Tropical Weather Discussion

axpz20 knhc 130910

Tropical weather discussion
NWS National Hurricane Center Miami FL
1005 UTC Thu Dec 13 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.

...Special features...

Gulf of Tehuantepec gale warning: a cold front forecast to move 
into the Gulf of Mexico later today will initiate strong gale 
force winds across the Gulf of Tehuantepec Fri afternoon, then 
continue through sun. Peak winds will be 40 kt on Saturday, with 
seas quickly building to 16-18 ft by early Sat.

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

The monsoon trough extends from 05n77w to 03n80w to 08n85w to 
05n99w. The ITCZ continues from 05n99w to 06n111w to 09n118w to 
08n140w. No significant convection is observed.


Offshore waters within 250 nm of Mexico... 

Over open waters off Baja California, another pulse of NW swell 
is expected to reach Baja California norte and Guadalupe island 
tonight. This new swell will sweep southeastward through early 
Sat, with significant wave heights reaching 10 ft. 

Strong high pressure building over the Great Basin will support 
fresh to strong winds in the northern Gulf of California today, 
eventually spreading across most of the Gulf through Fri with 
seas approaching 8 ft over the southern Gulf. 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...fresh to strong gap winds with seas to 9 ft 
will resume during overnight and early morning hours Sat night 
as high pressure builds north of the region.

Gulf of Panama...fresh northerly winds will pulse to around 20 
kt this morning, then back to the NW and diminish through Sat.

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

Remainder of the area... 

A large area of mixed seas persists over much of the North 
Pacific east of 110w, consisting of primarily NE and E swell 
from gap winds, merging with longer period NW swell. Maximum 
combined sea heights in this area are 10 ft, but will subside 
below 8 ft tonight.

Farther west, a surface trough continues from 08n to 13n along 
132w. The gradient between this trough and high pressure north 
of the region is supporting fresh trade winds from the ITCZ to 
20n, west of 115w. Scatterometer passes indicate strongest winds 
are between 16n and 17n. Seas are 10 ft in this area, in a mix 
wind waves and long period NW swell. The high will weaken today 
ahead of a cold front, allowing the trade winds to diminish.

A cold front will reach from 30n135w to 28n140w by early Fri, 
and be accompanied by a new round of NW swell of 12 to 15 ft. 
The front will dissipate later on 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 move into the area early sun.



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