AXPZ20 KNHC 290946

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1005 UTC Sat Jul 29 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 0830 UTC.


Tropical Storm Hilary is centered near 20.7N 120.8W at 0900 UTC or about 620 nm W of the southern tip of Baja California and moving NW at 9 kt. Estimated minimum central pressure is 996 mb. Maximum sustained wind speed is 55 kt with gusts to 65 kt. Scattered moderate isolated strong convection is from 19N to 23N between 118W and 122W. Satellite photos overnight has shown a ragged eye developing within the central circulation of Hilary, but convection has been limited across the NW semicircle. Hilary will continue moving off to the NW during the next few days and gradually weaken to a remnant low by 48 hours as it encounters cooler waters. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCMEP4/WTPZ24 for more details.

Tropical Storm Irwin is centered near 14.9N 124.9W at 0900 UTC or about 975 nm WSW of the southern tip of Baja California and drifting NW. Estimated minimum central pressure is 998 mb. Maximum sustained wind speed is 50 kt with gusts to 60 kt. Scattered moderate convection is from 12N to 16N between 123W and 127W. Irwin is expected to resume a northward motion today and then follow Hilary off to the NNW then NW Sunday through Tuesday, while also weakening as it reaches cooler waters. See latest NHC forecast/ advisory under AWIPS/WMO headers MIATCMEP5/WTPZ25 for more details.

...TROPICAL WAVES... A tropical wave IS ALONG 99W-100W moving W at 10 to 15 kt. Scattered moderate to strong convection is from 11N to 17N between 96W and 102W.


The monsoon trough extends from 10N83W to 09N90W to 11N100W to 14N115W. The ITCZ extends from 09N135W to beyond 09N140W. Other than the convection related to the tropical wave, scattered moderate to strong convection is from 11N to 15N between 87W and 92W. Scattered moderate convection is from 06N to 10N between 82W and 100W, from 07N to 16N between 103W and 115W, and within 90 nm of either side of the ITCZ axis.



High pressure centered NW of the area will support gentle to moderate NW winds within 120 nm of the Baja California peninsula through Sunday. Tropical Cyclone Hilary's affects are now mainly west of the area, with some small southerly swell to fade across the far outer waters today. However the NW movement of the system will allow a ridge axis to fill in between the departing cyclone and Baja California, which in turn will result in moderate to fresh NW winds Sunday through early next week. As these winds increase, seas will build into a range of 7 to 9 ft as the wind waves combine with a round of long-period southerly swell moving into the region over the next few days

Cross equatorial long period southerly swell with seas of 7 to 8 ft will reach the offshore waters between the Gulf of Tehuantepec and Cabo Corrientes on Sunday, and the waters between Los Cabos and Cabo Corrientes on Monday. Elsewhere, generally moderate NW winds and seas of 5 to 7 ft will prevail.


Across the Gulf of Papagayo, expect fresh winds to persist through early this morning and develop again tonight with the assistance of the nocturnal drainage flow, building maximum seas of 6 to 7 ft in a mix of E wind waves and long period SW swell.

Elsewhere, gentle to moderate S to SW winds are expected the next few days. Large long period cross-equatorial S-SW swell will continue to propagate into the forecast waters over the weekend, with seas 8 to 9 ft reaching as far north as 10N by tonight. The area of 8 ft seas will then reach just offshore all Central America Pacific coastal sections by Sunday. Seas will gradually subside starting Monday.


High pressure is located N of the area with a ridge axis extending across the northern forecast waters N of 25N. The pressure gradient between the high pressure system and the active zone of tropical cyclones will maintain moderate to fresh N to NE winds W of 120W through Saturday. Long period cross equatorial SW swell of 8 to 9 ft will spread across the waters S of 10N and E of 110W today, persisting through Sunday night. As the tropical cyclone activity shifts to the NW and eventually weakens over the discussion waters later this weekend, a weak pressure pattern will develop between the cyclones and the equatorial trough to the south. This will result in a broadening area of gentle to moderate winds between 10N and 20N, W of 115W early next week.

$$ Latto/Stripling