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Eastern North Pacific Tropical Weather Discussion

AXPZ20 KNHC 231545

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1319 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 1200 UTC surface analysis and satellite imagery through
1500 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. So far in
July, five named storms have developed.

Tropical Storm Greg is centered near 14.3N 129.0W at 23/1500 
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 to scattered strong convection is noted 
within 90 nm of the center. Little change in strength is anticipated 
through tonight, but some weakening is likely to occur Monday 
and Monday night as Greg tracks over cooler waters and a more 
stable atmosphere. Greg may weaken to a tropical depression on 
Wednesday morning. See the latest NHC forecast/advisory under 
AWIPS/WMO headers MIATCMEP2 WTPZ22 for more details.

Tropical Storm Irwin is centered near 15.0N 115.8W at 23/1500 UTC,
moving W at 6 kt with minimum central pressure of 1004 mb. 
Maximum sustained winds are 35 kt with gusts to 45 kt. Scattered 
moderate isolated strong convection is from 12N to 15N between 
112W 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 hurricane 
on Tuesday. See the latest NHC forecast/advisory under AWIPS/WMO
headers MIATCMEP5 WTPZ25 for more details.

Tropical Storm Hilary is centered near 12.7N 102.3W at 23/1500 
UTC, moving WNW at 9 kt. Estimated minimum central pressure is 
1003 mb. Maximum sustained winds are 40 kt with gusts to 50 kt. 
Numerous moderate scattered strong convection is in a band 
within 180 nm Ne semicircle of center. Scattered moderate 
isolated strong is within 150 nm SW semicircle. Conditions are 
favorable for significant strengthening during the next 24 to 48 
hours, and it is possible Hilary could intensify to a hurricane 
on Mon as it continues on a WNW track. 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 08N79W across western Panama and Costa Rica to 10N87W to 
09N92W to 12N97W. The ITCZ extends from 11N130W to beyond 07N140W.
Scattered moderate isolated strong convection is noted from 05N 
to 08N E of 84W. A cluster of moderate to strong convection is 
near the western end of the monsoon trough from 09N to 12N between
95W and 97W.



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 

Moderate E to SE 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 Chiapas and Oaxaca through tonight, then the 
offshore waters of Guerrero, Michoacan 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.