234 AXPZ20 KNHC 180938 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1005 UTC Tue Sep 18 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 0900 UTC. ...SPECIAL FEATURE... The low pressure currently centered southwest of the Revillagigedo Islands is expected to stay nearly stationary through this evening, then will start tracking NNE and reach central Baja early on Thu. Fresh to locally strong winds and building seas to 9 ft are forecast for the southern and central Gulf of California starting Wed evening. Winds and seas in this portion of the gulf will continue through Thu evening when the low/possible tropical cyclone will be inland Baja California or likely already dissipated. As indicated in the latest Tropical Weather Outlook, although environmental conditions appear conducive for tropical cyclone formation, the large size of the system and possible land interaction should prevent any significant or rapid development from occurring during the next two days. However, there is still a medium chance of this system becoming a tropical depression Wednesday or Thursday. Regardless of development, this broad disturbance will likely produce very heavy rainfall over Baja California Sur later this week. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from northern Colombia near 09N75W and continues to 10N86W to 10N95W to 08N105W, then resumes from 20N105W to a 1007 MB low near 18N114W to a 1008 mb low near 15N120W to 12N127W. The ITCZ begins near 12N128W and continues beyond 10N140W. Scattered moderate isolated strong convection is N of 06N E of 98W and from 12N to 20N between 106W and 118W, and from 13N to 18N between 119W and 125W. Scattered moderate convection is from 07N to 17N west of 134W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A surface trough over the Baja Peninsula will maintain light to moderate winds over the Gulf of California through this morning. Afterwards, the winds are forecast to increase to moderate to fresh speeds in response to a high pressure ridge building to the NW. Winds over the gulf N of 29N are forecast to become strong and from the S to SE early on Wed continuing through Thu morning. Fresh to strong winds are then expected to develop over the central and southern Gulf of California as a low pressure or possible tropical cyclone traverses the area Thu. See the Special Features section above for further details. Building pressure to the NW is generating fresh winds W of Baja California Norte continuing through Wed morning. On the other hand, N swell will cause seas to build to just above 8 ft generally N of 27N between 118W and 127W tonight through Thu night. Otherwise, pulses of long period SW swell will continue to impact the entrance of the Gulf of California, and the waters W of Baja California through tonight. Variable light to gentle winds will be elsewhere, except for moderate NE gap winds in the Gulf of Tehuantepec through Thu. Seas are forecast to be in the 4 to 7 ft range. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... The monsoon trough is expected to remain in the vicinity of 07N to 12N during the next several days. Winds will be light to gentle N of the trough and gentle to moderate S of the trough. Cross-equatorial SW swell will continue to impact the coast of Central America through tonight followed by a modest pulse of long period swell with up to a 20 second period reaching the coastal waters on Wed morning. Seas are expected to be in the 5 to 7 ft range. REMAINDER OF THE AREA... A slightly tight pressure gradient between a 1026 mb high centered northwest of the area and the ITCZ supports fresh winds from 16N to 20N west of 129W with seas to 9 ft. The center of high pressure is forecast to gradually strengthen while it moves east-southeast N of the area. This will allow for the re- development of fresh to strong winds in this region with seas to 9 ft. Enhanced winds and seas in this area is forecast to prevail through Thu afternoon. Finally, the center of low pressure located near 15N120W will continue to track WSW along with fresh to strong winds mainly within 300 nm northwest quadrant of it. Seas in this region of the low will be in the 8 to 9 ft range. The low is forecast to weaken gradually Fri and Sat, and the associated winds and seas will subside. $$ Ramos