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Tropical Storm Theta Forecast Discussion Number 8
2020-11-11 21:51:04| National Hurricane Center (Atlantic)
Issued at 900 PM GMT Wed Nov 11 2020 000 WTNT45 KNHC 112050 TCDAT5 Tropical Storm Theta Discussion Number 8 NWS National Hurricane Center Miami FL AL302020 900 PM GMT Wed Nov 11 2020 The deep convection associated with Theta has been trying to wrap around the cyclone's low-level center today, and the system consists of a large curved band feature with clouds tops as cold as -65 degrees C. There was no complete sampling of the cyclone's circulation by the scatterometers today. However, a partial ASCAT-C overpass this morning showed that 40-45 kt winds were occurring in the eastern semicircle. This portion of the circulation has previously been the weaker portion of Theta, which suggests some higher winds could be occurring in the western semicircle. Therefore, the initial intensity is being kept at a somewhat uncertain 50 kt. Theta appears to be holding its own in an environment of strong southwesterly shear and over relatively cool water temperatures of about 24 degrees C, within a favorable unstable atmosphere. The cyclone will be traversing over progressively cooler waters over the next couple of days, and the shear is expected to only abate slightly. These somewhat counteracting factors should either allow Theta to maintain its intensity or slowly weaken during that time. Over the weekend, the upper-level winds are expected to increase and shift out of the north, and force more stable air across the cyclone. This should cause the convection to become displaced to the south of the center and gradually dissipate. The GFS/CMC/ECMWF simulated satellite imagery all indicate that the system should degenerate to a remnant low by 96 h. The latest NHC intensity forecast is similar to the previous one, and remains near the various multimodel consensus aids. The storm is moving east-northeastward at around 11 kt, steered by mid-latitude westerlies to the north of a mid-level ridge. This steering pattern is expected to remain in place for the next couple of days. Model guidance is trending slower over the weekend, as they are indicating that the ridge will weaken at around the same time that the shear vector becomes northerly. This would cause the cyclone to slow its forward motion and turn to the right, which is now indicated in the official forecast. However, the latest NHC track remains a little north of the consensus track guidance during that time frame. By the end of the forecast period, an approaching mid-latitude trough and associated front should pick up what remains of Theta and begin to accelerate it to the northeast. FORECAST POSITIONS AND MAX WINDS INIT 11/2100Z 30.5N 31.9W 50 KT 60 MPH 12H 12/0600Z 31.1N 30.2W 50 KT 60 MPH 24H 12/1800Z 31.5N 27.8W 50 KT 60 MPH 36H 13/0600Z 31.9N 25.4W 45 KT 50 MPH 48H 13/1800Z 32.1N 23.5W 45 KT 50 MPH 60H 14/0600Z 32.0N 22.3W 45 KT 50 MPH 72H 14/1800Z 31.8N 21.3W 40 KT 45 MPH 96H 15/1800Z 31.7N 19.7W 30 KT 35 MPH...POST-TROP/REMNT LOW 120H 16/1800Z 35.1N 18.2W 30 KT 35 MPH...POST-TROP/REMNT LOW $$ Forecaster Latto
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