694 
AXPZ20 KNHC 210916
TWDEP 

Tropical Weather Discussion 
NWS National Hurricane Center Miami FL
1005 UTC Fri Sep 21 2018 

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 
0915 UTC.
    
...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... 

The monsoon trough extends W off the Caribbean coast of Colombia 
at 09N77W, and continues west across the northern Gulf of Panama 
and central Panama to the Pacific Coast of Costa Rica at 09N84W 
to 12N104W to 09N118W where it loses identity in the cyclonic 
circulation associated with a 1010 mb surface low at 
14.5N123.5W. The monsoon trough resumes southwest of the low at 
13N125W and continues southwest to 12N132W where scatterometer 
winds indicate a transition to an ITCZ which continues southwest 
to 11N140W. Scattered moderate isolated strong convection is 
observed within 180 nm of 05N78W and 12N93W, within 60 nm of 
17N100W and within the area bounded by 06N to 14N between 110W 
and 121W.  

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO... 

A ridge will meander from 22N116W to 14N97W through early next 
week. Gentle northwest flow is forecast west of the Baja 
California through Sat, except becoming a moderate NW breeze 
within 90 nm of the coast during the late afternoons and 
evenings. A tightening pressure gradient on Sat night through 
Tue will support moderate northwest flow west of Baja, except 
increasing to a fresh breeze during the evenings within 90 nm of 
the coast. 

Gulf of California: Gentle to locally moderate variable winds 
forecast across the gulf waters north of 30N through the 
upcoming weekend. lIght to gentle variable winds expected south 
of 30N through the middle of next week.

Gulf of Tehuantepec: Fresh to locally strong nocturnal flow 
forecast through Tue, with strong drainage flow then forecast 
for Tue night through Thu night with seas building to 8 ft.

Extended model guidance suggests a surface low will develop near 
12N103W on Sun night, and track northwest across the offshore 
waters seaward of 200 nm reaching near 17N109W on Wed.   

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

Gulf of Papagayo: Moderate to locally fresh east nocturnal 
drainage flow expected through Mon night. 
  
Light and variable winds are forecast elsewhere N of the monsoon 
trough which is meandering between 09N and 11N. Moderate 
southwest flow is forecast S of the monsoon trough through the 
middle of next week when long period southwest swell, in the 
form of 6 to 8 ft seas, will propagate northeast reaching the 
far offshore waters near 09N90W on Wed.  

Looking ahead, an increase in moist southwest flow is suggested 
by the major global models by early next week, possibly 
culminating in a Central American gyre pattern by the middle of 
next week.  This may bring increase showers and thunderstorms to 
the Pacific waters off Central America.

REMAINDER OF THE AREA...   

A 1010 mb surface low is analyzed near 14.5N123.5W and is 
accompanied by scattered moderate isolated strong convection 
northwest of the low within 60 nm of 16N124W. The surface low 
will weaken into a trough by Sun, and move west of the area 
early next week.

A broad ridge continues across the subtropics with an area of 
fresh north winds and 7 to 9 ft seas forecast across the waters 
north of 28N between 123W and 129W through early this morning. 
Fresh northeast trades and diminishing across the waters from 
13N to 19N west of 138W.
 
$$
Nelson