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AXPZ20 KNHC 192208
TWDEP

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
2205 UTC Thu Oct 19 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 2030 UTC.


...TROPICAL WAVES...

A tropical wave is N of 04N near 89W moving slowly W around 5 kt. Scattered moderate and isolated strong convection is noted from 06N to 08N between 84W and 90W. This convection is situated just SW of the coasts of Panama and Costa Rica.


...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...

The monsoon trough extends fro 09N78W to 10N121W. The ITCZ continues from 10N121W to beyond 10N140W. Scattered moderate convection exists within 60 nm of the trough from 95W to 110W. Scattered moderate and isolated strong convection is occurring within 60 nm of the ITCZ west of 138W.


...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

High surface pressure over the Gulf of Mexico along with lower pressure along the Pacific monsoon trough have been forcing gap wind flow though the Chivela Pass in southern Mexico. This has been producing a Gulf of Tehuantepec gap wind event, which previously was a gale. A partial ASCAT scatterometer pass at 1632Z over the western Gulf of Tehuantepec showed peak N to NE winds of 25 kt. It's likely that near gale winds are still occurring of the central and eastern portion of the Gulf. No observations of peak wave heights have been available in the Gulf of Tehuantepec, though they likely are still near 10 kt. Forcing for this gap wind event will gradually fade and drop to winds 20 kt or lower and seas less than 8 ft by Saturday afternoon.

The next cold front pushing across the Gulf of Mexico on Sunday will initiate the next Tehuantepecer wind event. This is likely to reach gale force on Monday through Wednesday and may approach storm force on Wednesday.

A cold front is currently northwest of our region. As the front approaches the Baja California peninsula on Friday, winds along the northwest coast will reach strong breeze out of the northwest Friday morning and continue only through Saturday afternoon. While winds associated with the cold front will quickly diminish, large 12 to 16 ft NW swell will be reaching the zones along the northwest coast of the Baja California peninsula starting Friday night. These swell are the result of a large and powerful low pressure system along the Alaska coastline. This large 15-20 second period swell will reach the zones near the southwestern coast of the Baja California peninsula on Saturday and then drop below 12 ft late Sunday. 8 to 12 ft NW swell will reach the zones near southwestern Mexico by early Sunday and fade by late Monday.

As high pressure builds in over the U.S. Great Basin, N to NW winds will set up over the Gulf of California from Sunday through Tuesday. Currently, these are forecast to reach strong breeze conditions, though near gale are certainly possible. Accordingly, wind waves from the long fetch of N to NW winds blowing lengthwise through the Gulf of California are anticipated to reach up to 8 ft.

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

No winds of strong breeze or greater are expected in the area for the next several days. Tonight, seas of 8 ft will be reaching the southernmost zones from a combined SE and S swell. This will diminish by early Saturday.

REMAINDER OF THE AREA...

A cold front is currently northwest of our region. As the front approaches the Baja California peninsula on Friday, winds along the northwest coast will reach strong breeze out of the northwest Friday morning and continue only through Saturday afternoon. Elsewhere winds associated with the front will remain at 20 kt or less. Rapidly building seas associated with long-period 15-20 second swell will reach the northwestern corner of our region tonight. These will reach 12 to 16 ft and are the result of a large and powerful low pressure system along the Alaska coastline. The swell will push southeastward across most of the region, while gradually diminishing over the next few days. Peaks seas will drop below 12 ft Sunday afternoon and the 8 ft swell will finally diminish by Wednesday.

The tradewinds are fresh breeze and weaker across the remainder of the areas. These should remain weak for the next several days.

No tropical cyclone formation is anticipated over the next several days.

$$ Forecaster Landsea

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