Flooding in South Dakota, Nebraska and Iowa

March 15th, 2019 |

GOES-16 Near-Infrared

GOES-16 Near-Infrared “Vegetation” (0.86 µm) and “Snow/Ice” (1.61 µm) images [click to play animation | MP4]

GOES-16 (GOES-East) Near-Infrared “Vegetation” (0.86 µm) and “Snow/Ice” (1.61 µm) images (above) revealed widespread river flooding (in the wake of rapid snow melt and heavy rainfall) across parts of southeastern South Dakota, eastern Nebraska and western/central Iowa on 15 March 2019. Water and flooded land appear as darkest shades of gray to black on both sets of images —  remaining snow cover also appeared as darker shades on the 1.61 µm imagery. Additional information regarding the flooding is available from NWS Sioux Falls

In a toggle between Suomi NPP VIIRS Visible (0.64 µm) and “Snow/Ice” (1.61 µm) images at 1821 UTC (below),1.61 µm imagery showed the darker shades of flooding over a north/south portion of Interstate 29 that was closed from State Highway 34 (west of Glenwood, Iowa) to the Iowa/Missouri border (south of Hamburg, Iowa).

Suomi NPP VIIRS Near-Infrared "Vegetation" (0.86 µm) and "Snow/Ice" (1.61 µm) images [click to enlarge]

Suomi NPP VIIRS Visible (0.64 µm) and “Snow/Ice” (1.61 µm) images; Interstate Highways are plotted in red, while State Highways are plotted in gray [click to enlarge]

Comparisons of Terra MODIS True Color and False Color Red-Green-Blue (RGB) images at 1720 UTC viewed using RealEarth are shown below. In the False color imagery, snow cover appears as lighter shades of cyan, while water appears as darker shades of blue.

Terra MODIS True Color and False Color RGB images [click to enlarge]

Terra MODIS True Color and False Color RGB images, centered over eastern Nebraska [click to enlarge]

Terra MODIS True Color and False Color RGB images, centered near Vermillion, South Dakota [click to enlarge]

Terra MODIS True Color and False Color RGB images, centered near Vermillion, South Dakota [click to enlarge]

Terra MODIS True Color and False Color RGB images, centered near Ames, Iowa [click to enlarge]

Terra MODIS True Color and False Color RGB images, centered near Ames, Iowa [click to enlarge]

===== 16 March Update =====

Landsat-8 False Color image. centered to the east of Sioux City, Iowa [click to enlarge]

Landsat-8 False Color image centered to the east of Sioux City, Iowa [click to enlarge]

An overpass of the Landsat-8 satellite at 1706 UTC on 16 March provided 30-meter resolution False Color imagery — 2 sections of the swath are shown above and below. The RealEarth link to interactively view the image is here.

Landsat-8 False Color image. centered to the south of Omaha, Nebraska [click to enlarge]

Landsat-8 False Color image centered to the south of Omaha, Nebraska [click to enlarge]

Closer views centered at the NWS Omaha forecast office — which had to be evacuated due to flooding — and just west of Offutt Air Force Base are shown below.

Landsat-8 False Color image. centered at the NWS forecast office in Valley, Nebraska [click to enlarge]

Landsat-8 False Color image centered at the NWS forecast office in Valley, Nebraska [click to enlarge]

Landsat-8 False Color image. centered near Offutt Air Force Base, Nebraska [click to enlarge]

Landsat-8 False Color image centered just west of Offutt Air Force Base, Nebraska [click to enlarge]

Standing wave clouds over Virginia and North Carolina

March 7th, 2019 |

GOES-16

GOES-16 “Red” Visible (0.64 µm), “Clean” Infrared Window (10.3 µm), Cloud Top Height, Cloud Particle Size Distribution, and Cloud Phase [click to play animation | MP4]

GOES-16 (GOES-East) “Red” Visible (0.64 µm), “Clean” Infrared Window (10.3 µm), Cloud Top Height, Cloud Particle Size Distribution, and Cloud Phase (above) helped to characterize standing wave clouds that developed to the lee of the Appalachian Mountains on 07 March 2019. The primary standing wave rotor clouds were composed of smaller supercooled water droplets,  with “banner clouds” composed of larger/colder ice crystals forming downwind of the rotor clouds. For example, at 1637 UTC cloud particle sizes associated with the rotor clouds were as small as 3-10 µm (darker shades of purple).

GOES-16 Day Cloud Phase Distinction Red-Green-Blue (RGB) images from the AOS site (below) also identified the rotor clouds as supercooled water droplet features (brighter shades of white), with the banner clouds being identified as high-level ice (shades of pink) or glaciating (shades of green) features. An unrelated phenomena was the brief brightening of the bare ground across much of the Southeast US midway through the animation — a result of transient solar reflectance that is seen around the Spring and Autumn equinox.

