464 
AXPZ20 KNHC 300923
TWDEP 

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
714 UTC Sun Sep 30 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
meteorological analysis.

Based on 0600 UTC surface analysis and satellite imagery through
0900 UTC.
    
...SPECIAL FEATURES... 

Hurricane Rosa is centered near 23.3N 118.8W at 30/0900 UTC or 
about 335 nm (625 km) SW of Punta Eugenia Mexico moving N or 050
degrees at 10 kt. On the forecast track, the center of Rosa will 
approach the central and northern Baja California peninsula on 
Monday. Rosa's remnants will then move quickly across the Desert 
Southwest on Tuesday. Estimated minimum central pressure is 975 
mb. Maximum sustained wind speed is 75 kt with gusts to 90 kt. 
Additional weakening is forecast during the next couple of days, 
and Rosa is expected to become a tropical storm by this evening. 
Numerous moderate to strong convection is noted within 90 nm of 
the center. Flooding rains from Rosa are expected across NW 
Mexico and the SW of United States over the next few days.
Swells generated by Rosa will affect portions of the coasts of 
southwestern Mexico, most of the west coast of the Baja California
peninsula, and southern California from today through Tuesday. 
These swells are likely to cause life-threatening surf and rip 
current conditions. See latest NHC forecast/advisory under 
AWIPS/WMO headers MIATCMEP5/WTPZ25 KNHC for more details.

Farther south, Tropical Storm Sergio is centered near 12.0N 
104.3W at 30/0900 UTC or 330 nm SSW of Acapulco Mexico moving W 
or 270 degrees 10 kt. Estimated minimum central pressure is 1001 mb.
Maximum sustained wind speed is 45 kt with gusts to 55 kt. 
Numerous moderate to strong convection is noted within 150 nm SE 
and 75 nm NW semicircles of center. A recent scatterometer pass 
indicated that the strongest winds remain on the east semicircle
of the center. Sergio will remain well offshore the SW coast of
Mexico, and it is expected to become a hurricane by tonight and 
be near major hurricane strength on Tuesday. See latest NHC 
forecast/advisory under AWIPS/WMO headers MIATCMEP1/WTPZ21 KNHC 
for more details.

...TROPICAL WAVES...
A tropical wave is over SE Mexico, and extends along 94W north 
of 05N. Scattered moderate convection is where the wave meets 
the monsoon trough from 08N-11N between 93W-97W. 
  
...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... 

The monsoon trough extends from 08N82W to 07N86W to 10N94W to 
11N98W, then continues from 07N105W to 06N115W. Another sector 
of the monsoon trough is SW of Hurricane Rosa, and extends from 
13N127W to 07N140W. Scattered moderate convection is over the
Gulf of Panama, and from 09N-12N between 126W-133W.

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO... 

See Special Features above for information on Hurricane Rosa and 
Tropical Storm Sergio.

Swell associated with Rosa will continue to propagate across the
offshore forecast waters W of Baja California. Seas in the form 
of mixed swell in excess of 8 ft are observed over most of the 
ocean from 10N to 28N between 110W and 128W. Weather conditions 
will gradually deteriorate as Rosa continues to approach Baja
California. A recent ASCAT pass shows fresh to strong winds
already reaching the western part of the forecast zone PMZ013 
that covers the area between Cabo San Lazaro and Punta Eugenia. 
A tropical storm warning is in effect along the west coast of 
Baja California.

In the Gulf of California, gentle to moderate southerly winds 
are expected through Sun night. The southerly flow will increase 
to near gale force N of 27N on Monday, with seas building to
around 10 ft late on Mon. Tropical storm conditions from Rosa 
are possible across the northern Gulf of California Mon and Mon 
night. 

In the Gulf of Tehuantepec, fresh to strong northerly winds are
expected, with seas building to 9 or 10 ft, mainly during the 
overnight and early morning hours. These marine conditions are
expected to persist most of the forecast period.

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

The monsoon trough will meander between 09N and 12N through mid
week, with gentle to moderate winds expected on either side of 
the trough axis. Moderate to fresh E nocturnal drainage flow is 
expected in the Gulf of Papagayo through tonight.

REMAINDER OF THE AREA...   

See Special Features above for information on Hurricane Rosa and
Tropical Storm Sergio.

A weak ridge dominates the waters north of 20N and west of Rosa 
producing gentle to moderate winds N of 23N W of 125W, and 
moderate to fresh trades S of 23N. A frontal trough is analyzed
30N135W to 27N140. A weak cold front is behind the frontal
trough, and will enter the forecast area early this evening. The
front is forecast to reach a position from 30N128W to 24N140W by
Mon evening. Long period NW swell will follow the front. This 
swell event will propagate across the NW forecast waters through 
Tue while seas associated with Rosa W of the Baja California 
Peninsula will subside to less than 8 ft. Later in the week, 
seas associated with Sergio will mix with additional pulses of NW
swell. By Thu, seas of 8 ft or greater are expected to cover 
most of the waters N of 10N W of 105W, including the entrance of 
the Gulf of California. 

$$
GR