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| #1151126 (Received by flhurricane at: 4:44 AM 03.Sep.2023) TCDAT4 Tropical Storm Katia Discussion Number 8 NWS National Hurricane Center Miami FL AL122023 900 AM GMT Sun Sep 03 2023 MET-10 proxy-vis and a series of AMSR2 microwave overpasses indicate that the surface center is farther south than earlier thought and is displaced about 170 mi to the south of a small patch of deep convection. Subsequently, Katia has been devoid of convection since 0100 UTC, and unless organized deep convection redevelops, it will likely be classified as a post-tropical cyclone within the next 24 hours. The initial intensity is lowered to 35 kt and is based on a blend of the subjective satellite intensity estimates from TAFB and SAB. The intensity forecast philosophy remains unchanged. A gradual spin-down of the cyclone should continue as deep-layer southerly shear is expected to increase while Katia moves into an inhibiting, dry and stable surrounding environment. As a result, The NHC intensity forecast is similar to the previous one except that it now shows Katia degenerating to a remnant low a little sooner, and within the next 24 hours. Katia's initial motion is estimated to be northwestward, or 310/8 kt. The cyclone is forecast to move between a large middle- to upper-tropospheric cut-off low to the west over the subtropical Atlantic and a northwest-to-southeast oriented mid-level ridge to the east during the next 36 hours or so. The picture is more explicit through the remaining portion of the forecast than in previous global model runs. As mentioned above, the cut-off feature situated west of Katia fills and retrogrades northwestward, while a deep-layer mid-latitude trough digs southeastward over the northeast Atlantic. This change in the synoptic steering pattern causes Katia to slow to a crawl and gradually turn northward, or meander, on Tuesday. The official track forecast is shifted toward the left of the previous advisory to agree more with the tightly clustered consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 03/0900Z 26.0N 31.9W 35 KT 40 MPH 12H 03/1800Z 26.6N 32.8W 30 KT 35 MPH 24H 04/0600Z 27.1N 33.7W 30 KT 35 MPH...POST-TROP/REMNT LOW 36H 04/1800Z 27.7N 34.3W 30 KT 35 MPH...POST-TROP/REMNT LOW 48H 05/0600Z 28.1N 34.7W 30 KT 35 MPH...POST-TROP/REMNT LOW 60H 05/1800Z 28.5N 34.7W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 06/0600Z 28.5N 34.2W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 07/0600Z...DISSIPATED $$ Forecaster Roberts |
