Numerous severe thunderstorms developed along the foothills of the Rockies and the High Plains during the afternoon hours on 19 June 2008. AWIPS images of the MODIS 11.0 µm “IR window” channel, Cloud Top Temperature product, and 3.7 µm “shortwave IR” channel (above) showed some of these areas of convection around 20:00 UTC (2 PM local time). Shortly after the time of these MODIS images, hail up to 2.75 inches in diameter was reported near Pueblo, Colorado (SPC storm reports). About 90 minutes after the time of the MODIS images, hail of 4.50 inches in diameter and a wind gust to 81 mph was produced by the storm that was seen developing in the Texas panhandle region. Although these storms exhibited similar cold cloud top temperatures on the IR window image (-60 to -77º C, red to black to gray color enhancement) and the Cloud Top Temperature product (-60 to -69º C, darker blue to light violet color enhancement), note the darker gray appearance of many of the westernmost storms on the 3.7 µm shortwave IR image — this darker signal is due to a dominance of smaller anvil top ice particles (in contrast with the brighter white appearance due to larger anvil top ice particles associated with the storms farther to the east). Anvils composed of smaller ice particles are more reflective of incident solar radiation, which results in significantly warmer shortwave IR brightness temperatures (in this case, +5 to +20º C, compared to -10 to -15º C in the brighter white anvil features composed of larger ice particles). According to Lindsey et al. (2006), regions such as the high plains and mountains (having environments with relatively dry boundary layers, steep lapse rates, and large vertical shear values) tend to favor thunderstorms with enhanced 3.9-μm reflectivity.

With cloud top temperatures in the -60 to -70º C range, no supercooled water droplets could have been present at the cirrus anvil top — this was confirmed by the MODIS “cirrus detection channel” image in tandem with the MODIS Cloud Phase product (below), which indicated ice phase (salmon color enhancement) for all the convective storm cirrus anvil features.

Additional reference:

  Cloud-top Structure of Northeast Colorado Thunderstorms May 24, 2005

View only this post Read Less

Both GOES-11 (GOES-West) and GOES-12 (GOES-East) were placed into Rapid Scan Operations (RSO) during the afternoon and early evening on 18 June 2008, to monitor the development of severe thunderstorms across the central US (SPC storm reports). In RSO mode, images are available at 5-7 minute intervals (instead of the usual 15 minute intervals for standard operations) — however, the RSO image times are not exactly the same for GOES-11 and GOES-12. A side-by-side comparison of GOES-11 and GOES-12 visible channel images centered on Bismarck, North Dakota (above) showed the formation and intensification of thunderstorms that produced hail as large as 2.75 inches in diameter at 22:48 UTC and 4.25 inches in diameter at 00:22 UTC (both times at a location between Bismarck KBIS and Garrison KN60), and a tornado around 00:25 UTC (just west of Bismarck KBIS). Both the GOES-11 and GOES-12 images are displayed in their native satellite projections, so the cloud features (and the area shown) appear a bit different due to the differing satellite viewing angles.

View only this post Read Less

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.

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).

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.

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.

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).

View only this post Read Less

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 June – 08 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).

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.

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.

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.

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.

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.

View only this post Read Less