Hurricane Norma Forecast Discussion Number 8

NOAA - Tropical Weather Updates

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Issued at 900 AM MDT Thu Oct 19 2023

WTPZ42 KNHC 191452
Hurricane Norma Discussion Number   8
NWS National Hurricane Center Miami FL       EP172023
900 AM MDT Thu Oct 19 2023
Norma has continued to show signs of strengthening this morning. The
15 to 20 n-mi-wide eye of the hurricane is surrounded by a thick
ring of convective cloud tops colder than -70 to -75C. The initial
intensity is raised to 115 kt based on consensus T6.0/115 kt
subjective Dvorak classifications from TAFB and SAB. The Air Force
Hurricane Hunters are scheduled to investigate Norma later today.
The eye of Norma has deviated right of track during the past 6-12 h,
and the longer-term motion is nearly due north (360/6 kt). The
track forecast remains challenging. Even in the near term, there is
significant spread among the various models, likely related to
differences in the steering flow based on the vertical depth of the
cyclone. Given recent trends, the NHC forecast has been adjusted to
the right of the previous one through 60 h, bringing it just east of
the multi-model consensus aids and favoring the stronger GFS and
regional hurricane models. Thereafter, it remains unclear whether
Norma will turn northeastward and approach the west coast of
mainland Mexico, or stall and meander to the south of the Baja
California peninsula. The official forecast continues to show Norma
moving toward mainland Mexico beyond 60 h, albeit slower than some
of the stronger model guidance (GFS, HAFS) with a deeper vortex.
Once again, confidence is low and future track and/or speed
adjustments could be required.
Recent satellite images and model shear analyses suggest that 
southerly shear is increasing over Norma and will continue to do 
so over the next couple of days. Therefore, the hurricane is likely 
near its peak intensity, although some small fluctuations cannot be 
ruled out today. By Friday, weakening is expected as Norma likely 
becomes more tilted by the shear and moves into a drier and more 
stable environment. Still, Norma could be at or near hurricane 
strength when it makes its closest approach to the southern tip of 
Baja California, where a Hurricane Watch is in effect. Beyond 72 h, 
the intensity forecast is more uncertain and highly dependent on 
Norma's track, structure, and the extent (if any) of land 
interaction with the Baja peninsula. If Norma moves faster than 
forecast, it could reach the west coast of mainland Mexico as a 
stronger storm. Given the track uncertainty described above, 
interests there are encouraged to closely monitor forecast updates.
Key Messages:
1. Norma is expected to be at or near hurricane strength as it
approaches the southern tip of Baja California, and a hurricane
watch has been issued for that 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.
INIT  19/1500Z 17.4N 107.6W  115 KT 130 MPH
 12H  20/0000Z 18.1N 107.7W  115 KT 130 MPH
 24H  20/1200Z 19.3N 108.3W  100 KT 115 MPH
 36H  21/0000Z 20.5N 108.8W   85 KT 100 MPH
 48H  21/1200Z 21.9N 109.2W   75 KT  85 MPH
 60H  22/0000Z 23.0N 109.3W   70 KT  80 MPH
 72H  22/1200Z 23.6N 109.0W   60 KT  70 MPH
 96H  23/1200Z 24.2N 108.3W   50 KT  60 MPH
120H  24/1200Z 24.8N 107.3W   30 KT  35 MPH...INLAND
Forecaster Reinhart

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