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Subtropical Storm Theta Forecast Discussion Number 3
2020-11-10 15:52:55| National Hurricane Center (Atlantic)
Issued at 300 PM GMT Tue Nov 10 2020 000 WTNT45 KNHC 101452 TCDAT5 Subtropical Storm Theta Discussion Number 3 NWS National Hurricane Center Miami FL AL302020 300 PM GMT Tue Nov 10 2020 Theta continues to exhibit a mix of tropical and subtropical characteristics. The cyclone has a fairly compact radius of maximum winds with a central dense overcast over the northern portion of the circulation. However, there is a strong subtropical jet located just to the south of Theta, and strong upper-level winds in the surrounding environment in the presence of an upper trough. Based on this inconclusive data, Theta is being maintained as a subtropical storm for this advisory. An ASCAT-B overpass this morning revealed 50-kt winds in the northwest and southwest quadrants, with several 55-60 kt wind vectors, some of those vectors outside of the deep convection making them more believable. Based on this, the initial advisory intensity has been set to 60 kt. The storm is moving just north of due east, or 085/13 kt. Theta should continue to be steered eastward to east-northeastward during the next several days on the north side of a mid-level ridge. This motion should take the cyclone across the subtropical eastern Atlantic throughout the forecast period. The latest model guidance is a little faster and slightly north of the previous forecast track, and so the latest NHC forecast has been adjusted slightly as well. Theta is still expected to transition to a tropical storm later today as it separates from the upper-level trough. Although Theta will be tracking over progressively cooler SSTs and within moderate wind shear conditions, the air mass is expected to remain unstable for the next couple of days, which should be supportive of deep convection. Therefore, little change is strength is indicated during that time. Some weakening is anticipated later in the forecast period as the airmass becomes more stable. The NHC intensity forecast is higher than the previous one primarily due to the higher initial intensity, and is near the IVCN and HCCA consensus models. FORECAST POSITIONS AND MAX WINDS INIT 10/1500Z 29.0N 37.4W 60 KT 70 MPH 12H 11/0000Z 29.1N 35.7W 60 KT 70 MPH 24H 11/1200Z 29.7N 33.4W 60 KT 70 MPH 36H 12/0000Z 30.4N 31.3W 55 KT 65 MPH 48H 12/1200Z 31.1N 28.7W 55 KT 65 MPH 60H 13/0000Z 31.7N 26.0W 50 KT 60 MPH 72H 13/1200Z 32.2N 23.7W 45 KT 50 MPH 96H 14/1200Z 33.0N 19.5W 40 KT 45 MPH 120H 15/1200Z 34.3N 17.0W 35 KT 40 MPH...POST-TROP/EXTRATROP $$ Forecaster Latto
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