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Tropical Storm Nora Discussion Number  17
NWS National Hurricane Center Miami FL       EP142021
300 PM MDT Sun Aug 29 2021
 
Visible satellite imagery and surface observations along the 
west-central coast of Mexico suggest that the center of Nora has 
re-formed closer to a mass of deep convection that has persisted 
today over the southern Gulf of California. Various satellite data 
sets indicate that Nora is weakening. The latest SSMIS microwave 
data reveal that the structure of Nora has degraded since this 
morning, especially in the mid-levels where an eyewall structure is 
no longer evident. Additionally, a 15 UTC ASCAT-A pass shows the 
winds are substantially weaker than previously estimated. Thus, the 
initial intensity has been lowered to 50 kt for this advisory.

The initial motion is somewhat uncertain given the earlier center 
relocation, but it is estimated to be north-northwestward, or 330/10 
kt. The global models suggest the tropical cyclone will move 
generally northwestward over the next couple of days, between an 
upper-level low offshore the Baja California peninsula and a 
mid-level ridge to the east of Nora. This motion should keep the 
center of Nora along the coast, or just inland over mainland 
west-central or northwestern Mexico. The official NHC track forecast 
is once again shifted a little to the right based on the latest 
track guidance, which brings the cyclone further inland by Tuesday.

Nora is forecast to gradually weaken over the next few days as the 
system continues to interact with the coastline of Mexico. Despite 
warm SSTs in the Gulf of California and weak environmental shear, it 
appears unlikely that Nora will move far enough away from the coast 
to take advantage of this favorable environment. In fact, it is 
certainly plausible that the center of Nora could move well inland 
earlier than forecast and weaken more rapidly. The NHC intensity 
forecast has been adjusted about 10 kt weaker at all forecast hours 
based on today's data supporting a much weaker initial intensity.

 
Key Messages:
 
1. Nora is forecast to be at or near tropical storm strength while 
it moves near the coast of Sinaloa and southern Sonora through early 
Tuesday, and tropical storm warnings and watches are in effect for 
portions of that coastline.  Interests in these areas should closely 
monitor the progress of Nora.
 
2. Heavy rain associated with Nora is expected across the west coast 
of Mexico from the states of Colima northward to southern Sonora.  
This rain will likely result in life-threatening flash flooding and 
mudslides across these regions.  Rainfall from Nora is likely to 
spread into the southwestern U.S. and central Rockies during the 
middle to latter portion of the week bringing the potential for 
flash flooding to the region.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  29/2100Z 24.3N 107.5W   50 KT  60 MPH...NEAR THE COAST
 12H  30/0600Z 25.1N 108.2W   45 KT  50 MPH...NEAR THE COAST
 24H  30/1800Z 25.8N 108.8W   40 KT  45 MPH...NEAR THE COAST
 36H  31/0600Z 26.5N 109.3W   40 KT  45 MPH...NEAR THE COAST
 48H  31/1800Z 27.2N 109.9W   35 KT  40 MPH...INLAND
 60H  01/0600Z 28.2N 110.6W   30 KT  35 MPH...INLAND
 72H  01/1800Z 28.9N 111.1W   30 KT  35 MPH...INLAND
 96H  02/1800Z...DISSIPATED
 
$$
Forecaster Reinhart
 
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