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Eastern North Pacific Tropical Weather Discussion



000
AXPZ20 KNHC 152200
TWDEP 

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1857 UTC Mon Oct 15 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 1800 UTC surface analysis and satellite imagery through
2100 UTC.

...SPECIAL FEATURES...

The center of Tropical Storm Tara is located near 18.0N 104.5W 
at 15/2100 UTC or 60 nm S of Manzanillo Mexico drifting NW or 
305 degrees at 2 kt. Estimated minimum central pressure is 1000 
mb. Maximum sustained wind speed is 45 kt with gusts to 55 kt. 
Numerous moderate to strong convection is noted within 90 nm NW 
and 60 nm SE semicircles. The tropical storm could become stationary
at times. A slightly faster westward motion is forecast to begin
after mid-week. On the forecast track, the center of Tara is 
expected to remain near or just offshore of the southwestern 
coast of Mexico during the next couple of days. Some slow 
strengthening is forecast during the next couple of days. See 
latest NHC forecast/advisory under AWIPS/WMO headers 
MIATCPEP2/WTPZ32 KNHC for more details.

Gulf of California: A Gale Warning remains in effect for the 
northern Gulf of California through this evening. A recent ASCAT 
pass provided observations of near gale force winds across the 
northern Gulf of California. These winds are the result of robust
high pressure building over the Great Basin of the United States.
Fresh to strong winds are expected to persist across much of the
Gulf through early Wed. 

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

The monsoon trough extends from a 1006 mb low pressure centered 
over the SW Caribbean near 15N83W, then across Central America
and the Gulf of Tehunatepec to near 16N100W to 13N110W to 10N120W
to 11N130W to 09N140W. Scattered moderate to isolated strong 
convection is within about 180 nm S of the monsoon trough between
93W and 105W, and within 120 nm between 105W and 114W. Numerous
moderate to scattered strong is from 09N to 11N between 127W and
136W. 

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO... 

Latest scatterometer data indicate moderate to locally fresh NW
winds N of Punta Eugenia, and gentle to moderate NW to N winds
elsewhere across the offshore forecast waters W of Baja
california. A ridge will continue to dominate the offshore 
waters W of Baja California Peninsula producing mainly gentle to 
moderate NW to N winds, and seas generally in the 4 to 6 ft 
range, with the exception of moderate to fresh winds N of Punta 
Eugenia tonight through Tue night. Seas are forecast to increase 
a foot or so by the end of the forecast period as mixed swell 
generated by Tropical Storm Tara arrives. 

Gulf of Tehuantepec: Next gap wind event is forecast to start 
early on Wed with seas rapidly building to 10 ft by Wed 
afternoon. This event will be associated with a ridge building
behind a cold front across the eastern slopes of Sierra Madre 
Mountains in Mexico and the western Gulf of Mexico.

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

Moderate to fresh SW monsoonal flow will continue across the 
region through Tue, with showers and thunderstorms expected to 
continue along the Pacific coast of Central America. Long period 
cross-equatorial SW swell will maintain 5 to 8 ft seas across the
forecast area during this time frame. By Tue night and Wed, 
marine guidance suggests an increase in winds and seas across the
offshore waters from northern Costa Rica to Guatemala. This 
appears to be associated with an area of low pressure forecast 
to develop a couple of hundred miles south of Guatemala and the 
southeastern coast of Mexico around mid-week. 

REMAINDER OF THE AREA...

A 1021 mb high pressure located near 30N127W extends a ridge 
across the northern forecast waters. The pressure gradient 
between the ridge and a cold front approaching from the W is
resulting in fresh to strong southerly winds across the far NW 
waters, mainly NW of a line from 30N138W to 26N140W. Moderate to
locally fresh trades are noted S of 15N and N of the monsoon
trough W of 125W. The cold front is forecast to reach a position
from 0N138W to 27N140W on Tue, and from 30N138W to 27N138W to 
25N140W on Wed, when it is forecast to become stationary. Long 
period NW swell will follow the front building seas of 8-10 ft.

Satellite-derived wind and altimeter data confirmed the presence
of moderate to fresh monsoonal flow across much of the forecast
waters. Winds increase near the convection. An area of 7 to 9 ft
in long period SW swell is noted south of the monsoon trough and
mainly between 100W and 120W.

Looking ahead, an area of low pressure is forecast to develop a 
couple of hundred miles south of Guatemala and the southeastern 
coast of Mexico around mid-week. Environmental conditions are 
forecast to be conducive for development, and a tropical 
depression is likely to form by late week while the system moves 
west-northwestward near the southern coast of Mexico. The latest 
Tropical Weather Outlook gives this system a high change of 
tropical cyclone formation through 5 days.

$$
GR