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AXPZ20 KNHC 252207
TWDEP

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
2205 UTC Mon Sep 25 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 1800 UTC surface analysis and satellite imagery through 2100 UTC.


...SPECIAL FEATURES...

Tropical Depression Pilar has degenerated into an elongated trough of low pressure today, now extending from near Cabo San Lucas in Baja California Sur to near the W coast of mainland Mexico, just north of Mazatlan in southern Sinaloa. All of the significant convection and heavy rainfall associated with this system has shifted NE and inland, and currently extends from southern Sinaloa across the Sierra Madre Occidentales to NE Mexico across portions of Coahuila. Winds and seas have quickly subsided across the Gulf of California, and the remaining weather threat of this remnant system is heavy rainfall across the mountainous interior and slopes of Mexico. See the last NHC Forecast/ Advisory for Pilar under AWIPS/WMO headers MIATCMEP3/WTNT23 KNHC for more details.


..INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...

The monsoon trough axis extends from 10N75W TO 15.5N96W TO 13N107W TO low pressure 12.5N126.5W 1010 MB TO beyond 11N140W. Scattered moderate to strong convection is from 03N to 14.5N E of 94W, from 10N to 15.5N between 94W and 104W, and from 60 nm N to 150 nm S of the trough between 121W and 140W.


...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

Wind and seas associated with the remnants of Pilar will affect the southern Gulf of California through Tuesday, where winds will remain at 10 to 20 kt and seas 4 to 6 ft.

A high pressure ridge reaches SE into the waters west of Baja California to near 19N116W, with the associated pressure gradient expected to maintain moderate NW winds along the Pacific coast of Baja through tonight. The ridge will weaken in response to low pressure passing well to the north and NW winds will become gentle to moderate Tuesday through Thursday night. Fresh SW to W monsoonal winds well offshore of the Gulf of Tehuantepec will generate SW wind waves in the SE waters and maintain seas in this area of 5 to 7 ft.

OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR...

An active monsoon trough near and along the coast of Central America from Guatemala to Panama will remain the focus for active convection over the coastal waters the next few days. Expect moderate to SW to W winds to prevail south of the trough, with gentle to moderate offshore or variable winds north of the trough through Friday night.

Long period SE to S swell will decay and allow seas west of Ecuador and south of the Equator to subside from around 6 ft to around 5 ft during the next couple of days.

REMAINDER OF THE AREA...

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.

Fresh to strong winds occurring around low pressure embedded in the monsoon trough near 12.5N126.5W are supporting a surrounding area of 8 to 10 ft seas in mixed swell. Fresh to strong winds extend farther E to near 120W there, where seas are 8-9 ft. Monsoonal SW winds will remain fresh to strong across this general area between 09N and 14N through Wed and maintain seas 8- 9 ft.

Otherwise, high pressure centered well N of the area, and low pressure associated with the monsoon trough will maintain moderate to occasionally fresh trade winds W of 120W through tonight. Low pressure passing north of the area will weaken the high, allowing trades to decrease for the remainder of the week.

$$ Stripling

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