Eastern North Pacific Tropical Weather Discussion (Text)

AXPZ20 KNHC 120251

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0405 UTC Tue Dec 12 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
0230 UTC.


Gulf of Tehuantepec Storm Warning: A very tight pressure gradient
is sustained across the Isthmus of Tehuantepec by 1028 mb high 
pressure centered just west of Tampico Mexico. This tight 
pressure gradient will maintain strong gale force winds in the 
range of 30-40 kt over the Gulf of Tehuantepec until early on 
Tuesday, then diminish to minimal gale force by early on 
Wednesday. Seas are in the 12-18 ft range with these strong gale 
force, and will subside to 10-15 ft early in Tuesday and remain 
near those values through Wednesday. Fresh to strong NE-E winds 
extend downstream from the gulf to near 10N and 100W, where seas 
are in the 9-14 ft range primarily due to a NE swell. A large 
area of NE-E 15-20 kt winds is confined from 02N-15N between 90W-
110W, with seas of 8-12 ft in mixed NE and SW swell. This area 
is forecast to gradually shrink in coverage through Thursday. 


The Monsoon Trough axis extends from a 1009 mb low over NW 
Colombia to 09N79W to low pressure near 07N86W 1010 mb to 04N95W 
where latest scatterometer data indicated the ITCZ begins and 
continues to 08N108W to 10N119W where it is bisected by a trough
that is along a position from 20N114W to 14N119W to 10N125W. The
ITCZ resumes at 10N129W to beyond the area at 08N140W. No
significant convection is noted.



Gulf of Tehuantepec: Please see Special Features section above 
for details on the ongoing gale event. 

A weaker pressure gradient than the past few days is presently 
over the SW U.S. This is maintaining generally gentle to 
moderate NW winds across the gulf. The gradient will between 
very strong high pressure that builds southward over the western 
U.S. and the thermal troughing will support the NW winds to 
increase over the northern portion of the gulf beginning on 
Tuesday, with winds there reaching the fresh category. These 
winds then increase further to the strong category on Wednesday 
and through Wednesday evening. Mainly moderate NW-N winds over 
the offshore Pacific waters along with seas of 4-6 ft will 
change little through Thursday.

WITHIN 750 NM OF ECUADOR...Corrected

Gulf of Papagayo: The tight pressure gradient over southeastern 
Mexico has slackened just enough to allow for the recent gale 
force NE winds that were present across the Gulf of Papagayo to 
diminish to strong to near gale force winds this morning. N-NE 
winds of 20-25 kt are elsewhere N of 08N between 85W-86W. Model 
guidance indicates that these winds will change little through 
Wednesday with seas in the range of 8-10 ft. These seas will 
propagate to the SW away from the fetch area, and reach to near 
08N and 98W on Thursday.


A dissipating stationary front is across the NW corner of the 
area from 30N136W to 28N140W. The main issue over the western 
half of the area is the long period NW swell that is located
to the W of a line from 32N128W to 21N132W to 14N128W to 09N140W.
The swell is inducing seas of 8-12 ft, with the highest of these
seas N of 22N. The swell will gradually decay through Thursday,
at which time it is forecast to be the W of a line from 32N134W
to 23N140W along with seas of 8-11 ft.

The pressure difference between a trough roughly along a position
from 20N114W to 14N119W to 10N125W and the high pressure over 
the northern and central waters is forecast to result in strong 
NE to E winds beginning late tonight from 13N-18N and between
128W-137W along with seas of about 8-10 ft. This area of strong 
winds will diminish on Tuesday, with winds diminishing to 15-20 


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Page last modified: Tuesday, 12-Dec-2017 02:51:45 UTC