000 AXPZ20 KNHC 150824 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 UTC Sun Oct 15 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 0600 UTC surface analysis and satellite imagery through 0900 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: A recent scatterometer pass provides observations of northerly winds in the 20-30 kt range over the Gulf of Tehuantepec. Winds are forecast to further increase to minimal gale force by early Monday morning as high pressure builds over the eastern slopes of the Sierra Madre Mountains in Mexico and the western Gulf of Mexico in the wake of a cold front moving across the region. This gap wind event is expected to continue through at least midweek. Seas will reach 13-15 ft during the overnight and early morning hours when winds will peak near 40 kt. A low pressure of 1007 mb remains embedded within the monsoon trough near 15.5N116.5W. A recent ASCAT pass indicates winds of 20-25 kt within about 210 nm on the E semicircle of the low center. A cluster of moderate to strong convection is within 75 nm NE quadrant of low. Scattered moderate isolated strong convection is noted elsewhere from 10N to 18N between 113W and 120W. This system is gradually becoming better defined. Environmental conditions appear conducive for a tropical depression to form during the next day or two while the system moves west-northwestward to northwestward at 10 to 15 kt. There is currently a high probability that this low will develop into a tropical cyclone within the next 48 hours. Please refer to the latest Tropical Weather Outlook for more information. ...TROPICAL WAVES... The axis of a tropical wave is analyzed near 90W N of 04N, moving westward at 10-15 kt. Convection has diminished in association with this wave, and now only a few showers are noted near the wave axis. INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 11N85W to 09N95W to 12N105W to low pres near 15.5N116.5W to low pres near 10N130W to 09N135W. The ITCZ extends from 09N135W to 09N140W. Scattered moderate convection was noted from 06N to 08N between 86W and 89W. Scattered moderate isolated strong convection was noted from 08N to 11N between 91W and 96W. Scattered moderate isolated strong convection was noted from 09N to 18N between 111W and 118W. Scattered moderate convection was noted from 10N to 12N between 126W and 129W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see Special Features section above for information about the Gulf of Tehuantepec. A surface ridge extends across the waters off Baja California producing gentle to moderate winds and seas of 6-7 ft. Today and tonight seas will build to 8-10 ft across the waters S of 20N and west of the Revillajijedo Islands as the aforementioned low pressure moves west of the offshore forecast waters. Otherwise, the ridge will remain in place during the next few days with little change in winds and seas. High pressure building over the Great Basin region will help to strengthen winds over the northern Gulf of California early Sunday, and continue through early Monday. The area of high pressure will then shift eastward which will help to decrease winds over this area. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Moderate to fresh offshore winds will develop across the Papagayo region tonight and continue through Tuesday with seas of 6-7 ft. Light and variable winds and seas of 4-6 ft seas prevail N of 09N, while gentle to moderate SW to W winds and 5-7 ft seas are currently observed across the area S of 09N. Little change is expected with these marine conditions through Monday. Seas propagating downstream of the Gulf of Tehuantepec (where a gale force gap wind event is expected) will reach the offshore waters of Guatemala and El Savador building seas to 9-10 ft Monday night and Tuesday. REMAINDER OF THE AREA... Please see special features section above for more information on low pressure centered near 15.5N116.5W. Elsewhere, high pressure of 1035 mb centered NW of the area near 39N148W extends a ridge southeast to near 25N115W. The pressure gradient has relaxed over the northern forecast waters, and winds have diminished to 20 kt or less. However, northerly swell continues to propagate across these waters, with seas of 8 to 10 ft from 10N to 20N W of 120W, and west of a line from 30N122W to 20N130W. The swell will continue to subside across the waters N of 20N W of 120W today. Cross equatorial southwesterly swell will continue to propagate across the south-central waters, particularly S of 15N between 100W-130W trough late Monday. $$ GR