Tropical Weather Discussion
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000
AXPZ20 KNHC 212204
TWDEP

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
2205 UTC Tue Feb 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 1800 UTC surface analysis and satellite imagery through
2100 UTC.

...SPECIAL FEATURE...

Gulf of Tehuantepec Gale Warning...High pressure is building
southward across eastern Mexico in the wake of a frontal system
moving slowly eastward across the Gulf of Mexico today. Strong
winds generated west of the front are beginning to funnel
through the Chivela pass into the Gulf of Tehuantepec, and are
believed to have increased to 20-30 kt late this afternoon.
These northerly gap winds are expected to increase further to
gale force through this evening, with seas building to 12 ft
tonight. This gap wind event will be brief as winds peak at
minimal gale force this evening and tonight, then diminish below
gale force by sunrise Wednesday morning and then gradually
diminish to 20-25 kt Wednesday afternoon.

Refer to the High Seas Forecast product under AWIPS/WMO headers
MIAHSFEP2/FZPN03 KNHC for additional details.

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

There is no ITCZ over the forecast waters north of the equator.

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

Please see above for information on the Gulf of Tehuantepec gale
force gap wind event.

Moderate to fresh northerly winds prevail across much of the
forecast waters west of Baja as indicated by the latest
satellite-derived wind data. Seas continue in the 6-9 ft range
in NW swell across the Baja offshore waters, and 5-8 ft across
the waters adjacent to southwest Mexico. A modest pressure
gradient between a 1026 mb high pressure centered near 28N123W
and lower pressure across the western flanks of the Sierra
Madres is producing fresh to locally strong northwesterly winds
across most of the Gulf of California, where seas are running 3-
6 ft. These winds will diminish very slowly over the next 24
hours while the strongest winds shift into N portions of the
gulf.

A fresh pulse of NW swell generated by a cold front west of the
area is moving toward the Baja California Norte offshore waters
this afternoon. This swell will continue to propagate across the
waters off the west coast of the Baja California peninsula and
maintain seas in the 8-12 ft range over this area through early
Friday. Building high pressure west of Baja California is
expected to produce fresh to strong NW winds along the western
Baja California coast north of 25N Wednesday night through
Thursday night and over the Gulf of California N of 30N on
Thursday morning. Winds will subside as the high weakens in
response to low pressure approaching from the west. Seas are
then expected to subside below 8 ft in this area Friday night
through the weekend. Another cold front could bring yet another
round of NW swell to Baja waters on Monday.

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

Gulf of Papagayo: Moderate to locally fresh winds this morning
will subside by this evening.

Gulf of Panama: Moderate winds will become light on Wednesday.

Otherwise, winds will be in the light to gentle range over the
forecast area.

REMAINDER OF THE AREA...

High pressure of 1026 mb is stationary ear 28N123W. A frontal
boundary has stalled across the northern waters from 30N125W TO
21N140W. Winds in the vicinity of this front have diminished to
20 kt or less. Large NW swell generated north of the front
continues to produce peak seas of 12-15 ft near 29N133W and
propagate SE across the forecast waters. The front is beginning
to weaken, and is expected to dissipate later today. This NW
swell will continue to dominate the forecast waters, with seas
greater than 8 ft covering much of the forecast waters north of
10N and west of 110W. A small area of 20 to 25 kt NE winds is
expected to affect the waters from 22N to 25N west of 133W along
the dissipating frontal boundary Wednesday and Wednesday night.
Areal coverage of seas greater than 8 ft will start to decrease
the second half of the week.

$$
Stripling



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