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Eastern North Pacific Tropical Weather Discussion

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.