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Hurricane Linda Discussion Number  36
NWS National Hurricane Center Miami FL       EP122021
500 PM HST Wed Aug 18 2021
 
The convective structure associated with long-lived Hurricane Linda 
continues to gradually decay, especially on its western flank. In 
fact, earlier visible satellite imagery showed that the mid-level 
eye was starting to become displaced to the northeast of the 
low-level center, a possible consequence of some sneaky westerly 
mid-level shear impinging on the storm and importing very dry 
mid-level air into the circulation from that direction. The latest 
round of subjective Dvorak CI intensity estimates were both 5.0/90 
kt from SAB and TAFB, respectively, but their data T numbers have 
started to decline. The latest NHC intensity estimate was lowered to 
80 kt for this advisory given additional deterioration of the 
hurricane's structure since that time.
 
Now that Linda is finally starting to lose its stable eyewall 
structure it has maintained for the last 4-5 days, weakening should 
begin in earnest under cooling sea-surface temperatures. While the 
deep-layer shear in the SHIPS guidance remains low, there also 
appears to be some mid-level westerly shear undercutting the outflow 
layer, allowing very dry mid-level air below 40 percent to get 
entrained into the circulation. As sea-surface temperatures decrease 
to near 24 C in 24 hours the weakening rate should increase, and the 
latest NHC intensity forecast has a faster rate of weakening than in 
the previous one, following the HCCA guidance aid closely. Both the 
ECMWF and GFS show Linda becoming devoid of deep convection between 
48 to 60 hours, and the latest forecast makes Linda post-tropical by 
that time.
 
The current motion of Linda continues off to the west-northwest, but 
a little faster, at 285/14 kt. This general motion is expected to 
continue throughout the forecast period as Linda remains steered by 
a prominent mid-level ridge, which is expected to build-in west 
along with the cyclone. The latest track guidance remains tightly 
clustered pretty close to the previous NHC forecast track and only a 
slight southward adjustment was made , following the HCCA guidance 
aid. On the current track, Linda will be crossing over in the 
Central Pacific basin in less than 24 hours, by 0000 UTC Friday.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  19/0300Z 19.2N 134.7W   80 KT  90 MPH
 12H  19/1200Z 19.7N 137.0W   70 KT  80 MPH
 24H  20/0000Z 20.4N 140.1W   55 KT  65 MPH
 36H  20/1200Z 20.8N 143.2W   45 KT  50 MPH
 48H  21/0000Z 21.1N 145.8W   40 KT  45 MPH
 60H  21/1200Z 21.5N 148.1W   40 KT  45 MPH...POST-TROPICAL
 72H  22/0000Z 21.9N 150.4W   40 KT  45 MPH...POST-TROPICAL
 96H  23/0000Z 22.8N 154.9W   35 KT  40 MPH...POST-TROPICAL
120H  24/0000Z 23.5N 160.1W   30 KT  35 MPH...POST-TROPICAL
 
$$
Forecaster Papin/Beven
 
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