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Tropical Storm Theta Forecast Discussion Number 4
2020-11-10 21:37:17| National Hurricane Center (Atlantic)
Issued at 900 PM GMT Tue Nov 10 2020 000 WTNT45 KNHC 102037 TCDAT5 Tropical Storm Theta Discussion Number 4 NWS National Hurricane Center Miami FL AL302020 900 PM GMT Tue Nov 10 2020 A central dense overcast has persisted near the center of Theta since yesterday, and although the clouds tops have warmed over the past several hours there remains a distinct curved band feature over the northern portion of the circulation. Water vapor imagery shows the mid- upper-level trough that was over the Azores is beginning to leave the cyclone behind. Based on these factors, and the earlier indications of a compact radius of maximum winds, it appears that Theta has completed a transition to a tropical cyclone. Even though the clouds tops have recently warmed, the overall structure of Theta has not degraded by much since the previous advisory. Therefore, the initial intensity is being held at 60 kt. The storm is moving 075/12 kt around the north side of a mid-level ridge. This feature should continue to steer Theta in a generally east-northeastward motion for the next few days. Late in the forecast period, the ridge will begin to weaken as another trough approaches from the northwest. This should cause the cyclone to slow its forward motion and begin to turn to the northeast. The latest model guidance has once again slowed down and the new NHC track forecast now lies between the previous one and the various consensus models. Although Theta will be moving over progressively cooler SSTs and within moderate wind shear conditions, the air mass is expected to remain unstable for the next day or so, 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. By the end of the 5-day forecast period, the combination of the cooler waters and an approaching trough should result in extratropical transition. The NHC intensity forecast has changed little from the previous one and remains near the IVCN and HCCA consensus models. FORECAST POSITIONS AND MAX WINDS INIT 10/2100Z 29.4N 36.2W 60 KT 70 MPH 12H 11/0600Z 29.8N 34.7W 60 KT 70 MPH 24H 11/1800Z 30.3N 32.8W 55 KT 65 MPH 36H 12/0600Z 30.8N 30.5W 55 KT 65 MPH 48H 12/1800Z 31.5N 28.0W 50 KT 60 MPH 60H 13/0600Z 32.1N 25.7W 50 KT 60 MPH 72H 13/1800Z 32.6N 23.8W 45 KT 50 MPH 96H 14/1800Z 33.2N 20.5W 40 KT 45 MPH 120H 15/1800Z 34.4N 19.0W 35 KT 40 MPH...POST-TROP/EXTRATROP $$ Forecaster Latto
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