ZCZC MIATCDEP2 ALL TTAA00 KNHC DDHHMM Tropical Storm Lowell Discussion Number 11 NWS National Hurricane Center Miami FL EP172020 1100 PM HST Tue Sep 22 2020 Lowell's center is located near the northern edge of a band of deep convection which extends over the eastern and southern portion of the circulation due to moderate northwesterly shear in the mid-levels below the cirrus layer. That part of the circulation also happens to be where the tropical storm force winds are predominantly situated, and a recent ASCAT pass showed that the strongest winds have increased to near 45 kt. Lowell's circulation will be straddling a tight sea surface temperature gradient during the next few days, with the center moving over gradually cooler waters and toward a drier air mass. As a result, little change in strength is expected during the next couple of days, and some weakening should begin by day 3 when water temperatures fall below 25 degrees Celsius and moderate westerly or southwesterly shear sets in. The new NHC intensity forecast is largely an update of the previous prediction and closely follows the HCCA, Florida State Superensemble, and IVCN intensity consensus. Lowell is likely to lose its deep convection and degenerate to a remnant low by day 4. Lowell has been moving steadily toward the west-northwest, or 295/10 kt, steered by a mid-tropospheric high pressure area centered just off the west coast of the Baja California peninsula. The subtropical ridge is expected to become a little more established to the north of Lowell, and that should cause the storm to turn westward by 36 hours and continue at that heading through the end of the forecast period. There continues to be very little cross-track spread among the track guidance, and the most noteworthy differences are the forward speeds depicted by the models, bracketed by the speedy ECMWF and the more sluggish GFS and COAMPS-TC models. The models overall have continued to trend faster, and the new NHC track forecast is again pushed ahead of the previous prediction, lying close to the TVCE consensus and the HCCA aid. FORECAST POSITIONS AND MAX WINDS INIT 23/0900Z 19.8N 119.9W 45 KT 50 MPH 12H 23/1800Z 20.3N 121.3W 45 KT 50 MPH 24H 24/0600Z 20.7N 123.0W 45 KT 50 MPH 36H 24/1800Z 21.0N 124.9W 45 KT 50 MPH 48H 25/0600Z 21.1N 126.9W 45 KT 50 MPH 60H 25/1800Z 21.2N 129.1W 45 KT 50 MPH 72H 26/0600Z 21.2N 131.3W 40 KT 45 MPH 96H 27/0600Z 21.0N 135.7W 30 KT 35 MPH...POST-TROP/REMNT LOW 120H 28/0600Z 21.1N 140.5W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Berg NNNN
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