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Hurricane SERGIO


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Hurricane Sergio Discussion Number  38
NWS National Hurricane Center Miami FL       EP212018
200 PM PDT Mon Oct 08 2018

Sergio still consists almost entirely of a solid ring of deep
convection surrounding a very large eye.  A pair of timely ASCAT
passes from around 1800 UTC show that the hurricane wind field
remains very symmetric with a large RMW.  Although we wouldn't
expect that instrument to capture the true magnitude of the
hurricane's maximum winds, the data does suggest that the winds have
decreased at least a little since this morning.  UW-CIMSS SATCON
values have also decreased, so the initial intensity is lowered
slightly to 75 kt.

The hurricane is moving very slowly northward, around 3 kt.  There
has been no change to the reasoning behind the track forecast and
Sergio should still accelerate northeastward in a day or so,
approaching the Baja California peninsula by the end of the week.
Nearly all of the models have shifted a little toward the south
beyond 24 h, and the NHC track forecast has been adjusted in that
direction as well, but now lies just north of the multi-model
consensus.

In the short-term, Sergio is still forecast to gradually weaken
while it moves very little and continues to upwell cold waters.
Beyond 24 h, the hurricane should reach additional cooler waters to
the north, which should cause additional gradual weakening.  In
general, the intensity guidance is forecasting Sergio to maintain
its intensity a little longer than previously forecast, so the NHC
intensity forecast has been adjusted a little higher at 48 h and
72 h.  It's worth noting that the hurricane would likely maintain
its intensity longer if it moves a little farther south over warmer
waters, and any further adjustments southward to the track forecast
could have implications on the intensity forecast.  By Friday
afternoon, the cyclone should have reached the Baja California
peninsula and more rapid weakening should follow.  Although the
low-level center of Sergio will likely quickly dissipate after
reaching mainland Mexico, its mid-level remnants and moisture will
continue northeastward, potentially causing heavy rainfall across
parts of the southwestern United States.


FORECAST POSITIONS AND MAX WINDS

INIT  08/2100Z 15.7N 128.5W   75 KT  85 MPH
 12H  09/0600Z 16.2N 128.1W   70 KT  80 MPH
 24H  09/1800Z 16.9N 127.0W   70 KT  80 MPH
 36H  10/0600Z 17.7N 125.4W   65 KT  75 MPH
 48H  10/1800Z 18.9N 123.2W   60 KT  70 MPH
 72H  11/1800Z 22.9N 118.0W   55 KT  65 MPH
 96H  12/1800Z 28.0N 111.5W   40 KT  45 MPH
120H  13/1800Z 33.5N 102.5W   25 KT  30 MPH...POST-TROP/REMNT LOW

$$
Forecaster Zelinsky

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