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Eastern North Pacific Tropical Weather Discussion (Text)



000
AXPZ20 KNHC 212212
TWDEP 

Tropical Weather Discussion 
NWS National Hurricane Center Miami FL 
2205 UTC Wed Sep 20 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
meteorological analysis.

Based on 1800 UTC surface analysis and satellite imagery through 
2115 UTC.

...SPECIAL FEATURES...

A broad area of low pressure across the southwest coast and 
coastal waters of Mexico persists this afternoon, where a weak 
surface low pressure center is analyzed near 17N103.5W at 1008 
mb. Just to the south of this, a broad area of fresh to strong 
SW monsoonal winds prevail between 97W and 112W, producing 
active convection across this area and creating a very unstable 
atmosphere. Computer model guidance indicates that low pressure 
center in this general area will shift slowly WNW and become 
better organized over the next 2-3 days. Environmental 
conditions are favorable for development into a tropical cyclone 
as the broad low moves slowly west-northwest. Extensive heavy 
rain is expected across parts of southern Mexico and 
Central America during the next several days.

...TROPICAL WAVES...

A tropical wave along about 90W north of 07N is moving slowly 
west and beginning to lose identity.  Scattered moderate to 
strong convection is from 07.5N to 15N between 86w and 95w 
associated with the wave. The wave is expected to eventually 
become absorbed into the larger monsoonal circulation described 
above.

..INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...         

The monsoon trough stretches across the entire basin from Panama 
near 09.5N74.5W TO 08N80W TO low pres near 17N103.5W 1008 MB TO 
low pres near 10N136.5W 1012 MB TO beyond 12N140W. Scattered 
moderate to strong convection is within 60 nm N and 240 nm S of 
the trough between 85W and 108W and between 112W and 140W. 

...DISCUSSION...   

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...  

A weak surface ridge extends ESE across the northern portions 
of the discussion area to the central part of Baja California 
near 26N. An approaching cold front moving south across the 
waters west of California is aiding in producing fresh to strong 
SW winds in the northern part of the Gulf of California, 
expected to persist through early Fri morning, with seas 
building to 5-7 ft north of 29N. The local effects will be less 
evident west of Baja California and south of 29N in the Gulf of 
California. Elsewhere, the possible development of low pressure 
along the southern coast of Mexico will increase winds and seas 
between 100W and 107W 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 help maintain active convection across 
coastal waters the next few days. Expect SW winds south of the 
trough to strengthen gradually to 20-25 knots through Saturday. 
Further south, gentle to moderate southerly winds are expected 
to persist south of 05N through the weekend.

REMAINDER OF THE AREA...

The post-tropical remnant low of Norma is near 23N117.5W as a 
swirl of low and mid level clouds and stratiform precipitation. 
Winds are estimated to be 20 kt near the center and seas to 7-9 
ft. The low will move slowly and steadily weaken through Friday.

The post-tropical remnant low of Otis is near 15N133.5W as a 
swirl of low level clouds and limited stratiform precipitation. 
Fresh N-NE winds and 8 ft seas are within 150 nm NW of the low 
center. The low is expected to move SW and weaken into a trough 
through Friday, with seas gradually diminishing to 6-7 ft.

NW swell associated with strong N-NW winds north of the area is 
producing combined seas of 8-10 ft north of 21N between 117W and 
140W, and is expected to contract and shift eastward through 
Friday. Another weaker round of NW swell associated with a cold 
front west of California is expected to arrive Fri night. High 
pressure centered well N of the area and lower pressure 
associated with the convergence zone will maintain moderate 
trade winds west of 120W through the weekend. 

$$
Stripling

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Page last modified: Thursday, 21-Sep-2017 22:13:36 UTC