Localized heavy rainfall and flooding in south-central Wisconsin

June 15th, 2016

GOES-13 Infrared Window (10.7 µm) images [click to play animation]

GOES-13 Infrared Window (10.7 µm) images [click to play animation]

GOES-13 Infrared Window (10.7 µm) images (above) showed the development of several rounds of deep convection which moved over parts of southern Wisconsin during the 14 June15 June 2016 period; these storms were responsible for heavy rainfall at some locations (NWS Milwaukee summary). As mentioned in a WPC Mesoscale Precipitation Discussion, some of these storms were focused along the nose of a low-level jet that was helping to push a warm frontal boundary (surface analyses) through the region. Moisture was also abundant south of the warm front, with a total precipitable water value of 55.1 mm (2.17 inches) seen in rawinsonde data from Davenport IA.

Landsat-8 false-color image [click to enlarge]

Landsat-8 false-color image [click to enlarge]

A timely cloud-free overpass of the Landsat-8 satellite on the morning of 15 June provided a 30-meter resolution false-color image as viewed using RealEarth (above), which showed areas of flooding — water appears as darker shades of blue — in the Black Earth area of western Dane County in southern Wisconsin. A before/after comparison of Landsat-8 images processed using an equation to highlight water as blue (below, courtesy of Shane Hubbard, SSEC/CIMSS) revealed the areas of inundation due to the 14-15 June thunderstorms.

Landsat-8 derived water change, 30 May vs 15 June 2016 [click to enlarge]

Landsat-8 derived water change, 30 May vs 15 June 2016 [click to enlarge]

Aerial footage from a drone flight (below) showed vivid images of the flooding along Black Earth Creek.

YouTube video from drone flight near Black Earth, Wisconsin [click to play]

YouTube video from drone flight near Black Earth, Wisconsin [click to play]

Landsat-8 Imagery

January 16th, 2016

Landsat-8 false-color image overpass [click to enlarge]

Landsat-8 false-color image overpass [click to enlarge]

Landsat-8 imagery — with a spatial resolution of 15 to 30 meters — is available for viewing via the SSEC RealEarth web map server. An example of a swath of false-color Red/Green/Blue (RGB) imagery across the central US between the times of 1630-1640 UTC on 16 January 2016 is shown above. Snow cover and ice (as well as ice crystal clouds) appear as varying shades of cyan in this type of RGB image.  Let’s take a closer look at 3 regions along this overpass to examine some interesting features.

The northerly flow of arctic air over the still-unfrozen waters of Lake Superior was aiding the development of lake effect snow (LES) bands, some of which were moving inland over the eastern portion of the Upper Peninsula of Michigan. One of the more well-defined LES bands was seen to be moving across the Grand Marais area — a cooperative observer 10 miles south of the city reported 8.5 inches of new snow during the 24-hour period from 12 UTC on 16 January to 12 UTC on 17 January.

Landsat-8 false-color RGB image over Lake Superior [click to enlarge]

Landsat-8 false-color RGB image over Lake Superior [click to enlarge]

Looking farther to the south, an interesting feature was seen in the southern part of ice-covered Green Bay, Wisconsin (below): a channel through the ice (red arrows) had been cut by the US Coast Guard icebreaker Mackinaw during the evening of 14 January, to allow passage for a ship to unload cargo at a dock along the mouth of the Fox River (which empties into the southern end of Green Bay). Hat tip to the NWS Green Bay for providing the information on which icebreaker was involved.

Landsat-8 Panchromatic Visible (0.59 µm) and False-color RGB images [click to enlarge]

Landsat-8 Panchromatic Visible (0.59 µm) and False-color RGB images [click to enlarge]

Finally, a look to the southern portion of the overpass: the Mississippi River, between the states of Louisiana and Mississippi. The Landsat satellites fly over the same portion of the Earth every 17 days, so taking advantage of this fact we can visualize the profound changes in the southern Mississippi River due to the flow of large amounts of water resulting from heavy rainfall farther to the north — over the Middle Mississippi River and Ohio River Valley regions — during December 2015 (as discussed in this blog post). Water appears as darker shades of blue in these particular Landsat RGB images, aiding in the identification of areas where flooding is occurring.

