Eastern North Pacific Tropical Weather Discussion (Text)

AXPZ20 KNHC 180935

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1005 UTC Thu Jan 18 2018

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 
0845 UTC.


Gulf of Tehuantepec Gale Warning: Strong high pressure continues
to build southward across eastern Mexico and the western Gulf of 
Mexico behind yet another cold front, and is supporting a tight 
pressure gradient across southern Mexico. Gale force winds of 40 
to 45 kt prevail across and downwind of Tehuantepec and are 
expected to continue through the early morning hours of Thu. 
Winds are then expected to gradually diminish below gale force 
by Friday afternoon. The resultant plume of northerly swell will 
continue to propagate well southward of the Gulf of Tehuantepec 
waters, mixing with long period NW swell to produce seas in 
excess of 8 ft to near 650 nm due S of Tehuantepec and over 800 
nm SW of the there through this morning. Maximum seas tonight 
will remain around 20 ft near the strongest winds, and gradually 
subside by the end of the week as the winds diminish.


A surface trough axis extends from 07N77W TO 09N86W TO 04N98W. 
Overnight scatterometer winds suggest a transition to ITCZ from 
04N98W continuing on to 06.5N109W to beyond 07N140W. Scattered 
moderate isolated strong convection is occurring from 04N to 10N 
between 77W and 86W. Scattered moderate isolated strong 
convection is within 60 nm of the axis between 90W and 107W. 
Scattered to locally numerous moderate to strong convection is 
occurring within 90 nm S and 150 nm N of ITCZ between 108W and 
121W, and from 06N to 14N between 121W and 136W.



Please see the special features section for information about 
the ongoing gale warning in the offshore waters of the Gulf of 

In the Gulf of California, light to moderate NW flow is expected 
across across the entire gulf waters through Friday afternoon.
Winds will become southerly Friday evening ahead of an 
approaching cold front, increasing to fresh to strong in the 
northern gulf Friday night, then shifting to NW to N behind the 
front. The front will gradually become ill defined as it moves 
southward through the gulf during the day Saturday with mainly 
moderate to fresh northerly flow in its wake for the end of the 
weekend. The ill defined remnants of the front are expected to 
push S to the entrance of the gulf by Sun afternoon, when the 
pressure gradient will begin to tight across the area leading to 
fresh to strong winds developing across the full length of the 
gulf Sun evening and night.

Elsewhere across the offshore waters of Mexico, large NW swell 
continues to propagate SE across the waters, with seas of 8-11 
ft prevailing, except 5-8 ft between 98W and 105W. This large 
swell continues to generate high and powerful surf along the 
coasts and outer reefs of the Baja California peninsula and 
mainland Mexico, which will continue through Thu, with coastal 
flooding possible. Another pulse of NW swell will reach the 
offshore waters off Baja California Norte Thursday night. Seas 
will peak near 13-15 ft by Friday, while seas of 12 ft or 
greater will spread across the offshore waters off the entire 
length of the Baja Peninsula through the upcoming weekend.


Fresh NE gap winds prevailing across the regional waters between 
Papagayo and Tehuantepec will pulse to strong each night and 
early morning across the Gulf of Papagayo and other typical gap 
wind areas through Saturday morning, diminishing thereafter. 
Elsewhere, mainly light to gentle offshore winds will prevail N 
of 09N, with light to gentle southerly flow S of 09N. NW swell 
originating from the gale wind event in the Gulf of Tehuantepec 
along with longer period NW swell will arrive across the area 
waters Thursday and Friday, building seas offshore to 5-7 ft.


Large, long period NW swell continues to propagate SE across the 
forecast waters, with seas of 8 to 12 ft across the waters W of 
100W. A weakening cold front has moved into the far NW portion 
of the area from 30N136W TO 28N140W, and will continue SE 
through early Thursday, and be reinforced by building high 
pressure Thursday evening. Winds NW of the reinforced front will 
increase to fresh to strong Thursday evening, and shift E and SE 
with the front as it moves through Baja California Fri and Sat. 
Strong high pressure behind the front will induce fresh to 
strong trades gradually spreading across the waters N of 10N W 
of 110W during the upcoming weekend as the front dissipates 
across the N central waters.


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Page last modified: Thursday, 18-Jan-2018 09:35:59 UTC