000 AXPZ20 KNHC 050354 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 UTC Wed Dec 5 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 0330 UTC. ...SPECIAL FEATURE... Gulf of Tehuantepec Gale Warning: Strong high pressure ridging southward along the eastern slope of the Sierra Madre mountains is helping to create a tight pressure gradient over southeastern Mexico. This has recently resulted in gale force northerly winds across the Gulf of Tehuantepec. The gradient will maintain these gale force winds through early on Thu. The southern extent of the strong winds will reach as far south as 12N98W on Wed morning. Maximum waveheights with this event are expected to be in the range of 8 to 12 ft on Wed before subsiding some late on Wed. Models suggest the next gap event will begin on Sun morning with strong gale force northerly winds developing on Sun afternoon and continuing into Sun night. .INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from NW Colombia near 08.5N74W westward across the Gulf of Panama to 08N92W to 09N101W to 08N106W, where Ascat data from during the day on Tue showed it transitioned to the ITCZ continuing to 09N120W to 08N130W to beyond 09N140W. Scattered moderate convection is within 120 nm south of the ITCZ between 119W and 123W, within 90 nm north of the monsoon trough between 85W and 88W, and within 60 nm north of the ITCZ between 118W and 123W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Gulf of Tehuantepec...See special features paragraph above. Gulf of California: Fresh northerly winds across the Gulf will diminish to light and variable winds by this afternoon. Fresh southerly winds will briefly occur over the northern Gulf of California on Wed evening ahead of a weakening cold that is expected to approach the extreme northern section of Baja California Norte and move across the northern and central Gulf of California Thu night through Fri night while dissipating. Moderate west to northwest winds will follow in behind the front. Gentle to locally moderate northerly flow is expected across the entire gulf waters on Sat. Fresh to locally strong northwest winds are expected across the southern gulf waters on Sun. Elsewhere, Light to gentle northerly flow, and 4 to 6 ft seas, are west 110W, while and north of 26N. Light to gentle northeast flow, and 3 to 5 ft seas to the east of 110W. Winds will become southwest to west in the fresh range range west of Baja California Norte on Wed in advance of a cold front that will move across the northern portion of the area and weaken as it approaches the northern part of the Baja California Peninsula. It will be accompanied by long-period northwest swell, with seas in the 6 to 9 ft range. These seas will propagate southward while building to 8 to 10 ft are they reach to near 19N by late on Fri. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... The Santa Maria Volcano located at 14.45N 91.33W has been observed on satellite imagery emitting steam and ash, and is spreading southwestward reaching the Pacific waters of Guatemala between 14N91.5W and near the Mexican border at 15N92W, extending west-southwestward to near 13.8N93.5W. This ash is dispersing quickly and is thought not to be falling to the surface. However, local mariners are urged to exercise caution across this area and the volcano remains active. Gulf of Papagayo...Nocturnal pulses of fresh to locally strong NE winds are expected across and downstream of the Gulf through Fri night, with peak winds in terms of areal coverage forecast for Wed Night through Thu night. The resultant northeast swell will bring seas in the range of 6 to 8 ft as far west as 08N96W by Thu evening. Elsewhere, the monsoon trough will exist near 08N through early Thu, before shifting slightly southward during Thu as it gradually becomes ill-defined through Sun night. Light to gentle variable flow, with seas of 3 to 5 ft mainly due to SW swell are forecast elsewhere to the north of the monsoon trough, and moderate southwesterly monsoonal flow, with seas of 4 to 6 ft in S to SW swell are expected south of the monsoon trough through the period. REMAINDER OF THE AREA... A cold front is analyzed from near 32N124W to 24N130W to 21N140W. High pressure is building eastward behind the front across the northwest part of the area. Strong south to southwest winds are within 60 nm east of the front north of 29N. The front will weaken as it reaches from near 32N121W to 23N130W and dissipating stationary to 21N140W by early Wed, with the strong winds ahead of diminishing to fresh intensity. Larges sea of 10 to 13 ft due to long-period NW swell will follow in behind the front and propagate through most of the area, with the leading edge of the 8 ft or greater seas reaching a line from near 23N113W to 10N122W to 05N140W by Late Fri. Another cold front is forecast to approach the far northwest corner of the area by early Sat preceded by fresh southwest winds. Yet another large set of long period swell will propagate through the northwest part of the area ahead of the front, with induced seas of 8 to 10 ft. A weak surface trough may be forming along 101W from 08N to 11N. The GFS model indicates that an inverted surface to low-level trough may form near 100W later in the week and propagate westward. $$ Aguirre