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Eastern North Pacific Tropical Weather Discussion



000
AXPZ20 KNHC 282157
TWDEP 

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
2205 UTC Fri Apr 28 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
2145 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... 

A surface trough axis extends from 10N86.5W to 06N93W to
07N103W to 04N110W, where the ITCZ axis forms and continues 
west-southwest to 02N121W to 02N130W to 01N140W. Scattered 
moderate to strong convection is within 180 nm southeast and 
south of the trough axis between 87W and 94.5W. Scattered 
moderate/isolated strong convection is within 180 nm south of the
between 96W and 101.5W. Scattered moderate convection is within 
60 nm south of the axis between 101.5W and 108W.

...DISCUSSION...   

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

Strong to near gale force northwest winds continue across the 
discussion waters from 28N to 30N and west of the Baja Peninsula 
to near 125W, with seas of 9 to 13 ft in northwest swell. These 
winds and seas will persist through Saturday as a strong pressure
gradient remains over the area between high pressure to the 
west, and low pressure over the southwestern United States. Seas 
of 8 to 10 ft in northwest swell will propagate as far south as 
20N between 114W and 130W on Saturday before conditions begin to 
slowly improve over these waters Saturday night into Sunday. 

Gulf of California: Mostly gentle to moderate southwesterly flow 
is expected through tonight, with brief fresh to locally strong 
northerly winds possible over the gulf waters north of 30N 
briefly this afternoon and evening, and then Sat as a cold front 
passes across the area. The fresh to strong NW winds with and 
behind this front will shift southward into the central portions
Sat through Sat night and gradually build seas 5 to 8 ft. Winds 
and seas will decrease on Sunday.

Gulf of Tehuantepec: Gentle to moderate south to southwest flow 
expected this weekend with fresh to strong north winds possible 
near daybreak on Monday as the gradient tightens over southeastern
Mexico as high pressure builds over the western Gulf of Mexico 
in the wake of cold front. Seas will be in the range of 3 to 5 ft
through Saturday night, then build to 5 to 7 ft Sunday through
Monday. 

OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND 
WITHIN 750 NM OF ECUADOR...

Mostly a gentle onshore breeze is expected during the next few 
days becoming offshore along the coasts at night. Combined seas 
of 4 to 5 ft in mainly southwest swell will continue through 
these waters through tonight. Wave model guidance forecasts 
large long-period southern hemispheric southwest swell of 6 to 8
ft to approach the offshore waters of Ecuador on Saturday 
through Sunday, then subside slightly before increasing again to 
6 to 8 ft early next week.

REMAINDER OF THE AREA...

A 1029 mb high pressure system well north of the area near 
37N135W has a ridge extending southeastward to 26N127W and to
near 19N120W. This high pressure system covers the area north of
the ITCZ and west of about 115W. A tight pressure gradient 
between the high and a thermal trough along the coast of 
California will continue to support strong northwest winds along
with seas of 10 to 13 ft north of 28N east of 125W through 
Saturday, before they begin subside through the remainder of the 
weekend as the gradient slackens. Fresh northeast trades are 
expected between the ridge and the ITCZ W of 125W over the next 
several days, with seas of 6 to 8 ft in mixed northeast and 
northwest swell expected through Saturday afternoon. Southern 
hemispheric swell will continue to propagate across the waters 
south of a line from the equator at 128W to 08N123W to 03N113W
to 03.4S97W through Saturday, and south of 05N between 109W and 
125W on Sunday, resulting in combined seas of the general range 
of 8 to 10 ft. These seas will subside to 8 ft on Sunday.

Weak low-level westward moving perturbations continue across
the tropical belt under mid/upper level ridging. The combination
of this and a series of disturbances aloft riding along a
relatively pronounced jet stream branch is allowing for clusters
of scattered showers and thunderstorms to develop from time to 
time across this area. Latest satellite imagery shows that the 
most concentration of the activity is confined to the eastern 
portion of the tropics between 85W and 103W as described above 
under the ITCZ/Monsoon Trough section. This activity is likely to
persist into the weekend, with the activity west of 103W expected
to exhibit more of a pulsing type nature.

$$
Aguirre