Tropical Weather Discussion
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AXPZ20 KNHC 280948

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1005 UTC Thu Jul 27 2017

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 0600 UTC surface analysis and satellite imagery through
0815 UTC.


Recently downgraded Tropical Storm Hilary is located near 18.7N
117.9W at 0900 UTC, or about 5155 nm WSW of the southern tip of
Baja California, moving WNW at 7 kt. Estimated minimum central
pressure is 992 mb. Maximum sustained wind speed is 60 kt with
gusts to 75 kt. Numerous moderate convection is within 60 nm of
the center. Hilary is forecast to continue moving WNW and weaken
slowly over the next 48 hours before weakening more rapidly by
72 hours as it reaches cooler waters. See latest NHC forecast/
advisory under AWIPS/WMO headers MIATCMEP4/WTPZ24 for more

Tropical Storm Irwin is centered near 14.9N 124.8W at 0900 UTC,
or about 975 nm WSW of the southern tip of Baja California,
moving W at 2 kt. Estimated minimum central pressure is 1001 mb.
Maximum sustained wind speed is 45 kt with gusts to 55 kt.
Numerous moderate and scattered strong convection are within 90
nm north and 120 nm south of the center. Some modest
fluctuations in intensity below hurricane force are expected
during the next 48 hours, or more, before Irwin interacts with
Hilary and begins to weaken considerably. See latest NHC
forecast/ advisory under AWIPS/WMO headers MIATCMEP5/WTPZ25 for
more details.


A tropical wave is analyzed along 94W-95W, north of 10N, moving
W at 10-15 kt. Isolated moderate convection is within 180 nm
east of the wave axis.

A tropical wave is analyzed along 110W-111W, north of 07N,
moving W at 5-10 kt. Scattered moderate convection is from 06N
to 15N between 107W and 116W.


The monsoon trough extends across Costa Rica near 10N84W to
08N95W to 09N105W to 13N112W, and resumes west of the tropical
cyclone activity near 11N130W to 08N137W. The ITCZ axis extends
from 08N137W to beyond 07N140W. Aside from convection associated
with the tropical waves, scattered moderate isolated strong
convection is from 05N to 10N between 89W and 104W, and from 03N
to 10N, east of 85W. Scattered moderate convection is within 90
nm of the monsoon trough and ITCZ axis, west of 130W.



High pressure centered northwest of the area will support gentle
to moderate NW winds within 120 nm of the Baja California
peninsula through Saturday. Seas of at least 8 ft associated
with tropical cyclone Hilary will continue to impact the
offshore zones of Baja California through the upcoming weekend.
As Hilary moves away from this area, a ridge axis will fill in
between the departing storm and Baja California, resulting in
moderate to fresh NW winds developing Sunday through early next

Nocturnal fresh northerly winds are forecast across the Gulf of
Tehuantepec through this morning with seas peaking around 8 ft.
Cross equatorial long period southerly swell with seas of 7 to 8
ft will reach the offshore waters between the Gulf of
Tehuantepec and Cabo Corrientes on Sun, and the waters between
Los Cabos and Cabo Corrientes on Mon. Elsewhere, generally
moderate NW winds and seas of 5 to 7 ft will prevail.


Across the Gulf of Papagayo, expect fresh winds to develop
tonight and again Saturday night with the assistance of the
nocturnal drainage flow, building maximum seas of 7 to 8 ft in a
mix of E wind waves and long period SW swell.

Otherwise, gentle to moderate S to SW winds are expected the
next few days. Strong long period cross-equatorial SSW swell
will continue to propagate into the forecast waters through
Saturday, with seas 8 to 9 ft reaching as far north as 10N later
today. The area of 8 ft seas will then reach just offshore all
central America Pacific coastal sections by Sunday.


High pressure is located N of the area with a ridge axis
extending across the northern forecast waters N of 20N. The
pressure gradient between this system and the active zone of
tropical cyclones will maintain moderate to fresh N to NE winds
W of 120W through Saturday. Long period cross equatorial SW
swell of 8 to 9 ft will spread across the waters S of 10N and E
of 110W, persisting through Sunday night. As the tropical
cyclone activity shifts to the NW over our waters later this
weekend, a weak pressure pattern will develop between the
cyclones and the equatorial trough to the south. This will
result in a broadening area of gentle to moderate winds between
10N and 20N, west of 115W early next week.

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