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Hurricane Genevieve Discussion Number   6
NWS National Hurricane Center Miami FL       EP122020
400 PM CDT Mon Aug 17 2020
 
Genevieve has continued to rapidly strengthen today, and has been 
undergoing RI since its formation yesterday morning. One-minute 
GOES-16 satellite imagery and an earlier GMI microwave overpass has 
revealed very impressive banding features, along with evidence of a 
small low-level eye feature. Since the time of that microwave data, 
banding has continued to increase near the center, and it appears 
that a banding-type eye may be forming.  The various satellite 
intensity estimates range from 70-80 kt, so the initial wind speed 
has been raised to 75 kt.
 
Genevieve remains within a very favorable oceanic and atmospheric 
environment, and the intensity guidance suggests that rapid 
strengthening is likely to continue for another day or so.  The 
SHIPS Rapid Intensification Index again shows a greater than 80- 
percent chance of a 30 kt increase in wind speed over the next 24 
hours and about a 60-percent chance of a 40 kt increase over that 
time period. The NHC intensity forecast continues to call for rapid 
strengthening and shows Genevieve reaching category 4 strength by 
late Tuesday.  This is in line with the latest SHIPS and HFIP 
corrected consensus models.  After 48 h, the hurricane will be 
moving over slightly cooler waters and weaken should begin, with a 
faster rate of weakening expected on days 4 and 5.
 
The hurricane has moved a bit right of track since yesterday, but 
the longer term motion is west-northwestward at 16 kt.  A strong 
ridge of high pressure over the western United States should 
continued to steer Genevieve west-northwestward for another 24 
hours. After that time, a slower northwestward motion should 
commence.  There is a bit more spread in the dynamical model 
guidance with the GFS, its ensemble mean, and the HWRF having 
shifted slightly eastward.  However, the consensus aids have not 
changed much, and the NHC track is similar to the previous advisory, 
near the middle of the guidance envelope.
 
Recent ASCAT data showed that the tropical-storm-force wind field
was a little larger than previously estimated over the eastern
semicircle of the storm.  The initial and forecast wind radii have
been adjusted outward accordingly.
 
Key Messages:
 
1. There is an increasing risk of tropical-storm-force winds over 
the southern portion of the Baja California peninsula beginning 
Wednesday afternoon and continuing into Thursday as Genevieve passes 
near or southwest of the southern tip of Baja California, and a 
Tropical Storm Watch has been issued for a portion of this area.
 
2. Large swells generated by Genevieve are affecting portions of the 
coast of southern Mexico and will spread northward along the coast 
of Mexico to the Baja California peninsula by Wednesday.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  17/2100Z 15.5N 104.6W   75 KT  85 MPH
 12H  18/0600Z 16.6N 106.6W   95 KT 110 MPH
 24H  18/1800Z 18.0N 108.5W  110 KT 125 MPH
 36H  19/0600Z 19.3N 109.8W  120 KT 140 MPH
 48H  19/1800Z 20.6N 110.8W  115 KT 130 MPH
 60H  20/0600Z 21.6N 111.6W  105 KT 120 MPH
 72H  20/1800Z 22.8N 113.1W   90 KT 105 MPH
 96H  21/1800Z 24.8N 116.0W   60 KT  70 MPH
120H  22/1800Z 27.2N 119.7W   45 KT  50 MPH
 
$$
Forecaster Brown
 
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