Tropical Storm Wanda Forecast Discussion Number 18
ActuCyclone
4 novembre 2021
000 WTNT41 KNHC 040847 TCDAT1 Tropical Storm Wanda Discussion Number 18 NWS National Hurricane Center Miami FL AL212021 900 AM GMT Thu Nov 04 2021 Wanda continues to exhibit bands of moderately deep convection, and these bands are strongest most numerous over the western portion of the circulation. The upper-level outflow has become better defined, also over the western semicircle. Overall, however, the intensity of the convection has diminished slightly over the past several hours. The advisory intensity is held at 45 kt, which is in agreement with Dvorak Current Intensity numbers from both SAB and TAFB. This is also in good agreement with earlier scatterometer measurements. The initial motion continues to be just east of north, or 010/8 kt along the eastern side of a mid-latitude shortwave trough. This trough is expected to weaken very soon and Wanda should slow its forward speed later this morning. During the next 48 hours, a narrow ridge is forecast to build to the northwest of the cyclone and force it to turn eastward tonight and then southward on Friday. By 72 hours, another mid-latitude trough approaching Wanda should finally cause the system to begin to accelerate northeastward. The dynamical model guidance is in reasonably good agreement on the evolution of the steering pattern over the next several days. There has been little change to the official track forecast, which remains close to the model consensus, and near the middle of the guidance envelope. Although Wanda is located over cool 20-21 deg C sea surface temperatures, it has been able to maintain some deep convection and winds of 45 kt. On its projected path during the next day or two, water temperatures beneath Wanda are not likely to get much cooler and the upper-tropospheric temperatures are forecast to decrease somewhat. This could allow for some slight strengthening, as indicated by the official intensity forecast. In 4 to 5 days, the global models show the system becoming embedded in a frontal zone over the north Atlantic, so the NHC forecast calls for Wanda to revert back to extratropical status by that time. FORECAST POSITIONS AND MAX WINDS INIT 04/0900Z 41.5N 39.5W 45 KT 50 MPH 12H 04/1800Z 42.1N 39.3W 50 KT 60 MPH 24H 05/0600Z 41.7N 38.2W 50 KT 60 MPH 36H 05/1800Z 40.1N 37.5W 50 KT 60 MPH 48H 06/0600Z 38.4N 37.5W 50 KT 60 MPH 60H 06/1800Z 38.2N 37.0W 45 KT 50 MPH 72H 07/0600Z 39.8N 35.0W 45 KT 50 MPH 96H 08/0600Z 47.0N 26.0W 45 KT 50 MPH...POST-TROP/EXTRATROP 120H 09/0600Z 52.0N 16.0W 40 KT 45 MPH...POST-TROP/EXTRATROP $$ Forecaster Pasch