How long can Tornado Scars last?

July 22nd, 2015
MODIS True-Color Image,  June 9, 2007 (left) and  July 15, 2015 (right) (click to enlarge)

MODIS True-Color Image, June 9, 2007 (left) and July 15, 2015 (right) (click to enlarge)

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.

Landsat-8 band 3 (0.56 µm) and Band 6 (1.61 µm) imagery, ~1640 UTC July 15, 2015 (click to enlarge)

Landsat-8 band 3 and Band 6 imagery, ~1640 UTC July 15, 2015 (click to enlarge)


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In April 2011, an historic tornadic event occurred over the Deep South that spawned numerous strong long-tracked 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.

MODIS True-Color Imagery over Alabama, 13 April and 29 April in 2011 and 01 May in 2015 (click to enlarge)

MODIS True-Color Imagery over Alabama, 13 April and 29 April in 2011 and 01 May in 2015 (click to enlarge)

Why 1-minute data matters: Beavertails

June 4th, 2015
GOES-14 Visible (0.6263 µm) Imagery, 04 June 2015.  1-minute imagery on the left, 5-minute imagery on the right (click to play animation)

GOES-14 Visible (0.6263 µm) Imagery, 04 June 2015. 1-minute imagery on the left, 5-minute imagery on the right (click to play animation)

Beavertails are ephemeral cloud features that form in the inflow of supercell thunderstorms. They are horizontally long and roughly parallel to the inflow warm front. Its appearance (and presence) is affected by and influences inflow into the storm, and by inference, it affects radar returns. That is — a change in the Beavertail cloud can precede a change in radar. Accurate detection of this cloud type, then, aids the understanding of evolving storm morphology. The animation above shows a severe convective system over southeastern Wyoming, viewed at 1-minute intervals (Left) and at 5-minute intervals. Beavertails that form persist for about 30 minutes, so 5-minute imagery will resolve them; however, the resolution of the 1-minute data is far better to monitor the small changes in size and shape that are related to storm inflow.

Do beavertail changes affect the radar? The animation below shows the ProbSevere product readout from 2000-2220 UTC (Courtesy John Cintineo, CIMSS) (Click here for a slow animation). (Click here for an animation (from 1918-2058 UTC) that includes warning polygons). The increases and decreases in the MRMS MESH appear unrelated to the formation/decay of the various beavertails.

NOAA/CIMSS ProbSevere Product, 2000-2020 UTC on 4 June 2015 (click to animate)

NOAA/CIMSS ProbSevere Product, 2000-2020 UTC on 4 June 2015 (click to play animation)

This storm was captured by different chasers. This YouTube video from Scott Longmore shows the evolution of the convective system from the ground. Hat/tip to Jennifer Laflin, NWS EAX and Chad Gravelle, OPG, for alerting us to this case.

Bore over Kansas

June 3rd, 2015
GOES-13 Imager 0.63 µm visible channel images (click to play animation)

GOES-13 Imager 0.63 µm visible channel images (click to play animation)

Visible imagery after sunrise on 3 June 2015 over Kansas, above, shows the parallel lines of low clouds that characterize a bore feature. As the bore penetrated southward, winds initially shifted before becoming more variable. Bore propagation requires the presence of an inversion, and 1200 UTC Soundings from both Dodge City and from Topeka contain inversions. Because inversions are present, it is unusual for convection to form in the presence of a bore.

The initial southward push the became the bore may have emerged from strong convection over central Nebraska early in the morning of 3 June. Suomi NPP VIIRS imagery captured that convection; the Day Night Band (under near-Full Moon conditions) and 11.45 µm infrared imagery, below, show the strong convection at 0848 UTC on 3 June 2015).

Suomi NPP VIIRS 0.70 µm visible Day Night Band and 11.45 µm infrared imagery at 0848 UTC on 3 June 2015 (click to enlarge)

Suomi NPP VIIRS 0.70 µm visible Day Night Band and 11.45 µm infrared imagery at 0848 UTC on 3 June 2015 (click to play animation)

GOES-14 was performing SRSO-R observations over Kansas on 3 June. One-minute imagery of the bore evolution is available here in animated gif format (74 M in size) and here in mp4 format (2.8M in size). The YouTube video is embedded below.



Water Vapor Animations for May 2014 and May 2015

June 1st, 2015
GOES-15 Imager 6.5 µm water vapor infrared channel images (click to play animation)

GOES-15 Imager 6.5 µm water vapor infrared channel images from May 2015 (click to play animation)

Historically heavy rains fell over the southern Plains in May of 2015, with numerous stations setting record monthly rainfall marks. For example, Oklahoma City reported 19.48″ of rain in May 2015; the previous record wet month was 14.66″, set in June 1989 (14.52″ of rain fell in May 2013). The three-hourly water vapor imagery, above (Click here for mp4 file; the animated gif above exceeds 90 M), from GOES-13 shows repeated thunderstorm development over western OK and western Texas that subsequently moved east. Persistent southwesterly flow is also apparent. In comparison, three-hourly water vapor imagery from GOES-13 for May 2014, below (Click here for mp4 file), shows less frequent convection and more northwesterly flow. Widespread convection is much less frequent over the Plains in May 2014 (a month that saw 4.44″ of rain fall in Oklahoma City).

GOES-15 Imager 6.5 µm water vapor infrared channel images (click to play animation)

GOES-15 Imager 6.5 µm water vapor infrared channel images from May 2014 (click to play animation)

The mean 6.5 channel GOES-13 Brightness Temperature for May 2015 was more than 2 degrees cooler than in May 2014 (237.2 K in 2015 vs. 239.6 K in 2014). It should not be surprising that the top of the moist layer in 2015 was higher (cooler) than in 2014.