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| #1152278 (Received by flhurricane at: 4:35 AM 11.Sep.2023) TCDAT4 Tropical Storm Margot Discussion Number 16 NWS National Hurricane Center Miami FL AL142023 900 AM GMT Mon Sep 11 2023 This morning's satellite presentation consists of an isolated area of deep convection near Margot's surface center and a curved band displaced about 160 mi to the northeast beneath upper-level southerly diffluent flow. This distinctive cloud pattern is a result of very dry mid-tropospheric air intruding from the southwest and wrapping around and into the northeast sector of the cyclone. The Dvorak satellite intensity estimates from TAFB and SAB haven't changed since last night, and the initial intensity is held at 55 kt for this advisory. The latest GFS and ECMWF sounding analyses show modest northwesterly shear undercutting the diffluent southerly flow aloft while drying and stabilizing the mid-level portion of the atmosphere. In fact, the statistical-dynamic SHIPS indicates 40 to 50% relative humidity in the surrounding environment. The deterministic and SHIPS models still indicate, however, that the upper-level trough providing these inhibiting conditions will lift northeastward soon, allowing anticyclonic upper-tropospheric flow to develop over Margot. As a result, the cyclone should strengthen, and the NHC intensity forecast follows suit and indicates the cyclone becoming a hurricane in less than 24 hours while intensifying further through mid-week. Weakening is predicted beyond day 3 as the thermodynamic environment in the mid-latitudes of the central Atlantic becomes even less favorable. The official intensity forecast follows the HFIP HCCA corrected consensus intensity model through 48 hours, then is based on a blend of the HCCA, Decay SHIPS, and the IVCN intensity aids. Margot's initial motion during the past 12 hours has been north, or 360/7 kt. A mid-tropospheric subtropical ridge extending from west Africa to the eastern subtropical Atlantic should steer the cyclone in a generally northward trajectory through an amplified weakness over the central Atlantic over the next 72 hours. Through the remaining period, Margot is expected to slow in forward speed, and possibly meander, in response to high pressure building to the north of the cyclone over the central north Atlantic. The NHC forecast track is adjusted slightly to the right beyond 48 hours, and lies between the previous forecast and the TVCA simple average multi-model consensus. FORECAST POSITIONS AND MAX WINDS INIT 11/0900Z 25.3N 40.0W 55 KT 65 MPH 12H 11/1800Z 26.6N 39.9W 60 KT 70 MPH 24H 12/0600Z 28.6N 39.8W 70 KT 80 MPH 36H 12/1800Z 30.8N 40.1W 75 KT 85 MPH 48H 13/0600Z 32.7N 40.8W 75 KT 85 MPH 60H 13/1800Z 34.0N 41.7W 75 KT 85 MPH 72H 14/0600Z 35.0N 42.0W 75 KT 85 MPH 96H 15/0600Z 36.7N 41.0W 70 KT 80 MPH 120H 16/0600Z 37.1N 40.9W 60 KT 70 MPH $$ Forecaster Roberts |
