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.

$$ HC/GR