Subtropical storm Raoni off the coast of South America

June 28th, 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]

GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed the circulation of Subtropical Storm Raoni (discussion issued by MARINHA) off the coast of Argentina/Uruguay on 28 June 2021.

In the corresponding GOES-16 “Clean” Infrared Window (10.35 µm) images (below), the coldest cloud tops exhibited infrared brightness temperatures around -50ºC (shades of yellow).

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]

===== 29 June 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]

GOES-16 Visible images (above) showed that Subtropical storm Raoni continued its northeastward motion, and was located off the coast of far southeastern Brazil on 29 June (12 UTC surface analysis | discussion).

GOES-16 Infrared images (below) indicated that Raoni was unable to maintain a persistent closed ring of cold clouds around its 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]

A sequence of ASCAT surface scatterometer winds (source) from Metop-A and Metop-C (below) revealed swaths of wind speeds of 40 knots or greater within the northeastern and southwestern sectors of the system.

ASCAT winds from Metop-A and Metop-C [click to enlarge]

ASCAT winds from Metop-A and Metop-C [click to enlarge]

Tropical Invest 90L becomes Subtropical Storm Ana in the Atlantic

May 21st, 2021 |

GOES-16 Visible and Infrared images [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

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 Visible 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.

GOES-16

GOES-16 “Red” Visible (0.64 µm) images, with plots of Visible GOES-16 Derived Motion Winds [click to play animation | MP4]

===== 22 May Update =====

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]

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.

A closer view of 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 "Red" Visible (0.64 µm) images [click to play animation | MP4]

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

GOES-16 Visible images with plots of Derived Motion Winds (below) indicated that the maximum near-surface wind speeds were 39 knots.

GOES-16 "Red" Visible (0.64 µm) images, with plots of Derived Motion Winds [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) images, with plots of Visible GOES-16 Derived Motion Winds [click to play animation | MP4]

GOES-16 "Red" Visible (0.64 µm) images, with plots of Metop-A ASCAT winds [click to enlarge]

GOES-16 “Red” Visible (0.64 µm) image at 1219 UTC, with plots of Metop-A ASCAT winds [click to enlarge]

An overpass of Metop-A at 1219 UTC provided ASCAT surface scatterometer winds centered on Ana (above), with a maximum speed value of 31 knots just northwest of the storm center. In general, Visible GOES-16 Derived Motion Wind speed values were around 5 knots faster than nearby ASCAT winds (below) — since the former are computed by tracking cloud targets that are above the surface, where winds speeds are greater (due to a lack of surface friction).

GOES-16 "Red" Visible (0.64 µm) image at 1219 UTC, with plots of Visible GOES-16 Derived Motion Winds and Metop-A ASCAT winds [click to enlarge]

GOES-16 “Red” Visible (0.64 µm) image at 1219 UTC, with plots of Visible GOES-16 Derived Motion Winds and Metop-A ASCAT winds [click to enlarge]

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]

Cyclone Habana in the South Indian Ocean

March 10th, 2021 |

US Space Force EWS-G1 Infrared Window (10.7 µm) images [click to play animation | MP4]

US Space Force EWS-G1 Infrared Window (10.7 µm) images [click to play animation | MP4]

US Space Force EWS-G1 Infrared Window (10.7 µm) images (above) displayed the well-defined eye and eyewall structure of Cyclone Habana in the South Indian Ocean on 10 March 2021. This was the second period of Category 4 intensity (ADT | SATCON) during the life cycle of Habana.

Meteosat-8 Infrared images with contours of deep-layer wind shear from the CIMSS Tropical Cyclones site (below) showed that Habana was moving through an environment of relatively low shear.

Meteosat-8 Infrared images, with contours of deep-layer wind shear [click to enlarge]

Meteosat-8 Infrared images, with contours of deep-layer wind shear [click to enlarge]

Meteosat-8 Infrared images with an overlay of 1505 UTC Metop ASCAT winds (below) depicted a fairly uniform distribution of winds within the eyewall region, as Habana developed an annular structure.

Meteosat-8 Infrared images, with a plot of Metop ASCAT winds [click to enlarge]

Meteosat-8 Infrared images, with a plot of Metop ASCAT winds [click to enlarge]

SSMIS Microwave (85 GHz) images from DMSP-16 at 1139 UTC and DMSP-18 at 2327 UTC are shown below.

DMSP-16 SSMIS Microwave (85 GHz) image at 1139 UTC [click to enlarge]

DMSP-16 SSMIS Microwave (85 GHz) image at 1139 UTC [click to enlarge]

DMSP-18 SSMIS Microwave (85 GHz) image at 2327 UTC [click to enlarge]

DMSP-18 SSMIS Microwave (85 GHz) image at 2327 UTC [click to enlarge]