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Eastern North Pacific Tropical Weather Discussion (Text)



605 
AXPZ20 KNHC 202040
TWDEP

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
2040 UTC Thu Sep 20 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 1800 UTC surface analysis and satellite imagery through
2100 UTC. 

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

The monsoon trough extends from 10N84W to 1007 mb low pressure 
near 09N87W, to 11N100W to 10N117W. Another segment of the 
monsoon trough continues from 1009 mb low pressure near 14N124W 
to 11N135W. A segment of the intertropical convergence zone
continues from 11N135W to 11N140W. Scattered moderate convection
within 90 nm either side of the monsoon trough between 78W and
80W, within 90 nm south of the monsoon trough between 105W and
108W, and within 120 nm either side of the monsoon trough between
110W and 115W. Scattered moderate to isolated strong convection
is evident within 90 nm of the low pressure near 11N135W.

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO... 

Generally southerly Winds have diminished across the Gulf of 
California as the remnant low pressure of T.D. Nineteen-E 
dissipates inland over the mountains of Sonora. Winds will veer
more northerly over the Gulf of California Friday through Sunday
as an early season frontal boundary moves into northern Mexico
east of the mountains. Elsewhere north of 20N, moderate to 
fresh NW winds persist off the Pacific coast of Baja California, 
funneling between the coastline and high pressure well northwest
of the area. A satellite altimeter pass from 11 UTC showed seas 
approaching 8 ft north likely due to NW swell entering the 
discussion area north of 29N and west of 116W. While this is 
expected to decay below 8 ft today leaving mainly 5 to 7 ft seas,
the NW swell and local wind waves will interact with southerly 
swell off the coast Baja California over the next several days. 

Farther south, fresh northerly gap winds persist into the Gulf of
Tehuantepec, diminishing from stronger winds earlier this
morning. Pulses of fresh gap winds will occur again tonight and
Fri night. Looking ahead, another strong pulse of gap winds is 
possible late Sat into early Sun ahead of a tropical wave moving 
through Central America and southern Mexico.

Looking further ahead, there is growing consensus among major
models of weak low pressure forming by late Mon into early Tue
between Manzanillo and Socorro Island.

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

Fresh offshore nocturnal winds will pulse across the Gulf of 
Papagayo the next several nights. Cross-equatorial SW swell 
reaching the Central American coast will slowly subside this 
weekend. The monsoon trough will meander near 10N the next few 
days.

Looking ahead, an increase in moist southwest flow is advertised
by the major global models by early next week, possibly
culminating in a Central American gyre pattern by mid week. This
may bring increase showers and thunderstorms to the Pacific
waters off Central America by early next week, and possibly
increased winds and seas thereafter.

REMAINDER OF THE AREA...   

An elongated surface trough extends from roughly Clarion Island
to 1009 mb low pressure near 15N123W, then connecting into the
monsoon trough. Surface ridging prevails over the waters NW of 
the trough axis. Moderate to locally fresh trades persist north 
of the trough west of 120W, supporting seas to 8 ft from 15N-18N
W of 130W. The low pressure area will weaken into a trough and
move west of the area through early next week, maintaining
moderate to fresh winds and at least 5 to 7 ft seas over much of
the area north of 15N. A broad circulation is noted along the
monsoon trough near 10N112W. There is some disagreement among
major models regarding development of this circulation, but at
least a weak low may form and drift westward to 130W along 10N
through Tue. 

$$
Christensen


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Page last modified: Thursday, 20-Sep-2018 20:41:03 UTC