Tropical Weather Discussion

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Tropical weather discussion
NWS National Hurricane Center Miami FL
0405 UTC Fri Jan 18 2019

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
0215 UTC.

...Intertropical convergence zone/monsoon trough... 

A surface surface trough extends from 02n78w to 01n84w to 06n87w
to 05n93w, where latest scatterometer data indicated the ITCZ
begins and continues to 04n104w to 05n109w to 05n115w where it
briefly stops. It resumes at 05n118w to 06n130w and to beyond 
07n140w. Scattered moderate convection is within 30 nm of the 
ITCZ between 135w and 140w.

...Discussion...

Offshore waters within 250 nm of Mexico... 

Strong to near-gale force winds prevail over the Gulf of 
Tehuantepec, with seas in the 8 to 10 ft range. Winds will
pulse again to near gale force tonight. Winds will then diminish
Fri as the pressure gradient weakens across the region. Fairly 
tranquil conditions will persist across the Gulf of Tehuantepec 
and downstream late Fri through Sat evening. The pattern will 
change abruptly Sat night, as a the leading edge of a strong cold
front moves through southern Mexico, across The Isthmus of 
Tehuantepec and into the adjacent waters of the Gulf of 
Tehuantepec. As strong high pressure surges southward behind the
front over east-central Mexico, and the bulk of the cold air 
reaches the southern Gulf of Mexico, the initial gale force winds
will intensify to a strong gale into Sun morning, possibly 
reaching minimal storm force. Seas will quickly build, with 
wave model guidance suggesting values reaching near 24 ft by 
Sun afternoon. Meanwhile, a large plume of 25-35 kt winds and 
seas in excess of 12 ft is expected to push far south of the 
Gulf of Tehuantepec to near 09n and between 95w and 99w by early
sun evening. Model guidance indicates that strong north to 
northeast gale force winds will last into early Mon, with seas
slowly subsiding. Marine interests transiting through the Gulf 
of Tehuantepec sun into early next week should be aware of this 
upcoming gap wind event, and take necessary action to avoid 
hazardous marine conditions over the affected waters.

Elsewhere over the offshore waters outside of Tehuantepec... 
mainly gentle to moderate north to northeast winds are across 
the region north of 25n, with gentle to moderate breezes 
elsewhere. Northwest swell producing seas of 8-9 ft remains over
the open waters beyond 120 nm north of Cabo Corrientes. A weak 
cold front will move into into northern Baja California norte 
this evening. While the front will dissipate as it moves across 
Baja California and the Gulf of California through Fri, it will 
be accompanied by a new set of long-period northwest swell of 
12-17 ft across the waters off Baja California. This swell will 
bring dangerous surf and large breaking waves across Baja 
California norte Thu night through Fri. High pressure building 
behind the front will support fresh to strong northwest winds 
north of Cabo San Lucas late Fri into Sat. 

Over the Gulf of California, high pressure building over the 
Great Basin north of the area will support fresh to strong
northwest winds extending the length of the Gulf from Fri night 
through Sat. The strength, fetch and duration of the winds 
support wave heights to 8 ft in the southern Gulf of California 
by Sat night. Winds and seas will diminish by sun as the high 
pressure weakens and shifts to the east.

Offshore waters within 250 nm of Central America, Colombia, and 
within 750 nm of Ecuador... 

The pressure gradient between high pressure north-northeast of
the area, over the Gulf of Mexico and northwestern Caribbean Sea,
and the equatorial trough will maintain strong gap winds across 
papagayo and Panama through early Sat. Over papagayo, fresh to 
strong gap winds will continue well to the west-southwest of
the Gulf, with winds pulsing to near-gale force during the 
overnight and early morning hours.  Over Panama, fresh to strong
northerly gap winds will impact mainly the western Gulf of 
Panama extending into the waters south of the azuero peninsula 
through late Fri night into early Sat.

Gap winds will diminish Sat and Sat night as high pressure north
of the region shifts eastward ahead of a cold front. This will 
allow for the present tight pressure gradient across the area
to the slacken. New high pressure will build in the wake of the 
front, supporting another round of even stronger gap winds 
through the gulfs of papagayo and Panama. Winds to gale force are
possible through the Gulf of papagayo Mon, with seas building 
to 8-11 ft from late Sun night through Mon.

Remainder of the area...  

Low pressure of 1011 mb is centered near 06n116w, moving 
westward at 10 to 15 kt. The tight pressure gradient between it 
and high pressure over the northern waters is sustaining fresh to
strong east winds from 07n to 12n between 112w and 115w along 
with seas of 10-12 ft. The low will continue to weaken through 
tonight and open into a trough by early on Fri as it reaches 
115w. The trough will weaken further as it continues westward 
along the ITCZ over the next several days. 

A dissipating cold front surrounding by high pressure extends 
from near 32n121w to 30n130w, where it transitions to a warm 
front northwestward from there. The front has ushered in a new 
set of NW swell. Large seas in the range of 12 to 21 ft continue
to the northwest of a line from 32n125w to 22n140w. Seas over 
the area associated to this swell have peaked and will slowly 
subside as the swell propagates southeastward. Elsewhere, seas 
in excess of 8 ft cover much of the forecast waters west of 105w.

A ridge will build across the waters north of 25n in the wake of
the front. This will result in a tightened pressure gradient,
and strengthening winds across the subtropics and tropics
regions. The ridge will weaken into sun, allowing for winds and 
seas to decrease across the tropics. Seas of 8 to 9 ft will 
continue from sun into next week south of about 26n and west of 
127w due to a a mix of northwest swell and remaining windwaves 
from local trade winds.

$$
Aguirre


		
		

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