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Hurricane Nora Discussion Number  14
NWS National Hurricane Center Miami FL       EP142021
1000 PM CDT Sat Aug 28 2021
 
Surface data from Mexico, data from an Air Force Reserve Hurricane
Hunter aircraft, and microwave imagery from an 2344 UTC SSMIS
indicate that the center of Nora moved over the far northwestern
coast of Jalisco earlier this evening. Since then, the cloud
pattern of the hurricane has degraded, but not enough to bring the
latest Dvorak estimates below hurricane strength. The advisory
intensity is therefore set at 65 kt based on the assumption that
interaction with land has caused weakening, however there is low
confidence in this assessment.
 
The ever-so-slight rightward deviation from the forecast track that
brought Nora inland, at least briefly, highlights the sensitivity of
the system's future to its exact track. A sizable portion of the
latest dynamical guidance, including the GFS, ECMWF, and HWRF models
indicate that Nora will move inland tonight or early Sunday and
dissipate. All three models also indicate it could reform over the
Gulf of California in a few days. Other models, like the UKMET and
CMC global models maintain Nora as a coherent tropical cyclone much
longer. While the models can easily flip flop from run to run, the
NHC forecast cannot drastically change solutions so cavalierly.
Therefore, the official forecast is based on the condition that Nora
will stay far enough offshore to persist as a tropical cyclone.
Regardless of its exact state, Nora is forecast to turn toward the
northwest on Sunday and then move along the coast toward northern
Mexico early next week. This general solution is supported by all of
the available guidance. A slight eastward adjustment has been made
to the NHC track forecast to account for the slightly east initial
position.
 
Given Nora's recent movement over land, the intensity forecast has
been lowered substantially at all forecast hours, but still
maintains Nora near hurricane strength for the next couple of days.
This is well above the most recent intensity consensus, which is
heavily influenced by the dynamical models that move Nora inland.
If it doesn't move inland sooner, Nora will likely quickly weaken
as it moves permanently inland by around 96 h, and become a remnant
low by the end of the forecast period.
 
 
Key Messages:
 
1. Nora is forecast to be at or near hurricane strength while
it moves near the coasts of Nayarit and Sinaloa through the
weekend, and hurricane warnings are in effect for portions of that
coastline.  Interests in these areas should closely monitor the
progress of Nora and subsequent updates to the forecast.
 
2. Heavy rain associated with Nora is expected across the west coast
of Mexico from the states of Michoacan northward to southern Sonora,
including  Baja California Sur.  This rain will likely result in
life-threatening flash flooding and mudslides across these regions.
Rainfall from Nora may spread into the southwestern U.S. and central
Rockies during the middle to latter portion of next week.
 
3. Nora is forecast to continue moving northward over the Gulf of
California Tuesday and Wednesday, bringing a risk of wind impacts to
portions of the Mexican states of Baja California Sur, northern
Sinaloa, and Sonora.  Given the above-average uncertainty in the
forecast intensity, confidence is not high enough to determine the
magnitude and location of these potential impacts.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  29/0300Z 21.3N 105.5W   65 KT  75 MPH
 12H  29/1200Z 22.8N 106.2W   65 KT  75 MPH
 24H  30/0000Z 23.7N 107.1W   60 KT  70 MPH
 36H  30/1200Z 24.4N 107.9W   60 KT  70 MPH
 48H  31/0000Z 24.9N 108.6W   60 KT  70 MPH
 60H  31/1200Z 25.6N 109.4W   55 KT  65 MPH
 72H  01/0000Z 26.8N 110.1W   55 KT  65 MPH
 96H  02/0000Z 28.6N 110.7W   35 KT  40 MPH...INLAND
120H  03/0000Z 30.2N 110.9W   20 KT  25 MPH...POST-TROP/REMNT LOW
 
$$
Forecaster D. Zelinsky
 
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