Sentinel-1A overflew the western Hawai’ian islands late on 4 April 2023, observing surface winds around the islands of Kaua’i and Ni’ihau. The image above shows the winds overlain on top of a GOES-18 infrared image. A pronounced region of light winds extends downwind of both islands — the region in purple shows winds of 5 knots or less.

MetopB overflew the Hawai’ian island chain about 3 hours after Sentinel-1A did (link), and its overpass was also bookended by two MetopC overpasses (shown here). Those two wind plots are shown below (from this website). Neither satellite gave information where the SAR Winds occurred, and the slack winds in the lee of the islands would likely not be resolved by ASCAT’s 25-km footprint.

A GOES-18 animation of visible imagery before and through the SAR overpass is shown below. It is very difficult to identify a region of slack winds around the islands from the visible imagery. Modest convection forms in the lee of Ni’ihau as the sun sets. The Band 13 animation at bottom shows the convection to be short-lived.

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Sentinel-1A SAR winds are available at this NOAA/NESDIS/STAR website. The toggle below shows the winds and the Normalized Radar Cross Section field at 0446 UTC on 4 April from that site.

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The 3-4 April 1974 Super Outbreak (NWS Wilmington OH | Wikipedia | StoryMap | Interacive WebMap | Monthly Weather Review) was one of the largest and most deadly tornado outbreaks on record in the United States. Several images from the ATS-3 satellite are shown below (thanks to the work of SSEC Satellite Data Services and Atmospheric, Oceanic and Space Sciences Library staff!). The University of Wisconsin-Madison Space Science and Engineering Center recently digitized over 66,000 Applications Technology Satellite (ATS)-1 and -3 images from the late 1960s to early 1970s. ATS-1 and -3 were experimental NASA geostationary satellites that carried Verner Suomi’s Spin-Scan Cloud Camera (SSCC). The camera, developed at UW/SSEC, allowed for nearly continuous viewing (usually every 30 minutes) of weather systems. Some of these images have been added to the UW Digital Collections (The “Super Outbreak“). Much work remains to prepare the larger dataset for use, including adding day/time stamps, quality control and navigation correction of the images.

The SSCC on ATS-1 and -3 had only visible spectral bands, hence only provided imagery during the daylight hours.

15-minute Imagery

Normally, the ATS-3 acquired a Full Disk scan approximately every 30 minutes — but during this event two Northern Hemisphere sectors were scanned, providing 15-minute imagery for part of April 3, 1974. Individual images from 1941 UTC to 2307 UTC are displayed below. Large clusters of thunderstorms that produced many of the tornadoes were very apparent, along with a hazy plume of blowing dust that moved across much of North Texas in the wake of a strong cold front (surface analysis).

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This year will mark the 50th anniversary of the “Super Outbreak” of April 1974. The event was unique for the number of tornado touchdowns, the number of F5 tornadoes, and the conditions that fostered their formation. Also unique is that the University of Wisconsin-Madison Space Science and Engineering Center recently digitized over 66,000 Applications Technology Satellite (ATS)-1 and -3 images from the late 1960s to early 1970s. These include ATS-3 visible images from April 3, 1974 that clearly show the development of the squall lines. ATS were experimental NASA geostationary satellites that carried the Spin Scan Cloud Camera. The camera, developed at SSEC, allowed for nearly continuous viewing of weather systems, like the Super Outbreak.

The 3-4 April 1974 Super Outbreak (NWS Wilmington OH | Wikipedia | Interacive WebMap | Monthly Weather Review) was one of the largest and most deadly tornado outbreaks on record in the United States. Several images from the ATS-3 satellite are shown below (thanks to the work of SSEC Satelite Data Services and Atmospheric, Oceanic and Space Sciences Library staff!). Large clusters of thunderstorms that produced the tornadoes are very apparent, along with a hazy plume of blowing dust that moved across much of North Texas.

HT

This blog post leverages a similar post from 2023.

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With a strong midlatitude cyclone centered over Iowa on 31 March 2023, the Storm Prediction Center (SPC) outlined 2 areas of relatively rare High Risk for severe weather — and GOES-16 (GOES-East) Total Precipitable Water along with the Lifted Index (LI) and Convective Available Potential Energy (CAPE) Derived Stability Indices (above) showed that a corridor of moisture and instability was in place along and ahead of the primary cold front (surface analyses).

1-minute Mesoscale Domain Sector GOES-16 “Clean” Infrared Window (10.3 µm) images (below) included plots of time-matched (+/- 3 minutes) SPC Storm Reports during the period from 1615 UTC on 31 March to 1137 UTC on 01 April.

One event of note was the EF3-rated tornado that affected Little Rock, Arkansas — GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images (below) included time-matched SPC Storm Reports.

1-minute GOES-16 Visible/Infrared Sandwich RGB images (below) included polygons of Severe Thunderstorm and Tornado Warnings — note that at one point a bold Tornado Emergency was issued.

Farther to the north, 1-minute GOES-16 Visible images (below) showed the widespread severe weather across the Midwest during the daytime hours.

1-minute GOES-16 Visible/Infrared Sandwich RGB images (below) included plots of time-matched Local Storm Reports — showing the storm which produced an EF4-rated tornado that moved from Wapello into Johnson County in eastern Iowa (NWS Quad Cities summary).

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