AXPZ20 KNHC 221541
Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1605 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 0600 UTC surface analysis and satellite imagery through
A broad elongated area of monsoonal low pressure persists along
the southwest coast of Mexico and coastal waters. A weak poorly
defined cyclonic circulation is evident from Metsat data within
this broad area near 17N104W, with an estimated pressure of 1007
mb. An large area of fresh to locally strong SW monsoon winds is
evident from scatterometer data, roughly from 09N to 13N between
100W AND 122W. Model guidance indicates this area of monsoonal
flow has the potential to develop into a tropical cyclone as it
lifts slowly northward. Convergent monsoon winds are generating
widespread active convection along the coast of Mexico between
Cabo Corrientes and Chiapas, 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 08N78W to 16N100W to low pres near 17N104W 1007 mb to
12N120W to 10N140W. Scattered moderate to strong convection is
within 60 nm of a line from 08N89W to 13N95W. Scattered moderate
isolated strong convection within 75 nm s of trough east of 83W.
Scattered moderate convection within 90 nm s of trough between
112W and 133W.
OFFSHORE WATERS WITHIN 250 NM OF MEXICO...
A weakening cold front extends across northern Baja California
into the Gulf of California. Scatterometer data at 0500 UTC
showed fresh to strong SW winds ahead of the front north of 30N
in the Gulf of California, and fresh northerly winds behind the
front. 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 along the coast of Central America from
Guatemala to Panama will remain focus for widespread 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 the rest of today.
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