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Hurricane Norma Discussion Number   9
NWS National Hurricane Center Miami FL       EP172023
300 PM MDT Thu Oct 19 2023
 
The satellite presentation of Norma has deteriorated since the last 
advisory. The eye has become less defined, and the inner core 
convection has become more asymmetric. The Air Force Reserve 
Hurricane Hunters that investigated Norma reported that the eyewall 
was open to the southeast during their final pass through the 
center. Still, the aircraft data confirm that Norma is a major 
hurricane. The Hurricane Hunters reported peak 700-mb flight-level 
winds of 111 kt, with SFMR retrievals as high as 102 kt. The minimum 
pressure from a recent center dropsonde was 945 mb with 12-kt winds. 
The initial intensity is lowered to 110 kt for this advisory, which 
could be a bit generous based on the recent aircraft data.

Based on recent satellite trends, it is likely that Norma has 
reached its peak intensity. An increase in southerly shear will 
likely cause Norma to become more vertically tilted during the next 
couple of days, while the hurricane moves into a drier and more 
stable environment as diagnosed from the SHIPS guidance. Therefore, 
weakening is forecast beginning tonight and continuing through the 
weekend and into early next week. Still, Norma is forecast to be a 
hurricane when it moves near or over the southern tip of the Baja 
California peninsula, and the government of Mexico has issued a 
Hurricane Warning for this area based on the increased risk of 
hurricane conditions. 
 
The eye of Norma has wobbled some today, but the long-term motion 
remains northward (350/5 kt). A turn toward the north-northwest is 
expected during the next couple of days while Norma approaches the 
southern tip of the Baja California peninsula. There are still speed 
differences in the various global and regional models, likely 
related to differences in the steering flow based on the vertical 
depth of the cyclone. The GFS and regional models suggest Norma will 
remain a deeper cyclone and move toward the west coast of mainland 
Mexico in 48-72 h. The 12z ECMWF, Canadian, and UKMET runs show 
Norma making it farther north than previous runs, but still stalling 
near the southern tip of Baja before moving inland over western 
Mexico early next week. The updated NHC track forecast has been 
nudged westward and is faster this cycle, which generally keeps it 
between the HCCA and TVCE aids. This update shows Norma inland by 96 
h and dissipated over western Mexico by day 5, but this could occur 
sooner than forecast if the GFS and regional hurricane models are 
correct. Interests in western Mexico should monitor the latest 
forecast updates, as future track and/or speed adjustments could be 
required.
 
 
Key Messages:
 
1. A Hurricane Warning is in effect for the far southern portion of 
the Baja California peninsula, where Norma is expected to bring 
hurricane conditions on Saturday when it passes near or over the 
area.
 
2. Heavy rains from Norma will begin to impact the far southern 
portions of California Baja Sur on late Friday, continuing through 
Sunday. This rainfall may produce flash and urban flooding, along 
with possible mudslides in areas of higher terrain.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  19/2100Z 17.5N 108.0W  110 KT 125 MPH
 12H  20/0600Z 18.5N 108.5W  105 KT 120 MPH
 24H  20/1800Z 19.8N 109.1W   95 KT 110 MPH
 36H  21/0600Z 21.2N 109.6W   80 KT  90 MPH
 48H  21/1800Z 22.5N 109.7W   70 KT  80 MPH
 60H  22/0600Z 23.6N 109.4W   60 KT  70 MPH
 72H  22/1800Z 24.2N 108.9W   50 KT  60 MPH
 96H  23/1800Z 25.0N 107.5W   30 KT  35 MPH...INLAND
120H  24/1800Z...DISSIPATED
 
$$
Forecaster Reinhart
 
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