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 113W.



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.

$$ Stripling