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| #1153044 (Received by flhurricane at: 4:56 AM 16.Sep.2023) TCDAT4 Tropical Storm Margot Discussion Number 36 NWS National Hurricane Center Miami FL AL142023 900 AM GMT Sat Sep 16 2023 This morning, Margo's structure on satellite imagery has degraded some. Cloud top temperatures surrounding the tropical cyclone have been gradually warming, and there is evidence of northerly vertical wind shear beginning to impinge on the storm due to flow from a poleward amplifying upper-level anticyclone. The subjective intensity estimates from TAFB and SAB have been slowly decreasing, though the AiDT, D-PRINT, & D-MINT estimates remain a bit higher. A compromise of these various data support a slightly weaker intensity of 50 kt on this advisory. Margot continues to execute a slow clockwise turn, with the estimated motion now southwestward at 220/6 kt. A gradual turn to the west and then northwest is anticipated over the next 24-36 hours as the cyclone rounds the southern periphery of a mid-level ridge shifting gradually northeast of Margot. It is interesting to note that Margot's track evolution over the last several days appears to have been remotely influenced by Lee, where mid-level height rises north of the tropical storm are in part related to diabatic ridge building downstream of Lee. Ultimately the same trough that is phasing with post-tropical cyclone Lee will pick up Margot as well, with the cyclone turning northeast and even eastward by the end of the forecast. The latest track forecast is not far off the previous forecast, but a little farther to the south and west over the first day or so, adjusting a bit towards the reliable consensus aids. The vertical wind shear diagnosed by SHIPS guidance is not expected to abate much over the next 24 hours, and Margot will be moving over its own cold wake it previously generated along its forecast track. Thus, weakening is anticipated, and simulated satellite imagery from both the GFS and ECMWF suggest that the cyclone may cease to produce enough convection to qualify as a tropical cyclone sometime in the 36-48 hour period, though this is not explicitly shown. However, most of the guidance agrees a favorable trough interaction may result in a convective resurgence in the 60-72 h time period, and the latest intensity forecast shows some re-intensification during that time period. The trough is expected to ultimately leave behind Margot, with increasing shear and cooler sea-surface temperatures likely to result in the system becoming a post-tropical cyclone for good in the day 4-5 day time period. FORECAST POSITIONS AND MAX WINDS INIT 16/0900Z 35.0N 38.3W 50 KT 60 MPH 12H 16/1800Z 34.5N 39.4W 45 KT 50 MPH 24H 17/0600Z 34.3N 41.1W 40 KT 45 MPH 36H 17/1800Z 34.8N 42.5W 35 KT 40 MPH 48H 18/0600Z 36.0N 43.3W 35 KT 40 MPH 60H 18/1800Z 37.7N 41.9W 40 KT 45 MPH 72H 19/0600Z 38.9N 39.3W 45 KT 50 MPH 96H 20/0600Z 38.5N 33.0W 35 KT 40 MPH...POST-TROPICAL 120H 21/0600Z 38.5N 29.5W 30 KT 35 MPH...POST-TROP/REMNT LOW $$ Forecaster Papin |
