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Hurricane Genevieve Discussion Number  15
NWS National Hurricane Center Miami FL       EP122020
900 PM MDT Wed Aug 19 2020
 
Genevieve's infrared satellite presentation has continued to become 
less defined since the previous advisory, with microwave imagery 
indicating that the eyewall has completely eroded in the southern 
semicircle. Satellite intensity estimates have decreased as a 
result, with TAFB and SAB now assessing intensity estimates of 
T4.5/77 kt. Therefore, the initial intensity has been lowered to 75 
kt.

Genevieve has made a slight right-of-track jog, and the initial 
motion estimate is now 345/06 kt. The recent north-northwestward 
motion is expected to be temporary and is likely due to the outer 
circulation interacting with the mountainous terrain of Baja 
California Sur. However, the global and regional models remain in 
good agreement that the deep-layer subtropical ridge to the north of 
the hurricane is expected to turn Genevieve back toward the 
northwest by early Thursday. That motion is then forecast to 
continue through the end of the 5-day forecast period.  On this 
track, the center of Genevieve will pass just to the southwest or 
west of the southern portion of the Baja California peninsula 
overnight and on Thursday. The new NHC track forecast is a little to 
the right or east of the previous advisory track through 24 hours to 
account for the recent northward jog. Thereafter, the new forecast 
track is similar to the previous advisory and lies near the eastern 
edge of the model guidance suite.
 
Genevieve will continue to move over gradually decreasing sea 
surface temperatures (SSTs) and shallower warm waters over the next 
day or so, which will produce cold upwelling, resulting in slow 
weakening during the next 24-36 hours. Thereafter, the cyclone will 
be moving over sub-25 deg C SSTs, which will induce a faster rate 
of weakening, with Genevieve forest to degenerate into a 
post-tropical remnant low by 72 hours. The official intensity 
forecast is similar to the IVCN simple consensus aid, due to the low 
vertical shear conditions that are expected to persist through 36-48 
hours, and is above the NOAA-HCCA corrected-consensus model.

Key Messages:
 
1. The center of Genevieve is forecast to pass just west of the Baja 
California peninsula tonight and Thursday.  Tropical storm 
conditions are expected to spread across southern Baja California 
Sur through Thursday.  Hurricane conditions are expected within the 
Hurricane Warning area tonight and continuing into Thursday.
 
2. Heavy rainfall from Genevieve may lead to life-threatening flash 
flooding and mudslides across portions of far southern Baja 
California Sur through Thursday.
 
3. Large swells generated by Genevieve will affect portions of
the west-central coast Mexico and the coast of the southern Baja
California peninsula through Friday.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  20/0300Z 22.0N 110.1W   75 KT  85 MPH
 12H  20/1200Z 22.8N 110.8W   70 KT  80 MPH
 24H  21/0000Z 23.6N 112.1W   65 KT  75 MPH
 36H  21/1200Z 24.5N 113.5W   60 KT  70 MPH
 48H  22/0000Z 25.7N 115.3W   50 KT  60 MPH
 60H  22/1200Z 26.8N 117.1W   40 KT  45 MPH
 72H  23/0000Z 28.0N 119.0W   30 KT  35 MPH...POST-TROP/REMNT LOW
 96H  24/0000Z 29.5N 121.1W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  25/0000Z 31.1N 121.9W   20 KT  25 MPH...POST-TROP/REMNT LOW
 
$$
Forecaster Stewart
 
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