AXPZ20 KNHC 242120

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
2205 UTC Mon Jul 24 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 1800 UTC surface analysis and satellite imagery through 2115 UTC.


The Eastern Pacific region remains very active with three tropical cyclones: from east to west, Hurricane Hilary, Tropical Storm Irwin and Tropical Storm Greg. So far in July, five named storms have developed in the basin.

Hurricane Hilary is centered near 14.5N 104.9W at 24/2100 UTC, moving WNW at 7 kt. Estimated minimum central pressure is 986 mb. Maximum sustained winds have increased to 75 kt with gusts to 90 kt. Numerous moderate scattered strong convection is within 120 nm of the center. Another cluster of similar convection is from 09N to 15N between 98W and 103W. Continued strengthening is forecast during the next 48 hours, and Hilary is likely to become a major hurricane on Tuesday as it continues on a WNW track about 200 to 250 nm west of the Mexican coast for the next couple of days. See the latest NHC forecast/advisory under AWIPS/WMO headers MIATCMEP4 WTPZ24 for more details.

Tropical Storm Irwin is centered near 15.0N 117.8W at 24/2100 UTC, moving W at 3 kt with a minimum central pressure of 997 mb. Maximum sustained winds have increased to 55 kt with gusts to 65 kt. Cluster of moderate to strong convection is within 120 nm in the N semicircle. Scattered moderate convection was noted elsewhere from 12N to 19N between 115W and 120W. Irwin will remain in relatively close proximity to Hilary the next few days. Gradual strengthening is expected during the next 48 hours, and Irwin is forecast to become a minimal hurricane tonight or Tue. See the latest NHC forecast/advisory under AWIPS/WMO headers MIATCMEP5 WTPZ25 for more details.

Tropical Storm Greg is centered near 14.5N 134.3W AT 24/2100 UTC, moving W at 10 kt. Estimated minimum central pressure is 1003 mb. Maximum sustained winds remain 40 kt with gusts to 50 kt. Scattered moderate isolated strong convection is within 90 nm in the S and 60 nm in the N semicircles of the center. Greg is expected to remain a minimal tropical storm through the next 36 hours or so, before weakening ensues. Greg could become a tropical depression by Wed, and a remnant low by Thu. See the latest NHC forecast/advisory under AWIPS/WMO headers MIATCMEP2 WTPZ22 for more details.


A tropical wave is just to the W of the Gulf of Tehuantepec along 96W north of 08N moving west at 10 to 15 kt. Isolated moderate convection is from 06N to 13N between 90W and 94W.


The monsoon trough is analyzed E of the tropical cyclone activity from 09N83W to 09N90W to 12N97W. The ITCZ extends from 11N136W to beyond 10N140W. Scattered moderate convection was from 05N to 10N east of 91W and within 90 nm if the trough axis between 91W and 96W.



Gentle to moderate NW winds off the Baja California peninsula are expected to continue through mid-week, as high pressure remains centered N of the area. Seas will remain 4 to 7 ft in a mix of long period north and southwesterly swell. Gentle southerly flow will generally prevail in the Gulf of California, except for moderate southerly flow over the northern Gulf.

Nocturnal fresh northerly winds are forecast over the Gulf of Tehuantepec Tuesday through Thursday nights. Hilary is expected to impact the offshore waters beyond 200 nm off the coasts of Guerrero, Michoacan, Colima and Jalisco through Tue, then pass south of the Revillagigedo Islands Wed as a major hurricane. Seas of at least 8 ft, associated with Hilary are forecast to reach the waters between Los Cabos and Cabo Corrientes on Wednesday.


Across the Gulf of Papagayo, expect fresh winds each night with the assistance of the nocturnal drainage flow through the week, occasionally building max seas to near 8 ft in a mix of east wind waves and long period southwest swell.

Gentle to moderate S to SW winds are expected across the forecast zones. Long period cross-equatorial SW swell creating 5-7 ft seas will continue to propagate into the forecast waters through mid week. Another set of cross-equatorial long period SW swell of 6 to 9 ft will reach the waters between Ecuador and the Galapagos Islands late Wednesday, and the coast of Central America on Thursday.


High pressure is located north of area with a ridge axis that extends across the forecast waters north of 20N. The pressure gradient between this system and an active zone of tropical cyclones between 12N and 20N will maintain fresh N to NE winds W of 125W through mid-week. Seas associated with T.S. Greg are already propagating across the waters N of 20N W of 130W. By Thursday night, cross equatorial southwesterly swell of 8 to 9 ft will spread over the waters south of 10N and east of 110W, persisting into next weekend.

$$ Cobb