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AXPZ20 KNHC 191456
TWDEP

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1304 UTC Wed Dec 19 2018

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 1500 UTC.


...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: A cold front will sweep across the Gulf of Mexico today through Thu. High pressure building in the wake of the front will help generate a tight pressure gradient over the area and usher in the next gale force gap wind event. Winds will rapidly increase to gale force gale force by late Thu. The plume of strong gap winds will reach at least 500 nm to the south and southwest of the Gulf of Tehuantepec by late Fri, with seas building as high as 18 ft with the area of strong winds. The gales will persist through Fri night, then diminish into Sat as the high pressure north of the area weakens and shifts east. Fresh to strong gap winds will then persist across the Gulf of Tehuantepec into early next week.


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

The ITCZ extends from 05N98W to 05N115W to 08N136W to 08N140W. Scattered moderate isolated strong convection is noted from 02N to 06N E of 80W. Scattered moderate convection is noted from 03N to 06N between 85W and 92W. Scattered moderate convection is noted from 04N to 07N between 101W and 105W. Scattered moderate isolated strong convection is noted within 60 nm of the ITCZ west of 132W.


...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

Please see above for more on the upcoming gale force gap wind event over the Gulf of Tehuantepec.

Large NW swell continues to impact the forecast waters, with seas in the 11 to 13 ft range over the waters off the Baja California Peninsula to the Revillagigedo Islands. This swell will continue to produce hazardous seas for mariners, and create large and powerful surf along the Pacific reefs and beaches. This high surf may also produce coastal flooding and beach erosion in many exposed locations from southern California to western Mexico. This swell will decay to 8 to 11 ft by this evening, just ahead of another round of NW swell to 12 ft reaching Guadalupe Island and the northern coast of Baja California early on Thu. This next swell will decay below 12 ft by Thu evening, with seas in the 8 to 10 ft range over the open waters off Mexico west of 110W through Sat.

High pressure building over the Great Basin will support fresh to strong winds across the central Gulf of California through Thu morning, with seas building to 5-8 ft.

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

Gulf of Papagayo: A cold front will move across the SW Caribbean on Fri morning. Strong northerly winds behind the front will funnel through the Gulf of Papagayo, increasing to near gale force by late Fri night. A tight pressure gradient between high pressure building behind the front and lower pressure in the SW Caribbean will support the continuation of the gap wind event through Sun night. Seas are expected to peak near 12 ft by Sat morning. Winds and seas will gradually diminish from Sun night to Mon night.

Northerly fresh winds are expected in the Gulf of Panama Sat night through early on Mon, with seas to 7 ft.

Elsewhere, gentle to moderate winds will persist, with seas in the 4 to 7 ft range.

REMAINDER OF THE AREA...

High pressure of 1027 mb is centered north of the area near 33N127W. The pressure gradient between this area of high pressure and lower pressure in the vicinity of the ITCZ will support moderate to fresh trade winds north of the ITCZ to around 20N. A sharp upper trough will cutoff west of the area, and help develop a quasi- stationary trough along the ITCZ west of 135W by late Thu. This will lead to a locally tighter pressure gradient over this area, with tradewinds strengthening N of the ITCZ to near 15N and west of 135W by late Thu into early Fri.

NW swell continues to prevail across the discussion area. Seas of 8 ft or greater are noted W of 103W. Another set of NW swell has entered the NW waters, with seas of 12 to 16 ft noted NW of a line from 30N133W to 24N140W. Seas will start to subside over the area today, falling below 8 ft N of 20N by Sat morning.

$$ AL

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