Landsat-8 false-color RGB images on 31 December 2015 and 16 January 2016 [click to enlarge]

Landsat-8 false-color RGB images on 31 December 2015 and 16 January 2016 [click to enlarge]

Flooding in the Missouri/Mississippi/Ohio River basins

January 2nd, 2016

Aqua MODIS false-color RGB images on 19 December 2015 and 02 January 2016 [click to enlarge]

Aqua MODIS false-color RGB images on 19 December 2015 and 02 January 2016 [click to enlarge]

A comparison of 250-meter resolution Aqua MODIS false-color Red/Green/Blue (RGB) images from the SSEC MODIS Today site on 19 December 2015 and 02 January 2016 (above) showed large increases in the width of portions of the Missouri/Mississippi/Ohio Rivers (as well as many of their tributaries and surrounding lakes) during that 14-day period. These false-color images use MODIS bands 7/2/1 as the R/G/B components — water appears as varying shades of darker blue. Some light snow cover (shades of cyan) can also be seen in the upper left corner of the 02 January image.

A comparison of Aqua MODIS true-color (created using bands 1/4/3) and false-color (created using bands 7/2/1) RGB images on 02 January (below) demonstrated the advantage of the false-color imagery for detection of the extent of river and lake flooding. The high sediment content of the area lakes and rivers made them appear as varying shades of tan to brown on the true-color image, making their boundaries more difficult to distinguish from the similar shades of the surrounding bare ground surfaces. (Note: when GOES-R is launched in late 2016, similar spectral bands on the ABI instrument will allow the creation of these types of true-color and false-color RGB images)

Aqua MODIS true-color and false-color RGB images on 02 January 2016 [click to enlarge]

Aqua MODIS true-color and false-color RGB images on 02 January 2016 [click to enlarge]

A more detailed view of flooding across the eastern portion of the MODIS images (in southern Indiana and northern Kentucky) was provided by 30-meter resolution Landsat-8 false-color imagery, as visualized using RealEarth (below). A magnified view of the Evansville, Indiana / Owensboro, Kentucky area can be seen here.

Landsat-8 false-color image [click to enlarge]

Landsat-8 false-color image [click to enlarge]

Maps of total observed precipitation and departure from normal (below) during the same 14-day period as the 2 MODIS false-color images shown at the top of the blog post revealed that widespread areas received upwards of 8-10 inches of rainfall, which was 6-8 inches above normal for that 2-week period of time.

19 December 2015 to 02 January 2016 total precipitation and departure from normal [click to enlarge]

19 December 2015 to 02 January 2016 total precipitation and departure from normal [click to enlarge]

As a result of water runoff from the heavy precipitation, new records for maximum river gauge height were set for the Mississippi River at Cape Girardeau, Missouri and Thebes, Illinois (below).

River gauge plot for the Mississippi River at Cape Girardeau, Missouri [click to enlarge]

River gauge plot for the Mississippi River at Cape Girardeau, Missouri [click to enlarge]

River gauge for the Mississippi River at Thebes, Illinois [click to enlarge]

River gauge for the Mississippi River at Thebes, Illinois [click to enlarge]

Additional information is available from the NWS Paducah.

Toxic Algal Bloom in Western Lake Erie

August 4th, 2014
Terra MODIS True Color Imagery (click to play animation)

Terra MODIS True Color Imagery (click to play animation)

As happened in 2011, an algae bloom is ongoing over Lake Erie. The current bloom has contaminated at least one water intake for Toledo, Ohio’s municipal water supply with microcystin, a cyanobacter that when ingested can damage the liver and nauseate people. (There is also significant danger to pets). A series of true-color images (from 4 July, 1 August and 4 August) taken from the MODIS Today website, above, (combining visible channels at 0.6465 µm [red], 0.5537 µm [green] and 0.4656 µm [blue]) shows changes in the water color over the past month. (Image Source: MODIS Today) Some changes are apparent over western Lake Erie that are associated with the toxic bloom.

The algal growth is more readily apparent in the false-color imagery below. This red/green/blue image is constructed with 2.1143 µm imagery as ‘red’, 0.8567 µm imagery as ‘green’ and 0.6465 µm imagery as ‘blue’. The animation including scenes from 4 July, 1 August and 4 August shows dramatic growth between 1 and 4 August. Near-infrared channels — such as 0.8567 µm — are sensitive to energy reflected by algae.

Terra MODIS True Color Imagery (click to play animation)

Terra MODIS True Color Imagery (click to play animation)

A series of True-Color images for six days this Spring/Summer is here. The increase in algae in the western part of Lake Erie is apparent, but it seems that the outbreak this year is less wide-spread than the outbreak in October of 2011. A series of False-Color images is here.

[Update, 5 August 2014: Toledo’s water supply has been deemed safe to drink]