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Eastern North Pacific Tropical Weather Discussion

AXPZ20 KNHC 220249

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0245 UTC Sat Jul 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 0000 UTC surface analysis and satellite imagery through
0215 UTC.


Tropical Storm Greg is centered near 14.9N 120.7W, moving W at 
11 kt. Estimated minimum central pressure is 1003 mb. Maximum 
sustained winds are 45 kt with gusts to 55 kt. Satellite imagery
showed the well defined low level center becoming completely 
exposed with convection displaced to the N of the center. 
Scattered moderate to strong convection is noted within 120 nm in
the N quadrant of the center. Greg is forecast to begin slowly 
intensifying on Sat with peak intensity expected to remain below 
hurricane strength on Sun. See the latest NHC forecast/advisory 
under AWIPS/WMO headers MIATCMEP2 WTPZ22 for more details.

Tropical Depression Nine-E is centered near 9.4N 95.7W, moving W
at 12 kt. Estimated minimum central pressure is 1006 mb. Maximum
sustained winds are 30 kt with gusts to 40 kt. Scattered 
moderate to strong convection is observed in banding features 
within 150 nm in the NW semicircle. An additional area of strong 
convection was noted from 11.5N to 13.5N between 96W and 99W. 
Environmental conditions are favorable for additional 
strengthening and the system could become a tropical storm earlt 
Sat morning, and a hurricane by Sun evening or Sun night. See 
the latest NHC forecast/advisory under AWIPS/WMO headers 
MIATCMEP4 WTPZ24 for more details.

A 1008 mb surface low continues near 14N111W in association with
a tropical wave along 111W. Scattered moderate to strong 
convection is confined to within 180 nm in the W semicircle of 
the low due to the presence of persistent northeasterly shear. 
Environmental conditions are forecast to be conducive for the 
formation of a tropical depression during the next couple of 
days before upper-level winds become unfavorable for 
development. This system is forecast to move westward to west-
northwestward at around 10 kt through early next week.


The monsoon trough extends from 10N85W to 08N93W. The monsoon 
trough breaks down in the vicinity of T.D. Nine-E and a surface 
low near 14N111W, then resumes from 14N122W to the remnant low 
of T.D. Eight-E near 11N128W. The ITCZ extends from 11N129W to 
10N140W. Except noted with the tropical systems decribed above...
minimal convection is associated with the trough axis. 



Gentle to moderate NW winds off the Baja California peninsula 
are expected to continue through Sat. Seas will remain 5 to 7 ft 
in a mix of long period north and southwesterly swell. Gentle 
southerly flow will persist in the Gulf of California, except 
for moderate southerly flow over the northern Gulf. 

Strong northerly gap winds of 20-25 kt are expected to pulse 
through the Gulf of Tehuantepec overnight into Sat morning 
toward developing T.D. Nine-E. Seas will build to 8 ft with an 
additional component of longer period southwest swell.


In the Gulf of Papagayo, moderate to fresh offshore winds will 
pulse to fresh each night with nocturnal drainage through the 
week, occasionally building max seas to 8 ft in a mix of east 
swell and longer period southwest swell.

Gentle to moderate southerly winds are expected south of the 
monsoon trough axis. Long period cross-equatorial southerly 
swell and 6-7 ft seas will continue to propagate into the waters 
reaching the coast of Central America through the day. Another 
pulse of large southerly swell will move into the region today 
and raise seas to 6-8 ft through tonight.


The remnant low of TD 8-E is analyzed near 11N128W and estimated
pressure of 1011 MB, with fresh to strong winds continuing 
within 90 nm SE quadrant of the center. The low will gradually 
dissipate through Sat. 

The pressure gradient between Fernanda (located west of area) 
and Greg and high pressure to the N of the area will maintain 
moderate to fresh NE winds N of 25N and W of 127W through the 
upcoming weekend. Northerly swell in the form of 7-8 ft seas will
propagate S of 32N between 125W and 135W early next week.