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| #1025212 (Received by flhurricane at: 9:39 PM 13.Nov.2020) TCDAT5 Tropical Storm Theta Discussion Number 17 NWS National Hurricane Center Miami FL AL302020 300 AM GMT Sat Nov 14 2020 Theta is beginning to show signs of weakening tonight. Infrared cloud top temperatures have warmed during the past several hours within the weakening convective band that curves around the northeastern semicircle of the storm. A partial 22 UTC ASCAT-B overpass indicates that Theta maintains a fairly symmetric low-level wind field, with 35-40 kt winds in the eastern semicircle of the storm. Therefore, the initial intensity is lowered to 45 kt with this advisory, which is consistent with UW-CIMSS objective current intensity estimates but slightly higher than the T2.5 subjective Dvorak classification from TAFB. Theta will encounter increasingly hostile environmental conditions over the next couple of days. The NHC intensity forecast calls for steady weakening through the weekend, as strong northerly wind shear and cool sea surface temperatures will likely inhibit the storm from sustaining convection near its center. This forecast closely follows the corrected consensus aid HCCA. Theta is expected to weaken to a tropical depression within 36 h and degenerate into a remnant low by 48 h, although the GFS simulated satellite imagery suggests this could occur even sooner than forecast. The remnant low should dissipate by the middle of next week. Theta is still moving eastward at around 9 kt around the northern periphery of a mid-level ridge that extends from western Africa across the eastern tropical Atlantic. An eastward or east-southeastward motion with a gradual decrease in forward speed is expected during the next 24-36 h. As the storm spins down and becomes a more shallow circulation, the remains of Theta will turn northward and then accelerate northeastward ahead of a mid-latitude cyclone and associated frontal system that will cross the northeastern Atlantic. The NHC track forecast lies close to the previous one and near the center of the guidance envelope. On the forecast track, the center of Theta is expected to pass northwest of the Canary Islands this weekend, then move near Madeira Island early Monday as a weak remnant low. FORECAST POSITIONS AND MAX WINDS INIT 14/0300Z 31.9N 21.6W 45 KT 50 MPH 12H 14/1200Z 31.8N 20.2W 40 KT 45 MPH 24H 15/0000Z 31.6N 18.6W 35 KT 40 MPH 36H 15/1200Z 31.7N 17.8W 30 KT 35 MPH 48H 16/0000Z 32.3N 17.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 60H 16/1200Z 33.7N 17.3W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 17/0000Z 35.9N 16.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 18/0000Z...DISSIPATED $$ Forecaster Reinhart/Cangialosi |