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AXPZ20 KNHC 121538
TWDEP

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1535 UTC Tue Dec 12 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 1200 UTC surface analysis and satellite imagery through 1430 UTC.


...SPECIAL FEATURES...

Gulf of Tehuantepec Gale Warning: A tight pressure gradient continues across the Isthmus of Tehuantepec in southern Mexico. This gradient will maintain gale force winds in the range of 30- 40 kt in the Gulf of Tehuantepec today, then diminish to minimal gale by midday Wed, becoming 30 kt on Wed night. Max seas of 16-17 ft will subside to 13-15 ft later today. Fresh to strong NE-E winds extend downstream from the gulf to near 12N99W. A large area of seas of 8-12 ft in mixed NE and SW swell extends from the gale as far south as 01N and as far west as 113W. This area will gradually shrink in coverage through Thu.


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

The monsoon trough extends from 08N78W to 04N92W. The ITCZ continues from 04N92W to 08N120W to 09N130W to 09N140W. A surface trough extends from the ITCZ near 10N127W to 16N123W. Scattered moderate and isolated strong convection are from 09N to 16N between 115W and 134W.


...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

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

The gradient between strong high pressure building southward over the western U.S. and thermal troughing will support fresh to locally strong NW winds in the northern part of the Gulf of California today through tonight. Mainly moderate NW-N winds over offshore Pacific waters along with seas of 4-6 ft will change little through Friday.

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

Gulf of Papagayo: A tight pressure gradient over Central America supports strong to near gale force winds this morning. Model guidance indicates that these winds will change little through Wed with seas in the range of 8-10 ft. These seas will propagate to the SW away from the fetch area, extending beyond the offshore zones from 06N to 10N through Thu. Another round of strong winds are expected for the gulf beginning early Sat.

Elsewhere, gentle to moderate winds and seas of 5 to 7 ft are expected north of the monsoon trough while mainly moderate southerly winds are expected south of the monsoon trough with seas of 4 to 6 ft for the next few days.

REMAINDER OF THE AREA...

The pressure gradient between a surface trough from the ITCZ near 10N127W to 16N123W, and a 1028 mb high pressure centered near 36N128W supports fresh to strong NE winds from 11N to 18N, west of the trough axis to 140W. These winds are expected to diminish below 20 kt later tonight. The combination of these winds and NW swell supports seas of 10 to 11 ft over this area. A broader area of NW swell covers this portion of the basin roughly west of 120W and north of 08N. This area of 8 ft or greater seas will spread to the equator through Wed, while being reinforced by another batch of NW swell of 10 to 14 ft arriving across 30N140W. The result will be seas 8 ft or greater west of 120W through the remainder of the week. A trough of low pressure is expected to form west of 140W late this week, which will tighten the pressure gradient N of 15N and west of 135W supporting strong NE to E winds Fri and Fri night.

$$ Latto

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