000 AXPZ20 KNHC 111401 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1505 UTC Tue Dec 11 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 1200 UTC surface analysis and satellite imagery through 1430 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: A tight pressure gradient over the Isthmus of Tehuantepec is producing a large area of strong gales across the Gulf of Tehuantepec. A scatterometer pass at 0400 UTC earlier this morning showed 40-45 kt winds extending from 16N95W to 14N95.5W and 30-40 kt winds between 94W and 97W north of 12.5N. The large area of strong gales will generate very large seas to 20 ft through this morning. Gale force winds will continue through the remainder of today and tonight, then rapidly decrease and become gentle to moderate by Wed 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 by early Wed, and merge with a larger 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 is analyzed from 05N77W to 05N93W. The ITCZ extends from 05N93W to 07N110W to 08N119W. The ITCZ resumes west of a surface trough from 08N125W to 08N140W. Scattered moderate convection is occurring from 06N to 14N between 114W and 139W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Gulf of Tehuantepec...After the ongoing high wind event tapers off on Wed, light to gentle winds are expected through Thu night. A strong cold front moving into the Gulf of Mexico will likely initiate another gale force wind event Fri through Sat night. High pressure NW of the area has a ridge axis that extends southeast to the Revillagigedo Islands. The pressure gradient between the high and troughing in the Gulf of California is supporting gentle to moderate NW winds across the entire Gulf of California. Model guidance suggests that the gradient will tighten early Thu, with fresh to strong winds expected over almost all of the Gulf of California Thu evening through Fri morning. 6 to 9 ft seas west of Baja California will continue over the region through Wed morning, then subside 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 near gale force tonight, remain fresh to strong Wed night, then diminish to 10-15 kt Thu. Fresh to strong winds will return Fri night. Seas of 8-10 ft can be expected under the stronger 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... A weakening cold front extends from 30N124W to 25N133W. NW swell associated with the front supports seas in excess of 8 ft across most of the area west of 120W. A tighter pressure gradient building between high pressure north of the front and lower pressures near the ITCZ will support fresh to strong NE trade winds from 09N to 28N west of 128W through Thu. 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 from the Gulf of Tehuantepec, and to a lesser extent those from the Gulf of Papagayo. 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 on Wed. A surface trough is analyzed from 13N125W to 06N127W. Associated winds are moderate to fresh, with seas to 8 ft. The trough is E 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. $$ Latto