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Hurricane Norma Discussion Number   7
NWS National Hurricane Center Miami FL       EP172023
300 AM MDT Thu Oct 19 2023
 
Norma has rapidly intensified into a major hurricane. Overnight, a
20 n mi wide eye emerged on infrared satellite imagery, with cold
cloud tops wrapping around the eyewall and some evidence of warming
within the eye.  Subjective intensity estimates from TAFB and SAB
were both T5.5/102 kt, and the initial intensity was raised to 105
kt, slightly above the estimates given the improved structural
organization.
 
The hurricane is likely nearing its peak intensity and environmental
conditions are expected to become increasingly hostile soon.  Global
model guidance is already analyzing moderate southerly deep-layer
wind shear over Norma.  However, there is still some potential for
strengthening in the next 12 h.  Beyond that time frame, strong
shear and dry mid-level humidities will likely induce a gradual
weakening trend through the end of the forecast period.  The latest
NHC peak intensity forecast has been raised to 115 kt in 12 h and is
on the upper bound of the intensity guidance envelope.
 
Norma is moving northward slower than expected, at an estimated 5
kt.  There is still a considerable spread in the model guidance
envelope and therefore a high level of uncertainty in the track
forecast.  The ECMWF continues to favor a slower forward speed that
essentially stalls Norma off the southern coast of the Baja
California peninsula this weekend and early next week.  This is
contrasted by the GFS which shows Norma accelerating and turning
northeastward prior to the peninsula in stronger steering flow.  The
official forecast is a blend of these solutions and shows the center
of Norma reaching the southern tip of the Baja California peninsula
in 72 h.  A slow northeastward motion is possible by days 4 and 5.
Based on the possibility of hurricane-force winds within 48 hours,
the government of Mexico has issued a hurricane watch for the
extreme southern portion of the Baja California peninsula.
 
 
Key Messages:
 
1. Norma is expected to be near hurricane strength as it approaches
the southern tip of Baja California and a hurricane watch has been
issued for that area.
 
2. Heavy rainfall from Norma will begin to impact the far southern
portions of Baja California Sur late Friday, continuing through
Sunday.  This rainfall may produce flash and urban flooding, along
with possible mudslides in areas of high terrain.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  19/0900Z 16.7N 107.7W  105 KT 120 MPH
 12H  19/1800Z 17.5N 108.1W  115 KT 130 MPH
 24H  20/0600Z 18.6N 108.5W  100 KT 115 MPH
 36H  20/1800Z 19.8N 109.1W   90 KT 105 MPH
 48H  21/0600Z 21.2N 109.6W   80 KT  90 MPH
 60H  21/1800Z 22.3N 109.6W   70 KT  80 MPH
 72H  22/0600Z 23.0N 109.7W   60 KT  70 MPH
 96H  23/0600Z 23.4N 109.3W   50 KT  60 MPH
120H  24/0600Z 24.0N 108.4W   40 KT  45 MPH
 
$$
Forecaster Bucci
 
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