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Tropical Storm Genevieve Discussion Number  18
NWS National Hurricane Center Miami FL       EP122020
300 PM MDT Thu Aug 20 2020
 
Dry and stable air continues to be drawn into Genevieve's 
circulation.  This is noted by a slow erosion of convection over 
the southwestern semicircle, and warming cloud tops over 
the past several hours, indicating weakening. An Air Force Reserve 
Hurricane Hunter aircraft investigating the system this afternoon 
measured peak 700 mb flight-level winds of 71 kt, which  reduce to 
64 kt at the surface, with peak SFMR winds of 57 kt. A blend of 
these values supports lowering the initial intensity to 60 kt.
 
Genevieve should continue to gradually weaken as it moves over 
progressively lower oceanic temperatures. By Friday, the cyclone is 
expected to cross the 26 C SST isotherm, and it will reach waters 
cooler than 24 C by early Saturday. These much cooler waters should 
cause the cyclone to degenerate to a remnant low by late Saturday. 
The latest NHC intensity forecast is little changed from the 
previous one, and is near the HFIP corrected consensus HCCA.
 
Genevieve continues to move northwestward at 10 kt, paralleling the 
coast of the southern Baja California Peninsula. This general motion 
is expected to continue until the cyclone dissipates later in the 
forecast period. On this track, Genevieve will begin to move away 
from the peninsula tonight. The NHC forecast track is very little 
changed from the previous one and is in the middle of the tightly 
clustered track guidance.
 
Key Messages:
 
1. The center of Genevieve is forecast to pass just west of the Baja 
California peninsula through this evening,  with tropical storm 
conditions expected to continue over portions of this area during 
this time. 
 
2. Rainfall from Genevieve will continue to decrease in intensity 
over southern Baja California Sur, although some instances of flash 
flooding and mudslides remain possible through this evening.
 
3. Large swells generated by Genevieve will affect portions of
the west-central coast of Mexico and the coast of the southern Baja
California peninsula through Friday.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  20/2100Z 23.9N 112.4W   60 KT  70 MPH
 12H  21/0600Z 24.8N 113.7W   50 KT  60 MPH
 24H  21/1800Z 26.1N 115.3W   40 KT  45 MPH
 36H  22/0600Z 27.4N 117.2W   30 KT  35 MPH
 48H  22/1800Z 28.6N 119.3W   25 KT  30 MPH...POST-TROP/REMNT LOW
 60H  23/0600Z 29.4N 120.9W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  23/1800Z 30.3N 122.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  24/1800Z...DISSIPATED
 
$$
Forecaster Latto
 
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