Wanda Transitions to a Tropical Storm

Former Subtropical Storm Wanda made a transition to a tropical storm on Monday afternoon. At 5:00 p.m. EDT on Monday the center of Tropical Storm Wanda was located at latitude 34.2°N and longitude 42.2°W which put it about 885 miles (1425 km) west-southwest of the Azores. Wanda was moving toward the east-northeast at 7 m.p.h. (11 km/h). The maximum sustained wind speed was 45 m.p.h. (75 km/h) and there were wind gusts to 60 m.p.h. (95 km/h). The minimum surface pressure was 996 mb.

The structure of former Subtropical Storm Wanda changed on Monday. The low level center of Wanda became separated from the upper level low that was previously over the top of it. So, the two centers were no longer vertically stacked. In addition, the wind field around Wanda contracted and the strongest winds were located closer to the center of circulation. Since the new structure of Wanda was more consistent with the structure of a tropical cyclone, the National Hurricane Center reclassified Wanda as a tropical storm.

The circulation around Tropical Storm Wanda was smaller. Winds to tropical storm force extended out 45 miles (75 km) from the center of Wanda. The strongest thunderstorms were occurring in bands on the eastern side of Wanda’s circulation. Since Wanda was over water where the Sea Surface Temperature is near 24˚C, the thunderstorms were not as tall as ones that occur in tropical storms farther south. Bands in the western half of the tropical storm consisted primarily of showers and lower clouds. The storms on the eastern side of Wanda generated upper level divergence that pumped mass away to the northeast of the tropical storm.

Tropical Storm Wanda will move through an environment that is somewhat favorable for intensification during the next 24 hours. Wanda will move over water where the Sea Surface Temperatures are near 24˚C. Tropical Storm Wanda will be on the eastern side of the axis of the upper level trough. The upper level trough will produce southwesterly winds that will blow toward the top of Wanda’s circulation. Those winds will cause some vertical wind shear but the wind shear may be weak enough to allow for some intensification. Sinking, drier air could limit the formation of new thunderstorms on the western side of Wanda’s circulation and that could also inhibit intensification. Since Tropical Storm Wanda is now a smaller, more compact storm, it could extract enough energy from the Atlantic Ocean to be able to strengthen during the next 24 hours.

Since Tropical Storm Wanda is east of the axis of the upper level trough, southwesterly winds will steer Wanda toward the north-northeast during the next 36 hours. Wanda could move more toward the east later this week when it reaches a region where westerly winds are stronger. On its anticipated track Tropical Storm Wanda could approach the western Azores at the end of the week.