Tropical Weather Discussion

axpz20 knhc 211545

Tropical weather discussion
NWS National Hurricane Center Miami FL
1545 UTC Sat Oct 21 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 1200 UTC surface analysis and satellite imagery through
1800 UTC.

...Tropical waves...

The axis of a tropical wave is near 89w north of 09n. Earlier
convection associated with this tropical wave was likely also
influenced by overnight coastal effects, and has since

The axis of a tropical wave is near 97w N of 08n, moving W at 10
to 15 kt. No significant convection is noted.

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

The monsoon trough extends from 08n82w to 09n120w, where it
transitions to an intertropical convergence zone and continues
west to beyond 10n140w. Scattered moderate convection is noted
from 07n to 19n between 95w and 105w. Scattered moderate to
isolated strong convection is noted from 07n to 10n between 112w
and 117w, and from 08n to 10n between 135w and 140w. 


Offshore waters within 250 nm of Mexico...
the main forecast issue will be strong gales in the Gulf of
Tehuantepec next week. Fresh winds will pulse overnight tonight 
through the Gulf of Tehuantepec, related to local drainage 
effects. The pressure gradient will tighten starting late Sunday,
as a cold front moves through the western Gulf of Mexico Sunday 
night ahead of the northern portion of a tropical wave moving 
across northern Central America and the Yucatan Peninsula. These 
factors, along with cool, dry air behind the front reinforcing 
already present local drainage effects will allow strong to 
minimal gale winds starting Monday morning through the Gulf of 
Tehuantepec. The gradient will tighten further as high pressure 
behind the settles over the Southern Plains, northeastern Mexico 
and the western Gulf of Mexico through late Monday, allowing for 
stronger gales by early Tuesday persisting through mid week. Seas
will build as the gale conditions continue, reaching 12 ft 
Monday, and in excess of 15 ft by late Wednesday. The shorter 
period northerly swell resulting from the strong gap winds will 
propagate well to the south of Tehuantepec, mixing with longer 
period northwesterly and southerly swell through mid week.

Farther north, strong northwest to north winds are ongoing off 
the coast of Baja California north of Cabo San Lazaro between 
strong high pressure west of the area and troughing over the 
southwest United States and north central Mexico. These winds
will diminish as the troughing weakens. Seas will are peaking near
18 ft off the northernmost coast of Baja California norte in
northerly swell and are expected to subside through early next 
week as winds diminish and the swell decays. The swell will 
propagate se, with seas 8 ft or greater covering all of the 
offshore forecast zones W of Baja California through the weekend 
before subsiding below 8 ft the middle of next week.

High pressure building over the Great Basin region of the 
western United States will cause NW winds to strengthen over the 
Gulf of California through Tuesday, diminishing thereafter as the
gradient weakens. Winds will be strongest on Sunday night 
through Monday when seas peak around 8 ft.

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

gentle to moderate winds will prevail over the forecast area the
next several days. NW swell originating from the Gulf of 
Tehuantepec will propagate into the offshore waters of Guatemala 
and El Salvador by the middle of next week. 

Remainder of the area...

A set of large NW swell with seas near 15 ft will continue to
propagate se while gradually subsiding into early next week. Seas
will subside to less than 12 ft Sunday afternoon. Seas 
associated to this swell are expected to further subside, to 
less than 8 ft, by midweek.



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