Eastern North Pacific Tropical Weather Discussion (Text)

AXPZ20 KNHC 182125

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
2115 UTC Wed Oct 18 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 1800 UTC surface analysis and satellite imagery through
2100 UTC.


Gulf of Tehuantepec Gale Warning: 
Gale force winds continue over the Gulf of Tehuantepec and will
persist through tonight, diminishing after sunrise Thursday once
the pressure gradient relaxes. Seas are up to 14 ft but will
gradually subside through Thursday. Expect winds to pulse to
fresh to strong, especially during the overnight hours, through
the upcoming weekend, with another gale force wind event 
possible early next week as the gradient tightens once again.


A tropical wave is N of 05N along 84W moving W at around 15 kt. 
Scattered to numerous moderate and isolated strong convection is
from 05N to 09N between 78W and 86W.


The monsoon trough axis extends from 10N76W to 09N94W to 08N102W
to 10N117W. The intertropical convergence zone axis extends from 
10N117W to 07N134W to 08N140W. Scattered moderate and isolated
strong convection is from 10N to 12N between 90W and 93W.
Scattered moderate convection is within 30 nm either side of the
axis between 94W and 102W, from 07N to 11N between 114W and 118W,
within 45 nm either side of the axis between 124W and 127W, and
also from 08N to 10N between 133W and 136W.



Please see the Special Features section above for information 
about the ongoing Gulf of Tehuantepec gale event.

A surface ridge extends SE into the waters off Baja California, 
producing mainly gentle to moderate NW to N winds and seas of 5 
to 7 ft. The ridge will remain in place during the next few days 
with little change in winds and seas over the offshore waters 
aside from the Gulf of Tehuantepec region as described above. By 
Friday evening a weakening cold front and accompanying set of 
large NW swell will propagate into the waters W of Baja 
California, causing seas to build to between 8 and 12 ft across 
the waters N of 26N. Seas will continue to build to 14 to 16 ft 
in NW swell N of 27N Friday night. This swell event will continue
propagating SE across the remaining offshore forecast waters W 
of Baja on Saturday. Also on Friday, expect increasing winds of 
20 to 25 kt over the waters adjacent to Baja California Norte as 
high pressure building in the wake of the front tightens the 
pressure gradient over the northern forecast waters. These winds 
will diminish on Saturday.

Mainly light and variable winds are expected over the Gulf of
California through Friday night. Winds will become northerly and
increase to moderate to fresh in the northern Gulf Saturday, 
then increasing to fresh to strong Sunday as the local pressure 
gradient tightens. The fresh to strong winds will then spread 
southward through the Gulf into early next week. Seas will stay 
mainly 2 ft or less, except for higher seas of 3 to 4 ft at the 
entrance to the gulf in SW swell, subsiding to 2 to 3 ft by 
Friday. The fresh to strong winds this weekend will build seas to
4 to 7 ft across the majority of the basin by early next week.


Moderate to fresh offshore winds will develop across the Papagayo
region each night through tonight, accompanied by seas of 5 to 7
ft. Otherwise, light and variable winds and seas of 4 to 6 ft in
SW swell will prevail N of the monsoon trough, while gentle to 
moderate SW to W winds and seas of 5 to 7 ft in SW swell will 
prevail S of the trough.

Long period S to SW swell will reach the area between Ecuador 
and the Galapagos Islands Thursday evening through Friday evening,
building seas to 7 to 8 ft on Friday.


Gentle to moderate winds are noted across the northern forecast 
waters under the influence of a ridge being weakened by an 
approaching cold front. Seas continue to subside across most of 
the region W of 110W. An area of 8 ft seas primarily in SE swell 
is present across the SW corner. A new set of long period S to 
SW swell is forecast to cross the Equator on Thursday and 
propagate across the far southern waters with resultant combined 
seas building back to 8 to 9 ft in the SW corner and far S 
central waters through Friday. The swell will then decay with 
seas subsiding to less than 8 ft during the upcoming weekend.

Models agree in bringing the cold front to the far NW corner of 
the discussion area by Thursday evening in a weakened state. A 
significant swell event will follow the front as it weakens and 
dissipates while moving across the area N of 28N. Seas will 
build to 10 to 17 ft over the NW waters Thursday night and 
Friday. The seas will spreading across all of the waters N of 08N
and W of 110W by Fri evening, then across all of the waters N of
the Equator and W of 108W by Sunday night. Seas of 8 ft or 
greater will reach all the way to 110W by early Sunday then 
continue to propagate SE, but begin to gradually decay 
thereafter through early next week.


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Page last modified: Wednesday, 18-Oct-2017 21:25:32 UTC