GOES-16 Day Cloud Phase Distinction RGB images [click to play animation | MP4]

GOES-16 Day Cloud Phase Distinction RGB images [click to play animation | MP4]

In a comparison of 1-km resolution Terra MODIS Visible (0.65 µm), Near-Infrared “Cirrus” (1.37 µm), Shortwave Infrared (3.7 µm) and Infrared Window (11.0 µm) images at 1631 UTC (below), note that the standing wave rotor clouds appeared much warmer (darker gray) in the Shortwave Infrared images — this is due to the fact that small supercooled water droplets are very efficient reflectors of incoming solar radiation.

Terra MODIS Visible (0.65 µm), Near-Infrared

Terra MODIS Visible (0.65 µm), Near-Infrared “Cirrus” (1.37 µm), Shortwave Infrared (3.7 µm) and Infrared Window (11.0 µm) images [click to enlarge]

There were a few pilot reports of light to moderate turbulence in the general vicinity of the standing waves, especially around 14 UTC (below).

Terra MODIS Visible (0.65 µm) image, with pilot reports of turbulence [click to enlarge]

Terra MODIS Visible (0.65 µm) image, with pilot reports of turbulence [click to enlarge]

Tornado outbreak in Alabama and Georgia

March 3rd, 2019 |

GOES-16

GOES-16 “Red” Visible (0.64 µm) images, with SPC storm reports plotted in red [click to play animation | MP4]

An outbreak of severe thunderstorms occurred during the afternoon hours of 03 March 2019, which produced large hail, damaging winds and tornadoes (SPC storm reports). 1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed the development of numerous thunderstorms along and ahead of an advancing cold front (surface analyses); many of those storms exhibited well-defined overshooting tops. Tornado track summaries for Alabama and Georgia are available from NWS Birmingham and NWS Atlanta.

The corresponding GOES-16 “Clean” Infrared Window (10.3 µm) images are shown below. Cloud-top infrared brightness temperatures cooled to around -70ºC (darker black enhancement) with many of the stronger storms — judging from rawinsonde data from Birmingham, Alabama (at 12 UTC) and Peachtree City, Georgia (at 18 UTC), this roughly corresponded to an air parcel rising significantly past the tropopause to an altitude of at least 15 km.

GOES-16 "Clean" Infrared Window (10.3 µm) images, with SPC storm reports plotted in red [click to play animation | MP4]

GOES-16 “Clean” Infrared Window (10.3 µm) images, with SPC storm reports plotted in cyan [click to play animation | MP4]

An area which included western Lee County (located in far eastern Alabama, adjacent to the Georgia border) was highlighted by a SPC MCD that was issued at 1900 UTC. Beginning about an hour later, 2 large tornadoes producing EF2 to EF4 damage moved across southern Lee County — initially beginning around 2000 UTC, then again beginning around 2050 UTC — and the formation of prominent overshooting tops was evident in GOES-16 Visible and Infrared imagery (below). Station identifier KAUO in Lee County is the Auburn-Opelika Airport. (side note: later, around 2204 UTC, the Weedon Field Airport KEUF METAR site to the south of Lee County was directly hit by a separate EF2 tornado, and rendered inoperative)

GOES-16 "Clean" Infrared Window (10.3 µm) images, with SPC storm reports plotted in cyan [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm, left) and “Clean” Infrared Window (10.3 µm, right) images, with SPC storm reports plotted in red/cyan — Lee County, Alabama is outlined in solid blue, with other affected counties in dashed blue [click to play animation | MP4]

In a plot of the GOES-16 “Clean” Infrared Window coldest brightness temperature for the EF4-tornado storm’s overshooting top as it moved from Macon/Lee Counties in Alabama to Muscogee/Harris/Talbot Counties in Georgia (below), 3 distinct periods of cooling/warming occurred — with the warming indicative of a temporary collapse of the overshooting top pulse. The first (and largest-magnitude) cold/warm pulse (-70.3ºC to -65.6ºC) occurred from 1953-1959 UTC — just prior to the beginning of the Beauregard-Smiths Station EF4 Tornado at 2000 UTC. A second cold/warm pulse (-70.8ºC to -66.9ºC) occurred from 2006-2012 UTC, with a third (-70.0ºC to -66.0ºC) from 2015-2022 UTC. At 2029 UTC the long-track tornado then crossed into Muscogee County in Georgia, producing EF3 damage.

