Ice jam flooding along the Yukon River in Galena, Alaska

May 28th, 2013
Suomi NPP VIIRS 1.61 µm

Suomi NPP VIIRS 1.61 µm “snow/ice discrimination channel” images

A sequence of AWIPS images of Suomi NPP VIIRS 1.61 µm near-IR “snow/ice discrimination channel” data covering the period from 13:47 UTC on 27 May to 23:24 UTC on 28 May 2013 (above) showed the effects of ice jam flooding along the Yukon River in the vicinity of Galena, Alaska (station identifier PAGA). In addition to snow and ice, water is also a strong absorber at the 1.61 µm near-IR wavelength — so it appears darker on the images. This dark signature of water inundation can be seen increasing in areal coverage during that 1.5 day period. This flooding forced the evacuation of aruond 300 residents of Galena, as many homes were extensively damaged by the flooding.

A comparison of Suomi NPP VIIRS 0.64 µm visible channel, 0.86 µm “land/water discrimination channel”, and 1.61 µm “snow/ice discrimination channel” images at 21:43 UTC on 28 May (below) showed that the Yukon River downstream of Galena was still snow/ice covered (appearing brighter white on the 0.64 µm and 0.86 µm images). Meanwhile, the darker signature of floodwaters near and upstream of Galena was evident to some extent on the 0.86 µm image, but was even more pronounced on the 1.61 µm image. The Yukon River ice jam flooding in the Galena area occurred about a week after similar ice jam floding occurred much farther upstream in the Fort Yukon area.

Suomi NPP VIIRS 0.64 µm visible channel, 0.86 µm land/water discrimination channel, and 1.61 µm snow/ice discriminatioon channel images

Suomi NPP VIIRS 0.64 µm visible channel, 0.86 µm land/water discrimination channel, and 1.61 µm snow/ice discriminatioon channel images

Flooding along the Yukon River in Alaska

May 20th, 2013
Suomi NPP VIIRS 1.61 µm near-IR "snow/ice channel" images

Suomi NPP VIIRS 1.61 µm near-IR “snow/ice channel” images

A comparison of AWIPS images of Suomi NPP VIIRS 1.61 µm “snow/ice discrimination channel” data from 19 May and 20 May 2013 (above) revealed the areal extent of flooding along the Yukon River upstream of the Fort Yukon (station identifier PFYU) area in northeastern Alaska. Both ice and water are strong absorbers at the 1.61 µm wavelength, so they appear very dark on the images. The flooding along the Yukon River began as a surge of ice and water moved through the Eagle, Alaska (station identifier PAEG) area on 17 May, then continued downstream to produce major flooding in the Circle, Alaska area on 19 May (Circle is located about halfway between PAEG and PFYU). An ice jam had formed about 12 miles upstream of Fort Yukon, which then impounded the flow of ice and water that had flooded Circle, leading to the increased flooding seen upstream of Fort Yukon on 20 May.

A comparison of Suomi NPP VIIRS 0.64 µm visible channel, 0.86 µm “land/water discrimination channel”, and 1.61 µm “snow/ice discrimination channel” at 20:52 UTC on 20 May (below) showed how the 0.86 µm and 1.61 µm images can be used to identify the darker flooded portions of the Yukon River that are not apparent on the 0.64 µm visible image.

Suomi NPP VIIRS 0.64 µm visible channel, 0.86 µm "land/water" channel, and 1.61 µm "snow/ice channel" images

Suomi NPP VIIRS 0.64 µm visible channel, 0.86 µm “land/water” channel, and 1.61 µm “snow/ice channel” images

The effect of heavy precipitation on rivers in Illinois

April 21st, 2013
Total observed precipitation during the 07-21 April 2013 period

Total observed precipitation during the 07-21 April 2013 period

The middle part of April 2013 brought periods of very heavy rainfall to portions of Illinois and the Upper Midwest region, with many areas receiving 5-7 inches of rainfall. A map of the 14-day total observed precipitation during the 07-21 April period (above) shows the widespread distribution of the heavy rainfall, which was 4-5 inches above normal and 300-400% of normal at many locations for this time of the year. Additional information can be found at the NWS Chicago and NWS Lincoln sites.

