000
AXPZ20 KNHC 201536
TWDEP

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1536 UTC Tue Jun 20 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.

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

The monsoon trough axis extends from 11N86W to 12N93W to 10N130W.
The intertropical convergence zone axis extends from 10N130W to
beyond 07N140W. Scattered moderate to isolated strong convection
is ongoing within 120 nm north of the monsoon trough between 89W
and 95W, along the coast from the Gulf of Fonseca to just east of the
Gulf of Tehuantepec. Scattered moderate convection is also noted
within 60 nm of the monsoon trough between 105W and 115W, and
within 90 nm south of the intertropical convergence zone between
128W and 138W.

A surface trough related to broad low pressure in the Gulf of
Mexico will continue extend across the Yucatan Peninsula into
northern Central America, acting as the focus for locally heavy 
rains.
  
...DISCUSSION...   

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

Weak ridging from the north central Pacific through the
Revillagigedo Islands will shift west through late Wednesday as a
surface trough currently over the Gulf of California moves
westward. The trough development and movement is related to an
upper low currently centered south of Los Cabos, moving slowly
west. Broad and weak low pressure will form along the surface 
trough 18N115W, by Clarion Island Wednesday night. Moderate
northwest winds off the coast of Baja California will shift to
the southwest off Baja California Sur starting Wednesday in the
wake of the trough/low passage to the west. Northwest winds off
Baja California Norte will diminish accordingly, but light
southeast flow noted over the Gulf of California will increase to
moderate to fresh. 

Long period northwest swell will propagate into the waters off
Baja California Norte beyond 150 nm tonight through Friday. 

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

Gentle to moderate SW to W winds are expected across the entire 
forecast area through Wed, then the pressure gradient will 
gradually relax with a gentle SW breeze continuing through Sat 
night. Long period S swell in the form of 5 to 8 ft seas 
currently across the area will subside through the day, with
seas less than 8 ft everywhere by Wed afternoon.

REMAINDER OF THE AREA...
 
Weakening surface high pressure is centered near 34N137W.
Scatterometer and altimeter passes from the past several hours
indicated a band of fresh to strong northeast winds and seas of 8
to 9 ft over much of the discussion area from 22N to 31N between
125W and 140W. The winds will diminish through tonight as the
high pressure weakens, but northerly swell will propagate into
the region north of 20N west of 120W through late week with 8 to
11 ft seas, decaying this weekend. 

An area of 6 to 9 ft seas primarily due to southwest swell are 
observed across the tropical waters to the S of 14N, except 3 to 
6 ft seas are forecast to the lee of the Galapagos Islands. These
seas are already subsiding from the north, and are forecast at 5
to 7 ft by late Thursday.

$$
Christensen