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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
 
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