The effect of this heavy rainfall was very apparent in a before (05 April) and after (21 April) comparison of 250-meter resolution MODIS false-color Red/Green/Blue (RGB) images from the SSEC MODIS Today site (below) — obvious changes can be seen in the width of sections of the Illinois River (which runs fron northeast through southwest across the center of the images) and many of its tributaries. 138 river gauges were reporting moderate to major flooding levels on 21 April.

MODIS false-color Red/Green/Blue (RGB) images from 05 April and 21 April 2013

MODIS false-color Red/Green/Blue (RGB) images from 05 April and 21 April 2013

AWIPS image comparisons of the standard 0.64/0.65 µm visible channel with the corresponding 0.86 µm visible channel from the VIIRS and MODIS instruments (below) show that the 0.86 µm imagery can be useful for helping to monitor the areal coverage of significant water inundation following heavy rainfall events such as this. Rivers, lakes, and flooded areas show up as darker features on the 0.86 µm images.

Suomi NPP VIIRS 0.64 µm visible and 0.86 µm visible channel images

Suomi NPP VIIRS 0.64 µm visible and 0.86 µm visible channel images

MODIS 0.65 µm (Band 1) visible channel and 0.86 µm (Band 2) visible channel images

MODIS 0.65 µm (Band 1) visible channel and 0.86 µm (Band 2) visible channel images

Precipitation variability across the Upper Midwest region

June 21st, 2012
MODIS true-color image, Sea Surface Temperature product, and 0.65 µm visible channel image

MODIS true-color image, Sea Surface Temperature product, and 0.65 µm visible channel image

AWIPS comparisons of a 250-meter resolution MODIS true-color Red/Green/Blue (RGB) image at 16:46 UTC on 21 June 2012 with the corresponding 1-km resolution MODIS Sea Surface Temperature product and 0.65 µm visible channel image (above) revealed the vivid signature of iron and/or copper rich runoff sediment in the near-shore waters of western Lake Superior following the historic heavy rainfall event of 19 June20 June 2012 (for more details on this event, see the Duluth National Weather Service).

A “before” (21 May 2012) and “after” (21 June 2012) true color image from the SSEC MODIS Today site (below) showed the dramatic change in appearance of the western Lake Superior near-shore waters.

MODIS true-color images (21 May 2012 and 21 June 2012)

MODIS true-color images (21 May 2012 and 21 June 2012)

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7-day total precipitation, percent of normal, and departure from normal

7-day total precipitation, percent of normal, and departure from normal

Maps of the total 7-day precipitation, percent of normal precipitation, and precipitation departure from normal (above) highlighted the extreme nature of the event in the Duluth region, but also showed the large amount of variability in precipitation across other portions of the Upper Midwest states during this period.

In particular, note the large southwest-to-northeast oriented swath across northeastern Nebraska, northwestern Iowa, southeastern South Dakota, and southwestern Minnesota (below): in this highly agricultural area, the stress on the crops within this rain-free swath was apparent on MODIS 0.65 µm visible imagery (lighter gray where the vegetation was less healthy), the MODIS Land Surface Temperature (LST) product (LST values in the upper 80s to mid 90s F, surrounded by LST values in the 70s F), and the Normalized Difference Vegetation Index (NDVI values as low as 0.43 in southwestern Minnesota, surrounded by NDVI values of 0.7 to 0.8 to the north and to the south where ample rainfall had been occurring).

MODIS 0.65 µm visible image, Land Surface Temperature product, and Normalized Difference Vegetation Index product

MODIS 0.65 µm visible image, Land Surface Temperature product, and Normalized Difference Vegetation Index product