Convection and Flooding over northern Wisconsin

June 17th, 2018 |

GOES-16 ABI Clean Window (10.3 µm) Infrared Imagery, 0200-0559 UTC on 17 June 2018 (Click to animate)

Persistent convection over northern Wisconsin, Minnesota and upper Michigan late Saturday (16 June)/early Sunday (17 June) caused significant flooding.  The animation above shows GOES-16 ABI “Clean Window” Infrared Imagery from 0200-0600 UTC on 17 June.  Note the persistence of the cold overshooting tops over western Bayfield County in northwestern Wisconsin! A longer Infrared animation (0110-1200 UTC) which includes hourly plots of precipitation type (yellow) and SPC storm reports of damaging winds (cyan) is available here. 7-day precipitation departures in some areas were 4 to 8 inches above normal for that period (or 600% of normal).

This link from Wisconsin Emergency Management shows aerial pictures of the flood damage. Of note is the break in US Highway 2 to the west of Ashland WI.

The heavy rains also affected runoff into Lake Superior. MODIS imagery, below, from the MODIS Today site (also available from RealEarth: Link), shows considerable offshore flow of sediment on 19 June (a similar image from 18 June is here, with a toggle between the 2 days here).

True-Color Imagery from Aqua MODIS on 19 June 2018 (Click to enlarge)

A Landsat-8 False-Color image, below, showed pockets of flooding (darker blue) adjacent to the Nemadji River in Superior WI on the morning of 19 June — water also cover a portion of US Highway 2/53. The Nemadji River had crested in Superior at a record 29.5 feet on the evening of 17 June (NWS Duluth summary).

Landsat-8 False-Color image (Click to enlarge)

False-Color image from Landsat-8 on 19 June 2018 (Click to enlarge)


============================ Added 22 June ==============================
 

NOAA’s Hydrometeorological Design Studies Center (Link) created an Exceedance Probability Analysis for this event at 6-hour, 24-hour and 72-hout time spans, available here (from this link). Probabilities suggest this was an exceedingly rare event.

The continuation of sediment flow into Lake Superior could be seen in a series of daily MODIS True-Color images here.

Transverse banding around a decaying MCS

June 14th, 2018 |

Aqua MODIS Visible (0.65 µm), Near-Infrared

Aqua MODIS Visible (0.65 µm), Near-Infrared “Cirrus” (1.37 µm), Water Vapor (6.7 µm) and Infrared Window (11.0 µm) images, with pilot reports of turbulence plotted in cyan [click to enlarge]

A comparison of Aqua MODIS Visible (0.65 µm), Near-Infrared “Cirrus” (1.37 µm), Water Vapor (6.7 µm) and Infrared Window (11.0 µm) images (above) showed widespread transverse banding along the northern and eastern periphery of a decaying Mesoscale Convective System (MCS) that was moving from Iowa into Illinois and Missouri on 14 June 2018.

GOES-16 (GOES-East) Near-Infrared “Cirrus” (1.37 µm), Mid-level Water Vapor (6.9 µm) and “Clean” Infrared Window (10.3 µm) images with pilot reports of turbulence are shown below.

GOES-16 Near-Infrared

GOES-16 Near-Infrared “Cirrus” (1.37 µm) images, with hourly plots of turbulence [click to play MP4 animation]

GOES-16 Mid-level Water Vapor (6.9 µm) images, with hourly plots of turbulence [click to play MP4 animation]

GOES-16 Mid-level Water Vapor (6.9 µm) images, with hourly plots of turbulence [click to play MP4 animation]

GOES-16 "Clean" Infrared Window (10.3 µm) images, with hourly plots of turbulence [click to play MP4 animation]

GOES-16 “Clean” Infrared Window (10.3 µm) images, with hourly plots of turbulence [click to play MP4 animation]

 

Mesoscale Convective System in the Plains

June 11th, 2018 |

GOES-16

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

A Mesoscale Convective System (MCS) developed over eastern Nebraska early in the evening on 11 June 2018, then propagated southward across the Plains during the subsequent overnight hours. GOES-16 (GOES-East) “Clean” Infrared Window (10.3 µm) images with plots of SPC storm reports are shown above; a Mesoscale Sector was positioned over the region, providing images at 1-minute intervals.

