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Eastern North Pacific Tropical Weather Discussion



000
AXPZ20 KNHC 170408 RRA
TWDEP 

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0405 UTC WED Oct 17 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 0000 UTC surface analysis and satellite imagery through 
0300 UTC.

...SPECIAL FEATURES...

The remnants of Tropical Depression Tara are located near 20.0N 
105.5W at 0300 UTC, or about 90 nm NW of Manzanillo Mexico, 
moving NW  at 5 kt. Estimated minimum central pressure is 1005 
mb. Maximum sustained wind speeds are 30 kt with gusts to 40 kt. 
Scattered moderate isolated strong convection is within 75 nm of 
the northern quadrant. Strong upper level winds and interaction 
with the mountainous terrain of Mexico have caused the small 
circulation of Tara to weaken. Tara is expected to dissipate 
during the next 24 hours. Heavy rainfall will continue to impact 
coastal areas through Wed. See latest NHC forecast/advisory 
under AWIPS/WMO headers MIATCMEP2/WTPZ22 KNHC for more details.

Heavy rainfall will also continue to affect portions of Central 
America and SE Mexico for the next several days as broad area of 
low pressure centered over Guatemala near 16N91W drifts west, 
pulling in abundant tropical moisture along with it. A long 
fetch of fresh to strong SW winds are also transporting tropical 
moisture from the tropical eastern Pacific into Central America. 
The combination of all this moisture and instability, and the 
potential development of yet another low during the next 48 
hours between the Gulf of Papagayo and the Gulf of Tehuantepec 
will maintain very unsettle weather across the region. Consult 
your local meteorological service for details.

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

The monsoon trough extends from the low pressure near 16N91W to 
16N98W to 11N122W. The ITCZ extends from 11N122W to 10N140W.
Scattered moderate to strong convection is found within 75 nm of 
the coastline between 84W and 85W. Scattered moderate isolated 
strong convection is from 08N to 12N between 131W and 137W.

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO... 

High pressure ridge north of the area extending SSE to near the 
Revillagigedo Islands is maintaining moderate to locally fresh 
NW winds over the offshore forecast waters W of Baja California. 
The ridge will maintain its influence over the offshore waters W 
of Baja California throughout the week, yielding seas of 4-7 ft.

Fresh to strong NW winds continue across the Gulf of California. 
Winds will gradually subside Wed as high pressure over the Great 
Basin moves E and weakens.

A gap wind event is forecast to start this evening in the Gulf 
of Tehuantepec from high pressure building behind a cold front 
in the SW Gulf of Mexico, with winds reaching 30 kt late tonight 
through Wed and seas rapidly building to 11 ft by Wed afternoon. 
Strong gap winds may continue for the next few days, and pulse 
to around 30 kt each night. Global models continue to suggest 
that another low pressure center will develop near the Pacific 
coast of Central America in the next few days, somewhere between 
Papagayo and Tehuantepec. The gap wind event across Tehuantepec 
will act to enhance this low level circulation...and there is a 
medium chance for a tropical cyclone to develop across this area 
within the next 48 hours, and a high chance to form within the 
next 5 days.

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 Wed, with active showers and thunderstorms 
expected to continue across much of Central America and the 
adjacent Pacific coastal waters, spreading well inland. Long 
period cross-equatorial SW swell will maintain 5 to 8 ft seas 
across the forecast area during the next few days. As mentioned 
above, global weather models suggest the chance for low pressure 
to develop offshore of the coast between Papgayo and south of 
Gulf of Tehuantepec in the next few days, which will help to 
focus very heavy rainfall across the region. 

REMAINDER OF THE AREA...

The pressure gradient between the high pressure ridge to the W 
of the Baja Peninsula and a cold front approaching from the W is 
generating fresh to strong southerly winds across the far NW 
waters, mainly N of 28N and within 150 nm east of the front. 
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 
from 30N138W to 27N138W to 25N140W as a weakening stationary 
front on Wed. Long period NW swell will follow the front and 
cause seas to build to between 8 and 10 ft generally N of 15N 
and W of 132W.

Satellite-derived wind and altimeter data confirmed the presence
of moderate to fresh monsoonal flow over the forecast waters N 
of 07N and S of the monsoon trough. An area of 7 to 9 ft in long 
period SW swell is noted south of the monsoon trough and mainly 
between 97W and 115W, and is expected to prevail across this 
general area through through early Thu.

$$
Mundell