AXPZ20 KNHC 301518
Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1518 UTC Sat Jul 30 2016
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
Based on 1200 UTC surface analysis and satellite imagery through
An area of low pressure is embedded along the monsoon trough
near 12.5N118.5W with an estimated minimum central pressure of
1008 mb, moving west-northwest at around 10 kt. Scattered moderate
convection is within 420 nm in the south semicircle. There have
been no recent scatterometer passes, however winds are likely
approaching 20 kt on the southeast to south side where combined
seas of 8 to 9 ft are observed by altimeter passes. Conditions
are forecast to become more conducive for development of this low
over the next few days, and it has a medium chance of tropical
cyclone formation through the next 48 hours.
A tropical wave is along 98W and is moving west at 10 to 15 kt.
Associated convection is difficult to differentiate from a nearby
area of low pressure, while additional convection is behind the
wave which developed over Central America during the overnight
hours before propagating offshore.
..INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
The monsoon trough axis extends from 09N80W to low pressure near
08N100W to low pressure near 12.5N118.5W to 11N126W. The
intertropical convergence zone axis extends from 11N126W to
09N140W. Scattered moderate convection is from 10N to 16N between
90W and 94W, which developed over Central America during the
overnight hours before propagating offshore. Similar convection is
within 120 nm either side of the ITCZ to the west of 133W.
Also, scattered moderate to strong convection is occurring
from 03N to 09N to the east of 80W, including over nearby western
Colombia around low pressure located along the northwest Colombian
N of 15N E of 120W:
In the Gulf of California, surface troughing will linger along
the Baja California peninsula for the next few days. Moderate to
fresh south to southeasterly flow will prevail in the central and
northern Gulf on the east side of this troughing, with light and
variable winds across the southern Gulf. Winds in the central and
northern Gulf will diminish late in the weekend as the pressure
Across the Gulf of Tehuantepec, nocturnal northerly flow increased
to fresh to strong in the immediate Gulf. Similar conditions are
expected again late tonight into early Sunday, and then slightly
stronger late Sunday night into early Monday. Seas will build to 8
ft again by early Sunday, then up to 8 to 10 ft by early Monday
with the stronger winds. The fresh to strong nocturnal drainage
flow will then persist each night through Wednesday night.
Elsewhere, A weak surface ridge extends into the area from the
northwest, partially disrupted by the remnant circulation of Frank
located well to the west. This ridging will support mainly gentle
west to northwest flow across the open Pacific waters,
occasionally pulsing to moderate just offshore of the Baja
California peninsula. Seas will remain in the 4 to 6 ft range.
S of 15N E of 120W:
Across the Gulf of Papagayo, nocturnal drainage flow has pulsed
to fresh to strong overnight, but is in the process of
diminishing. Another pulse of fresh to strong flow is expected
late tonight into early Sunday, and then again late Sunday night
into early Monday. Weaker winds are expected through the middle of
next week as the monsoon trough drifts slightly northward.
Otherwise, light to moderate flow is anticipated on either side of
the monsoon trough.
Long-period cross-equatorial southwesterly swell producing seas
of 6 to 8 ft, will gradually decay through the weekend. Broad and
weak low pressure is near 08N100W at 1009 mb with scattered
moderate convection within 240 nm in the north and 120 nm in the
south semicircles. The low is forecast to gradually weaken through
the next 48 hours, then may strengthen thereafter.
W of 120W:
Ridging extending from northwest of the area is disrupted by the
remnant 1011 mb circulation of Frank, currently near 24N128W. This
low remnant will become a trough later today or tonight.
Fresh to strong northerly winds offshore of California will
generate fresh northerly swells. Seas of 8 ft will propagate down
to 29N by late Sunday night into early Monday, decaying to less
than 8 ft by the middle of the week.