000 AXPZ20 KNHC 140735 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 UTC Sat Oct 14 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... A 1007 mb low pressure is centered near 12N111.5W. Shower and thunderstorm activity associated with this low continues to show signs of organization. Satellite imagery indicates some banding feature on the east side of the low center with moderate to isolated convection from 10N to 12N between 110W and 112W. A cluster of moderate to strong convection is noted from 12N to 13N between 110W and 111W. Additional development is expected, and a tropical depression is likely to form over the next day or two while the system moves toward the west- northwest at 10 to 15 mph. There is 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... A tropical wave is along 85W N of 04N. The wave is embedded within an area of deep layer moisture as depicted in the TPW animation. Clusters of moderate to isolated strong convection are noted behind the wave axis, but mainly over the SW Caribbean Sea, eastern Panama, and from 06N to 7.5N E of 79W. INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 10N85W to 09N95W to 1007 mb low pressure near 12N111.5W to 11N119W to 10N137W. The ITCZ extends from 10N137W to beyond 11N140W. Scattered moderate convection can be found from 06N to 08N between 94W and 96W, from 10N to 14N between 98W and 101W, from 08N to 11N between 112W and 115W, from 10N to 13N between 115W and 119W, and within 30 nm of the trough between 123W and 130W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A surface ridge extends across the waters off Baja California. The pressure gradient between the ridge and a trough over the Gulf of California is supporting gentle to moderate NW winds in the offshore waters of Baja California. Seas of 4 to 7 ft prevail over the offshore waters west of the Baja California peninsula, with northerly swell just pushing into the waters north of 26N and west of 118W raising seas to 7 to 9 ft. The ridge will remain in place this weekend with little change in winds. By this evening, seas of 5-7 ft will prevail across most of the offshore waters W of 110W. On Sunday, marine guidance suggests moderate easterly winds and building seas just west of the Revillagigedo Islands in association with a developing low pressure to the south. High pressure across the eastern slopes of the Sierra Madre Mountains in Mexico continues to induce strong northerly gap winds across the Gulf of Tehuantepec. The strong winds over the Gulf will pulse to near gale force during the overnight and early morning hours the next couple of days. Winds will further increase to gale force Monday through early Wednesday morning as high pressure builds behind a front moving into the Gulf of Mexico. Seas downstream from the Gulf will build to 8-11 ft during the times of maximum winds through Monday. Maximum seas of 13-15 ft are expected with the gale force winds, forecast to increase to 35-40 kt at night. 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 Sat and continue through Mon with seas of 5-7 ft. Light and variable winds and seas of 4 to 5 ft seas prevail N of 09N, while gentle to moderate SW to W winds and 5 to 7 ft seas are currently observed across the area S of 09N. Little change is expected in the wind direction. Seas will increase slightly through the weekend as cross-equatorial SW swell reaches the region. REMAINDER OF THE AREA... Please see special features section above for more information on low pressure centered near 12N111.5W. Elsewhere, high pressure of 1040 mb centered NW of the area near 42N144W extends a ridge southeast to near 23N115W. The pressure gradient between the ridge and the monsoon trough is producing an area of fresh to strong NE winds northwest of a line from 30N125W to 25N130W to 20N136W with seas of 8-12 ft based on altimeter data. Winds are forecast to diminish across the northern forecast waters today as high pressure weakens some and the resulting pressure gradient loosens. Seas will gradually subside, but 8-9 ft seas will continue to affect much of the area N of 20N W of 120W by this evening. In addition, long period SW swells from the Southern Hemisphere will continue to propagate across the south- central waters, particularly S of 15N between 105W-115W over the next couple of days. $$ GR