ZCZC MIATCDEP2 ALL TTAA00 KNHC DDHHMM Tropical Storm Lowell Discussion Number 9 NWS National Hurricane Center Miami FL EP172020 200 PM PDT Tue Sep 22 2020 Lowell has been undergoing a bursting pattern today, with the original mass dissipating and a new one developing in its place. This is typical of sheared tropical cyclones. Just in the past couple of hours, visible satellite imagery has shown a low-level swirl ejecting to the northwest from the deep convection. Based on the center position from an ASCAT overpass around 1700 UTC, the exposed swirl may indeed be the primary center of the cyclone. This same ASCAT overpass showed peak winds of 37 kt, and based on the evolution of the cyclone's structure in the past couple of hours, the initial intensity is being lowered to 40 kt. The northeasterly shear causing the developmental issues for Lowell may abate somewhat in a day or so. This may provide the cyclone with an opportunity for some strengthening before it reaches cooler waters in a couple of days. After 72 h, Lowell is forecast to begin moving over waters of 24-25 degrees C, and enter an increasingly hostile environment with strong westerly shear and mid-level relative humidity values around 30 percent by the end of the forecast period. These conditions should cause the cyclone to weaken starting late this week. There is a possibility that the cyclone could lose its deep convection late in the forecast period, and although the latest advisory does not indicate it, Lowell could degenerate into a remnant low by day 5. The latest NHC intensity forecast is near the various intensity consensus values. The initial motion of the cyclone is 295/12 kt, but this is uncertain due to the recent northwestern motion of the low-level center. A general west-northwest motion is expected through Wednesday as Lowell moves south of a subtropical ridge. A turn to the west is expected Wednesday night as the ridge changes its orientation slightly. The latest NHC track forecast is little changed from the previous one and is near the tightly clustered track guidance. FORECAST POSITIONS AND MAX WINDS INIT 22/2100Z 19.2N 117.9W 40 KT 45 MPH 12H 23/0600Z 19.7N 119.6W 40 KT 45 MPH 24H 23/1800Z 20.0N 121.2W 40 KT 45 MPH 36H 24/0600Z 20.4N 122.9W 45 KT 50 MPH 48H 24/1800Z 20.6N 124.6W 50 KT 60 MPH 60H 25/0600Z 20.7N 126.4W 50 KT 60 MPH 72H 25/1800Z 20.7N 128.2W 50 KT 60 MPH 96H 26/1800Z 20.7N 132.3W 40 KT 45 MPH 120H 27/1800Z 20.7N 136.2W 35 KT 40 MPH $$ Forecaster Latto NNNN
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