918 WTNT45 KNHC 232039 TCDAT5 Hurricane Tammy Discussion Number 22 NWS National Hurricane Center Miami FL AL202023 500 PM AST Mon Oct 23 2023 Moderate southwesterly vertical wind shear seems to be disrupting Tammy's circulation. Deep convection is being pulled northward away from the estimated low-level center and mid-level dry air is working its way around the southern side of the cyclone. Satellite intensity estimate have decreased this cycle to 55 and 65 kt from SAB and TAFB, respectively. The initial intensity has therefore been lowered to 65 kt. While ASCAT missed the majority of the hurricane's core, it did show winds on the western portion of the circulation have decreased and the radii have been adjusted inward accordingly. Tammy is moving north-northeastward at 6 kt. A turn toward the northeast is forecast shortly as Tammy is steered by a mid-level ridge centered over the central subtropical Atlantic and the flow ahead of a mid-latitude trough over the western Atlantic. Between 48-60 h, the model solutions begin to bifurcate. The ECMWF turns the hurricane northward and then westward by the end of the forecast period. The GFS and regional models tend to turn Tammy toward the north and northeastward by day 5. The official forecast still favors the ECMWF forecast and is similar to the previous advisory. Models suggest that environmental conditions will be relatively unfavorable. The deep-layer vertical wind shear is forecast to increase and surrounding mid-level moisture to decrease through most of the forecast period. However, in a day or so, when the hurricane begins to interacts with the trough to its west, upper-level divergence could enhance convection and cause some strengthening through about 48 h. Tammy is then expected to gradually weaken and complete its transition into an extratropical cyclone by day 3. The NHC intensity forecast is similar to the previous prediction, with a slightly lower peak intensity of 75 kt. FORECAST POSITIONS AND MAX WINDS INIT 23/2100Z 22.3N 63.6W 65 KT 75 MPH 12H 24/0600Z 23.0N 62.9W 70 KT 80 MPH 24H 24/1800Z 24.0N 61.7W 75 KT 85 MPH 36H 25/0600Z 25.3N 60.3W 75 KT 85 MPH 48H 25/1800Z 26.8N 59.0W 75 KT 85 MPH 60H 26/0600Z 28.9N 58.6W 70 KT 80 MPH 72H 26/1800Z 30.3N 59.3W 60 KT 70 MPH...POST-TROP/EXTRATROP 96H 27/1800Z 31.7N 62.1W 50 KT 60 MPH...POST-TROP/EXTRATROP 120H 28/1800Z 32.5N 65.2W 45 KT 50 MPH...POST-TROP/EXTRATROP $$ Forecaster Bucci