axpz20 knhc 140335

Tropical weather discussion
NWS National Hurricane Center Miami FL
0405 UTC Fri Dec 14 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 0000 UTC surface analysis and satellite imagery through 
0230 UTC.

...Special features...

Gulf of Tehuantepec gale warning: a cold front has entered the 
NW Gulf of Mexico early tonight and will move quickly 
southeastward through the Bay of Campeche Fri to initiate gale to 
strong gale force winds across the Gulf of Tehuantepec by late 
Fri afternoon. Computer model guidance suggests that these gales 
will continue through the weekend and will last until Mon 
afternoon. Peak winds are forecast to be around 40 kt on Sat as 
corresponding seas quickly building to near 18 ft. The first 
blast of strong northerly winds associated with this event is 
expected to start across the Gulf of Tehuantepec Fri afternoon.

...Intertropical convergence zone/monsoon trough...

The monsoon trough extends from 08n75w to 10n86w to 06n101w. The 
ITCZ continues from 06n101w to 10n136w to beyond 08n140w. 
Scattered moderate isolated strong convection is observed from 
01n to 08.5n to the east of 93w. An upper level trough across 
far NW portions of the area is creating a large area of overcast 
middle and high level clouds, and scattered light to moderate 
elevated convection from 16n to 26n between 122w and 134w.


Offshore waters within 250 nm of Mexico... 

Over the open waters off Baja California, gentle northerly winds 
and modest seas of 4-6 ft prevail early tonight. Another pulse 
of NW swell is expected to reach Baja California norte and 
Guadalupe island overnight and cause seas to build to between 7 
and 11 ft for the offshore waters along the length of the Baja 
Peninsula by Fri afternoon. A cold front approaching 30n140w 
late tonight will introduce more long period NW swell to baja 
waters by Sun morning and maintain sea heights at 7-9 ft through 
Mon morning. Looking ahead, a much stronger cold front will 
reach Baja California norte by Mon night. Strong winds 
associated with this front could brush along 30n as the front 
crosses 30n140w. Long period NW swell of 10-18 ft will enter the 
waters adjacent to Baja California norte during this time frame. 
Swell of this size and period will present hazardous seas for 
mariners, as well as cause very powerful and dangerous surf 
along the Pacific reefs and beaches.

Strong high pressure building over the Great Basin is supporting 
the development of fresh to strong winds over the Gulf of 
California between 25n and 29n early tonight, and will prevail 
across the Gulf through Fri morning. Seas will reach 7-8 ft over 
the southern Gulf tonight. Winds and seas will subside through 
Sat as the high pressure shifts eastward.

Offshore waters within 250 nm of Central America, Colombia, and 
within 750 nm of Ecuador... 

Gulf of papagayo...strong gap winds tapered off this afternoon 
but will pulse to around 20 kt tonight and Fri night before 
returning to fresh to strong during the overnight and early 
morning hours Sat night. These conditions will then persist 
through Mon night as high pressure builds north of the region. 
Seas are expected to Max out near 10 ft Sun morning.

Gulf of Panama...fresh northerly winds across and downstream of 
the Gulf have begun to back to the NW this evening and will 
slowly diminish through Sat, then become fresh from the north 
Sat night through sun.

Elsewhere, gentle to moderate winds will persist on either side 
of the monsoon trough through the remainder of the week, with 
seas remaining in the 4-6 ft range.

Remainder of the area... 

A large area of mixed seas persists over much of the North 
Pacific between 98w and 120w. This area consists of NE and E 
swell generated by recent Central American gap wind events, 
merging with longer period NW swell. Maximum combined sea 
heights in this area are now down to 9 ft, and will 
diminish by late tonight as these swell decay.

Farther west, a persistent surface trough extends from 09n137w 
to 18n132w. The gradient between this trough and high pressure 
north of the region is supporting strong trade winds from 15n to 
20n between 125w and 140w. Recent satellite-derived wave height 
data indicate seas as high as 12 ft. The high will weaken 
tonight ahead of an approaching cold front, allowing the trade 
winds to diminish to around 20 kt by Fri morning.

A cold front will reach from 30n135w to 28n140w by early Fri, 
and be accompanied by a new round of NW swell with seas of 12 to 
15 ft. The front will dissipate late Fri, with the swell 
subsiding as well. Elsewhere NW swell in excess of 8 ft will 
more or less dominate the waters west of 110w through sun. Very 
large NW swell, in excess of 20 ft, will enter NW portions of 
the forecast area early sun in conjunction with the arrival of a 
strong cold front. Seas of 12 ft or higher could encompass 
almost all of the forecast waters N of 07n and W of 115w by Tue 


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