Plot of the coldest GOES-16

Plot of the coldest GOES-16 “Clean” Infrared Window (10.3 µm) overshooting top brightness temperatures, 2040-2115 UTC [click to enlarge]

The NOAA/CIMSS ProbSevere product (below) displayed a high tornado probability for the cells that approached Lee County, as discussed by the Hazardous Weather Testbed. The ProbSevere model incorporates GOES-derived Normalized vertical growth rate and Cloud-top glaciation rate as 2 of its predictors.

MRMS MergedReflectivity composite, with countours of the ProbSevere parameter [click for link to HWT blog post]

MRMS MergedReflectivity composite, with countours of the ProbSevere parameter [click for link to HWT blog post]

A comparison of Aqua MODIS Visible (0.65 µm) and Infrared Window (11.0 µm) images along with the Total Precipitable Water derived product at 1836 UTC (below) showed that a few large thunderstorms had begun to develop by that time; TPW values were as high as 43 mm (1.7 inches) over far southwestern Georgia.

Aqua MODIS Visible (0.65 µm), Infrared Window (11.0 µm) and Total Precipitable Water images at 1836 UTC [click to enlarge]

Aqua MODIS Visible (0.65 µm), Infrared Window (11.0 µm) and Total Precipitable Water images at 1836 UTC [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm) image, with plots of available NUCAPS soundings [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm) image, with plots of available NUCAPS soundings [click to enlarge]

An overpass of the Suomi NPP satellite around 1850 UTC provided NUCAPS soundings in non-cloudy areas (above). One of the Good quality (green) NUCAPS soundings in the pre-storm environment was located over southwestern Georgia (circled in magenta) — it showed a Most Unstable CAPE value of 1264 J/kg, with a Lifted Index value of -4 (below).

NUCAPS sounding over southwestern Georgia [click to enlarge]

NUCAPS sounding over southwestern Georgia [click to enlarge]

The GOES-16 All Sky CAPE product (below) showed a trend of destabilization across southern Alabama and southern Georgia during the 5 hours leading up to the fatal tornadoes in Lee County AL.

GOES-16 All Sky CAPE product [click to play animation]

GOES-16 All Sky CAPE product [click to play animation]

===== 05 March Update =====

Comparison between Terra MODIS True Color and False Color RGB images on 24 February and 05 March 2019 [click to enlarge]

Comparison between Terra MODIS True Color and False Color RGB images on 24 February and 05 March 2019 [click to enlarge]

A toggle between before/after (24 February / 05 March 2019) Terra MODIS True Color and False Color Red-Green-Blue (RGB) images from the MODIS Today site (above) showed subtle evidence of portions of a tornado damage path — presumably that of the EF4 tornado that began in/near Lee County, Alabama and ended in far western Georgia. Click an additional time on the image to view at full magnification.

Sentinel-2 True Color images (below) provided a higher-resolution view of the tornado damage path. Imagery courtesy of Sentinel Hub.

Sentinel-2 True Color RGB images from 24 February and 06 March [click to enlarge]

Sentinel-2 True Color RGB images from 24 February and 06 March [click to enlarge]

River flooding in the Lower Mississippi and Tennessee River Valley

February 24th, 2019 |

30-day Precipitation and Percent of Normal Precipitation [click to enlarge]

30-day Precipitation and Percent of Normal Precipitation [click to enlarge]

A toggle between Observed Precipitation and Percent of Normal Precipitation for the 30-day period ending at 12 UTC on 24 February 2019 (above) showed a large area that received 10-15 inches of rainfall — which was 200-400% of normal — across the Lower Mississippi River and Tennessee River Valleys.

A before/after comparison of Terra MODIS False Color Red-Green-Blue (RGB) images from 25 January and 24 February 2019 (below) revealed the extensive area of flooding that resulted. Flooded areas appear as varying shades of blue on the False Color imagery (source).

Terra MODIS False Color RGB images from 25 January and 24 February 2019 [click to enlarge]

Terra MODIS False Color RGB images from 25 January and 24 February 2019 [click to enlarge]

In a comparison of Terra MODIS True Color and False Color RGB images from 24 February (below), many of the flooded rivers exhibit a tan-colored appearance in the True Color image due to large amounts of sediment suspended in the water.

Terra MODIS True Color and False Color RGB images from 24 February [click to enlarge]

Terra MODIS True Color and False Color RGB images from 24 February [click to enlarge]

A Flood Map derived using NOAA-20 VIIRS data (below) quantitatively showed the extent of the flooding. CIMSS scientists Jay Hoffman and William Straka contributed to the development of this food monitoring product.

NOAA-20 VIIRS Flood Map [click to enlarge]

NOAA-20 VIIRS Flood Map [click to enlarge]