ABPZ20 KNHC 201130
Tropical Weather Outlook
NWS National Hurricane Center Miami FL
500 AM PDT Thu Jul 20 2017
For the eastern North Pacific...east of 140 degrees west longitude:
The National Hurricane Center is issuing advisories on Tropical
Storm Fernanda, located more than a thousand miles east of Hilo,
Hawaii, on Tropical Storm Greg, located several hundred miles south-
southwest of the southern tip of the Baja California peninsula, and
on Tropical Depression Eight-E, located more than a thousand miles
southwest of the southern tip of the Baja California peninsula.
Showers and thunderstorms centered about 600 miles south of
Manzanillo, Mexico, are showing some signs of organization in
association with a broad low pressure system. Environmental
conditions are expected to be conducive for development of this
system while it moves westward to west-northwestward at 10 to 15
mph, and a tropical depression is expected to form well southwest of
Mexico over the weekend.
* Formation chance through 48 hours...high...70 percent.
* Formation chance through 5 days...high...90 percent.
Disorganized cloudiness and showers in the far eastern Pacific
near and west of Central America are associated with a tropical
wave. Environmental conditions are forecast to become increasingly
favorable for development, and a tropical depression could form by
early next week while the system moves west-northwestward at 10 to
* Formation chance through 48 hours...low...10 percent.
* Formation chance through 5 days...medium...60 percent.
AXPZ20 KNHC 201013
Tropical Weather Discussion
NWS National Hurricane Center Miami FL
945 UTC Thu Jul 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
Based on 0600 UTC surface analysis and satellite imagery through
Recently downgraded Tropical Storm Fernanda is centered near
18.2N 137.7W at 20/0900 UTC moving WNW at 8 kt. Estimated
minimum central pressure is 992 mb. Maximum sustained winds are
60 kt with gusts to 75 kt. Scattered moderate to strong
convection within 90 nm of center. Fernanda will continue to
weaken as it moves west of 140W late Thu. Large swell will
continue to expand and spread out ahead of Fernanda to the NW and
W during the next few days. See latest NHC forecast/advisory
under AWIPS/WMO headers MIATCMEP1/WTPZ21 for more details.
Tropical Storm Greg is centered near 14.1N 114.7, or 585 nm SSW
of the southern tip of the Baja Peninsula at 20/0900 UTC, moving
W at 9 kt. Estimated minimum central pressure is 1006 mb.
Maximum sustained winds are 35 kt with gusts to 45 kt. Scattered
moderate to strong convection is noted within 120 nm of the
center. Despite recently weakening Greg is expected to intensify
and reach hurricane strength within 48 hours. See the latest NHC
forecast/advisory under AWIPS/WMO headers MIATCMEP2/WTPZ22 for
Tropical Depression Eight-E is centered near 13.7N 122.6W, or
about 890 nm SW of the southern tip of the Baja Peninsula at
20/0900 UTC, moving WSW at 5 kt. Estimated minimum central
pressure is 1009 mb. Eight-E is experiencing northerly shear
and is not expected to reach tropical storm strength. See the
latest NHC forecast/advisory under AWIPS/WMO headers
MIATCMEP3/WTPZ23 for more details.
A tropical wave is analyzed from 06N to 18N along 103W. A surface
low is embedded in the wave near 11N103W with an estimated
pressure of 1009 mb. A recent scatterometer satellite pass
indicated fresh to strong winds within 150 nm of the center in
the northeast quadrant. The low pressure may become a tropical
cyclone as continues to the WNW with the wave at 10 to 15 kt over
the next couple of days. Scattered moderate isolated strong
convection observed from 07N to 12N between 97W and 108W, mainly
along the monsoon trough.
...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
The monsoon trough extends from 08N77W to low pressure 1010 mb
near 07N84W to the developing low pressure 1009 mb near 11N103W,
where the monsoon trough loses definition near T.S. Greg. The
intertropical convergence zone is west of the area. Other than
convection already discussed above, scattered to moderate
convection is noted within 60 nm either side of the low pressure
between 85W and 90W.
OFFSHORE WATERS WITHIN 250 NM OF MEXICO...
Please see the special features for information on Tropical
Storm Greg southwest of Manzanillo, Mexico.
A weak trough west of the the Baja California peninsula will
continue to block the advance of the subtropical ridge
maintaining gentle to moderate NW winds off the Baja California
peninsula through Fri. Seas will remain 5 to 7 ft in a mix of
long period north and southwesterly swell. Gentle southerly flow
will persist in the Gulf of California, except for moderate
southerly flow over the northern Gulf.
Fresh to strong northerly gap winds will once again pulse to
around 20 kt during mainly overnight and early morning hours
through early Friday, with a shorter pulse of strong gap winds
again Friday night into Saturday. Seas will build to 8 ft with an
additional component of longer period southwest swell.
OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND
WITHIN 750 NM OF ECUADOR...
In the Gulf of Papagayo, moderate to fresh offshore winds will
pulse to fresh each night with nocturnal drainage through the
week, occasionally building max seas to 8 ft in a mix of east
swell and longer period southwest swell.
Gentle to moderate southerly winds are expected south of the
monsoon trough axis. Long period cross-equatorial southerly
swell and 6-7 ft seas will continue to propagate into the waters
reaching the coast of Central America through the day. Another
pulse of large southerly swell will move into the region today
and raise seas to 6-8 ft through tonight.
REMAINDER OF THE AREA...
Please see the special features section for information on
T.S. Fernanda and Tropical Depression Eight-E.
The gradient between Fernanda, and eventually the approaching
Greg, will maintaining moderate to fresh northeast winds north
of 25N, with seas 5 to 7 ft including components of northerly
swell mixing with southerly swell emerging from Fernanda. Looking
ahead, northerly swell to 8 ft will propagate south of 32N and
west of 120W.