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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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