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KF5JRV > WX 18.10.17 13:22l 141 Lines 6361 Bytes #999 (0) @ NA
BID : 6173_KF5JRV
Read: GUEST
Subj: NWS NHC Eastern N Pacific WX 10/18
Path: IW8PGT<CX2SA<XE1FH<N9PMO<NS2B<KF5JRV
Sent: 171018/1121Z 6173@KF5JRV.#NWAR.AR.USA.NA BPQK6.0.14
000
AXPZ20 KNHC 180930
TWDEP
Tropical Weather Discussion
NWS National Hurricane Center Miami FL
601 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 0600 UTC surface analysis and satellite imagery through
0900 UTC.
...SPECIAL FEATURES...
Gulf of Tehuantepec Gale Warning:
Gale force winds are blowing across the Tehuantepec area. Salinas
Cruz, Mexico is reporting sustained N winds of 25 kt. This gap
wind event is the result of a tight pressure gradient between
high pressure across the eastern slopes of the Sierra Madre
Mountains in Mexico, and across the western Gulf of Mexico in the
wake of a stationary front which extends from N to S over the
central Bay of Campeche. Seas are in the range of 10 to 15 ft
across the area of gale force winds, with seas of 8 ft or
greater spilling out to areas downwind of the gale. Global model
guidance indicates that the high pressure will weaken through
Thursday, with the corresponding tight gradient slackening. This
will allow for the gale force winds to eventually diminish to
below gale force just after sunrise on Thursday, however,
northerly winds of 20 to 30 kt will continue through Friday along
with seas of 8 to 10 ft. Looking ahead, another gale force wind
event is possible early next week.
...TROPICAL WAVES...
A tropical wave is N of 06N along 83W, moving W at 10 to 15 kt.
A cluster of moderate to isolated strong convection is along the
wave axis near 13N. This convective activity is currently
affecting Nicaragua.
...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
The monsoon trough axis extends across parts of Panama and Costa
Rica near 10N86W to 08N100W to 09N110W. The intertropical
convergence zone axis continues from 09N110W to 10N120W to 07N135W
to beyond 09N140W. Scattered moderate to strong convection is
noted along the coast of Colombia N of 03N, and in the Gulf of
Panama N of 07N. Scattered moderate isolated strong convection
is from 08N to 11N between 94W and 100W, and from 08N to 11N
between 110W and 130W.
...DISCUSSION...
OFFSHORE WATERS WITHIN 250 NM OF MEXICO...
Please see the Special Features section above for information
about the ongoing Gulf of Tehuantepec gale event.
A surface ridge extends across 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 afternoon into Friday evening a weakening cold front and
accompanying set of large NW swell will propagate through the
waters W of Baja California building seas to 8 to 12 ft across
the waters N of 27N. Seas will continue to build to 14-15 ft in
NW swell by Friday night. This swell event will continue to
propagate across the offshore forecast waters on Saturday. Also
on Friday, expect increasing winds of 20to 25 kt over the waters
adjacent to Baja California Norte as high pressure in the wake
of the front begins to dominate the northern forecast waters.
Mainly gentle to moderate NW to N winds are expected over most
of the Gulf of California through early Wednesday, then winds
become light and variable through Friday. Seas will be mainly 2
ft or less, except for higher seas of 3 to 5 ft at the entrance
to the gulf in SW swell subsiding to 3 to 4 ft Wednesday through
Thursday night, and then to 2 to 3 ft on Friday. Seas will build
back to 3 to 5 ft near the entrance during the upcoming weekend
as southerly swell reaches the area.
OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND
WITHIN 750 NM OF ECUADOR...
Moderate to fresh offshore winds will develop across the Papagayo
region each night through Thursday night, with seas of 5 to 7
ft. 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.
Swells originating from the gale force wind event in the Gulf of
Tehuantepec will reach the far western section of the offshore
waters of Guatemala and El Salvador, building seas to 8 to 10 ft
there through this afternoon, subsiding to 6 to 8 ft this
evening, and to 5 to 6 ft on Thursday. Long period SW swell is
forecast to reach the area between Ecuador and the Galapagos
Islands from Thursday evening into Friday, building seas to 7 to
8 ft on Friday.
REMAINDER OF THE AREA...
The low pressure area previously located near 24N128W has
weakened, and a surface trough is analyzed on the 0600 UTC
surface map extending from 22N128W to 27N128.5W. Winds and seas
have diminished in association with this feature.
The low pressure area located over the west-central waters near
16N140W has also weakened and now a trough is analyzed west of
the forecast region. Seas of 8 to 9 ft in mixed NE and NW swell
are still noted over the forecast waters in association with
this trough from 15N to 21N W of 136W. A pair of altimeter
passes confirmed the presence of these sea heights.
Elsewhere, gentle to moderate winds are noted across the
northern forecast waters under the influence of a weak ridge.
Seas continue to subside across most of the region W of 110W
with an area of 8 ft seas in mixed swell S of 05N W of 130W. A
new set of long period southerly 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 before decaying
during the upcoming weekend.
Looking ahead, a cold front is forecast by the global models to
reach the far NW corner of the forecast region by Thursday night.
A significant swell event will follow the front, with seas
building to 10 to 17 ft over the NW waters Thursday night into
early Friday before spreading across all the northern waters W
of 115W, and across the west-central waters by late Friday night.
Seas of 8 ft or greater will reach all the way to 110W by early
Sunday then will begin to gradually decay while reaching to 100W
thereafter.
$$
GR
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