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Eastern North Pacific Tropical Weather Discussion

AXPZ20 KNHC 220943

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1005 UTC Sat Jul 22 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 15.2N 123.1W, moving W at 
11 kt. Estimated minimum central pressure is 1001 mb. Maximum 
sustained winds are 45 kt with gusts to 55 kt. Satellite imagery 
shows the low level center has moved back under the convective 
cirrus canopy. Scattered moderate to strong convection is noted 
within 120 nm north of the center. Greg is forecast to intensify 
only slightly during the next 48 to 72 hours. See the latest NHC 
forecast/advisory under AWIPS/WMO headers MIATCMEP2 WTPZ22 for 
more details.

Tropical Depression Nine-E is centered about 480 nm SSE of 
Acapulco Mexico near 9.6N 96.6W, moving WNW at 11 kt. Estimated 
minimum central pressure is 1006 mb. Maximum sustained winds are 
30 kt with gusts to 40 kt. Scattered moderate to strong 
convection is observed in bands within 150 nm NW of the center. 
Conditions are favorable for significant strengthening during 
the next 24 to 48 hours, and it is forecast to become a tropical 
storm later today, intensifying to a hurricane by early Monday. 
See the latest NHC forecast/advisory under AWIPS/WMO headers 
MIATCMEP4 WTPZ24 for more details.

A 1007 mb surface low continues near 14N112W in association with 
a tropical wave along 112W. Scattered moderate to strong 
convection is within 120 nm SW of the low due to the presence of 
persistent northeasterly shear. Environmental conditions are 
conducive for a tropical depression to form during the next 
couple of days, before upper-level winds become unfavorable for 
development. This system is forecast to move westward to west-
northwestward at around 10 kt through early next week.


The monsoon trough is ill-defined in the Eastern Pacific due to 
the presence of numerous lows and tropical cyclones. The ITCZ 
extends westward from a 1011 mb low near 11N127W to 09N140W. 
Except noted with the tropical systems decribed above, minimal 
convection is associated with the trough axis. 



Gentle to moderate NW winds off the Baja California peninsula 
are expected to continue through the weekend. Seas will remain 5 
to 7 ft in a mix of long period north and southwesterly swell. 
Gentle southerly flow will persist in the Gulf of California, 
except for moderate southerly flow over the northern Gulf. 

Fresh northerly gap winds are expected this morning in response 
to developing T.D. Nine-E. Seas will build to 7-8 ft with an 
additional component of longer period southwest swell.


In 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 8 ft in a mix of 
east swell and longer period southwest swell.

Gentle to moderate southerly winds are expected south of the 
monsoon trough axis. Long period cross-equatorial southerly 
swell and 6-7 ft seas will continue to propagate into the waters 
reaching the coast of Central America through the day. Another 
pulse of large southerly swell will move into the region today 
and raise seas to 6-8 ft through tonight.


The remnant low of T.D. 8-E is analyzed near 11N127W, with fresh 
cyclonic winds within 90 nm SE of the center. The weak low will 
dissipate by tonight. 

The pressure gradient between high pressure north of the area 
and an active zone of tropical systems between 10N and 16N 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.