A closer look over Kansas using Infrared imagery from polar-orbiting satellites (below) revealed some very cold cloud-top infrared brightness temperatures, which included -87ºC on MODIS, -90ºC on VIIRS and -92ºC on AVHRR.

POES AVHRR, Terra/Aqua MODIS and Suomi NPP VIIRS Infrared images, with plots of SPC storm reports [click to enlarge]

Metop-B AVHRR, Terra/Aqua MODIS and Suomi NPP VIIRS Infrared images, with plots of SPC storm reports [click to enlarge]

The coldest air temperature on 00 UTC rawinsonde data from Dodge City and Topeka, Kansas (below) was -69.5ºC (at altitudes of 14.6 km/49,900 feet at Dodge City, and 17.6 km/57,700 feet at Topeka) — so in theory air parcels and cloud material within a vigorous overshooting top could have ascended a few km (or thousands of feet) beyond those altitudes to exhibit an infrared brightness temperature of -92ºC.

Plots of rawinsonde data from Dodge City and Topeka, Kansas [click to enlarge]

Plots of rawinsonde data from Dodge City and Topeka, Kansas [click to enlarge]

A toggle between re-mapped versions of the GOES-16 ABI and Metop-B AVHRR Infrared imagery over Kansas at the time of the very cold cloud-top infrared brightness temperature (below) revealed 2 important points: (1) with improved spatial resolution (1 km for AVHRR, vs 2 km *at satellite sub-point* for ABI) the instrument detectors sensed much colder temperatures (-92.6ºC with AVHRR vs -81.2ºC with ABI), and (2) due to parallax. the GOES-16 image features are displaced to the northwest. In addition to the isolated cold overshooting top in south-central Kansas, note the pronounced “Enhanced-V” storm top signature in far northeastern Kansas.

Comparison of GOES-16 ABI and Metop-B AVHRR Infrared images [click to enlarge]

Comparison of GOES-16 ABI and Metop-B AVHRR Infrared images [click to enlarge]

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Cape Newenham, Alaska bow shock waves

June 10th, 2018 |

GOES-15 Visible (0.63 µm) images, with hourly plots of wind barbs [click to play animation]

GOES-15 Visible (0.63 µm) images, with hourly plots of wind barbs [click to play animation]

GOES-15 (GOES-West) Visible (0.63 µm) images (above) showed patches of fog and low stratus moving southwestward off Southwest Alaska and across the adjacent offshore waters of the Bering Sea on 10 June 2018.

A closer look using 250-meter resolution Terra/Aqua MODIS and 375-meter resolution Suomi NPP VIIRS true-color Red-Green-Blue (RGB) images from RealEarth (below) revealed a packet of “bow shock waves” created as the shallow fog/stratus interacted with the relatively rugged terrain of the narrow Cape Newenham land feature (Google Maps). Other examples of similar bow shock wave cloud features have been documented here, here and here.

Terra MODIS, Aqua MODIS and Suomi NPP VIIRS true-color RGB images [click to enlarge]

Terra MODIS, Aqua MODIS and Suomi NPP VIIRS true-color RGB images [click to enlarge]

A 30-meter resolution Landsat-8 false-color RGB image (below) provided a more detailed view of the bow shock wave structure. Snow cover (cyan) could be seen on some of the higher-elevation land features.

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

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

A time series plot of Cape Newenham surface observations (below) showed the fluctuations in visibility as northerly winds brought patches of fog over the site.

Time series plot of Cape Newenham surface observations [click to enlarge]

Time series plot of Cape Newenham surface observations [click to enlarge]