AXPZ20 KNHC 230945

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1005 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 0600 UTC surface analysis and satellite imagery through 0900 UTC.


Tropical Storm Greg is centered near 14.7N 127.7W, moving W at 12 kt. Estimated minimum central pressure is 1001 mb. Maximum sustained winds are 45 kt with gusts to 55 kt. Scattered moderate to strong convection is noted within 90 nm SW of the center, with scattered moderate isolated strong convection elsewhere within 120 nm. Little change in intensity is forecast through the next 24 hours, with slow weakening expected thereafter as Greg tracks over cooler waters and a more stable atmosphere. Greg may weaken to a tropical depression by late Tue. See the latest NHC forecast/advisory under AWIPS/WMO headers MIATCMEP2 WTPZ22 for more details.

Tropical Storm Hilary centered near 12.5N 101.6W, or about 280 nm S of Acapulco Mexico, is moving WNW at 13 kt. Estimated minimum central pressure is 1005 mb. Maximum sustained winds are 35 kt with gusts to 45 kt. Scattered moderate to strong convection is observed in bands within 120 nm NE and 60 nm SW of the center. Conditions are favorable for significant strengthening during the next 24 to 48 hours, and it is possible Hilary could intensify to a hurricane by late Mon as it continues on a WNW track. See the latest NHC forecast/advisory under AWIPS/WMO headers MIATCMEP4 WTPZ24 for more details.

Newly formed Tropical Storm Irwin is centered near 14.7N 115.2W, moving WNW at 8 kt with minimum central pressure of 1005 mb. Maximum sustained winds are 35 kt with gusts to 45 kt. Scattered moderate to strong convection is within 150 nm of the southern semicircle. This system is encountering strong northerly shear, but is expected to intensify once the vertical shear diminishes. It will remain in relatively close proximity to Hilary the next few days, and some interaction between the two tropical cyclones may occur later this week. See the latest NHC forecast/advisory under AWIPS/WMO headers MIATCMEP5 WTPZ25 for more details.


A monsoon trough is analyzed E of the tropical cyclone activity from 10N85W to 12N97W. The ITCZ extends from 11N129W to 07N140W. Scattered moderate isolated strong convection is noted from 07N to 10N between 93W and 102W.



Gentle to moderate NW winds off the Baja California peninsula are expected to continue through Monday, as high pressure remains centered NW of the area and shifts NW. 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 winds are expected across most of the area between Tehuantepec and Acapulco today, becoming SE 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 Oaxaca and Chiapas through tonight, then the offshore waters of Michoacan, Guerrero and Jalisco through Tue.


Across the Gulf of Papagayo, moderate to fresh offshore winds will pulse to fresh each night with 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 southerly winds are expected south of the monsoon trough axis E of 95W. Long period cross-equatorial SW swell creating 5-7 ft seas will continue to propagate into the waters reaching the coast of Central America through the weekend. Another pulse of large southerly swell will move into the region Mon and Tue.


T.S. Greg will gradually dissipate through Tue. The pressure gradient between high pressure north of the area and an active zone of tropical systems between 12N and 20N will maintain fresh trade winds and 6-7 ft seas north of 20N the next several days. Northerly swell in the form of 7-8 ft seas will propagate S of 32N between 125W and 135W the next two days.

$$ Mundell