000 AXPZ20 KNHC 100301 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 031 UTC Mon Dec 10 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 0215 UTC. ...SPECIAL FEATURE... Gulf of Tehuantepec Gale Warning: High pressure is ridging southward along the eastern slopes of the Sierra Madre Oriental mountains of Mexico. The large pressure difference between the high and lower pressure south of Mexico will maintain gale to strong gale force winds over the Gulf until Tue night. Seas in the gale area are forecast to build to between 12 and 18 ft by late tonight. The strong gale force winds will continue through Tue, then diminish to minimal gale force Tue night. Winds will then rapidly decrease and become light by Wed evening as the strong high over the Gulf weakens and shifts E. Swell from this event is forecast to propagate S and SW well away from the Gulf of Tehuantepec region, with the leading edge of the 8 ft seas expected to reach near 09N110W by late Tue night or Wed. This area of 8 ft seas will merge with a larger area of 8 ft seas approaching from the NW by Wed night. 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 axis extends from 03N77W to 04N85W to 05N93W. The ITCZ continues from 05N93W to 09N108W, then resumes from 09N112W to 07N121W to 07N128W to beyond 07N140W. Scattered moderate and isolated strong convection is noted from 06N to 09N W of 123W. A surface trough splits the ITCZ from 07N110W to 10N110W to 14N109W. Scattered moderate and isolated strong convection is seen from 11N to 14N between 104W and 111W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A 1025 mb high pressure area is centered west of northern Baja California Norte near 33N124W. Strong high pressure is currently centered over the Great Basin as well. The pressure gradient between these high pressure areas and enhanced troughing across the Gulf of California is supporting fresh to strong NW winds across mainly southern half of the Gulf of California. Model guidance suggests seas in this area are as high as 6 ft. Looking ahead, strong high pressure building over the Great Basin well north of the area will support strong NW winds over almost all of the Gulf of California within 60 nm of the Baja Peninsula on Thu and Thu night. The most recent satellite-derived sea height data show that the long period NW swell arriving on the W coast of Baja have decayed and allowed seas in this region to fall to between 5 and 7 ft. A new group of NW swell in excess of 8 ft will reach the waters off the northern Baja California coast and near Guadalupe Island by late Mon, then spread east to cover most of the waters off the entire Baja California peninsula and the Revillagigedo Islands through Tue night, before subsiding below 8 ft through Wed evening. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo...Winds will pulse to strong speeds during the overnight and early morning hours over the Gulf of Papagayo tonight through Wed night as high pressure over the Gulf of Mexico builds SE toward the NW Caribbean Sea and Central America. Elsewhere, gentle to moderate winds will persist on either side of a weakening monsoon trough and seas in the range of 4 to 6 ft. REMAINDER OF THE AREA... A cold front extends from near 32N120W to 27N140W. The front is slowing down, which has allowed long period NW swell generated by winds behind the front to run out ahead of the front toward the SE. This will bring seas in excess of 8 ft to most of the area west of 120W through early Tue. This will reinforce the decaying NW swell lingering south of 20N which are mixed with shorter period trade wind swell. High pressure building behind the front will support generally fresh trade winds from 10N to 20N west of 125W through mid week, with fresh to strong winds possible west of 133W. Wave model guidance suggests that a rather large area of 8 ft seas associated with mixed swell will stretch from about 03N to 13N between 94W and 110W as a result of long period NW swell mixing with shorter period NE swell that propagate downstream from the Gulf of Tehuantepec and to a smaller extent those induced by the Gulf of Papagayo strong pulsing NE winds. This area will begin to merge with an even larger area of seas associated with NW swell which will encompass almost all of the forecast area W of 110W. $$ CAM