Tag Archives: visible

VIIRS View of March 2 Tornadic Storms

Posted on by
Reply

NPP/VIIRS passed over Southern Indiana on March 2 about thirty minutes before the most devastating tornadoes struck the towns of New Pekin and Henryville (among others).  At 1935 UTC, a pair of rotating thunderstorms, also known as supercells, were advancing eastward across Indiana.  The easternmost storm spawned the most damaging tornadoes.  Below is a VIIRS true color image from the NPP pass at 1935 UTC.

VIIRS True Color image of the severe storms on 2 March 2012 at 1935 UTC.

A zoomed-in visible view of the storms is below.

VIIRS I-band 1 (375-m resolution) from 2 March 2012 at 1935 UTC

The infrared (I-band 5) image is below, along with some annotations pointing out the two active supercells discussed above.  Note that the brightness temperatures associated with the overshooting top (OST) of the westernmost storm are colder than the easternmost storm, although both storms were quite strong at the time and the eastern storm ended up producing the deadlier tornadoes.  OSTs are transitory, so it’s possible that a new cold OST formed with the eastern storm shortly after the NPP pass.  These very high resolution infrared views of tornadic storms are among the first documented, given the recent launch of NPP.

VIIRS I-band 5 Infrared view from 2 March 2012 at 1935 UTC

To illustrate the effect of high resolution in the IR, below is a GOES-13 10.7 micrometer IR image from 1932 UTC, which has 4-km resolution at nadir.  The coldest brightness temperature in the westernmost storm in southern Indiana from GOES is 206.6 K, but with VIIRS it’s 195 K.

GOES-13 4-km IR Image from 1932 UTC on 2 March. Compare this image to the 375-m VIIRS image above to see the improvement provided by VIIRS over GOES.

The day after the tornadoes, relatively cloud-free skies in eastern Kentucky allowed VIIRS to see some of the tornado tracks.  In the image below, the faint white lines circled in red in Kentucky and West Virginia denote the new tornado damage paths.  When green vegetation is disrupted/destroyed, the result is typically a brighter scene at visible wavelengths.

VIIRS I-band 1 from 3 March 2012 over eastern KY and western WV. The tornado tracks are circled and show up as faint white lines

 

Tropical Cyclone Giovanna

Posted on by
Reply

Back in January, Madagascar was brushed by tropical cyclone Funso, which caused periods of heavy rain, but was a bigger deal for neighboring Mozambique. This time around, Madagascar took a direct hit from tropical cyclone Giovanna, which reached “Super Cyclone” status as category 4 storm just prior to making landfall.

VIIRS got a great look at Giovanna while it was a category 4 storm.

Visible image of Super Cyclone Giovanna

A visible image of Super Cyclone Giovanna from VIIRS channel I-1 taken at 09:47 UTC, 13 February 2012 (Thanks to Dan Lindsey)

IR-window image of Super Cyclone Giovanna

IR-window image of Super Cyclone Giovanna taken by VIIRS channel I-5 at 09:47 UTC, 13 February 2012 (Thanks to Dan Lindsey)

Fortunately, Giovanna weakened rapidly upon making landfall. Moving east to west across the center of the island and over the mountains of central Madagascar, Giovanna could not maintain its Super Cyclone status. At the time of this post, Giovanna was located over the west coast of Madagascar and down to sustained winds of 35 knots, making it a weak tropical storm. Early reports suggest between 2 and 5 people were killed, and some towns on the east coast had 60% or more of their buildings damaged or destroyed.

All things considered, the situation could have been much worse, considering residents were only given a half a day’s warning, and the primary method for disseminating weather warnings is through the use of town criers.