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Eastern North Pacific Tropical Weather Discussion



441 
AXPZ20 KNHC 160353
TWDEP 

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0405 UTC Thu Aug 16 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 
0230 UTC. 

...SPECIAL FEATURE...

Tropical Storm Lane is centered near 10.4N 125.6W at 0300 UTC, 
moving W at 11 kt. Estimated minimum central pressure is 1003 
mb. Maximum sustained wind speed is 45 kt with gusts to 55 kt 
and extend out to 30 nm across the SE quadrant. Peak seas are 
about 14 ft just NE of the center. Scattered to numerous 
moderate to strong convection is occurring within 120 nm across 
the SE and 30 nm across the NW semicircles, while scattered 
moderate isolated strong convection is elsewhere within 180 nm 
across the NW and 240 nm across the SE semicircles. Lane is 
expected to continue moving westward through Thu morning and 
gradually intensify, reaching hurricane strength Thu evening, 
then begin to veer more WNW and intensify further to major 
hurricane status around Sat. The small size of Lane is 
anticipated to retain gale force winds of less than 100 nm 
radius and will limit the extent of 12 ft seas during the next 
few days. See latest NHC forecast/ advisory under AWIPS/WMO 
headers MIATCMEP4/WTPZ24 KNHC for more details.

The Fuego Volcano in Guatemala near 14.3N90.5W emitted an ash 
cloud or plume this afternoon around 1916 UTC, and spread 
potential ash westward in the prevailing easterly low level 
winds. Ash may be reaching the surface as the easterly winds 
transport this ash cloud westward over the Pacific waters to the 
west and across the Gulf of Tehuantepec tonight, generally from 
14N to 16N between 91W and 95W. Mariners operating in this area 
are advised to exercise caution. If you encounter volcanic ash 
or floating volcanic debris, please report your observation to 
the National Weather Service at 305-229-4425.

...TROPICAL WAVES...

A tropical wave extends from the northwestern Caribbean, across 
Central America, and into the Pacific down to about 08N near 
83W. Scattered moderate to strong convection is occurring ahead 
of the wave along the monsoon trough from 04.5N to 08.5N between 
83W and 94W, while scattered moderate convection is seen behind 
the wave across interior Costa Rica and Panama and across the SW 
Caribbean.

A tropical wave along 102W-103W extends from 05N to 19N moving W 
10-15 kt. Scattered moderate to strong convection is observed 
about the wave from 07.5N to 14.5N between 97W and 111W. A 1010 
mb surface low is lingering along the monsoon trough ahead of 
the wave near 09.5N109.5W.

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

The monsoon trough extends from 09N74W TO 08N92W to low pres near 
09.5N109.5W TO 11N114W. The ITCZ extends from 13.5N137W TO 
beyond 11N140W. Scattered moderate to strong convection is seen 
in satellite imagery from 04.5N to 08.5N between 83W and 94W, 
and from 07.5N to 14.5N between 97W and 111W. Scattered moderate 
to strong convection is observed within 90 nm SE of the ITCZ 
west of 137W. 

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO... 

Weak surface ridging extends from the NE Pacific Se into the 
area from around 30N135W to near las Islas Revillagigedo. A weak 
trough associated with the remnants of tropical cyclone John 
area across the coastal waters near Punta Eugenio, and aiding in 
producing gentle N to NW winds across the near shore waters of 
Baja California, and moderate NW winds further offshore. NW 
winds should remain moderate or weaker for the next several days 
and this weak ridge prevails. No significant gap wind events are 
expected in the Gulf of Tehuantepec, although nocturnal 
northerly drainage flow to around 20 kt is expected there each 
night.  

Long-period S to SW swell originating south of the equator is 
impacting the Mexico offshore zones from Cabo Corrientes 
southeastward, producing seas of 7 to 10 ft. This swell is 
generating very large and dangerous surf conditions along the 
coastlines and outer reefs with localized breaking waves of 15 
to 20 ft expected through Thu morning. These swell will 
gradually be diminishing during the next two to three days.  

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

The monsoon trough should remain near 10N during the next few 
days.  Easterly winds north of the trough will be moderate or 
weaker, while southwesterly winds south of the trough will also 
be moderate breeze or weaker.  

Long-period SW swell originating south of the equator is also 
impacting the Central America, Colombia, and Ecuador offshore 
zones, producing seas of 6 to 9 ft. Large breaking waves are 
also occurring across these coastlines and outer reefs with 
localized breaking waves of 10-15 ft expected through Thu 
morning. These swell will gradually be diminishing during the 
next two to three days.

REMAINDER OF THE AREA...   

See discussion above for Tropical Storm Lane.

A weak 1012 mb low pressure center is located near 18N138.5W and 
moving westward near 15 kt. Scattered moderate isolated strong 
convection is observed within 150 nm across the NW semicircle 
and within 90 nm of the center in the northern semicircle. 
across the SE quadrant. Fresh to strong easterly winds are 
occurring across the northern periphery of the low center, due 
to the pressure gradient imposed by the ridge centered north of 
the area. Seas within this area of winds are 7-9 ft. Building 
high pressure north of the area will maintain this area of fresh 
easterly winds today, even as the low pressure opens into a 
trough over the next couple of days, and moves to the 
west of 140W late Thu. 

Long-period cross-equatorial S southerly swell, in the form of 7 
to 9 ft seas, will propagate N across the tropical waters S of 
20N E of 120W tonight through Thu, and then subside to less than 
8 ft on Thu night. 

$$
Stripling