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Eastern North Pacific Tropical Weather Discussion

AXPZ20 KNHC 210240

Tropical Weather Discussion 
NWS National Hurricane Center Miami FL 
0405 UTC Wed Sep 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 0000 UTC surface analysis and satellite imagery through 
0200 UTC.


A tropical wave previously along 98W N OF 09N can no longer be 
detected in evening data and has likely become absorbed in 
elongated troughing extending across the waters of southeastern 
Mexico. Afternoon ASCAT imagery suggested a weak 1008 mb low 
pres center near 14.5N96W this still lingers there. Scattered 
moderate to strong convection is occurring from 10N to 16N 
between 92W and 102W. Global models suggest this elongated 
trough will persist offshore of the coast across this region, 
and that environmental conditions are favorable for low pres to 
become organized S of Mexico during the next few days.


The monsoon trough stretches across the entire basin from 
Colombia near 09N72.5W TO 10N83W TO 15N92W TO 11N126W TO low 
pres near 1009 mb to 12N136W TO beyond 13N140W. Scattered 
moderate to strong convection is from 06N to 11N between 80W and 
86W, and within 120 nm N and 210 nm S of trough from 92W to 



A surface ridge extends SE into the region from a 1033 mb high 
near 40N150W to near 27N118W. Low pressure over southern Arizona 
and an approaching cold front pushing southward along the coast 
of central California will induce fresh to strong SW winds in 
the northern part of the Gulf of California tonight through 
early Fri morning, with max seas building to 5-7 ft north of 
30N. The local effects will be less evident west of Baja 
California and south of 29N in the Gulf of California, until Fri 
night when winds will freshen from N to S along the Pacific 
coast of Baja. Elsewhere, the possible development of low 
pressure along the coastal waters of southern Mexico Thu through 
the weekend will increase winds and seas south of the Mexican 
coast between 97W and 105W. 


A fairly active monsoon trough along the coast of Central 
America from Guatemala to Panama will maintain active convection 
across the coastal waters the next few days. Expect SW winds 
south of the trough axis to gradually strengthen to 10-15 kt and 
become more westerly by Fri. Further south, gentle to moderate 
southerly winds are expected to persist south of 05N through the 
weekend. S to SW swell continues to propagate across the area 
with seas in the 5 to 6 foot range east of 100W.


The post-tropical remnant low of Norma 1007 mb is near 22N117.5W 
and is a well defined swirl of low and mid level clouds and 
stratiform convection. Winds are estimated to be 20-25 kt within 
90 nm NW of the center and seas to 8 ft. The low will move 
slowly NW and weaken through Friday.

The post-tropical remnant low of Otis of 1009 mb is near 
16N131.5W and remains a swirl of low level clouds and limited 
stratiform convection. Fresh to strong N-NE winds and 8-9 ft 
seas are with 150 nm NW of the low center. The low is expected 
to move SW and weaken into a trough through Friday, with seas 
gradually diminishing to 6-7 ft.

NW swell associated with strong N-NW winds north of the area is 
producing combined seas of 8-10 ft north of a line from 30N118W 
TO 23N133W TO 21.5N140W. This area of NW seas is expected to 
contract and shift slightly eastward through Thu night. Another 
weaker round of NW swell associated with a cold front west of 
California is expected to arrive Fri night. High pressure 
centered well N of the area and lower pressure associated with 
the convergence zone will maintain moderate trade winds across 
most of the remainder of the area through the weekend.