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Tropical Storm Peter Forecast Discussion Number 7
2021-09-20 10:48:50| National Hurricane Center (Atlantic)
Issued at 500 AM AST Mon Sep 20 2021 000 WTNT41 KNHC 200848 CCA TCDAT1 Tropical Storm Peter Discussion Number 7...Corrected NWS National Hurricane Center Miami FL AL162021 500 AM AST Mon Sep 20 2021 Corrected name of storm in first and second paragraphs Peter is a strongly sheared tropical storm. Reconnaissance wind data, conventional satellite imagery, and passive microwave satellite data indicate that Peter's center is located just to the west of the deep convection. Data from the aircraft support holding the intensity at 45 kt for now based on 925-mb flight-level and SFMR winds of 53 kt and 41 kt, respectively, on their last leg when the aircraft came in from the northeast. The central pressure had also increased only slightly to 1006 mb. Peter has continued to move west-northwestward, or 295/12 kt. There are no significant changes to the previous track forecast or reasoning. Peter is expected to move around the southwestern and western periphery of a subtropical ridge for the next couple of days, followed by a slow northward motion on days 3-5 as the cyclone moves through a weakness in the ridge induced by the southward-moving former Tropical Storm Odette. The new NHC track forecast is very similar to the previous advisory track, and lies just to the east of the tightly packed consensus track models. Some fluctuations in intensity will be possible during the next 24-36 hours owing to 5-10 kt fluctuations in the magnitude and also the direction of the deep-layer vertical wind shear. However, by 48 hours and beyond, a slow weakening trend is expected due to the shear increasing from the southwest and west-southwest of near 30 kt. The new official intensity forecast is essentially just an update of the previous advisory, and closely follows the IVCN and HCCA intensity consensus models. Based on the latest track, intensity, and wind radii forecasts, no tropical storm watches or warnings are required for the northern Leeward Islands, Virgin Islands, or Puerto Rico at this time. However, locally heavy rain is possible on Monday and Tuesday when Peter is expected to pass to the north of these locations. Key Messages: Rainfall around the southern periphery of Tropical Storm Peter may lead to areas of urban and small stream flooding through Tuesday across Puerto Rico, the Virgin Islands, and the Northern Leeward Islands. FORECAST POSITIONS AND MAX WINDS INIT 20/0900Z 19.1N 59.5W 45 KT 50 MPH 12H 20/1800Z 19.7N 61.4W 40 KT 45 MPH 24H 21/0600Z 20.4N 63.6W 40 KT 45 MPH 36H 21/1800Z 21.4N 65.5W 35 KT 40 MPH 48H 22/0600Z 22.4N 67.2W 35 KT 40 MPH 60H 22/1800Z 23.2N 68.0W 30 KT 35 MPH 72H 23/0600Z 24.2N 68.4W 30 KT 35 MPH 96H 24/0600Z 26.2N 67.8W 25 KT 30 MPH 120H 25/0600Z 28.5N 66.8W 30 KT 35 MPH $$ Forecaster Stewart
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