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Tropical Storm Nora Discussion Number   6
NWS National Hurricane Center Miami FL       EP142021
1000 PM CDT Thu Aug 26 2021
 
A large area of deep convection has developed over the southern and 
western portions of Nora's circulation over the past several hours. 
Almost all of the convection is displaced to the southwest of Nora's 
center by some moderate northeasterly shear. Based on the slightly 
improved satellite appearance of the cyclone, the initial intensity 
is raised to 40 kt for this advisory. This is in best agreement with 
the objective UW-CIMSS ADT and SATCON estimates of around 40 kt.

Nora has turned a bit to the right and accelerated slightly this 
evening, and it is now moving west-northwestward or 295/10 kt. The 
mid-level ridge over the southern United States that is steering 
Nora is being eroded by a shortwave trough over the Rocky Mountains. 
In response, Nora is expected to turn toward the northwest on Friday 
and then the north-northwest on Saturday. This will bring the center 
of the cyclone close to the southwestern coast of Mexico. The ECMWF 
and UKMET as well as almost all the ECMWF ensemble members keep Nora 
offshore, passing just offshore of Cabo Corrientes before moving 
toward the entrance to the Gulf of California and Baja California 
Sur. However, the GFS and many of its ensemble members still show 
Nora moving inland over southwestern Mexico on Saturday. Overall, 
the multi-model track guidance consensus changed little this cycle, 
and so the official NHC track forecast remains very close to the 
previous one. The extended forecast still shows Nora moving near or 
over Baja California Sur and the Gulf of California on days 4 and 5. 
However, it is worth noting that the degree of uncertainty in this 
portion of the forecast is above average.

The moderate northeasterly wind shear over Nora is expected to 
diminish over the next 12-24 h, which should allow the cyclone to 
intensify within a moist and unstable environment over SSTs around 
29 deg C. Thus, Nora is forecast to strengthen over the next few 
days and become a hurricane on Saturday. Of course, this is highly 
dependent on Nora remaining offshore and not moving inland over 
mainland Mexico. Since the NHC track forecast keeps Nora offshore, 
the official intensity forecast lies on the high end of the 
intensity guidance and is closest to the ECMWF-based SHIPS and LGEM 
models. In this case, the normally reliable intensity consensus aids 
are of limited use since several of the consensus members bring Nora 
inland. Weakening is forecast on days 4-5 due to expected land 
interaction with Baja California Sur.  
 
The government of Mexico has extended the Tropical Storm Warning 
northward from Manzanillo to Cabo Corrientes, and issued a Tropical 
Storm Watch north of Cabo Corrientes to San Blas. Additional 
watches and warnings may be required on Friday.
 
 
Key Messages:
 
1. Nora is forecast to strengthen to a hurricane on Saturday while 
it is near the coast of southwestern Mexico, and a hurricane watch 
and tropical storm warning are in effect for portions of that area.  
Interests along the southwestern coast of Mexico should closely 
monitor the progress of this system and updates to the forecast.
 
2. Heavy rain associated with Tropical Storm Nora is expected across 
coastal sections of the Mexican states of Oaxaca, Guerrero, 
Michoacan, Colima, and Jalisco. Life-threatening flash flooding and 
mudslides may occur.
 
3. Nora is forecast to be near or over the southern portion of Baja 
California Sur as a hurricane early next week, bringing a risk of 
wind and rain impacts to that area.  Given the above average 
uncertainty in the forecast, it is still too soon to determine the 
magnitude and location of these potential impacts.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  27/0300Z 14.1N 102.6W   40 KT  45 MPH
 12H  27/1200Z 14.9N 103.6W   45 KT  50 MPH
 24H  28/0000Z 16.3N 104.7W   55 KT  65 MPH
 36H  28/1200Z 18.0N 105.6W   60 KT  70 MPH
 48H  29/0000Z 19.9N 106.5W   65 KT  75 MPH
 60H  29/1200Z 21.5N 107.5W   70 KT  80 MPH
 72H  30/0000Z 22.7N 108.7W   75 KT  85 MPH
 96H  31/0000Z 24.4N 110.6W   65 KT  75 MPH...NEAR BAJA CAL SUR
120H  01/0000Z 26.0N 112.1W   45 KT  50 MPH...OVER BAJA CAL SUR
 
$$
Forecaster Reinhart/Cangialosi
 
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