Continued flooding in the Upper Midwest

June 17th, 2008 |

MODIS false color images (Animated GIF)

The historic Central US river flooding event of 2008 continued into mid-June across parts of the Upper Midwest states (Google Earth map of river gauges). A sequence of MODIS false-color images from the SSEC MODIS Today site (above) covers the period from 01 June to 17 June, and shows the increase in flooded and inundated rivers across eastern Iowa, northwestern Illinois, and southwestern Wisconsin. Water has a much darker appearance in these false color images, so the swollen rivers tend to stand out in contrast to the densely-vegetated areas (green colors) which were characterized by a high concentration of trees, or the sparsely-vegetated agricultural fields (tan to light brown colors) where crops had only recently been planted.In particular, the MODIS images show the flooding of a large area of Iowa farmland adjacent to the Missisippi River (near the bottom center of the images), after the Iowa River broke through a levee near Oakville, Iowa on 16 June.

MODIS true color image (Google Earth)

Flooding also forced the closure of the Great River Bridge that connects Iowa and Illinois along Highway 34 near Burlington, Iowa. On the MODIS true color image from 17 June (above; displayed using Google Earth), note the well-defined southern edge of the flooded area (darker brown colors) between Oakfield and Kingston, Iowa — this west-to-east oriented water boundary was likely due to a massive sandbagging effort along a diversion channel that runs eastward into the Mississippi River. This narrow diversion channel can be seen in more detail using Google Maps satellite imagery (below).

Google Maps satellite image

Farther to the west, a June 2007 vs. June 2008 comparison of MODIS true color images centered over southern Minnesota and northern Iowa (below; interactive image fader) revealed how delayed the “green-up” of cultivated crops (primarily corn and soybeans) was across that particular region. Cooler than normal temperatures in May 2008 followed by the unusually heavy rainfall and flooding in June 2008 conspired to delay the planting of crops across much of that area.

MODIS true color images (Animated GIF)

An AWIPS image of the MODIS Normalized Difference Vegetation Index (NDVI) product from 16 June (below) showed that NDVI values were as low as 0.2 to 0.3 over some portions of Minnesota and Iowa.

MODIS Normalized Difference Vegatation Index (NDVI)

The “normal” Vegetation Fraction over that same region for the month of June (below) should be in the 0.5 to 0.7 range (based upon a 5-year monthly climatology).

June mean vegetation fraction

River flooding in the Upper Midwest

June 14th, 2008 |

MODIS true color image showing rivers in flood

Parts of the Upper Midwest and Great Lakes states received unusually heavy rainfall during the first 2 weeks of June 2008, which caused widespread flash flooding and river flooding to occur — as a result, many rivers in eastern Iowa and southern Wisconsin crested at record high levels. During the 07 June08 June 2008 period, 48-hour storm total rainfall amounts included 13.50 inches at Watertown, Wisconsin, 12.36 inches at Dorchester, Iowa, and 10.10 inches at Reno, Minnesota. In southern Wisconsin, Milwaukee set a new record for 48-hour precipitation (7.18 inches), and 4.11 inches in 24 hours was a daily record for Madison (and only the 4th instance of a daily precipitation amount greater than 4 inches since records have been kept). The thunderstorms that were responsible for that 2-day heavy rain event also produced an EF2 tornado and hail up to 5.0 inches in diameter in southern Wisconsin. Lake Delton (a 267-acre man-made lake in Wisconsin Dells) was nearly drained empty in a matter of hours after a dam breach.

A MODIS true color image (above; courtesy of Sam Batzli, SSEC Environmental Remote Sensing Center, using data from the Dartmouth Flood Observatory) shows the rivers that were inundated or in flood (colored red) across southern Wisconsin (with counties labeled) and adjacent portions of Minnesota, Iowa, and Illinois (determined by comparing MODIS data from 01 June and 10 June 2008 where cloud-free).

MODIS false color images (Animated GIF)

A comparison of 250-meter resolution SSEC MODIS Today false color images (above) from “before” the flooding event (01 June 2008, which was mostly cloud-free) and “after” the flooding event (14 June 2008, which had some clouds over the northern portion of the scene) reveals the changes to a few of the rivers that were experiencing major flooding (particularly evident in far southwestern Wisconsin and far northwestern Illinois). Since water has a much darker appearance in these false color images, the swollen rivers tend to stand out in contrast to the densely-vegetated areas (green colors) which were characterized by a high concentration of trees, or the sparsely-vegetated agricultural fields (tan to light brown colors) where crops had only recently been planted. The”disappearance” of Lake Delton is not very obvious in the false color imagery — the lake appeared as a dark feature on 01 June, but the drained lake bed still appeared as a similar dark feature on 14 June (due to the very high soil moisture content of the lake bed and adjacent areas).

In the corresponding set of “before” and “after” MODIS true color images (below), plumes of offshore sediment flow into parts of Lake Michigan could be seen. The”disappearance” of Lake Delton is a bit more obvious in the true color imagery — the lake appears as a dark feature on 01 June, but the drained lake bed appears as a light tan to light brown colored feature on 14 June.

MODIS true color images (Animated GIF)

Farther to the southwest, “before” (01 June) and “after” (13 June) MODIS false-color images show the changes to many rivers due to historic flooding across much of the state of Iowa (below). The National Weather Service at Des Moines posted a similar MODIS false color image comparison showing river flooding over Iowa.

