Apr 19, 2017

Rare April Subtropical Depression Forms in the Atlantic

Atlantic Ocean
by
Jeff Masters
,
Category 6

A rare April Atlantic subtropical depression was born on Wednesday morning, when Subtropical Depression One formed in the Eastern Atlantic about 890 miles west-southwest of the Azores Islands. The ASCAT satellite instrument estimated that storm had top winds of about 35 mph on Wednesday morning. Subtropical Depression One has very marginal conditions for development: waters are about 20°C (69°F), well below the 26.5°C (80°F) temperatures usually needed to sustain a tropical storm. However, upper-air temperatures are quite cold, which is making the atmosphere unstable enough to support the sustained heavy thunderstorms needed to classify this as a subtropical depression. Wind shear is high, 20 – 25 knots, which should prevent much intensification.