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Tropical Weather Discussion


Issued Active alert

Start Time

Tue 09/18/2018 10:39 AM EDT

End Time

Tue 10/02/2018 10:39 AM EDT



Full Alert Message

Tropical Weather Discussion NWS National Hurricane Center Miami FL 1439 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 1200 UTC surface analysis and satellite imagery through 1445 UTC. ...SPECIAL FEATURE... The broad area of low pressure currently centered SW of the Cabo San Lucas is expected to organize slowly and remain nearly stationary until tonight, then will slowly develop and start tracking NNE to 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 as the low/possible tropical cyclone passes inland over interior Mexico from the Gulf of California or dissipates. 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 the coast of northern Colombia near 12N73W to 09N79W to 10N86W to 11N90W to 09N104W to 10N110W, then resumes from 14N123W to 11N136W. The ITCZ continues from 11N136W to beyond 11N140W. Scattered moderate isolated strong convection is present within 150 nm of the coast of South America, Central America and Mexico between 77W and 100W, from 07N to 12N between 105W and 110W and from 10N to 12N W of 130W. ...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 arrive on the coast of Central America. A modest pulse of long period swell with up to a 20 second period is forecast to reach the coastal waters on Wed morning. Seas are expected to be in the 5 to 7 ft range. REMAINDER OF THE AREA... A slightly tighter pressure gradient between a 1027 mb high centered northwest of the area near 37N145W and the ITCZ supports fresh winds from 12N to 22N west of 122W with seas to 9 ft. The center of high pressure is forecast to gradually strengthen while it moves ESE but remains N of the area. This will sustain the fresh to strong winds in this region with seas up to 9 ft through Thu afternoon. Finally, the center of low pressure located near 16N121W will continue to track WSW, accompanied by fresh to strong winds mainly within 300 nm in the NW quadrant. Seas in this sector of the low will range between 8 to 9 ft. The low is forecast to weaken gradually Fri and Sat, and the associated winds and seas will subside.