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AXPZ20 KNHC 110920
TWDEP

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
841 UTC Mon Dec 11 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 0900 UTC.


...SPECIAL FEATURES...

Gulf of Tehuantepec Storm Warning: A very tight pressure gradient is sustained across the Isthmus of Tehuantepec by 1032 mb high pres centered just west of Tampico Mexico. This pressure gradient will be augmented by nocturnal drainage flow to maintain storm force winds of 40-50 kt over the Gulf of Tehuantepec until around dawn on Mon, with seas in the 14-21 ft range. A swath of 30 to 40 kt gale force winds surrounds the area of storm force winds within 60 nm either side of a line from 16N95W to 14N96W to 13N97W, with corresponding seas in the 12-18 ft range. Fresh to strong NE-E winds extend downstream from the gulf to near 10N and 100W, where seas run 8-11 ft primarily in NE swell. Seas 8 ft or greater are propagating well away from the Gulf to near 106W this evening. The area seas 8 ft or higher will spread even farther W to near 110W on Monday. Gales are forecast to continue over the Gulf of Tehuantepec through Wednesday night, then abruptly subside to below 20 kt by noon on Thu.

Gulf of Papagayo Gale Warning: Strong high pres ridging SSE over Central America and the SW Caribbean Sea has induced NE gale force winds of 30 to 35 kt over the Gulf of Papagayo. N to NE winds of 20 to 30 kt are occurring elsewhere downstream from the gale force winds over an area from 06.5N to 11N between 85.5W and 90W. The pressure gradient will loosen enough to allow for these gale conditions to diminish to strong to near gale force NE winds late Monday morning and then to strong NE winds Tuesday evening. Seas of 8 to 10 ft will propagate to the SW well away from the fetch area and reaching from 05N to 11N between 86W and 91W by Monday evening. The area of seas 8 ft or greater will begin to diminish on Tuesday as winds subside and the swell decay.


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

The Monsoon Trough axis extends from east Panama at 08N78W to 06N93W. The ITCZ continues from 06N93W to 08N114W to 11N118W. THE itcz resumes from 09N123W to beyond 08N140w. Scattered moderate convection is from 07N to 09N between 104W and 107W.


...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

Gulf of Tehuantepec: Please see Special Features section above for details the ongoing storm event.

High pressure over the Great Basin has weakened enough to allow fresh to strong northerly winds over the northern Gulf of California to subside. N to NE winds funneling through the Baja California peninsula into the Pacific waters have diminished to light and variable. High pres ridging to the NW will maintain gentle to moderate winds and 4-6 ft seas will persist through Thu night.

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

Gulf of Papagayo: See the Special Features section above for details on the ongoing gale event that will last a few more hours.

Strong high pressure ridging southeastward over Central America and the NW Caribbean is generating strong to gale force NE winds over the Gulf of Papagayo and nearby waters. Large NE swell from a Tehuantepec gap wind event will spread across the offshore waters of Guatemala and El Salvador through Mon. Localized gap pulses of strong NE winds are expected off the coast of El Salvador and Guatemala, including Gulf of Fonseca through Mon morning.

REMAINDER OF THE AREA...

A cold front crosses the NW corner of the area from 30N136W to 26N140W. Strong S to SW winds ahead of the front and N of 29N have subsided as the front begins to weaken. Seas will run 8 to 14 ft in NW swell N of a line from 30N133W to 21N140W. The front will dissipate by late Monday night, however, long period NW swell will maintain seas of 8-11 ft W of a line from 30N126W to 20N129W to 13N128W to 09N140W. The swell will gradually decay through Wed morning, with seas of 8-11 ft expected W of a line from 20N122W to 00N137W. The pressure difference between the tropics along 10N and the high pressure over the northern waters is forecast to result in strong NE to E winds beginning late Monday night from 13N-18N, and to the W of 129W along with seas of 8 to 10 ft. This area of strong winds will shift W of 130W by noon on Tuesday, then diminish to between 15 and 20 kt late Tuesday.

$$ Formosa

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