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Eastern North Pacific Tropical Weather Discussion (Text)



000
AXPZ20 KNHC 200202
TWDEP 

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0405 UTC Fri Oct 20 2017

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 
0430 UTC.

...TROPICAL WAVES...

A tropical wave is N of 04N near 90W moving slowly W around 5 
kt. Scattered moderate and isolated strong convection is noted 
from 06N to 08N between 89W and 92W. 

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

The monsoon trough extends from 10N82W to 09N121W.  The ITCZ 
continues from 09N121W to beyond 10N140W.  Scattered moderate 
convection exists within 60 nm of the trough from 93W to 98W. 
Scattered moderate and isolated strong convection is occurring 
within 60 nm of the ITCZ west of 138W.  

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

High surface pressure over the Gulf of Mexico along with lower 
pressure along the Pacific monsoon trough have been forcing gap 
wind flow though the Chivela Pass in southeastern Mexico. 
This has been producing a Gulf of Tehuantepec gap wind event, 
which has weakened to near gale conditions, though no new 
observations have been available recently, and peak seas near 8 
ft.  Forcing for this gap wind event will gradually fade and 
drop to winds 20 kt or lower and seas less than 8 ft by Saturday 
afternoon.  

The next cold front pushing across the Gulf of Mexico on Sunday 
will initiate the next Tehuantepecer wind event.  This is likely 
to reach gale force on Monday through Wednesday and may approach 
storm force on Wednesday.

A cold front has reached the northwest corner of our region at 
30N140W.  As the front approaches the Baja California peninsula 
on Friday, winds along the northwest coast will reach strong 
breeze out of the northwest Friday morning and continue only 
through Saturday afternoon. While winds associated with the cold 
front will quickly diminish, large 12 to 16 ft NW swell will be 
reaching the zones along the northwest coast of the Baja 
California peninsula starting Friday night.  These swell are the 
result of a large and powerful low pressure system along the 
Alaska coastline. This large 15-20 second period swell will 
reach the zones near the southwestern coast of the Baja 
California peninsula on Saturday and then drop below 12 ft late 
Sunday.  8 to 12 ft NW swell will reach the zones near 
southwestern Mexico by early Sunday and fade by late Monday.  

As high pressure builds in over the U.S. Great Basin, N to NW 
winds will set up over the Gulf of California from Sunday 
through Tuesday.  Currently, these are forecast to reach strong 
breeze conditions, though near gale are certainly possible. 
Accordingly, wind waves from the long fetch of N to NW winds 
blowing lengthwise through the Gulf of California are 
anticipated to reach up to 8 ft.  

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

No winds of strong breeze or greater are expected in the area 
for the next several days.  Tonight, seas of 8 ft will be 
reaching the southernmost zones from a combined SE and S swell. 
This will diminish by early Saturday.  

REMAINDER OF THE AREA...

A cold front has reached the northwest corner of our region at 
30N140w.  As the front approaches the Baja California peninsula 
on Friday, winds along the northwest coast will reach strong 
breeze out of the northwest Friday morning and continue only 
through Saturday afternoon. Elsewhere winds associated with the 
front will remain at 20 kt or less.  Rapidly building seas 
associated with long-period 15-20 second swell have approached 
the northwestern corner of our region, as observed by a 23Z 
altimeter pass.  These seas will reach 12 to 16 ft and are the 
result of a large and powerful low pressure system along the 
Alaska coastline. The swell will push southeastward across most 
of the region, while gradually diminishing over the next few 
days. Peaks seas will drop below 12 ft Sunday afternoon and the 
8 ft swell will finally diminish by Wednesday.  

The tradewinds are fresh breeze and weaker across the remainder 
of the areas.  These should remain weak for the next several 
days.

No tropical cyclone formation is anticipated over the next 
several days.

$$ 
Forecaster Landsea

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Page last modified: Friday, 20-Oct-2017 02:02:55 UTC