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Tropical Storm Genevieve Discussion Number  20
NWS National Hurricane Center Miami FL       EP122020
300 AM MDT Fri Aug 21 2020
 
The combination of moderate southerly vertical wind shear, cooler 
sea-surface temperatures (SST) near 26 deg C, and dry mid-level air 
has caused Genevieve to rapidly weaken over the past 24 hours.  Very 
little deep convection remains, and what convection there is has 
been displaced well to the northeast of the low-level center. An 
ASCAT-A scatterometer pass at 0428Z indicated one surface wind 
vector of 43 kt in the northeastern quadrant about 40 nmi from the 
center. Thus, the initial intensity has been lowered  to 45 kt. The 
34-kt wind radii have also been decreased in all quadrants based on 
the scatterometer data.
 
Passive microwave imagery the scatterometer data indicate that 
Genevieve's center is southwest of the previous advisory track, and 
the initial motion is now 295/09 kt. The weakening cyclone and its 
remnants should continue to move west-northwestward to northwestward 
during the next few days, accompanied by a decrease in forward speed 
as the system weakens and becomes more vertically shallow. The 
decoupled remnant mid-level circulation and its attendant moisture 
plume, however, are expected to move northward today through Sunday, 
and move into the southwestern United States on Monday. On the 
forecast track, Genevieve should gradually move away from the Baja 
California coast throughout the forecast period.  The NHC track 
forecast lies very near the multi-model consensus aids TVCE and 
HCCA, and is a little to the left of the previous advisory track.
 
Continued weakening is expected due to a combination of increasingly 
southerly wind shear, dry air, and progressively cooler SSTs.  
Genevieve is forecast to weaken to a tropical depression by tonight, 
and degenerate into a remnant low by Saturday morning.
 
Key Messages:
 
1. Tropical storm conditions are expected to diminish over the 
southwestern coast of the Baja California peninsula later this 
morning.
 
2. Large swells generated by Genevieve will continue to affect the
coast of the southern and central Baja California peninsula through
Friday.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  21/0900Z 24.3N 114.3W   45 KT  50 MPH
 12H  21/1800Z 25.4N 115.6W   35 KT  40 MPH
 24H  22/0600Z 26.9N 117.4W   30 KT  35 MPH...POST-TROP/REMNT LOW
 36H  22/1800Z 28.2N 119.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
 48H  23/0600Z 29.1N 121.1W   25 KT  30 MPH...POST-TROP/REMNT LOW
 60H  23/1800Z 30.0N 122.2W   20 KT  25 MPH...POST-TROP/REMNT LOW
 72H  24/0600Z 31.0N 122.8W   15 KT  15 MPH...POST-TROP/REMNT LOW
 96H  25/0600Z...DISSIPATED
 
$$
Forecaster Stewart
 
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