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000
AXPZ20 KNHC 180336
TWDEP

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0405 UTC Fri Jan 18 2019

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 0000 UTC surface analysis and satellite imagery through 0215 UTC.


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

A surface surface trough extends from 02N78W to 01N84W to 06N87W to 05N93W, where latest scatterometer data indicated the ITCZ begins and continues to 04N104W to 05N109W to 05N115W where it briefly stops. It resumes at 05N118W to 06N130W and to beyond 07N140W. Scattered moderate convection is within 30 nm of the ITCZ between 135W and 140W.


...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

Strong to near-gale force winds prevail over the Gulf of Tehuantepec, with seas in the 8 to 10 ft range. Winds will pulse again to near gale force tonight. Winds will then diminish Fri as the pressure gradient weakens across the region. Fairly tranquil conditions will persist across the Gulf of Tehuantepec and downstream late Fri through Sat evening. The pattern will change abruptly Sat night, as a the leading edge of a strong cold front moves through southern Mexico, across the isthmus of Tehuantepec and into the adjacent waters of the Gulf of Tehuantepec. As strong high pressure surges southward behind the front over east-central Mexico, and the bulk of the cold air reaches the southern Gulf of Mexico, the initial gale force winds will intensify to a strong gale into Sun morning, possibly reaching minimal storm force. Seas will quickly build, with Wave model guidance suggesting values reaching near 24 ft by Sun afternoon. Meanwhile, a large plume of 25-35 kt winds and seas in excess of 12 ft is expected to push far south of the Gulf of Tehuantepec to near 09N and between 95W and 99W by early Sun evening. Model guidance indicates that strong north to northeast gale force winds will last into early Mon, with seas slowly subsiding. Marine interests transiting through the Gulf of Tehuantepec Sun into early next week should be aware of this upcoming gap wind event, and take necessary action to avoid hazardous marine conditions over the affected waters.

Elsewhere over the offshore waters outside of Tehuantepec... mainly gentle to moderate north to northeast winds are across the region north of 25N, with gentle to moderate breezes elsewhere. Northwest swell producing seas of 8-9 ft remains over the open waters beyond 120 nm north of Cabo Corrientes. A weak cold front will move into into northern Baja California Norte this evening. While the front will dissipate as it moves across Baja California and the Gulf of California through Fri, it will be accompanied by a new set of long-period northwest swell of 12-17 ft across the waters off Baja California. This swell will bring dangerous surf and large breaking waves across Baja California Norte Thu night through Fri. High pressure building behind the front will support fresh to strong northwest winds north of Cabo San Lucas late Fri into Sat.

Over the Gulf of California, high pressure building over the Great Basin north of the area will support fresh to strong northwest winds extending the length of the Gulf from Fri night through Sat. The strength, fetch and duration of the winds support wave heights to 8 ft in the southern Gulf of California by Sat night. Winds and seas will diminish by Sun as the high pressure weakens and shifts to the east.

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

The pressure gradient between high pressure north-northeast of the area, over the Gulf of Mexico and northwestern Caribbean Sea, and the equatorial trough will maintain strong gap winds across Papagayo and Panama through early Sat. Over Papagayo, fresh to strong gap winds will continue well to the west-southwest of the Gulf, with winds pulsing to near-gale force during the overnight and early morning hours. Over Panama, fresh to strong northerly gap winds will impact mainly the western Gulf of Panama extending into the waters south of the Azuero peninsula through late Fri night into early Sat.

Gap winds will diminish Sat and Sat night as high pressure north of the region shifts eastward ahead of a cold front. This will allow for the present tight pressure gradient across the area to the slacken. New high pressure will build in the wake of the front, supporting another round of even stronger gap winds through the Gulfs of Papagayo and Panama. Winds to gale force are possible through the Gulf of Papagayo Mon, with seas building to 8-11 ft from late Sun night through Mon.

REMAINDER OF THE AREA...

Low pressure of 1011 mb is centered near 06N116W, moving westward at 10 to 15 kt. The tight pressure gradient between it and high pressure over the northern waters is sustaining fresh to strong east winds from 07N to 12N between 112W and 115W along with seas of 10-12 ft. The low will continue to weaken through tonight and open into a trough by early on Fri as it reaches 115W. The trough will weaken further as it continues westward along the ITCZ over the next several days.

A dissipating cold front surrounding by high pressure extends from near 32N121W to 30N130W, where it transitions to a warm front northwestward from there. The front has ushered in a new set of NW swell. Large seas in the range of 12 to 21 ft continue to the northwest of a line from 32N125W to 22N140W. Seas over the area associated to this swell have peaked and will slowly subside as the swell propagates southeastward. Elsewhere, seas in excess of 8 ft cover much of the forecast waters west of 105W.

A ridge will build across the waters north of 25N in the wake of the front. This will result in a tightened pressure gradient, and strengthening winds across the subtropics and tropics regions. The ridge will weaken into Sun, allowing for winds and seas to decrease across the tropics. Seas of 8 to 9 ft will continue from Sun into next week south of about 26N and west of 127W due to a a mix of northwest swell and remaining windwaves from local trade winds.

$$ Aguirre

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