Tropical Storm Wanda Forecast Discussion Number 20
ActuCyclone
4 novembre 2021
000 WTNT41 KNHC 042042 TCDAT1 Tropical Storm Wanda Discussion Number 20 NWS National Hurricane Center Miami FL AL212021 900 PM GMT Thu Nov 04 2021 Wanda continues to maintain bands of moderately deep convection near the center, mainly over the northwestern semicircle. The cyclone also continues to show anticyclonic outflow. However, cold air clouds continue to wrap around the southern side of the circulation, and in the big picture Wanda still gives the appearance of being embedded in a larger-scale baroclinic low. There has been little change in the satellite intensity estimates since the previous advisory, so the initial intensity is held at 40 kt. Wanda is starting its anticipated turn and the initial motion is now 045/5. During the next day or two, a narrow mid-latitude ridge is forecast to build to the northwest of the cyclone, and this should cause Wanda to turn southeastward and southward by the 48 h point. By 60-72 h, another mid-latitude trough approaching Wanda should cause a northeastward turn with acceleration, with this motion persisting through the end of the forecast period. The new guidance again shows a little more southward motion by 48 h than the previous guidance, and the new forecast track is adjusted a little southward near that time. Little change in strength is likely during the next 24 h as Wanda remains over sea surface temperatures of near 20C. By 48 h, the southward motion brings the center over slightly warmer water, and at that time the cyclone should interact with an upper-level low that develops nearby. This combination could allow some strengthening, and the intensity forecast show modest strengthening from 24-48 h. Many of the guidance models continue to show more strengthening and a higher intensity than the official forecast between 48-72 h, and some adjustment may be needed to that part of the forecast in later advisories if this trend persists. Between 72-96 h, Wanda is expected to merge with a frontal system and become extratropical over the northeastern Atlantic. FORECAST POSITIONS AND MAX WINDS INIT 04/2100Z 42.4N 39.2W 40 KT 45 MPH 12H 05/0600Z 41.9N 38.7W 40 KT 45 MPH 24H 05/1800Z 40.1N 38.2W 40 KT 45 MPH 36H 06/0600Z 38.5N 38.1W 45 KT 50 MPH 48H 06/1800Z 38.0N 37.7W 50 KT 60 MPH 60H 07/0600Z 39.2N 35.9W 50 KT 60 MPH 72H 07/1800Z 42.6N 32.2W 50 KT 60 MPH 96H 08/1800Z 49.0N 23.0W 45 KT 50 MPH...POST-TROP/EXTRATROP 120H 09/1800Z 53.0N 12.5W 35 KT 40 MPH...POST-TROP/EXTRATROP $$ Forecaster Beven