389 AXPZ20 KNHC 080858 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0858 UTC Sat Sep 8 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 0600 UTC surface analysis and satellite imagery through 0830 UTC. ...SPECIAL FEATURES... Hurricane Olivia centered near 21.2N 136.6W at 08/0900 UTC or 1040 nm E of Hilo Hawaii moving WNW at 13 kt. Estimated minimum central pressure is 980 mb. Maximum sustained wind speed is 80 kt with gusts to 100 kt. Numerous moderate to strong convection is occurring within 45 nm in the N semicircle of Olivia, and within 90 nm in the S semicircle. Olivia is forecast to continue moving WNW and gradually weaken, and will pass across 140W and into the Central Pacific basin Sat night while maintaining minimal hurricane strength. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCPEP2/WTPZ32 KNHC for more details. Elongated low pressure of 1008 mb is analyzed near 15N115.5W is moving westward around 5 to 10 kt. Associated scattered moderate to strong convection is within 180 nm in the S semicircle and between 240 nm and 390 nm in the SW quadrant. This system is expected to bring increasing winds and seas over a portion of the Pacific waters roughly from 08N to 20N between 108W and 125W through at least Mon, as it gradually becomes better organized. This low has a high chance of tropical cyclone formation during the next 48 hours. ...TROPICAL WAVES... A tropical wave has an axis N of 03N along 93W with the northern portion extending across eastern Mexico, moving westward at 10 to 15 kt. Associated scattered moderate and isolated strong convection is from 05N to 09N between 91W and 94W, and also N of 13.5N between 92W and 94W near the Gulf of Tehuantepec. A tropical wave has an axis N of 05N along 102W to the southern coast of Mexico, moving westward at around 10 kt. Associated convection has diminished with isolated showers and thunderstorms near the wave axis. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from near 11N85W to 08N97W to 14N106W to low pres near 15N115.5W to 11N122W. No significant convection outside of the convection mentioned with the tropical waves above is present. Scattered moderate and isolated strong convection is located in the W central waters where the monsoon trough has become diffuse. This convection is from 10N to 13N between 132W and 135W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A surface trough will meander between the the Gulf of California and the Baja California Peninsula the next few days. A ridge building between Baja California and departing Hurricane Olivia will produce moderate to fresh NW winds W of the Baja peninsula through early today, eventually diminishing to gentle by Sun. SW swell from a developing tropical low SW of the offshore waters of southern Mexico will spread N and NE to build seas across the offshore waters to 7 to 8 ft through the day. Gentle to moderate winds are expected elsewhere over the Mexico offshore waters through the weekend, with seas of 5 to 7 ft over the Pacific waters. In the Gulf of California, moderate winds varying in direction on either side of the trough will increase to moderate to fresh in the northern Gulf late tonight even briefly reaching strong early Sun. Seas will start out in the 1 to 3 ft range across the Gulf, except 3 to 5 ft near the entrance, and will build to 2 to 4 ft elsewhere by late tonight into Sun as the winds increase. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... The monsoon trough will meander between 08N and 10N during the next few days. Winds on both sides of the trough axis will be gentle to moderate. Long period cross equatorial SW swell propagating into the area has resulted in seas building to 7 to 9 ft between Ecuador and the Galapagos Islands. This swell is spreading into the waters off Colombia, and will persist through much of the weekend. The swell will begin to subside by the end of the weekend into early next week, with another pulse arriving by late Mon through Wed night. REMAINDER OF THE AREA... Please see the Special Features section for details on Hurricane Olivia, and on developing low pressure near 15N115.5W. Otherwise, a ridge drapes across Olivia and dominates the forecast waters N of 20N W of 120W, producing gentle to moderate easterly winds south of 30N and west of 122W. Seas generated by Olivia will continue to spread across the waters north of 12N and west of 120W over the upcoming weekend. $$ Lewitsky