AXPZ20 KNHC 260952

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
635 UTC Tue Sep 26 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 0830 UTC.


The remnants of Tropical Depression Pilar in the form of a small cluster of weak convection are located about halfway between Mazatlan and Culiacan Mexico near 24N107W. A residual trough of low pressure lingering in the wake of Pilar extends from near Cabo San Lucas in Baja California Sur to near Mazatlan Sinaloa. Surface observations and initial model wind fields both suggest winds in this area are 15 knots or less. Seas in the 4 to 6 ft range near the mouth of the gulf of California should subside to between 2 and 4 ft by Wednesday afternoon. Low level moisture still pooling along the western slopes of the Sierra Madre Occidental and the coastal zones from Guadalajara to central Sinaloa through tonight will produce scattered showers and thunderstorms, some yielding very heavy rain.


The monsoon trough axis extends from 11N72W to 09N80W to 17N93W to 13N103W to low pressure near 13.5N124.5W 1008 MB to 10N133W to beyond 11N140W. Scattered moderate and isolated strong convection is present in an area bounded by 09N83W to 05N89W to 10N107W to 16N94W to 09N83W and within 90 NM either side of the trough axis between 119W and 128W.



As described above, winds and seas associated with the remnants of Pilar have subsided to 15 kt or less and 6 ft or less, respectively over the southern Gulf of California. Winds and seas will continue to diminish through tonight. Light to gentle winds are then expected to prevail over the southern Gulf of California through Fri. Winds will be gentle to moderate over the northern Gulf of California during the same time frame.

A weakening high pressure ridge reaches SE into the waters west of Baja California to near 20N118W. The weakened pressure gradient on the east side of the ridge will maintain light to moderate NW winds along the Pacific coast of Baja through Thu night. The ridge will remain weaken as low pressure passes well to the north. Fresh SW to W monsoonal winds well offshore of the Gulf of Tehuantepec will generate SW swell and wind waves which will maintain seas of 5 to 7 ft in this area.


An active monsoon trough along and inland of the coasts of Central America from Guatemala to Panama will remain the focus for active convection over the coastal waters the next few days. Expect moderate SW to W winds to prevail south of the trough, with gentle to moderate variable winds north of the trough through Friday night. Winds will freshen in this region over the weekend in response to a developing area of low pressure over Central America. Active convection will prevail across the regional waters for the next few days.

Long period SE to S swell will maintain 5 to 6 ft seas west of Ecuador and south of the Equator during the next few days.


NW to N swell generated by strong winds north of the area are producing 6 to 7 ft seas N of 20N and W of 120W. Pulses of reinforcing N swell will maintain seas in the region between 6 and 8 feet through Wed night, then seas will subside.

Fresh to strong winds occurring around low pressure embedded in the monsoon trough near 13N124.5W are supporting an associated area of 8 to 11 ft seas in mixed swell. Mixed swell are maintaining seas of 8 to 9 ft from 10N to 16N between 120W and 128W. Monsoonal SW winds will remain fresh to strong across this general area through Wed, then subside.

Otherwise, weakened high pressure centered well N of the area and low pressure associated with the monsoon trough will maintain light to moderate trade winds W of 120W through Fri night.

$$ CAM