May 21st, 2021 | Scott Bachmeier
1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images (above) displayed the exposed low-level circulation of Invest 90L, in the Atlantic Ocean (about 150 miles northeast of Bermuda, TXKF) on 21 May 2021.
GOES-16 Visible images with plots of Derived Motion Winds (below) revealed a few wind speeds of 50 knots or greater (red wind barbs) within its northwest quadrant — but since no organized and sustained deep convection remained in close proximity to the low-level circulation, Invest 90L was not yet considered to be a tropical cyclone.
===== 22 May Update =====
During the overnight hours, convection organized and intensified around the low-level circulation of Invest 90L — and as of 0900 UTC it was classified as Subtropical Storm Ana. GOES-16 Infrared images of Ana are shown above.
GOES-16 Visible images (below) indicated that the center of Ana eventually stopped moving southwestward toward Bermuda, performed a counterclockwise loop, then began moving to the northeast.
GOES-16 Visible images with plots of Derived Motion Winds (below) indicated that the maximum near-surface wind speeds were 39 knots.