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WTPZ42 KNHC 192053

TCDEP2

 

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