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Eastern North Pacific Tropical Weather Discussion (Text)



000
AXPZ20 KNHC 131525
TWDEP 

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1310 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 1200 UTC surface analysis and satellite imagery through
1445 UTC.

...SPECIAL FEATURES...

Gulf of Tehuantepec Gale Warning: A cold front forecast to enter
the NW Gulf of Mexico this afternoon will initiate gale to 
strong gale force winds across the Gulf of Tehuantepec by this 
evening. This long lived gale event will last until Mon 
afternoon. Peak winds will be 40 kt on Saturday as corresponding 
seas quickly building to between 16 and 18 ft.

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

The monsoon trough extends from 07N73W to 07N91W to 05N96W to 
05N102W. The ITCZ continues from 05N102W to 10N119W to 09N133W, 
then resumes from 07N136W to beyond 07N140W. Numerous moderate 
and scattered strong convection is observed within 30 nm either 
side of a line from 05.5N77W to 01.5N81W. Scattered moderate and 
isolated strong convection is occurring within 30 nm either side 
of a line from 05.5N92W to 06N103W.

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO... 

Over the open waters off Baja California, another pulse of NW 
swell is expected to reach Baja California Norte and Guadalupe 
Island tonight. This latest round of swell will sweep SE 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. A much stronger cold front will reach Baja 
California Norte by Mon night. Strong winds associated with this
front could brush 30N as the front crosses 30N140W. Long period 
NW swell as high as 18 ft could enter the waters adjacent to Baja
California Norte during this time frame. Swell as high as this 
would present a hazard to mariners as well as cause dangerously 
high surf along the Pacific Beaches.

Strong high pressure building over the Great Basin will support 
fresh to strong winds over the Gulf of California between 25N and
29N this afternoon through Fri morning. seas could approach 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 will taper off today but will 
return during the overnight and early morning hours Sat night,
then persist through Mon night as high pressure builds north of 
the region. Seas are expected to top out around 10 ft on Sun.

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 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 95W and 120W. This area consists of NE and E 
swell generated by gap winds, merging with longer period NW 
swell. Maximum combined sea heights in this area are 10 ft. This 
area of 8 ft seas will vanish by late tonight as these swell
decay.

Farther west, a persistent surface trough extends from 09N133W 
to 15N133W. The gradient between this trough and high pressure 
north of the region is supporting strong trade winds from 15N to
20N between 128W and 134W. Recent satellite-derived sea height
data indicate seas as high as 11 ft. The high will weaken today 
ahead of an approaching cold front, allowing the trade winds to 
diminish by tomorrow morning.

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 enter the forecast area early 
Sun in conjunction with the arrival of a strong cold front. Seas
of 12 ft or above could encompass almost all of the forecast
waters N of 07N and W of 115W by Tue morning.

$$
CAM

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Page last modified: Thursday, 13-Dec-2018 15:25:36 UTC