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Tropical Storm Peter Forecast Discussion Number 9
2021-09-20 22:33:04| National Hurricane Center (Atlantic)
Issued at 500 PM AST Mon Sep 20 2021 000 WTNT41 KNHC 202032 TCDAT1 Tropical Storm Peter Discussion Number 9 NWS National Hurricane Center Miami FL AL162021 500 PM AST Mon Sep 20 2021 Peter's evolution on satellite today is nearly a repeat of yesterday, with the deep convection having been stripped well east of the center in the morning and then redeveloping over and east of the center by the afternoon. An Air Force Reserve Hurricane Hunter aircraft investigating Peter this morning and early afternoon provided data during a few different passes through the northeast quadrant that supported peak surface winds of 40-45 kt. Since the convection has returned it is reasonable to assume that no weakening has occurred since the aircraft departed the cyclone, and the initial advisory intensity remains 45 kt. Vertical wind shear is forecast to remain near 30 kt for the next few days as Peter interacts with an upper trough to its west, so some weakening is anticipated during that time. By late in the forecast period, the shear should lessen somewhat as the cyclone lifts north of the upper trough. Therefore, slow strengthening is indicated by late this week. There remains a possibility that Peter does not survive the shear over the next few days. However, the storm thus far has shown some resiliency to the hostile environment. The latest NHC intensity forecast is little changed from the previous one and remains near the various intensity consensus solutions. Peter continues to move west-northwest but at a slightly slower pace of around 12 kt. The forecast track reasoning for the cyclone remains the same. The west-northwestward motion is forecast to continue for the next two days as the system remains to the southwest of a subtropical ridge. By Wednesday, Peter should slow down and turn northwest then north as it reaches a developing weakness in the ridge carved out by a mid-latitude trough moving across the northeastern United States. There were no significant changes to the track or the track guidance from the previous advisory, and the latest NHC track is closest to the TVCN and GFEX consensus tracks. 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 today and Tuesday when Peter is expected to pass to the north of these locations. Key Messages: 1. Rainfall around the southern periphery of Tropical Storm Peter may lead to areas of urban and small stream flooding through Tuesday across northern Hispaniola, Puerto Rico, the Virgin Islands, and the Northern Leeward Islands. FORECAST POSITIONS AND MAX WINDS INIT 20/2100Z 20.0N 61.8W 45 KT 50 MPH 12H 21/0600Z 20.6N 63.5W 45 KT 50 MPH 24H 21/1800Z 21.4N 65.4W 40 KT 45 MPH 36H 22/0600Z 22.2N 66.9W 40 KT 45 MPH 48H 22/1800Z 23.1N 68.0W 35 KT 40 MPH 60H 23/0600Z 24.0N 68.3W 35 KT 40 MPH 72H 23/1800Z 25.1N 68.0W 30 KT 35 MPH 96H 24/1800Z 27.8N 66.9W 30 KT 35 MPH 120H 25/1800Z 30.5N 65.8W 35 KT 40 MPH $$ Forecaster Latto
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