000
AXPZ20 KNHC 141605
TWDEP 

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1605 UTC Sat Oct 14 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 
1545 UTC.

...SPECIAL FEATURES...
A 1007 mb low pressure is centered near 13N113W moving WNW around
12 kt. Latest satellite imagery shows that this the overall cloud 
pattern associated with this low pressure has become somewhat better
organized since last night primarily over its eastern semicircle
where there the cloud pattern is exhibiting more curvature. Deep
convection of the strong intensity type is within 60 nm of the center 
in the SE quadrant. Scattered moderate convection is elsewhere within 
90 nm of the center in the SE quadrant. Scattered moderate isolated
strong convection is elsewhere within 210 nm of the center in the SE and 
120 nm of the center in the S quadrant of the low. Similar convection is
within 45 nm of line from 10N115W to 12N117W, and within 30 nm of line from
13N116W to 13N118W. Expect seas to gradually build in association with 
this low going into early next week. Global models suggest that atmospheric
conditions are expected to become more favorable over the next 48 hours for
this system to become a tropical depression as it continues to track 
in a west-northwest direction. There is presently a high probability
that this system will develop into a tropical cyclone within the next
48 hours. Please refer to the latest Tropical Weather Outlook for
updates on the status of this system.

Gulf of Tehuantepec Gale Warning: The combination of high 
pressure across the eastern slopes of the Sierra Madre Mountains 
of Mexico and lower pressures S of Mexico continues to result in 
strong northerly gap winds across the Gulf of Tehuantepec during 
the overnight hours. These winds will pulse again to the strong 
range tonight, and into the early morning of Sunday. Model 
guidance suggests that these winds will significantly increase 
to gale force early Monday morning and again late at night and 
into the morning hours through Wednesday, at which time they may 
reach strong gale force, as strong high pressure builds behind a 
cold front forecast to move across the Gulf of Mexico. The gale 
force winds will increase in coverage as they spread well to the 
S of the Gulf of Tehuantepec Monday night into Tuesday. Wave 
guidance indicates that seas downstream from the Gulf will build 
to 8-12 ft during the times of maximum winds through Monday. 
Seas are then forecast to build much higher, around the range of 
12-16 ft Monday night into Tuesday and again from Tuesday night 
into Wednesday morning as strong gale force winds expand in 
coverage downwind of the Gulf. 

...TROPICAL WAVES...
A tropical wave axis is analyzed along 84W N of 04N, moving westward
near 17 kt. The wave is embedded within an area of deep layer moisture
as depicted in the SSMI TPW animation. A mid-level inverted trough 
is W of the wave roughly along 87W. Although no deep convection 
is currently occurring directly in association with these 
features, latest satellite imagery shows scattered moderate to 
strong convection to the E of these features over much of 
eastern Nicaragua, over portions of the W Caribbean Sea, and 
eastern Panama. The activity over eastern Panama extends S to 
near 06N and between 79W and 82W. 

INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... 

The monsoon trough axis from NW Colombia to 10N84W to 08N94W to 
10N105W to low pressure near 13N113W 1007 mb to 11N119W to 
11N126W to 09N134W where scatterometer data from last night 
indicates that the ITCZ then begins and extends to beyond 
10N140W. Scattered strong convection is within 120 nm N of the 
trough axis between 90W-91W. Scattered moderate convection is 
within 120 nm S of the trough axis between 108W-110W, within 30 
nm of the trough axis between 124W-128W and also between 130W-
133W.

...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

A surface ridge extends across the waters off Baja California. 
The pressure gradient between the ridge and a trough over the 
Gulf of California is supporting gentle to moderate NW winds in 
the offshore waters of Baja California. Seas of 4 to 7 ft prevail
over the offshore waters west of the Baja California peninsula, 
with northerly swell just pushing into the waters north of 26N 
and west of 118W inducing seas to the range of 7-9 ft there. The 
ridge will gradually weaken into early next week. The 
aforementioned northerly swell will decay through tonight 
allowing for the 7-9 ft seas to lower to 5-7 ft across most of 
the offshore waters. Winds are forecast to become SE to S fresh 
to strong in intensity over the far SW portion of zone PMZ015 on 
Sunday as the pressure gradient there increases between the 
Special Features low and the high pressure ridging across the 
waters W of Baja California. Seas are forecast by Wave model to 
build to the range of 8-12 ft in association with these winds.

Moderate to fresh NW-N winds are expected across the northern
Gulf of California tonight through Monday as a high pressure 
settles over the Great Basin and interacts with low pressure 
troughing over NW Mexico. Fresh to locally strong winds are 
expected on Sunday morning. 

High pressure across the eastern slopes of the Sierra Madre
Mountains in Mexico continues to induce strong northerly gap 
winds across the Gulf of Tehuantepec. The strong winds over the 
Gulf will pulse to near gale force during the overnight and 
early morning hours through Sunday. Winds will further increase 
to gale force early Monday morning through early Wednesday 
morning as high pressure builds behind a cold front moving into 
the Gulf of Mexico. Seas downstream from the Gulf will build to 
8-11 ft during the times of maximum winds through Monday. Maximum
seas of 13-15 ft are expected with the gale force winds, 
forecast to increase to 35-40 kt at night.

OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND 
WITHIN 750 NM OF ECUADOR...
   
Moderate to fresh offshore winds will develop across the 
Papagayo region tonight and continue through Tuesday with seas 
of 6-7 ft. Light and variable winds and seas of 4-6 ft seas 
prevail N of 09N, while gentle to moderate SW to W winds and 5-7 
ft seas are currently observed across the area S of 09N. Little 
change is expected with these conditions through Monday.

REMAINDER OF THE AREA...

Please see special features section above for more information 
on low pressure centered near 13N113W. Elsewhere, high pressure 
of 1039 mb centered well NW of the area near 41N145W extends a 
ridge southeastward to near 23N115W. The pressure gradient 
between the ridge and the monsoon trough is producing an area of 
fresh to strong NE winds to the NW of a line from 30N125W to 
25N130W to 20N136W with seas of 8-12 ft based on latest 
available altimeter data. Winds are forecast to diminish across 
the northern forecast waters today as high pressure weakens some 
and the resulting pressure gradient slackens. Seas will 
gradually subside, but 8-9 ft seas will continue to affect much 
of the area N of 20N W of 120W by this evening. In addition, 
long period SW swell generated from the Southern Hemisphere will 
continue to propagate across the south-central waters, 
particularly S of 15N between 100W-125W through Monday.

$$
Aguirre