Subtropical Storm Potira off the coast of Brazil

April 20th, 2021 |

GOES-16 “Red” Visible (0.64 µm) images [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) images [click to play animation | MP4]

1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed the circulation of Subtropical Storm Potira (warning issued by MARINHA) off the southeast coast of Brazil on 20 April 2021.

In the corresponding 1-minute GOES-16 “Clean” Infrared Window (10.35 µm) images (below), intermittent convective overshooting tops exhibited infrared brightness temperatures as cold as -60 to -65ºC (shades of orange).

GOES-16 “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

GOES-16 “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

Combined plots of all GOES-16 Atmospheric Motion Vector types — Visible, Infrared and Water Vapor — and pressure levels at 15-minute intervals (below) displayed the cloud motions of Potira (credit: Dave Stettner and Chris Velden, CIMSS). The algorithm used to generate these AMVs differs slightly from that used to create operational Derived Motion Winds: some constraints are relaxed/removed, and Visible winds are calculated at pressure levels above 700 hPa — all of which results in the display of a higher density of tracked targets and their calculated wind vectors.

Combined plot of all GOES-16 Atmospheric Motion Vector types (Visible, Infrared and Water Vapor) at 15-minute intervals [click to play animation | MP4]

Combined plots of all GOES-16 Atmospheric Motion Vector types (Visible, Infrared and Water Vapor) and pressure levels, at 15-minute intervals [click to play animation | MP4]

A sequence of EUMETSAT Metop ASCAT surface scatterometer winds (source) is is shown below — the strongest winds were located within the southern sector of the storm, well away from the center of circulation.

Metop ASCAT surface scatterometer winds [click to enlarge]

Metop ASCAT surface scatterometer winds [click to enlarge]

===== 22 April Update =====

GOES-16 “Red” Visible (0.64 µm) images [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) images [click to play animation | MP4]

1-minute GOES-16 Visible images (above) showed that the low-level circulation center of Potira remained exposed on 22 April — while GOES-16 Infrared images (below) indicated that deep convection remained south and west of the storm center.

GOES-16 “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

GOES-16 “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]