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Eastern North Pacific Tropical Weather Discussion

AXPZ20 KNHC 200945

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1005 UTC Mon May 20 2019

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
0945 UTC.


The monsoon trough axis extends from a 1010 mb low centered over
Colombia near 07N74W, west-northwestward to across northern 
Panama and southern Costa Rica to 10N86W, then to a 1008 mb low 
near 10N91W and to 09N100W to 09N110W and to 08N120W, where 
overnight scatterometer data indicated that it transitions to the
ITCZ and continues to 06N130W and to beyond the area at 05N140W.
Scattered moderate to isolated strong convection is within 180 
nm south of the trough between 84W and 87W, within 180 nm either 
side of the ITCZ between 135W and 140W, and also from 03N to 07N 
between 87W and 91W. Scattered moderate convection is within 120 
nm south of the trough between 106W and 109W, between 117W and 
125W and within 60 nm north of the trough between 110W and 115W.



A cold front extends from far northwest Mexico southwestward
over the southern half of Baja California Norte to the coast 
at Punta Eugenia, and continues from there to 02N120W and to 
near 21N135W. The gradient behind the front as high pressure 
builds in its wake is bringing moderate to fresh northwest to
north over the waters off the Pacific coast of Baja California.
Waveheights are presently 5-7 ft, except for higher waveheights 
of 7-11 ft in northwest swell north of 28N. Over the far 
northern Gulf of California, strong northwest winds have begin 
there, while gentle to moderate northwest winds are over the 
remainder of the Gulf of California, with the exception of 
extreme southern section where light to gentle winds exist. 
Waveheights are in the 4-6 ft range over the northern section of 
the Gulf, 2-4 ft in the central part of the Gulf and 3-5 ft in 
the southern part due to a southeast swell.

The cold front will weaken today as it continues across the rest
of Baja California Norte and over northern part of Baja California
Sur, where it begins to dissipate. The northwest swell with 
waveheights of 7-11 ft N of 28N will spread southeastward through
offshore waters zone through Wed night, while gradually 
decaying. A large set of long-period southerly swell will 
continue to propagate through the Mexican offshore waters through
today before it begins to mix with the northwest swell tonight. 
Like the earlier mentioned cold front, another cold front will 
move across Baja California Norte and the northern Gulf of 
California Tue night and early on Wed, then across the rest of 
Baja California and the Gulf of California from late Wed through 
Thu while dissipating. Model guidance indicates that this front 
will be followed by much stronger high pressure than seen in 
recent days. The associated tight gradient will bring strong 
northwest winds to the northern offshore waters from Tue night 
through most of Wed. With these winds, a rather extensive set of 
long-period swell will infiltrate the northern offshore waters 
Wed, with waveheights expected to build to the range of 9-12 ft 
Wed night before slowly decaying through the end of the week.


To the south of the monsoon trough, mainly light to gentle
southwest winds are noted, except for gentle to moderate winds 
south of 05N as indicated in the latest Ascat pass. Little change
is expected with these winds through end of the week. To the 
north of the monsoon trough, light to gentle winds will continue
over these waters through the end of the week, with the exception
of gentle to moderate east to southeast winds developing over 
the waters near Guatemala and El Salvador on Thu as the gradient 
increases to the east of low pressure that persists near 11N91W. 
Waveheights over these waters are in the 5-8 ft range in a 
southwest swell. Slightly higher waveheights peaking to 9 ft also
due to a southwest swell are over the waters south of 02N, 
except in the lee of the Galapagos. The waveheights south of 02N 
are forecast to subside beginning on Wed.

The availability of deep atmospheric moisture, along with 
favorable large scale lift over this region will help contribute 
to the development of scattered to numerous showers and 
thunderstorms through the remainder of the week, especially 
near the low pressure presently centered along the monsoon 
trough near 10N91W. Some of this shower and thunderstorm 
activity could produce heavy rain and strong gusty winds.


A cold front analyzed from central Baja California to near 
21N135W will continue to move across the waters north of 20N 
through this afternoon. Recent scatterometer and altimeter 
satellite data show moderate to fresh northwest winds following 
the front along with waveheights in the range of 7-11 ft due to 
northwest swell. High pressure building behind the front is 
supporting moderate to fresh trade winds farther south into the 
deep tropics along the ITCZ, with waveheights in the range of 5-7
ft, except for slightly higher waveheights of 6-8 ft from 07N to
18N between 109W and 122W and from 13N to 21N west of 130W from 
the combination of the northerly swell, southerly swell and local
winds. These waveheights will continue through at least Thu as 
stronger high pressure builds over the area in the wake of 
another cold front that will sweep across the northeast part of 
the area Tue night through through Thu before they subside. The 
pressure gradient between the high pressure behind this front and
lower pressure in tropics will allow for the moderate to fresh 
trade winds to increase in coverage mainly west of about 125W. 
Convection over this area is limited to that occurring near 
and along the ITCZ and Monsoon Trough as described above.