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Eastern North Pacific Tropical Weather Discussion



986 
AXPZ20 KNHC 240915
TWDEP 

Tropical Weather Discussion 
NWS National Hurricane Center Miami FL
1005 UTC Mon Sep 24 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.

...SPECIAL FEATURE... 

A broad area of low pressure is analyzed as 1009 mb surface low 
near 13.5N 102.5W. Scattered moderate isolated strong convection 
is observed within 90 nm south of the low with intermittent 
banding features. The associated tightening pressure gradient 
will increase the southwesterly monsoonal flow to a fresh to 
locally strong breeze well south of the low, across the tropical 
waters from 06N to 12N between 178W and 116W over the next 24 
hours. Environmental conditions are very favorable for tropical 
formation as this low tracks west-northwest over the next few 
days. Much uncertainty at this time, but for now expect fresh to 
strong easterly winds, and building seas, to spread north across 
the offshore waters from 16.5N to 23N on Wed through Sat, with 
southerly swell, in the form of 8 to 12 ft seas, to propagate 
north across the waters west of the Baja Peninsula during the 
upcoming weekend. Refer to the East pacific tropical Weather 
Outlook under WMO/AWIPS headers ABPZ20 KMIA/MIATWOEP for 
additional information.

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

The monsoon trough extends W off the Caribbean coast of Colombia 
at 09N76W, and continues west across the extreme southwest 
Caribbean to the Pacific coast of Costa Rica at 10N86W through a 
tropical wave along 10N94.5W, then turns northwest through the 
surface low at 13.5N 102.5W, then turns southwest to 12N109w to 
to 13.5n116.5W to 10N140W. Scattered moderate isolated strong 
convection is observed across the gulfs of Panama and 
Tehuantepec and within 75 nm of 20N106W. Isolated moderate and 
strong convection is noted elsewhere within 270 nm either side 
of a line from 05N82W to 13N98W, and from 07N to 17N 
between 98W and 137W. 

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO... 

See the Special Features paragraph above. A ridge extending from 
22N116W to 20N108W will gradually retract north during the 
middle of the week as a surface low, possibly a tropical 
cyclone, tracks northerly beyond 250 nm seaward. Gentle 
northwest flow is forecast west of the Baja California through 
mid week, except becoming a moderate northwest breeze within 90 
nm of the coast during the late afternoons and evenings.  

Gulf of California: Gentle to locally moderate variable winds 
forecast across the gulf waters north of 30N through this 
evening. Otherwise, light to gentle variable winds expected 
across the gulf waters through the middle of the week.

Gulf of Tehuantepec: Strong northerly flow forecast through late 
this afternoon, then fresh to locally strong nocturnal drainage 
forecast to resume tonight with a strong event expected on 
Fri night.

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 Thu night with seas building to 
8 ft. 

Light and variable winds are forecast elsewhere north of the 
monsoon trough which is meandering between 09N and 12N. Moderate 
southwest flow is forecast south of the monsoon trough.

REMAINDER OF THE AREA...   

See the Special Features paragraph above. A broad ridge 
continues across the subtropics accompanied by moderate to 
locally fresh anticyclonic flow south of 23N west of 120W.

$$
Nelson