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Hurricane Larry Forecast Discussion Number 14
2021-09-04 04:37:23| National Hurricane Center (Atlantic)
Issued at 1100 PM AST Fri Sep 03 2021 078 WTNT42 KNHC 040237 TCDAT2 Hurricane Larry Discussion Number 14 NWS National Hurricane Center Miami FL AL122021 1100 PM AST Fri Sep 03 2021 Larry has had a distinct but slightly ragged 15 n mi wide eye during the past few hours, while convective cloud tops within the eyewall have been gradually cooling. Intensity estimates have responded, somewhat significantly, to the improved structure, and TAFB and SAB Dvorak fixes at 0000 UTC were T5.5/102 kt and T5.0/90 kt, respectively. In addition, objective UW-CIMSS ADT and SATCON estimates are near 105 kt. Larry has become a major hurricane, the third of the Atlantic season, with estimated 100-kt sustained winds. The hurricane is located due south of a mid-tropospheric high centered over the central Atlantic, and continues to move toward the west-northwest (285/14 kt). Larry is generally expected to move around the southwestern periphery of the high, turning northwestward at a slower speed by Sunday and then north-northwestward by Wednesday as a deep-layer trough moves eastward across the eastern United States. There is fairly high confidence in the track forecast, with model guidance showing a below- to near-normal amount of spread through day 5. The new NHC track forecast is right along the forecast from the previous advisory through day 3, and then nudged slightly westward on days 4 and 5. It should be noted that a few of the consensus aids, including HCCA, are still a little bit west of the official forecast at day 5, which might portend additional westward nudges in future advisories. By strict definition, Larry hasn't quite rapidly intensified since this time yesterday, but it has still strengthened quickly over waters that are considered only marginally warm (26-27 degrees Celsius). For the next couple of days, low shear, higher oceanic heat content, and a more unstable environment should favor additional intensification. However, there are still indications that Larry could run into an environment of higher shear and less upper-level divergence in 2-3 days as it approaches a mid-/upper-level trough currently located north and northeast of the Leeward Islands. In addition, internal processes within the hurricane's core itself, such as eyewall replacement cycles, could affect the intensity. In light of all these factors, the NHC intensity forecast relies on persistence to show additional strengthening during the next 36 hours, and then holds Larry steady through 60 hours at an intensity that is near the upper end of the guidance. Very gradual weakening is anticipated on days 3 through 5 while Larry heads in the direction of higher latitudes, yet the hurricane is forecast to remain at major hurricane intensity for the entire 5-day forecast period. Significant ocean swells generated by Larry's growing wind field are expected to reach the Lesser Antilles on Sunday, and then spread westward to portions of the Greater Antilles, the Bahamas, and Bermuda on Monday and Tuesday. These swells could cause life-threatening rip currents and high surf conditions. Large swells are also likely to spread to the east coast of the United States by midweek. FORECAST POSITIONS AND MAX WINDS INIT 04/0300Z 15.5N 43.3W 100 KT 115 MPH 12H 04/1200Z 16.2N 45.3W 110 KT 125 MPH 24H 05/0000Z 17.4N 47.6W 115 KT 130 MPH 36H 05/1200Z 18.7N 49.7W 120 KT 140 MPH 48H 06/0000Z 20.0N 51.7W 120 KT 140 MPH 60H 06/1200Z 21.2N 53.6W 120 KT 140 MPH 72H 07/0000Z 22.4N 55.3W 115 KT 130 MPH 96H 08/0000Z 25.4N 58.5W 115 KT 130 MPH 120H 09/0000Z 29.5N 61.5W 105 KT 120 MPH $$ Forecaster Berg
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