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 Eastern Pacific Basin Tropical Discussion Atlantic | East Pacific 
AXPZ20 KNHC 220332

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0405 UTC Wed Jan 22 2020

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  0 UTC surface analysis and satellite imagery through 
0315 UTC.


Gulf of Tehuantepec Gale Warning: The edge of a Tue afternoon 
Ascat pass suggested that strong gale force north to northeast 
winds are occurring across the Gulf of Tehuantepec and adjacent 
waters. Minimal gale force winds are well downstream of these 
winds to near downstream to near 13N96W. Maximum wave heights 
are up to around 18 ft within the area of the strong gale force 
winds, while the leading edge of waveheights greater than 8 ft 
in north to northeast swell reaches as far south as 04N98W. A 
tight pressure gradient associated with strong high pressure 
centered over southern Mexico will maintain the gale force winds 
in the Tehuantepec region through late tonight. These winds will 
begin to diminish Wed morning as the high pressure weakens and 
the tight gradient begins to slacken. Winds will further 
diminish through Wed afternoon as the high pressure over Mexico 
weakens further. Residual swell welll downstream of the Gulf of 
Tehuantepec will decay by Thu afternoon. Marine interests 
transiting across or in the vicinity of the Gulf of Tehuantepec 
through tonight should take necessary action to avoid hazardous 
marine conditions. 

Please see the latest High Seas Forecast issued by the National 
Hurricane Center under AWIPS/WMO headers FZPN03 KNHC/HSFEP2 or at
website https://www.nhc.noaa.gov/text/MIAHSFEP2.shtml for 
further details on this Gale Warning.


A surface trough axis extends from low pressure of 1007 mb over 
northwestern Colombia near 10N75W southwestward to the coast at 
06N77W, and continues to 08N84W to low pressure of 1009 mb near 
07N87W and to 04N92W to 10N102W, where latest scatterometer data 
indicates that it transitions to the ITCZ and continues to 
06N118W to 08N125W and to beyond the area at 07N140W. Scattered 
moderate isolated strong convection is noted within 180 nm south 
of low and trough between 84W and 87W, and within 60 nm north of 
trough between 90W and 94W. Scattered moderate convection is 
within 120 nm north of the ITCZ west of 133W and within 60 nm 
north of ITCZ between 105W and 112W.


Please see the Special Features above for details on an ongoing 
strong gale force gap wind event in the Gulf of Tehuantepec.

Weakening high pressure of 1023 mb is located near 28N135W, with 
and an associated ridge extending southeastward across the Baja 
California Sur waters. Gentle to moderate northerly winds 
continue over the offshore waters between Cabo San Lazaro and 
Cabo Corrientes, as well as over the southern Gulf of 
California. Meanwhile, weakening low pressure has moved to over 
the offshore waters west of Punta Eugenia near 28N118W. The low 
will continue on a weakening trend and dissipate late tonight 
into early Wed. Moderate to fresh northerly winds will develop 
west of Baja California Wed into Thu as high pressure slides 
eastward along 29N/30N. Elsewhere, expect moderate to fresh 
northwest winds over the central and southern Gulf of California 
Wed night through Thu night as high pressure and associated 
tightening pressure gradient builds over the Great Basin region 
of the U.S.

Long-period northwest swell is propagating through the Baja 
California Norte waters this morning, with seas expected to build
to 8-10 ft north of Punta Eugenia tonight. The swell will 
propagate SE across the region and reach the Revillagigedo 
Islands Wed. Seas will gradually subside through Fri as the swell
decays. Another round of long period northwest swell associated 
with an approaching cold front will reach the Baja California 
waters beginning late Fri night and build seas to 8 ft or greater
there during the upcoming weekend.


Mainly scattered moderate convection is observed over the 
offshore waters of Costa Rica and western Panama this afternoon 
due to atmospheric instability from a 1009 mb low pressure 
centered near 07N87W. Showers and thunderstorms will likely 
continue through tonight, as the weak low persists offshore and 
the upper-level environment remains conducive for convection due 
to the passage of a Kelvin wave.

Strong trades occurring over the southwestern Caribbean will 
continue to support strong to near gale force northeast to 
east winds over and downstream of the Papagayo region through 
Thu morning. Winds will be strongest during overnight and early 
morning hours assisted by nocturnal drainage. Waveheights will 
build to 10 ft each morning during the period of peak winds. 
Elsewhere, moderate to fresh northerly winds will continue in 
the Gulf of Panama region this week and into the upcoming 

Swell generated by a strong Tehuantepec gale force wind event 
will impact the Guatemala and El Salvador offshore waters 
through Wed night, with seas of 8-12 ft continuing through
early Wed.


The presence of the weak 1018 mb low centered near 28N118W, as 
described above, has disrupted the subtropical ridge over the 
area, resulting in weaker trades in the deep tropics east of 
about 125W.

Farther west, a broad area of fresh to strong northeast winds is
present roughly from 09N to 16N and west of 124W between the 
ITCZ and high pressure building across the far northwest portion
of the area. These winds will likely continue for the next 
couple days as the subtropical ridge strengthens and low-level 
troughing remains north of the ITCZ roughly along 135W. Wave 
heights greater than 8 ft due to long-period northwest swell 
will dominate the region west of 117W by late tonight, with peak 
heights of around 11-14 ft associated with the strongest winds. 
By Thu afternoon, the leading edge of waveheights of 8 ft and 
greater is expected to have reach as far southeast as 98W.

By early Thu, another set of long period northwest swell will 
reach the northwest part of the area, then propagate
southeastward through the high seas during the upcoming 
weekend while gradually decaying. The culprit cold front
is expected to be on the weak side as it moves across the
far northern waters Sat and Sun.


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