AXPZ20 KNHC 150903

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
903 UTC Sat Dec 15 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 0600 UTC surface analysis and satellite imagery through 0900 UTC.


Gulf of Tehuantepec Gale Warning: Gap winds into the Gulf of Tehuantepec are reaching gale force this morning, and will likely increase slightly to a strong gale through today as a cool and dry area of high pressure builds north of the region. Peak winds will reach 40 kt today with seas to 18 ft. The gales are expected to persist into Monday.


The monsoon trough extends from 06N77W to 05N93W. The ITCZ continues from 05N93W to 09N128W. Scattered moderate convection is noted within 90 nm either side of the ITCZ between 118W and 128W.



The weak ridge over the area has diminished ahead of a weak cold front approaching the region from the west. The relaxed pressure gradient is maintaining light to gentle breezes across the area. NW swell with seas to 9 ft persist in the offshore waters of Baja California through the Revillagigedo Islands. The front will dissipate through today before reaching the area, but associated NW swell will reinforce the existing swell through Sun.

Looking ahead, a second cold front will approach the region early next week. This will bring a new group of NW swell, with seas in excess of 12 ft reaching the northern coast of Baja California Norte and Guadalupe Island by early Mon. Swell of 12 to 15 ft will cover the Baja offshore waters to the Revillagigedo Islands into mid week. Swell of this size and period will present hazardous seas for mariners, cause very powerful and dangerous surf along the Pacific reefs and beaches, and likely produce areas of modest coastal flooding and beach erosion.

Over the Gulf of California, strong high pressure north of region have been supporting moderate to fresh breezes across the basin. These winds will diminish through today as the high pressure weakens and shifts eastward.

A mid to upper-level disturbance approaching the area from the west may bring a few showers to the central and southern portions of the Baja California Peninsula and Gulf of California through Sun.


Gulf of Papagayo...Fresh to strong gap winds will pulse starting tonight and persist into early next week as high pressure builds north of the area. The gap winds will diminish into mid week, but strong pulses may persist during mainly overnight and early morning hours. Seas are expected to max out near 10 ft Sun morning.

Fresh winds will also pulse across the Gulf of Panama and Gulf of Fonseca tonight and Sun.

Elsewhere, gentle to moderate winds will persist on either side of the monsoon trough through early next week, as seas remain in the 4 to 6 ft range.


A mid to upper level disturbance passing 125W north of 18N is supporting scattered moderate convection from 18N to 21N between 120W and 125W. The upper feature has also been supporting a surface trough, currently reaching from 07N135W to 17N125W. a scatterometer satellite pass from 0230 UTC indicated fresh to strong winds on the northern end of the surface from 17N to 19N between 121W and 128W. Concurrent altimeter passes showed seas to be as high as 12 ft in this area, due to the local winds and a component of longer period NW swell. NW swell in excess of 8 ft covers most of the area north of 06N and west of 115W.

Farther north, a weakening cold front reaches from 30N131W to 25N140W. The front will dissipate through late today as it moves eastward. A second front approaching from the northwest will enter the region tonight, and move eastward across the waters north of 20N through early next week. The main impact will be a new round of NW swell, with combined seas in excess of of 12 ft to as high as 20 ft propagating across most of the region north of 12N and west of 120W Sun through late Mon.

Looking ahead toward early to mid week, the leading edge of this next round of NW swell will be mixing with shorter period NE and E swell emerging from the gap wind areas, and possibly even southerly swell, to create an area of confused seas south of 12N between 95W and 110W.

$$ Christensen