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Hurricane Larry Forecast Discussion Number 10
2021-09-03 04:33:58| National Hurricane Center (Atlantic)
Issued at 1100 PM AST Thu Sep 02 2021 000 WTNT42 KNHC 030233 TCDAT2 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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