On 07 June 2007, severe thunderstorms moved through the Upper Midwest (blog post on that event), spawning strong tornadoes; from the SPC Storm Reports comments:

HUNDREDS OF TREES DOWN NORTH OF ZOAR. (GRB)

NUMEROUS TREES DOWN OF 1 FOOT DIAMETER AND GREATER. TRACK WAS APPROXIMATELY 1/4 MILE IN LENGTH AND 125 YARDS WIDE (MQT)

Terra MODIS data on 09 June 2007 (in the image above, at left) showed a tornado scar (much longer than 1/4 mile in length) running southwest-to-northeast through heavily forested Menominee County into Langlade County and then Oconto County in northeast Wisconsin. Terra MODIS True-Color imagery from 15 July 2015 (also in the image above, at right) (cropped from imagery at the MODIS Today website), shows that a scar persists more than 8 years later! (This persistent scar has been mentioned before on this blog here in 2009 and here in 2011).

Landsat-8 overflew northeast Wisconsin on 15 July 2015, at nearly the same time as the Terra MODIS imagery above, and those views, captured via SSEC‘s RealEarth are shown below. The scar is more evident in the shortwave infrared (Band 6, 1.61 µm) than the visible (Band 3, 0.56 µm) because the shortwave infrared channel is more sensitive to changes in vegetation. Lakes are also far more apparent in the 1.61 µm imagery because water absorbs 1.61 µm radiation; little is scattered back to the satellite for detection and water therefore appears black.

===========================================================In April 2011, an historic tornadic event occurred over the Deep South that spawned numerous strong long-track tornadoes (blog post). The tornado paths from this event were also visible from both MODIS and GOES imagery (Link). The animation below shows MODIS true color imagery from before the tornadoes, from several days after, and from early May this year. Three distinct tornado scars remain in Alabama: One runs from Tuscaloosa to Birmingham, a second is south of Tuscaloosa, and a third is north of Tuscaloosa.

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GOES-13 sounder Convective Available Potential Energy (CAPE) derived product images (above; click to play animation) showed a large cluster of of severe thunderstorms that developed in eastern Kansas and moved southeastward across southern Missouri into northern Arkansas during the day on 14 July 2015. Due to strong surface heating and ample low-level moisture ahead of the storms, the atmosphere became quite unstable with GOES sounder CAPE values reaching the 5800-6000 J/kg range (lighter violet color enhancement) by 16 UTC. A long swath of damaging winds (SPC storm reports) was produced by these storms.

The visible and infrared images below show snapshots of this severe convective cluster at 3 different times, using high-resolution data from instruments on polar-orbiting satellites: Terra MODIS at 1657 UTC, Suomi NPP VIIRS at 1851 UTC, and POES AVHRR at 1916 UTC. The coldest cloud-top IR brightness temperatures were -83º C on the MODIS image, -86º C on the VIIRS image, and -87º C on the AVHRR image.

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Himawari-8 10.35 µm infrared imagery showed an unusual (for infrared imagery) double-eyewall structure in Typhoon Nangka over the western Pacific Ocean on 13 July 2015. For such a feature to appear in infrared imagery, the secondary circulations of both the inner and outer eyewall need to be intense enough to support the downdraft/cloud-clearing necessary to create the “moats” between them. Microwave imagery of the storm, below, viewed via MIMIC (from this site), also showed the double eyewall structure quite well. This double-eyewall signature typically indicates that a tropical cyclone is experiencing an eyewall replacement cycle (ERC), which signals that a (temporary) decrease in intensity is soon to follow.

Several hours later, a DMSP SSMIS 85 GHz microwave image at 1756 UTC, below, indicated that the ERC was essentially complete. Subsequently, the Joint Typhoon Warning Center slightly downgraded the intensity of Typhoon Nangka for their 21 UTC advisory. While not as well-defined as in the Himawari-8 imagery, the double-eyewall signature was still evident in the lower-resolution (4-km, vs  2-km) MTSAT-2 IR imagery (animation).

The Himawari-8 Target Sector was centered over Typhoon Nangka during this time; an IR image animation with a 2.5-minute timestep, below (courtesy of William Straka, SSEC), showed the evolution of the double eyewall signature, along with 2 pulses of storm-top gravity waves which propagated radially outward away from the center in the northern semicircle of the typhoon.

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A strong mesoscale convective system (MCS) moving southeastward through the Upper Midwest from late 12 July 2015 into early morning 13 July caused numerous severe wind reports across Minnesota and Wisconsin. This MCS was forecast to drop southeastward and continue to produce severe weather during the day on 13 July 2015 (Storm Prediction Center outlook). The toggle above shows the 0420 UTC Terra MODIS 11.0 µm image and the 0400 UTC GOES-13 Sounder DPI Lifted Index product (which is available in realtime here). As the MCS moved over southern Wisconsin, the coldest cloud-top IR brightness temperature on the 0826 UTC MODIS 11.0 µm IR image was -85º C. The strong system continued to move southeastward as very unstable air as diagnosed by the Sounder fed into it (click here for 850-mb RAOB plots). The 0746 UTC Suomi NPP VIIRS 11.45 µm IR image, below, also toggled with a GOES-13 Sounder Lifted Index product, showed a similar story: very strong convection downwind of a source of strong instability. The GOES Sounder can also diagnose Convective Available Potential Energy (CAPE), with values from 5000-6000 J/kg seen over southern Minnesota and eastern Iowa.

The Suomi NPP VIIRS Day/Night Band, below, which is a source of visible imagery at night, depicted signatures of the active lightning that accompanied this system: numerous along-scan bright streaks over southern Wisconsin were caused by lightning illuminating the cloud as the VIIRS instruments scanned the cloud top. This toggle showed a comparison of Day/Night Band and 11.45 µm Infrared imagery.

A closer view comparing the 0746 UTC VIIRS IR and Day/Night Band images, below, includes overlays of METAR reports and both 15-minute and 1-hour cloud-to-ground lightning strikes. The coldest VIIRS cloud-top IR brightness temperature was -78º C.

At 0805 UTC, the coldest CLAVR-x POES AVHRR Cloud Top Temperature value was -81º C, with maximum Cloud Top Height values of 15 km along the southwestern portion of the MCS.

This image of Radar Composites of the main line of storms was produced by Greg Carbin of SPC and was posted on Facebook on 13 July 2015.

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