Tropical Weather Discussion
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000
AXPZ20 KNHC 201819 CCA
TWDEP

Tropical Weather Discussion...corrected
NWS National Hurricane Center Miami FL
1605 UTC Thu Jul 20 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 1200 UTC surface analysis and satellite imagery through
1515 UTC.

...SPECIAL FEATURES...

Tropical Storm Fernanda is centered near 18.2N 139.2W at 20/1500
UTC moving WNW at 10 kt. Estimated minimum central pressure is
995 mb. Maximum sustained winds are 55 kt with gusts to 65 kt.
Scattered moderate to strong convection within 120 nm NE
quadrant of center. Fernanda will continue to weaken as it moves
west of 140W later today. Large swell will continue to expand
and spread out ahead of Fernanda to the NW and W during the next
few days. See latest NHC forecast/advisory under AWIPS/WMO
headers MIATCMEP1/WTPZ21 for more details.

Tropical Storm Greg is centered near 14.1N 115.4, or 585 nm SSW
of the southern tip of the Baja Peninsula at 20/1500 UTC, moving
W at 9 kt. Estimated minimum central pressure is 1003 mb.
Maximum sustained winds have increased to 45 kt with gusts to 55
kt. Scattered moderate to strong convection is noted within 90
nm of the center, except in the NW quadrant. Greg is forecast to
slowly intensify and reach hurricane strength within 48 hours.
See the latest NHC forecast/advisory under AWIPS/WMO headers
MIATCMEP2/WTPZ22 for more details.

Tropical Depression Eight-E is centered near 13.4N 123.1W, or
about 890 nm SW of the southern tip of the Baja Peninsula at
20/1500 UTC, moving WSW at 5 kt. Estimated minimum central
pressure is 1009 mb. Maximum sustained winds remain 25 kt with
gusts to 35 kt. Eight-E is now experiencing southwesterly shear
and is not expected to reach tropical storm strength. See the
latest NHC forecast/advisory under AWIPS/WMO headers
MIATCMEP3/WTPZ23 for more details.

A tropical wave is analyzed from 06N to 19N along 104W. A
surface low is embedded in the wave near 12N104W with an
estimated pressure of 1010 mb. An overnight scatterometer
satellite pass indicated fresh to strong winds within 180 nm to
240 nm of the center in the northeast quadrant. The low pressure
may become a tropical cyclone as continues to the WNW with the
wave at 10 to 15 kt over the next couple of days. Scattered
moderate isolated strong convection observed from 07N to 12N
between 104W and 110W, mainly along the monsoon trough.
An additional area of scattered moderate to strong convection
was noted within 120 nm of the coast of Mexico between 100W and
106W.

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

The monsoon trough extends from 08N78W to low pressure 1010 mb
near 08N86W to the developing low pressure 1010 mb near 11N104W,
where the monsoon trough loses definition near T.S. Greg. The
intertropical convergence zone is west of the area. Other than
convection already discussed above, scattered to moderate
convection is noted within 120 nm either side of the monsoon
trough between 87W and 94W.

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

Please see the special features for information on Tropical
Storm Greg southwest of Manzanillo, Mexico.

The weak trough west of the the Baja California peninsula has
dissipated and has allowed the subtropical ridge to advance to
the east. However, gentle to moderate NW winds off the Baja
California peninsula are expected to continue through Fri. Seas
will remain 5 to 7 ft in a mix of long period north and
southwesterly swell. Gentle southerly flow will persist in the
Gulf of California, except for moderate southerly flow over the
northern Gulf.

Fresh to strong northerly gap winds will once again pulse to
around 20 kt during mainly overnight and early morning hours
through early Friday, with a shorter pulse of strong gap winds
again Friday night into Saturday. Seas will build to 8 ft with an
additional component of longer period southwest swell.

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

In the Gulf of Papagayo, moderate to fresh offshore winds will
pulse to fresh each night with nocturnal drainage through the
week, occasionally building max seas to 8 ft in a mix of east
swell and longer period southwest swell.

Gentle to moderate southerly winds are expected south of the
monsoon trough axis. Long period cross-equatorial southerly
swell and 6-7 ft seas will continue to propagate into the waters
reaching the coast of Central America through the day. Another
pulse of large southerly swell will move into the region today
and raise seas to 6-8 ft through tonight.

REMAINDER OF THE AREA...

Please see the special features section for information on
T.S. Fernanda and Tropical Depression Eight-E.

The pressure gradient between Fernanda, and eventually the
approaching Greg, will maintaining moderate to fresh northeast
winds north of 25N, with seas 5 to 8 ft including components of
northerly swell mixing with southerly swell emerging from
Fernanda. Looking ahead, northerly swell to 8 ft will propagate
south of 32N and west of 120W.

$$
Cobb



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