000 WTPZ42 KNHC 240838 TCDEP2 Tropical Storm Lowell Discussion Number 15 NWS National Hurricane Center Miami FL EP172020 1100 PM HST Wed Sep 23 2020 Lowell is maintaining status quo, with a few bands of deep convection located 30 n mi or more to the east of the exposed center. A recent ASCAT-C pass just clipped the eastern edge of the tropical-storm-force wind field and had vectors as high as 36 to 37 kt, so it is assumed that Lowell's intensity is still 40 kt. The available shear analyses indicate that the deep-layer shear over Lowell is low--maybe slightly moderate--but this seems odd given the cyclone's sheared appearance. Regardless of what the shear is now, the relative shear magnitude is expected to begin increasing in about 36 hours as Lowell moves closer to an upper-level jet stream. The storm will also be moving over gradually decreasing sea surface temperatures and into a much drier air mass, and all of these factors should conspire to cause weakening over the next several days. Global model guidance indicates that Lowell should lose its deep convection and become a remnant low by 60 hours, although the ECMWF suggests this could happen as early as in a day or two. Lowell has been locked into a west-northwestward motion of 285/9 kt, but the track models insist that it should turn toward the west very soon as the subtropical ridge to its north strengthens. The ridge is forecast to remain anchored north of Lowell for the entire forecast period, causing a gradual acceleration toward the west or even just south of due west into early next week. The earlier-noted speed differences among some of the models appear to have resolved themselves a bit, although the models overall have sped up. In response, the new NHC track forecast is faster than the previous prediction, and yet it is still not as fast as the TVCE multi-model consensus aid or the HCCA model. This probably means that additional adjustments to forecast speeds are likely in subsequent advisories. FORECAST POSITIONS AND MAX WINDS INIT 24/0900Z 21.2N 123.7W 40 KT 45 MPH 12H 24/1800Z 21.4N 125.1W 40 KT 45 MPH 24H 25/0600Z 21.7N 127.3W 35 KT 40 MPH 36H 25/1800Z 21.6N 129.6W 35 KT 40 MPH 48H 26/0600Z 21.5N 132.1W 30 KT 35 MPH 60H 26/1800Z 21.3N 134.7W 30 KT 35 MPH...POST-TROP/REMNT LOW 72H 27/0600Z 21.2N 137.4W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 28/0600Z 21.2N 142.7W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 29/0600Z 21.7N 146.9W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Berg