AXPZ20 KNHC 251009
Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1005 UTC Tue Oct 25 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
Hurricane Seymour has continued to move westward around 13 kt
overnight, with a 10 nm wide eye appearing on and off throughout
the night. The latest satellite images show a clearing eye and
improved appearance in the core of Seymour, and the rapid
intensification process is clearly underway. Seymour is located
near 15.6N 113.8W 970 mb AT 0900 UTC with maximum sustained
winds 100 kt gusting to 120 kt. Numerous strong convection is
seen within 45 nm across the SW semicircle, while scattered to
numerous moderate to strong convection is elsewhere within 120
nm of the eye. Arching rainbands of scattered to numerous
moderate to strong convection spiral outward from Seymour to 270
nm across the NW and S quadrants.
A west to west-northwest motion of Seymour is expected through
this evening before it begins to turn toward the northwest
Wednesday and Thursday and gradually weaken. The current rapid
intensification trend is expected to continue today and Seymour
is forecast to become a category 3 hurricane this afternoon near
16.0N115.9W, with maximum sustained winds near 115 kt, which
will likely be its peak intensity. 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 through early this
morning and PMZ015 through tonight. For additional details on
Seymour, 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. By Thursday night into
early Friday 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 08N74W to 09.5N84W to 07N92W to
9N104W...where it remains separated from Seymour, then resumes
from 13.5N118W to low pres near 14N128W. The ITCZ stretches from
10N133W to beyond 10N140W. Scattered moderate to strong
convection is noted from 03N to 08N E of 82.5W, and within 60 nm
N and 180 nm S of the trough between 90W and 104W.
OFFSHORE WATERS WITHIN 250 NM OF MEXICO...
See special features for details on the persistent Gulf of
Tehuantepec gap wind event. High pres of 1020 mb is centered
near 28.5N120W and is producing light to gentle anticyclonic
winds across the waters W of the Baja California Peninsula.
Combined seas are 5-7 ft prevail N of 24N in NW swell. Seas
increase to 8-11 ft across parts of forecast zones PMZ023 and
PMZ115, particularly S of 20N...including the Revillagigedo
Islands, due to moderate NW swell mixing with swell from
Hurricane Seymour located just S of these forecast areas. The
high pres will shift slightly N-NE during the next 24 hours.
This will result in moderate NW winds across the offshore waters.
Inside the Gulf of California, mainly gentle southerly winds
prevail across the north half, while gentle N to NW winds
prevail across far southern portions. As the high center shifts
farther N-NE today, light to moderate NW winds will spill down
the entire length of the Gulf of California and continue through
Wednesday. Afternoon heating is likely to enhance winds near
select coastal areas to 15-20 kt through the evening hours.
OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND
WITHIN 750 NM OF ECUADOR...
Gulf of Papagayo: NE winds will pulse to near 20 kt over the
Gulf of Papagayo during the night time and morning hours over
the next couple of days, then diminish to near 15 kt during the
afternoon and early evening hours.
Elsewhere gentle to moderate S to SW winds are noted S of the
monsoon trough, while mainly gentle W to NW winds prevail N of
the monsoon trough. Combined seas are in the 4 to 6 ft range,
primarily in long period SW swell which is dominating the offshore
waters. These marine conditions will persist over the next few
REMAINDER OF THE AREA...
A weak ridge dominates most of the north waters N of 20N, and is
producing light to moderate anticyclonic winds between 20N and
30N. Outside Seymour, two weak low pres centers are noted along
the monsoon trough, one is near 18N119.5W and the second one is
near 14N128W. Seas are 6 to 8 ft in the vicinity of these lows as
moderate NW swell is mixing with NEly wind waves. These lows
will shift W and weaken further during the next 48 hours.
A cold front is over the NW waters and extends from 30N132.5W to
beyond 27N140W. Moderate to fresh SW winds are noted N of 28N
ahead of the front to 127W. This front will become stationary
later this extending from 30N135W TO 27.5N140W. At the same
time...a second and stronger cold front will approach 30N140W.
These fronts are forecast to merge by this evening and tonight.
SW winds of 20-25 kt and seas of 8-9 ft are expected NW of a
line from 30N132W to 27N140W by early Tue morning. A new pulse
of long period NW swell will follow the merging cold front
building seas behind the front to 10 ft by Wed afternoon.