Eastern North Pacific Tropical Weather Discussion (Text)

AXPZ20 KNHC 300228

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0405 UTC Sun Apr 30 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 0000 UTC surface analysis and satellite imagery through
0215 UTC.


A surface trough axis extends from 09N84W to 09N91W to 05N110W.
The ITCZ extends from 05N110W to 04N120W to 05N130W to 02N140W. 
Scattered strong convection is occurring from 04N to 09N between 
84W and 88W. Scattered moderate convection is within 60 nm of the 
axis between 117W and 120W, and within 60 nm north of the axis
between 125W and 129W.



Scatterometer data from Saturday afternoon indicated that the 
fresh to strong northwest winds that were occurring earlier 
offshore the coast of Baja California Norte have diminished to 
the moderate to fresh range. Light to gentle northwest to north 
winds prevail elsewhere over the forecast waters. Seas are in the
8 to 10 ft range over the coastal waters off the coast of Baja 
California Norte and 6 to 8 ft off the coast of Baja California 
Sur. The moderate to fresh northwest winds will diminish further 
to the light to gentle range on Monday, with seas subsiding to 5 
to 6 ft. 

Gulf of California: Ascat data from Saturday afternoon depicted 
a swath of fresh to strong northwest to north winds over the 
northern sector of the Gulf with seas in the range of 5 to 7 ft. 
Moderate to fresh northwest winds are over the central sector of 
the Gulf, while gentle to moderate northwest winds are over the 
remainder of the Gulf. Seas are in the range of 3 to 4 ft in the 
central sector and 2 to 3 ft in the southern sector except in the
entrance to the Gulf where seas are 4 to 5 ft. The fresh to 
strong northwest winds are shifting southward to the central 
sector this evening, then diminish to the fresh range early on 
Sunday as the gradient weakens. By Monday, winds are expected to 
be light and variable over much of the Gulf, except light to 
gentle northwest winds over the southern sector, with seas of 2 
to 4 ft south of 25N, and 1 to 2 ft north of 25N.

Gulf of Tehuantepec: Gentle to moderate south to southwest flow 
will continue through Sunday night, then the flow becomes
northerly at fresh category on Monday as the gradient tightens 
over southeastern Mexico with the passage of a cold front 
across the western Gulf of Mexico. Seas will be in the range of 
5 to 6 ft into early on Monday, then build to 6 to 7 ft during
Monday afternoon.


Light to gentle winds will prevail trough early next week under
a weak pressure pattern, with seas of about 5 to 6 ft except
for slighter higher seas of 6 to 7 ft over the offshore waters 
west of Colombia.


A nearly stationary high pressure system of 1031 mb centered 
north of the area near 36N135W extends a ridge southeastward to 
27N127W to near 21N120W. The pressure gradient between the area 
of high pressure and lower pressure in the vicinity of the ITCZ 
is maintaining gentle to moderate trades north of the ITCZ, with 
seas in the 6 to 8 ft range in a southwest swell. Northerly swell
continues to propagate into the northern waters bringing 
combined seas of 8 to 10 ft within an area bounded by 32N128W to 
32N116W to 22N115W to 20N120W to 22N134W to 32N128W. The 
northerly swell will begin to mix with southwest swell on Sunday 
to the north of 24N between 122W and 132W, and within an area 
bounded by 32N128W to 32N122W to 26N127W to 26N133W to 32N128W on
Monday. Cross-equatorial southwest swell has propagated into the
southern portion of the discussion area to the south of 09.5N 
between 104W and 115W, and also to the south of 02N between 94W 
and 104W with seas in the 7 to 8 ft. This swell will shrink in 
coverage through Sunday. Yet another round of southwest swell 
will propagate into the far southern waters beginning Sunday 
night through Monday, with seas in the range of 7 to 8 ft.

Weak low-level westward moving perturbations continue across
the ITCZ region under mid/upper level ridging. The combination 
of these features along with occasional 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, although dry aloft 
has intruded into the deep tropics keeping the activity to a 
minimum for the time being. Latest satellite imagery shows that 
the most concentrated of this activity remains confined to the 
eastern portion of the tropics between 84W and 88W as described 
above under the ITCZ/Monsoon Trough section, and also from just 
inland Colombia west from there to 80W. Heavy rainfall with 
possible flooding is occurring from within 70 miles inland the 
Colombian coast from 70 miles southwest of Buenaventura north to
near 04N77W. The added factors of upper level diffluence present
across this portion of the area as noted in upper level 
streamline analysis as well as in the trajectory of high level 
clouds within this area is helping to sustain this deep 
convective activity. In addition, a kelvin wave moved through 
the ITCZ region during the past several days helping to give 
addition momentum and support to the aforementioned convective 
activity. The satellite representation of this activity appears 
more like what is expected during the month of May for that 
portion of the area. The activity is expected to persist into 
early next week.


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Page last modified: Sunday, 30-Apr-2017 02:28:21 UTC