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#1059826 (Received by flhurricane at: 11:08 AM 01.Sep.2021) TCDAT5 Tropical Depression Kate Discussion Number 18 NWS National Hurricane Center Miami FL AL102021 1100 AM AST Wed Sep 01 2021 It has been difficult to pinpoint where the low-level circulation of Kate is this morning. After last night`s diurnal convective maximum, the remaining convection has taken on a very disorganized structure, with a mid-level vortex being left behind to the south, while deeper, but more outflow driven convection is racing off to the north, ahead of the estimated low-level center position. A recently received 1211 UTC ASCAT-A pass indicated that Kate`s low-level circulation is still closed, but just barely. The scatterometer wind data supports maintaining the current intensity at 30-kt, which also agrees with the latest subjective and objective Dvorak estimates. The estimated motion is continuing off to the north-northwest, at 340/9 kt. Kate appears to now be primarily steered by the low-level flow around a subtropical ridge located to its east. A general north-northwest motion is expected to continue today, followed by a turn to the north and north-northeast around the periphery of this ridge. The latest NHC track guidance has been adjusted a bit right of the previous track, shifting towards the latest consensus guidance (TVCN) that can still track the cyclone beyond 24 hours. A 0958 UTC SSMIS microwave pass suggested that the better organized structure observed last night has decayed, with the low- and mid-level centers quite misaligned. Vertical wind shear diagnosed by SHIPS is now between 15-20 kt out of the north. This shear is likely contributing to the vortex tilt, while also helping to import very dry mid-level air, preventing Kate`s convective activity from organizing. The bulk of the intensity guidance is in agreement that gradual spin down of the low-level circulation will occur over the next several days, with the deterministic ECMWF model suggesting Kate could open up to a trough as soon as tomorrow. The latest NHC intensity forecast makes Kate a remnant low in 36 hours, with dissipation after 48 hours. However, given the current structure, this could occur sooner than forecast. FORECAST POSITIONS AND MAX WINDS INIT 01/1500Z 26.8N 52.3W 30 KT 35 MPH 12H 02/0000Z 27.9N 52.7W 25 KT 30 MPH 24H 02/1200Z 29.6N 53.1W 25 KT 30 MPH 36H 03/0000Z 31.1N 53.2W 20 KT 25 MPH...POST-TROP/REMNT LOW 48H 03/1200Z 32.4N 52.5W 20 KT 25 MPH...POST-TROP/REMNT LOW 60H 04/0000Z...DISSIPATED $$ Forecaster Papin |