GOES-16 visible imagery above (click to animate) shows the development of standing waves upwind of southwestern Nova Scotia. These winds developed in a region of low-level southwesterly (i.e., onshore) flow, as shown in the 1806 UTC image below that includes surface observations.  Higher clouds are moving from a more westerly direction, suggesting veering and warm-air advection.

Note the very warm temperatures over interior Nova Scotia in the image below.  This suggests a strong inversion such as is necessary to trap energy that is then manifest as the standing waves.  Indeed, the Yarmouth, NS sounding at 1200 UTC shows surface temperatures near 12 C with temperatures closer to 20 C between 900 and 950 mb;  that works out to be a potential temperature difference of 16.5 K across the inversion.

(Thanks to Richard DiMaio, Lewis University, for bringing this event to our attention!)

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GOES-16 visible imagery, above, shows a line of convection moving over Lake Superior late in the day on 25 May 2021. Merged MRMS Radar Reflectivity at 2340 UTC, below, (from this website) shows radar echoes approaching 45 dBz (at a fair distance from the radars being used to produce the imagery). What kind of surface winds are likely associated with this system in the middle of Lake?

Synthetic Aperture Radar data from the Canadian satellite RADARSat Constellation Mission-3 (RCM3), below, (from this website), shows winds in excess of 50 knots. The winds show a bowing structure as well. RCM data are very useful in lake/oceanic regions where surface data are sparse.

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GOES-16 (GOES-East) Split Window Difference images (above) showed widespread strong winds across the Dakotas and northern Minnesota which were responsible for producing plumes of blowing dust (darker shades of gray) — most notably from eastern North Dakota into northwestern Minnesota — on 24 May 2021.

The corresponding GOES-16 Split Window Difference images with plots of surface visibility are shown below — at 23 UTC the visibility dropped to 4 miles at Grand Forks, North Dakota as a dense dust plume moved through that location (where southwesterly winds were gusting to 31 knots at that time).

GOES-16 True Color RGB images (above) and Dust RGB images (below) created using Geo2Grid highlighted the more dense plumes of blowing dust — the source region for the more prominent dust plumes appeared to be dry agricultural fields in southeastern North Dakota that had received very little rainfall during the preceding week.

Ground-based lidar data from Grand Forks indicated that the dust was lofted to altitudes of around 10,000 feet.

Plenty of backscatter thanks to the dust pic.twitter.com/bQDpSIwXry

— Aaron Kennedy (@KennedyClouds) May 24, 2021

===== 25 May Update =====

Strong winds persisted across that same region on 25 May — and GOES-16 Dust RGB images (above) again displayed the subtle signature of blowing dust (light shades of pink/magenta) along the leading edge of cloudiness that was moving eastward into northwestern Minnesota.

GOES-16 True Color RGB images (below) once again showed the hazy signature of blowing dust.

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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.

===== 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.

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

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).

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