Eastern North Pacific Tropical Weather Discussion (Text)

AXPZ20 KNHC 180954

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1005 UTC Sun Mar 18 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
0945 UTC. 


Gale Warning: Deepening surface low pres northwest of the area 
will drop southeastward towards the far northwest corner of the 
area behind a strong cold front that will move into the extreme 
northwest part of the area Mon night. The pres gradient ahead of 
the low will intensify increasing the wind field to the gale 
force range (25 to 35 kt) from the southwest in direction there,
with seas in the range of 11 to 14 ft. Strong to near gale force
southwest to west winds are forecast elsewhere to the north of 
27N and west of 138W on Mon night, with seas 9 to 13 ft Mon 
night. By Tue evening the low pres is expected to have lifted 
just far enough north of the area to allow the culprit tight 
gradient to relax, and winds to lower to just below gale force. 
Please refer to the Pacific high seas forecast for more details 
on this upcoming event under AWIPS/WMO headers MIAHSFEP2/FZPN03.


A surface trough axis extends from low pres over NW Colombia
to the Pacific coast of Colombia at 08N84W to 06N92W to 05N101W 
to 05N107W, where latest scatterometer winds indicate the ITCZ 
axis begins and continues westward to 06N120W to beyond 06N140W.
Scattered moderate convection is within 60 nm south of the axis 
between 92W and 94W, and within 30 nm south of the axis between
97W and 99W.



A dissipating cold front extends from extreme southwestern 
Arizona to across the extreme northwest portion of the Gulf of 
California, and continues southwestward to near 27N121W. A 1021
mb high is centered at 25N120W, with a ridge extending 
southeastward to just west of the Revillagigedo Islands. The 
cold front will dissipate this afternoon as its upper level
support shifts eastward to across Baja California and over
northern/central Mexico. The 1021 mb high will remain about 
stationary through tonight, then become centered slightly to the 
southwest on Mon and Tue. Fresh to locally strong northerly winds
will develop from 21N to 22N between 110W and 112W this morning,
diminish to fresh winds this afternoon and start up again late 
tonight. By early on Mon, these winds are expected to develop 
again generally from 18.5N to 20N between 105.5W and 106.5W, with
little change into Mon night. Seas associated with these winds 
are forecast to reach a maximum value of 8 ft.

Mid to upper level moisture in the form of overcast cloudiness is
well west of these waters, but is streaming eastward in advance 
of a strong mid to upper level trough that is presently well to
the west of the discussion area. Some of this moisture may 
begin to move in over the far northern portion of Baja 
California and southern California on Tue.

Gulf of California: A dissipating cold front is moving across 
the far NW portion of the gulf this morning. Strong southwest to
west winds are occurring from 29.5N to 30.5N. The front will be 
followed by strong northwest to north winds through this morning,
diminishing to moderate winds this afternoon. Elsewhere over the 
gulf, moderate northwest flow will be present, except increasing 
to fresh northwest to north winds over the southern portion 
tonight, and continue through Mon before increasing to strong 
early Mon evening and continuing through Tue. Seas with these 
winds will be in the range of 5 to 6 ft.

Gulf of Tehuantepec: Strong north flow will surge through the 
gulf waters on Tue night, increasing to minimal gale force 
early on Wed. Gale conditions of 30 to 40 kt are then expected 
to continue through late Thu night, with seas reach a range 
from 10 to 15 ft downstream of the gulf near 14.5N95.5W on Wed 


Gulf of Papagayo: Fresh to locally strong NE nocturnal winds,
with seas of 5 to 7 ft will diminish to moderate intensity 
this afternoon, then increase again to strong tonight, and
continue through Mon.

Gulf of Panama: Fresh northerly winds will diminish to moderate
winds this afternoon, then briefly increase to fresh tonight
before diminishing again to moderate intensity on Mon.

Elsewhere, gentle to moderate offshore flow will prevail N of 
08N while light to gentle SW winds are forecast S of 08N. 


Please see see Special Features Section above for details on 
upcoming gale force winds to impact the far NW portion of the 
area in the short-term.

A cold front will approach the far NW corner this morning, with 
the pres gradient tightening up ahead of it. This will develop 
strong south to southwest winds from 26N to 28N W of 136W 
tonight. The cold front will reach from near 32N134W to 24N140W 
by early on Mon. Strong south to southwest winds are forecast 
for N of 25N within 300 nm east of the cold front, with seas of 
8 to 10 ft. Southwest to west strong winds are expected N of 29N 
and W of 138W early on Mon, with seas of 8 to 10 ft in advance of 
a second cold front. By early Mon evening, strong to near gale 
force SW to W winds along with seas of 9 to 12 ft are expected 
within 120 nm east and southeast of this second cold front along
a position from 32N138W to 29N140W. Deepening surface low pres 
northwest of the area will drop southeastward towards the far 
northwest corner of the area behind the second cold front late 
Mon night intensifying the wind field there leading to gale force
winds southwest winds there, and strong to near gale force 
southwest to west winds elsewhere to the north of 27N and west of
138W. Rather large seas, around the range of 10 to 18 ft, are 
forecast to move into the NW and N central portions over the area
Mon through Tue night. 

The mid/upper level low pres system and related trough that 
will induce and drive the aforementioned surface low and cold 
front will be preceded by mid to upper level moisture in the form
of overcast cloudiness. Areas of rain along with scattered 
showers and isolated thunderstorms under upper level divergence 
that is present to the the east and southeast of the mid/upper 
low have moved over the area north of about 26N and west of 125W.
This moisture and related precipitation is expected to move 
east-northeast through Tue per model moisture guidance fields.


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Page last modified: Sunday, 18-Mar-2018 09:55:06 UTC