MODIS false color images (Animated GIF)

The National Weather Service Advanced Hydrologic Prediction Service Precipitation Analysis for the 14-day period ending at 12 UTC (7 AM local time) on 14 June 2008 (below) indicated that as much as 10-15 inches of rain fell over a number of counties, with a wide swath of precipitation that was 5-8 inches above normal (or over 600 percent of normal) for that 2-week period. The maximum total rainfall from 01 June to 12 June was 17.84 inches at Portage, Wisconsin.

14-day precipitation (Animated GIF)

Radar-estimated precipitation products from the NOAA/NSSL/University of Oklahoma NMQ site (below) revealed that widespread rainfall amounts of 3-8 inches occurred during the two 24-hour periods ending at 12 UTC (7 AM local time) on 08 and 09 June.

radar-estimated precipitation (Animated GIF)

UPDATE: Sam Batzli provided  maps derived from RADARSAT-1 data (below) which shows areas of probable flooding (red features) across southern Wisconsin on 15 June. This is probably the first time that RADARSAT imagery has been used to map flooding in Wisconsin, since no single agency in the state has previously been able to afford RADARSAT imagery, or known how to acquire or process this type of imagery. The collective and collaborative nature of WisconsinView and its ties to Wisconsin Emergency Management, and the activation of the “International Charter” facilitated this application of remote sensing technology in a successful way.

map of flooding (derived from RADARSAT data)

RADARSAT-1 image

RADARSAT-1 image coverage

Wildfire in North Carolina

June 7th, 2008 |

MODIS visible + shortwave IR images (Animated GIF)

AWIPS images of the MODIS visible and 3.7 µm shortwave IR channels (above) showed smoke and a “hot spot” associated with a large wildfire that had burned over 30,000 acres in the Pocosin Lakes National Wildlife Refuge in northeastern North Carolina on 07 June 2008.

The fire was started by lightning about a week earlier — an animation of MODIS true color images (below) revealed the changing shape and direction of the smoke plume during the 02-07 June period. At times the smoke was causing air quality problems as it drifted northward over the urban areas of southeastern Virginia — note the elevated MODIS Aerosol Optical Depth (AOD) values that had spread northward across southeastern Virginia on 06 June.

MODIS true color images (Animated GIF)

A closer view using 250-meter resolution MODIS true color imagery on from the SSEC MODIS Today site (below) shows the thick smoke drifting southeastward across the Outer Banks of North Carolina, then dispersing over the waters of the Atlantic Ocean on 07 June. Note the appearance of small pyrocumulus clouds that had formed over the hottest portions of the fire area, which cast a small shadow onto the smoke plume located below the cloud tops.

MODIS true color image

It was quite warm across the mid-Atlantic region on 07 June, which worsened the already-favorable fire conditions – the MODIS Land Surface Temperature (LST) product (below) indicated widespread LST values of 100-120º F (darker red colors) around 18 UTC (2 PM local time). Surface air temperatures reached 100º F at a few locations in southeastern Virginia (the 101º F at Norfolk and the 100º F at Richmond were record highs for the date).

MODIS Land Surface Temperature product

UPDATE #1: A MODIS Sea Surface Temperature (SST) image from 09 June (below) showed that the water temperatures in the Chesapeake Bay had risen to unusually high values (upper 70s to low 80s F) for early June, as a result of several consecutive days of record or near-record high temperatures. Note that the MODIS SST values in Chesapeake Bay were significantly warmer than those suggested by the High Resolution RTG_SST model analysis.

MODIS Sea Surface Temperature (SST) image

UPDATE #2: The large Pocosin Lakes National Wildlife Refuge fire continued to burn on 13 June, while another fire had started in the Great Dismal Swamp area along the North Carolina/Virginia border. With an easterly flow present, the smoke plumes were now drifting inland toward the west, as seen on GOES-12 visible images (below). A significant amount of smoke had drifted inland across central North Carolina on the previous day (12 June), and was dense enough to restrict surface visibility to 1/2 mile as far to the west as Raleigh; that smoke pall remained thick enough on 13 June to apparently have the effect of inhibiting the formation of cumulus clouds (by reducing the amount of surface heating).

GOES-12 visible images (Animated GIF)

Advection fog over the western Great Lakes

June 7th, 2008 |

MODIS SST image (01 June 2008)

An AWIPS image of the MODIS Sea Surface Temperature (SST) product (above) revealed that the water temperatures were still quite cool across much of the western Great Lakes on 01 June 2008. Several days later, a northward surge of warm and humid air brought daytime temperatures into the 80s F with dew points into the mid-upper 60s F over a good deal of the region on 06 June 2008. As this warm and humid air flowed over the still-cool waters of Lakes Superior, Michigan, and Huron, dense advection fog formed which lasted into the early morning hours on 07 June 2008.

A comparison of the 4-km resolution GOES-12 IR window, fog/stratus product, and Low Cloud Base product images with the 1-km resolution MODIS fog/stratus product image (below) showed the extensive coverage of fog over the lakes just after 08 UTC (3am local time).

MODIS + GOES images (Animated GIF)

250-meter resolution MODIS true color images from the SSEC MODIS Today site (below) show interesting small-scale structure in the fog over Lake Superior on 06 June and over Lake Michigan on 07 June, including “bow shock waves” where the southerly flow of wind and lake fog was interacting with various islands and coastal features.

MODIS true color image

MODIS true color image