AXPZ20 KNHC 230241
Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0405 UTC Sat Sep 23 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
Based on 0000 UTC surface analysis and satellite imagery through
A broad elongated area of low pressure persists along the
southwestern coast of Mexico and coastal waters, from Manzanillo
to just south of the Gulf of Tehuantepec. A few weak cyclonic
circulations are evident in satellite imagery within this broad
area, with one near 17.5N104.5W, with an estimated pressure of
1006 mb. Scattered moderate to strong convection is occurring NW
of the weak low from 16.5N TO 21.5N between 104.5W and 108.5W.
To the S of this low is a large area of fresh to locally strong
SW monsoon winds, roughly from 10N to 13N between 103W and 115W.
Model guidance indicates that this low pressure center occurring
N of the zone of strong monsoonal flow has the potential to
develop into a tropical cyclone as it drifts NW. The convergent
monsoon winds will continue to generate widespread active
convection along and near the coast of Mexico, with heavy rains
likely to persist in this area several more days.
..INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
The monsoon trough stretches across the entire basin from Panama
near 08N74W TO 09N83.5W TO 14N92W TO low pres near 17.5N104.5W
1006 MB TO 12N112W TO low pres near 14N137W 1010 MB TO beyond
10N140W. Scattered moderate to strong convection is from 07N TO
14N between 87W and 125W...AND from 08N TO 13N between 128W AND
OFFSHORE WATERS WITHIN 250 NM OF MEXICO...
A weakening cold front extends from southern Arizona SW across
the northern Gulf of California and Baja California Norte then
WSW to beyond 24N126W. Afternoon scatterometer data showed fresh
northerly winds behind the front across the offshore waters.
Expect the front to push further south and weaken through early
Sat, then dissipate by Sat afternoon. High pressure will build
north of 25N behind the front through Sun, with NW winds
increasing slightly west of Baja California Norte. Elsewhere,
the possible development of low pressure along the southern
coast of Mexico will increase winds and seas between 101W and
115W the next few days.
OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND
WITHIN 750 NM OF ECUADOR...
An active monsoon trough meandering along the coast of Central
America from Guatemala to Panama will remain the focus for
active convection over the coastal waters the next few days.
Expect SW winds south of the trough to gradually become 20-25
knots through Saturday. Farther south, gentle to moderate south
to southwest winds will persist south of 05N through the
weekend. Long period SE swell from the Southern Hemisphere will
maintain seas west of Ecuador and south of 01N around 7-8 ft
through Sat morning.
REMAINDER OF THE AREA...
NW swell generated by strong N to NW winds north of the area are
producing combined seas to 8 ft north of 25N between 114W and
122W. This area of combined seas will slowly subside during the
next 24 hours. High pressure centered well N of the area and
lower pressure associated with the monsoon trough will maintain
moderate to occasionally fresh trade winds west of 120W through