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Eastern North Pacific Tropical Weather Discussion

AXPZ20 KNHC 220944

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
655 UTC Fri Sep 22 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
0830 UTC.


A broad and elongated area of monsoonal low pressure persists 
along the southwest coast and coastal waters of Mexico this 
morning. A weak 1007 mb surface low pressure center is analyzed 
within this broad area of low pressure near 16.5N104.5W. An area 
of associated fresh to strong SW monsoonal winds is evident from 
08N to 12N between 110W and 116W. Convergent monsoonal winds 
continue to produce vigorous convection along the coast of mexico
between Cabo Corrientes and Chiapas and also along the coast of 
Guatemala. Computer model guidance continues to show that the low
will shift slowly NW and gradually become better organized 
during the next several days. The area of vigorous convection 
will continue to plague parts of southern Mexico and Central 
America with heavy rains during the next several days.


The monsoon trough stretches across the entire basin from NW 
Colombia near 09N73W TO 08N79W to 13N90W to low pres 1007 mb near
16.5N104.5W to 14N115W to 12N119W to low pres 1012 mb near 
11N137W to beyond 12N140W. Scattered moderate and isolated strong
convection is seen within 60 nm NE and 210 nm SW of the trough 
axis between 87W and 96W, from 16N to 20N between 105W and 108W 
and from 07N to 11N between 135W and 140W. Scattered moderate 
convection is present along and up to 210 nm S of the trough axis
between 97W and 133W.



A surface ridge extends SE across the northern portions of the 
discussion area to the central part of Baja California near 26N. 
An cold front pushing south into northern waters curves west from
31N116W to 27.5N125W to 30N138W. The cold front is producing 
fresh to strong SW winds in the northern part of the Gulf of 
California. These winds are expected to linger a while longer 
this morning until the front departs to the east, with associated
seas of 5-7 ft north of 29N. As the high pressure behind the 
dissipating front builds SE into the area during the next couple 
of days, NW winds will freshen slightly west of Baja California 
Norte, while little influence from the high will be seen south of
29N in the Gulf of California. Elsewhere, the possible 
development of low pressure along the southern coast of Mexico 
will increase winds and seas between 101W and 117W the next few 


An active monsoon trough following the coast of Central America 
from Guatemala to Panama will remain a focus for active 
convection over the coastal waters during the next few days. 
Expect SW winds south of the trough to strengthen gradually to 
20-25 knots through Saturday. Farther south, gentle to moderate 
south to southwest winds are expected to persist south of 05N 
through the weekend. Long period SE swell from the Southern 
Hemisphere will maintain seas west of Ecuador and south of 02S 
around 8 ft today before the swell decay and seas subside below 8


The post-tropical remnant low of Norma is centered near 22N116W 
as a swirl of low to mid level clouds. Winds are estimated to be 
20 kt near the center. Seas of 8 to 9 ft are confined to the west
quadrant within 270 nm of the center of the low. The low will 
drift slowly SE and weaken into a trough by Saturday morning.

NW swell generated by strong N to NW winds north of the area are
producing combined seas to 8 ft north of 25N between 117W and 
127W. This area of combined seas is expected to subside below 8 
ft by this evening. Another weaker round of NW swell associated 
with a cold front west of California is expected to arrive 
tonight. High pressure centered well N of the area and lower 
pressure associated with the monsoon trough will maintain 
moderate to occasionally fresh trade winds west of 120W through 
the weekend.