AXPZ20 KNHC 222206
Tropical Weather Discussion
NWS National Hurricane Center Miami FL
2205 UTC Fri Sep 22 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 1800 UTC surface analysis and satellite imagery through
A broad elongated area of low pressure persists along the
southern coast of Mexico and coastal waters, from Manzanillo to
Puerto Angel. A weak cyclonic circulation is evident in
satellite imagery within this broad area near 17N104W, with an
estimated pressure of 1007 mb. Scattered moderate to strong
convection is occurring NW of the weak low from 16.5N to 23N
between 105W and 107.5W. To the S of this low is a large area of
fresh to locally strong SW monsoon winds, roughly from 10N to
14N between 98W and 117W. 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 07N73.5W TO 09N83W TO low pres near 17N104W 1007 MB TO
13.5N117W TO 12.5N130W TO beyond 10N140W. Scattered moderate to
strong convection is from 05N to 08.5N between 77.5W and
84W...within 90 nm N and 240 nm S of the trough between 87W and
100W...and within 120 nm S of the through between 105W and 131W.
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 25N126W. 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
117W 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 02S 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 29N between 118W 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