force winds N of 25N and W of 130W, with the possibility for these winds to reach minimal gale force over this area Monday. $$ Aguirre