AXPZ20 KNHC 232119

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1925 UTC Sun Jul 23 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 2100 UTC.


The Eastern Pacific region remains very active with three tropical cyclones: from west to east, Greg, Irwin and Hilary. Irwin and Hilary are forecast to become hurricanes, and Hilary a major hurricane. So far in July, five named storms have developed.

Tropical Storm Greg is centered near 14.4N 130.1W at 23/2100 UTC, moving W at 12 kt. Estimated minimum central pressure is 1001 mb. Maximum sustained winds are 45 kt with gusts to 55 kt. Numerous moderate isolated strong convection is noted within 120 nm east semicircle of the center. Greg is forecast to maintain its intensity for another 24 hours, followed by gradual weakening due to the dry air, increasing shear, and cooler sea surface temperatures after 48 hours. Greg is expected to weaken to a tropical depression on Wednesday, and to a remnant low on Thursday. See the latest NHC forecast/advisory under AWIPS/WMO headers MIATCMEP2 WTPZ22 for more details.

Tropical Storm Irwin is centered near 14.9N 116.6W at 23/2100 UTC, moving W at 7 kt with minimum central pressure of 1003 mb. Maximum sustained winds are 40 kt with gusts to 50 kt. Scattered moderate isolated strong convection is from 12.5N to 15.5N between 113W and 118W. 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 on Tuesday. See the latest NHC forecast/advisory under AWIPS/WMO headers MIATCMEP5 WTPZ25 for more details.

Tropical Storm Hilary is centered near 13.2N 102.9W at 23/2100 UTC, moving WNW at 8 kt. Estimated minimum central pressure is 999 mb. Maximum sustained winds have increased to 50 kt with gusts to 60 kt. Numerous moderate scattered strong convection is in a band within 180 nm NE semicircle of center. Scattered moderate isolated strong is within 120 nm SW semicircle. Conditions are favorable for significant strengthening during the next 24 to 48 hours, and Hilary will likely become a hurricane on Monday, and a major hurricane on Tuesday as it continues on a WNW track for the next couple of days. See the latest NHC forecast/advisory under AWIPS/WMO headers MIATCMEP4 WTPZ24 for more details.


The monsoon trough is analyzed E of the tropical cyclone activity from 09N84W to 11N98W. The ITCZ extends from 11N132W to beyond 07N140W. Scattered moderate isolated strong convection is noted from 05N to 10N E of 88W. A cluster of moderate to isolated strong convection is from 11N to 13.5W between 96W and 99W.



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.

Moderate E to SE winds are expected across most of the area between Tehuantepec and Acapulco through early Mon. The forecast track and intensity of T.S. Hilary is expected to impact the offshore waters within 250 nm of the coast of the Mexican States of Chiapas and Oaxaca through tonight, then the offshore waters of Guerrero, Michoacan and Jalisco through Tue. Hilary is forecast to cross south of the Revillagigedo Islands on Wednesday as a major hurricane. Seas of at least 10 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 the week. Another set of cross-equatorial long period SW swell will reach the waters between Ecuador and the Galapagos Islands on Tuesday, and the coast of Central America on Wednesday.


High pressure located north of area extends a ridge across the forecast waters north of 20N. The pressure gradient between this system and an active zone of tropical ciclones between 12N and 20N will maintain fresh N to NE winds mainly west of 125W through mid-week. Seas associated with T.S. Greg are already propagating across the waters N of 20N W of 130W. Northerly swell in the form of 7-8 ft seas will propagate S of 32N between 125W and 135W the next two days.

$$ GR