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Tropical Storm Larry Forecast Discussion Number 4
2021-09-01 16:50:32| National Hurricane Center (Atlantic)
Issued at 200 PM CVT Wed Sep 01 2021 000 WTNT42 KNHC 011450 TCDAT2 Tropical Storm Larry Discussion Number 4 NWS National Hurricane Center Miami FL AL122021 200 PM CVT Wed Sep 01 2021 Satellite imagery this morning shows that Larry is becoming better organized, with curved convective bands increasing around the center. Various subjective and objective satellite intensity estimates were in the 35-55 kt range around 12Z, and ASCAT data near the time showed 40 kt winds. Based on increasing organization since that time, the initial intensity is increased to 45 kt. Larry is moving quickly westward, although there is some uncertainty in the forward speed due to the possibility the center re-formed during the night. The best estimate of the motion is 270/19 kt. As noted in the previous advisory, the cyclone is expected to move around the southern and southwestern periphery of the sprawling Bermuda-Azores ridge for the next 5 days, resulting in a general west motion for 24-36 h, followed by a turn toward the west-northwest and, by 96-120 h, a turn toward the northwest. After 36 h, there is some spread in the track guidance, with the GFS generally on the right side of the guidance envelope and the UKMET on the left side, a spread often seen for westward-moving cyclones south of the Bermuda-Azores high. Due to a more westerly initial position, the guidance has shifted a little more to the west, and the new forecast track is again shifted to the west of the previous track. The new forecast lies a little to the south of the various consensus models. Conditions appear favorable for steady to rapid strengthening during the next 48-60 h due to light shear, a moist environment, and sea surface temperatures of 27-28C along the forecast track. The new intensity forecast calls for Larry to become a hurricane in about 24 h and a major hurricane near 60 h. After that time, the global models suggest the possibility of dry air entrainment, and by 120 h there is likely to be moderate westerly shear over the cyclone. Based on this forecast environment and the guidance trends, the intensity forecast calls for little change in strength from 72-120 h. The new intensity forecast lies near the upper edge of the intensity guidance. FORECAST POSITIONS AND MAX WINDS INIT 01/1500Z 12.3N 27.6W 45 KT 50 MPH 12H 02/0000Z 12.4N 30.4W 55 KT 65 MPH 24H 02/1200Z 12.7N 33.4W 65 KT 75 MPH 36H 03/0000Z 13.2N 36.5W 75 KT 85 MPH 48H 03/1200Z 13.9N 39.2W 90 KT 105 MPH 60H 04/0000Z 15.0N 41.9W 100 KT 115 MPH 72H 04/1200Z 16.2N 44.6W 105 KT 120 MPH 96H 05/1200Z 19.0N 49.5W 105 KT 120 MPH 120H 06/1200Z 22.0N 52.5W 105 KT 120 MPH $$ Forecaster Beven
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