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Hurricane Larry Discussion Number  10
NWS National Hurricane Center Miami FL       AL122021
1100 PM AST Thu Sep 02 2021
 
A series of SSMIS microwave passes earlier this afternoon indicated 
that Larry may have been starting an eyewall replacement.  However, 
the last pass at 2058 UTC suggested that the eyewall replacement 
failed, with the western part of the outer eyewall being eroded, 
possibly by some modest mid-level shear and some dry air, and the 
tighter inner eyewall trying to re-establish itself.  As a result, 
the convective pattern has reverted back to a small Central Dense 
Overcast.  Subjective Dvorak intensity estimates are now T4.5/77 kt 
from TAFB and T4.0/65 kt from SAB, and the latest objective 
estimates range from 72 to 78 kt.  Overall these numbers have risen 
a bit, and Larry's maximum winds are now estimated to be 75 kt.

Larry continues moving toward the west but perhaps slightly faster 
(280/17 kt).  There is no change to the track forecast reasoning.  
A fairly stagnant pattern consisting of a strong mid-level high 
over the central Atlantic and broad-scale troughing over the 
eastern United States and western Atlantic should persist through 
the 5-day forecast period.  Larry is therefore forecast to turn 
toward the west-northwest on Friday and then take on a northwest 
heading Sunday through Tuesday while it moves around the 
southwestern periphery of the high.  The updated NHC track forecast 
lies right along the previous forecast and is very close to the 
various consensus aids.

Low shear, gradually increasing sea surface temperatures, and the 
potential for an upper-level outflow jet to form north of the 
hurricane during the next 24-48 hours should support continued 
strengthening.  During the first 48 hours, the NHC forecast shows a 
steady increase of 10 kt every 24 hours, close to the HCCA 
consensus aids and near the top of the guidance envelope.  By days 
3 and 4, there continue to be indications that increasing westerly 
or northwesterly shear could become a factor, and the NHC forecast 
therefore shows a leveling off of the intensity, with some slight 
weakening by the end of the forecast period.  If Larry becomes a 
strong hurricane, eyewall replacements would also be a possibility, 
which would likely lead to difficult-to-forecast fluctuations in 
intensity.
 
The leading swell front from Larry is expected to reach the Lesser 
Antilles on Sunday, increasing the risk of life-threatening rip 
currents and surf conditions on those islands early next week.  
Large swells are likely to spread to areas surrounding the western 
Atlantic later in the week as well.

 
FORECAST POSITIONS AND MAX WINDS
 
INIT  03/0300Z 14.1N  37.5W   75 KT  85 MPH
 12H  03/1200Z 14.5N  39.9W   85 KT 100 MPH
 24H  04/0000Z 15.3N  42.6W   95 KT 110 MPH
 36H  04/1200Z 16.4N  45.2W  105 KT 120 MPH
 48H  05/0000Z 17.6N  47.5W  115 KT 130 MPH
 60H  05/1200Z 19.0N  49.7W  120 KT 140 MPH
 72H  06/0000Z 20.4N  51.8W  120 KT 140 MPH
 96H  07/0000Z 22.9N  55.0W  115 KT 130 MPH
120H  08/0000Z 25.9N  58.0W  110 KT 125 MPH
 
$$
Forecaster Berg
 
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