AXPZ20 KNHC 160926
Tropical Weather Discussion
NWS National Hurricane Center Miami FL
701 UTC Tue Oct 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
Based on 0600 UTC surface analysis and satellite imagery through
The center of Tropical Storm Tara is located near 18.7N 104.5W
at 16/0900 UTC or 20 nm SSW of Manzanillo Mexico drifting NNW or
335 degrees at 2 kt. Estimated minimum central pressure is 998
mb. Maximum sustained wind speed is 50 kt with gusts to 60 kt.
Numerous moderate and scattered strong convection is noted within
60 nm in the NW and within 30 nm in the SE semicircle. Scattered
moderate and isolated strong convection is seen elsewhere from
17.5N to 20N between 103.5W and 106W. The system is forecast to
move slowly toward the northwest during the next day or so. On
the forecast track, the center of Tara should pass very close to
the coast of southwestern Mexico, or possibly move inland, today
or Wednesday. Gradual weakening is forecast as Tara interacts
with the mountains of southwestern Mexico. See latest NHC
forecast/advisory under AWIPS/WMO headers MIATCPEP2/WTPZ32 KNHC
for more details.
Gulf of California: Frequent gusts to gale force over the
northern Gulf of California have ended as winds begin to subside.
A recent ASCAT pass from around 04Z provided observations of 20
to 25 kt sustained winds over Gulf of California N of 27N. These
winds are caused by high pressure over the Great Basin of the
United States. The fresh to strong winds are expected to subside
by Wed morning as the high moves E and weakens.
...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
The monsoon trough extends from 17N85W to a 1007 mb low pressure
centered over the far SW Caribbean near 16N87W, then across
Central America to near the Gulf of Tehuantepec at 17N95W to
12N106W to 12N116W to 09N121W to 10N130W to beyond 08N140W.
Numerous moderate and scattered strong convection is found from
04N to 07N E of 78W. Scattered moderate and isolated strong
convection is seen N of a line from 07N82W to 11N92W and within
180 nm of the monsoon trough axis W of 95W.
OFFSHORE WATERS WITHIN 250 NM OF MEXICO...
Latest scatterometer data indicate moderate to locally fresh NW
winds over the offshore forecast waters W of Baja California. A
ridge currently extending from 1022 mb high pressure centered
near 35N127W to near the Revillagigedo Islands will maintain its
influence over the offshore waters W of Baja California
Peninsula. Gentle to moderate NW to N winds, and seas generally
in the 4 to 6 ft range will prevail through Thu night. Seas are
forecast to remain largely unaffected by Tropical Storm Tara.
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 sliding S along the eastern slopes of the
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. This system retains
a high chance of becoming a tropical depression during the next
5 days as it tracks WNW along the southern coast of Mexico.
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 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 30N138W to 27N140W on Tue, and then 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. 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 115W.
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 by late Wed. 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.