MODIS false-color images show areas of flooding in Montana

August 26th, 2014
Before (12 August) and after (26 August) MODIS false-color RGB images

Before (12 August) and after (26 August) MODIS false-color RGB images

Some locations in northeastern Montana received up to 7-8 inches of rainfall over a 5-day period (NWS Glasgow rainfall map), which led to flooding in many areas. A comparison of before (12 August) and after (26 August) 250-meter resolution MODIS false-color Red/Green/Blue (RGB) images from the SSEC MODIS Today site (above) showed the areal extent of flooding (cyan to darker blue areas on the 26 August image). The RGB images use MODIS bands 7/2/1 to help highlight the areas of of floodwater.

The maps below show the total observed rainfall, the departure from normal, and the percent of normal for the 7-day period ending on 26 August.

Observed 7-day rainfall

Observed 7-day rainfall

7-day rainfall departure from normal

7-day rainfall departure from normal

7-day rainfall percent of normal

7-day rainfall percent of normal

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]

Fog over Lake Superior

July 21st, 2014
GOES-13 0.63 µm visible channel images (click to play animation)

GOES-13 0.63 µm visible channel images (click to play animation)

The southerly flow of warm, moist air over the still-cold waters of Lake Superior on 21 July 2014 led to the formation of some interesting lake fog patterns, as seen in McIDAS images of GOES-13 0.63 µm visible channel data (above; click image to play animation; also available as an MP4 movie file). The images above are shown in their native GOES-13 satellite projection.

A similar animation of AWIPS images of re-mapped GOES-13 visible channel data with overlays of METAR surface reports and buoy reports (below; click image to play animation) showed that three of the northern Lake Superior buoys were reporting a water temperature of 38 to 39º F. As far north as Thunder Bay, Ontario (CYQT), air temperatures exceeded 90º F and the dew point exceeded 70º F.

GOES-13 0.63 µm visible images, with METAR and Buoy reports (click to play animation)

GOES-13 0.63 µm visible images, with METAR and Buoy reports (click to play animation)

A Terra MODIS Sea Surface Temperature (SST) product at 17:37 UTC (below) revealed that parts of the western half of Lake Superior exhibited SST values in the 40s F (cyan to blue color enhancement).

Terra MODIS Sea Surface Temperature product

Terra MODIS Sea Surface Temperature product

During the overnight hours preceding the images shown above, a Suomi NPP VIIRS IR brightness temperature difference “fog/stratus product” image at 07:43 UTC (below) showed a signal of widespread fog/stratus (yellow to red color enhancement) across much of the eastern half of Lake Superior.

Suomi NPP VIIRS IR brightness temperature difference

Suomi NPP VIIRS IR brightness temperature difference “fog/stratus product”

Large “hole punch cloud” over Wisconsin

July 18th, 2014

GOES-13 0.63 µm visible (upper left), 3.9 µm shortwave IR (upper right), 10.7 µm IR (lower left), and 6.5 µm water vapor (lower right) images [click to play animation]

GOES-13 0.63 µm visible (upper left), 3.9 µm shortwave IR (upper right), 10.7 µm IR (lower left), and 6.5 µm water vapor (lower right) images [click to play animation]

A large (approximately 50-mile diameter) “hole punch cloud” or “fall steak cloud” was seen over northwestern Wisconsin during the morning hours of 18 July 2014. An AWIPS 4-panel comparison of GOES-13 0.63 µm visible channel, 3.9 µm shortwave IR channel, 10.7 µm IR window channel, and 6.5 µm water vapor channel images (above; click image to play animation) showed that 10.7 µm IR cloud top brightness temperatures were not particularly cold with this feature (generally in the 0º C to -4º C range), and while 3.9 µm shortwave IR brightness temperatures warmed within the broad cloud deck surrounding the hole punch cloud after sunrise (due to reflection of solar radiation off of water cloud droplets), the center of the feature continued to exhibit colder (lighter gray enhancment) IR brightness temperatures which suggests cloud glaciation.

POES AVHRR Cloud Type, Cloud Top Height, and Cloud Top Temperature products at 09:32 UTC

POES AVHRR Cloud Type, Cloud Top Height, and Cloud Top Temperature products at 09:32 UTC

A comparison of CLAVR-x POES AVHRR Cloud Type, Cloud Top Height (CTH), and Cloud Top Temperature (CTT) products at 09:32 UTC or 4:32 am Central time (above) showed patches of water droplet clouds with CTH values in the 3-4 km range and CTT values in the 0º C to -4º C range.

A similar comparison at 12:05 UTC or 7:05 am Central time (below) revealed two areas of “cirrus” cloud type (orange color enhancement) exhibiting CTT values in the -35º to -40º C range (darker blue color enhancement) along the northern and southern periphery of the forming hole punch cloud.

POES AVHRR Cloud Type, Cloud Top Height, and Cloud Top Temperature prodcts at 12:05 UTC

POES AVHRR Cloud Type, Cloud Top Height, and Cloud Top Temperature prodcts at 12:05 UTC

These ranges of AVHRR Cloud Top Temperature and Cloud Top Height values agreed well with the regional rawinsonde data from Davenport IA (KDVN), Minneapolis MN (KMPX) and Green Bay WI (KGRB) shown below.

Davenport IA, Minneapolis MN, and Green Bay WI rawinsonde data at 12 UTC

Davenport IA, Minneapolis MN, and Green Bay WI rawinsonde data at 12 UTC

Terra MODIS visible and Cloud Phase products at 17:07 UTC or 12:07 pm Central time (below) indicated that a large area of glaciated ice cloud (salmon color enhancement) existed in the center portion of the hole punch cloud feature.

Terra MODIS 0.65 µm visible image and Cloud Phase products

Terra MODIS 0.65 µm visible image and Cloud Phase products

The cause of this large hole punch or fall streak cloud feature — and the other similar but smaller features seen across the region — was likely aircraft that had either ascended or descended through the cloud layer; particles in the aircraft exhaust acted as ice condensation nuclei, causing the process of cloud glaciation to begin.

GOES-15 0.62 µm visible images [click to play animation]

GOES-15 0.62 µm visible images [click to play animation]

GOES-15 imagery (above) shows the Hole Punch cloud from an oblique angle, and highlights how the region was overrun by smoke from wildfires in Canada. Smoke is most easily seen in visible satellite imagery when the sun is low in the sky, allowing for forward scatter. The smoke becomes less apparent in the imagery as the Sun rises. A similar animation for GOES-13 is below. Smoke is not quite so evident in this image because there is less forward scatter to GOES-13 over 75º W. Animations from both satellites show a hole punch cloud in Iowa as well.

GOES-15 0.62 µm visible images [click to play animation]

GOES-15 0.62 µm visible images [click to play animation]