AXPZ20 KNHC 241008
Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1005 UTC Mon Oct 24 2016
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
Based on 0600 UTC surface analysis and satellite imagery through
Tropical storm Seymour is located near 14.9N 108.5W at 0900
UTC, about 345 nm, or 640 km, SW of Manzanillo Mexico, moving W-
NW or 290 deg at 13 kt. Maximum sustained winds have increased
to 55 kt with gusts to 65 kt. Minimum central pressure is 999
mb. Cloud tops have cooled overnight near the center of Seymour,
where numerous strong convection is occurring within 90 nm of
the center. Conditions appear favorable for continued
strengthening during the next few days as Seymour continues
moving W-NW to NW, and hurricane force winds are expected later
this afternoon. In fact, some computer model guidance suggests
rapid intensification during the next 24 to 48 hours, and winds
with Seymour are forecast to strengthen to 100 kt within 48
hours. Although the forecast track keeps Seymour just outside of
the Mexican offshore zones, fresh to strong winds and seas in
the 8-10 ft range are expected to affect the southern part of
zones PMZ023 and PMZ025 through late Monday, then PMZ015 tonight
and Tue. For additional details, refer to the latest NHC
forecast/advisory under AWIPS/WMO headers MIATCMEP5/WTPZ25.
A gale warning will remain in effect for the Gulf of Tehuantepec
during the next 48 hours, as strong northerly winds will persist
throughout the week across this region. Marine guidance
continues to suggest minimal gale force winds during the
overnight and early morning hours each day, probably through the
end of the week. By Thu night into early Fri morning, the aerial
extent of the gale force winds will increase as high pres builds
across the western Gulf of Mexico. At that time, seas are
expected to build to 10-14 ft.
...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
The monsoon trough extends from 09N74W to 09.5N84W to 07N93W to
11N102W, where it has fractured away from Seymour, then resumes
W of Seymour from low pres near 17N116W to low pres near
14N126.5W to 09N133W to beyond 12N140W. Widely scattered to
scattered moderate isolated strong convection is noted within
150 nm S of the trough between 77W and 86W, and between 95W
OFFSHORE WATERS WITHIN 250 NM OF MEXICO...
See special features for details on Seymour and for the
Tehuantepec area. High pres of 1017 mb is centered near 27N123W
and is producing light anticyclonic winds across the waters W of
the Baja California Peninsula. Combined seas there are 4-6 ft
across southern portions of the peninsula, and 5 to 8 ft N of
27N due to long period NW swell moving into the region. Seas
here will subside below 8 ft by Tuesday. The high pres will
shift slightly N-NE during the next 24 hours, allowing for an
increase to moderate NW winds across the offshore waters.
Inside the Gulf of California, mainly gentle southerly winds
were detected by scatterometer and surface observations across
the north half, while gentle N to NW winds had developed across
far southern portions. This general wind pattern will persist
today. By this evening, gentle to moderate NW winds will
dominate all the waters S of 27N extending SE to between Los
Cabos and Las Tres Marias Islands. Then on Tuesday as the high
center shifts farther N-NE, NW winds will spill down then
entire length of the Gulf of California.
OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND
WITHIN 750 NM OF ECUADOR...
Gulf of Papagayo: moderate to fresh NE winds and seas to around 6
ft are expected across and just downstream of the Gulf of
Papagayo through this morning before winds and seas subside
modestly this afternoon. Look for ENE winds to increase to near
20 kt again late tonight through Tuesday morning.
Gentle to moderate S to SW winds are noted S of 06N, while gentle
to moderate W to NW winds are N of 06N, with the exception of
moderate to fresh southerly winds from 05N to 07N E of 80W.
Combined seas of 4 to 6 ft, primarily in long- period SW swell
dominate the offshore waters. These marine conditions will
persist over the few days.
REMAINDER OF THE AREA...
A weak NE to SW ridge dominates most of the north waters N of
20N, and is producing mainly light and variable winds between
20N and 30N. Outside Seymour, two weak low pres centers of 1010
mb are noted along the monsoon trough near 17N116W and near
14N126.5W. Overnight scatterometer data suggested that winds
were 20 kt or less surrounding these lows, and computer models
do not indicate any strengthening during the next few days as
they shift slowly W to NW.
Seas of 8-10 ft in NW swell are noted per altimeter data N of
15N between 117W and 134W, and area forecast to subside to less
than 8 ft across by Tuesday afternoon.
A cold front will enter the NW waters near 30N140W this morning
and will move across the NW waters, becoming stationary from
30N134W to 27N140W by this evening. This front will be
reinforcing by a second cold front reaching the same area on
Tue. The merging cold front is forecast to extend from 30N132W
to beyond 26N140W by Tue night. Expect increasing SW winds to 20-
25 kt within 90 nm ahead of the front and building seas of 8-10
ft across most of the NW waters with these fronts on Tue.