Thunderstorms affecting American Samoa

June 20th, 2020 |

VIIRS Infrared Window (11.45 µm) images from NOAA-20 and Suomi NPP [click to enlarge]

VIIRS Infrared Window (11.45 µm) images from NOAA-20 and Suomi NPP [click to enlarge]

VIIRS Infrared Window (11.45 µm) images from NOAA-20 and Suomi NPP as viewed using RealEarth (above) showed thunderstorms beginning to increase in areal coverage north of and in the vicinity of American Samoa on 20 June 2020, as a surface trough north of the islands began to move southward.

To monitor the flash flooding potential of these thunderstorms, a GOES-17 (GOES-West) Mesoscale Domain Sector was positioned over the American Samoa region — which provided “Clean” Infrared Window (10.35 µm) images at 1-minute intervals (below). Some of these storms exhibited minimum cloud-top infrared brightness temperatures around -80ºC (black enhancement), producing heavy rainfall (over 6 inches in 9 hours) and strong winds (gusting to 60 mph) according to the NWS Pago Pago compilation of local storm reports.

GOES-17 "Clean" Infrared Window (10.35 µm) images [click to play animation | MP4]

GOES-17 “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

Tropical Storm Cristobal makes landfall along the coast of Louisiana

June 7th, 2020 |

GOES-16 “Red” Visible (0.64 µm) images [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) images [click to play animation | MP4]

1-minute Mesoscale Domain Sector GOES-16 “Red” Visible (0.64 µm) images (above) revealed low-level vortices that were pivoting around the analyzed center of Tropical Storm Cristobal as it approached the coast of Louisiana on 07 June 2020, making landfall at 2200 UTC. Wind gusts were as high as 57 mph in Louisiana and 64 mph in Mississippi.

GOES-16 Visible images with overlays of GLM Flash Extent Density (below) indicated that there was very little satellite-detected lightning associated with Cristobal.

GOES-16 “Red” Visible (0.64 µm) images, with overlays of GLM Flash Extent Density and surface reports [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) images, with overlays of GLM Flash Extent Density and surface reports [click to play animation | MP4]

GOES-16 “Clean” Infrared Window (10.35 µm) images (below) showed numerous cloud-top infrared brightness temperatures as cold as -70 to -77ºC (darker shades of red) within some of the convective bands.

GOES-16 “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

GOES-16 “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

GOES-16 Longwave Infrared Window (11.2 µm) images with plots of Derived Motion Winds (below) showed the broad low-, mid- and upper-level circulation of the tropical storm.

GOES-16 Longwave Infrared Window (11.2 µm) images, with plots of Derived Motion Winds [click to play animation | MP4]

GOES-16 Longwave Infrared Window (11.2 µm) images, with plots of Derived Motion Winds [click to play animation | MP4]

Rich tropical moisture was being transported northward across the Gulf of Mexico by Cristobal — the Blended Total Precipitable Water (TPW) and Percent of Normal TPW product (below) portrayed a large area with TPW values in the 2.5-3.0 inch range, which represented departures of 175-200% of normal. This led to areas of flash flooding along parts of the Gulf Coast, with some locations receiving 4-8 inches of rainfall.

Blended TPW and Percent Normal TPW images [click to play animation | MP4]

Blended TPW and Percent of Normal TPW images [click to play animation | MP4]

The MIMIC TPW product during the period 03-07 June (below) provided a larger-scale view of the origins of the tropical moisture associated with Cristobal.

MIMIC TPW product, 03-07 June [click to play animation | MP4]

MIMIC TPW product, 03-07 June [click to play animation | MP4]

Heavy rainfall and flash flooding in South Florida

May 26th, 2020 |

GOES-16 “Red” Visible (0.64 µm) and

GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images (above) showed training and back-building thunderstorms that produced very heavy rainfall and flash flooding across parts of South Florida — particularly in the Miami (KMIA) area — on 26 May 2020. Pulsing overshooting tops were evident, with cloud-top infrared brightness temperatures as cold as -77ºC.

The GOES-16 Total Precipitable Water product (below) revealed clear-sky TPW values as high as 2.2 inches (lighter shades of magenta).

GOES-16 Total Precipitable Water product [click to play animation | MP4]

GOES-16 Total Precipitable Water product [click to play animation | MP4]

Hourly images of the MIMIC Total Precipitable Water product (below) showed the rich tropical moisture associated with a tropical disturbance that had resided over the region for several days.

MIMIC Total Precipitable Water product [click to enlarge]

MIMIC Total Precipitable Water product [click to enlarge]

Flooding along the Tittabawassee River in Michigan

May 20th, 2020 |

GOES-16 ABI Band 2 (0.64 µm), Band 3 (0.86 µm) and CIMSS Natural Color at 1521 UTC on 20 May 2020 (Click to enlarge)

Dam failures in central lower Michigan along the Tittabawassee River (one of the rivers in the Saginaw Bay basin) caused extensive flooding on 20 May 2020 in Midland County, including the city of Midland. Much of this region received between 4 and 5 inches of rain in the past week (analysis, from this site). The Tittabawassee River gauge at Midland (shown here, from this site), was projected to exceed its previous maximum by 4 feet (It ended up exceeding it by just over 1 foot).  The heavy rains have produced a notable silt plume into Saginaw Bay in the imagery above (a plume that is rotating cyclonically).

GOES-16’s Advanced Baseline Imager (ABI) has spatial and spectral resolution to identify flooded regions near Midland, as shown in the imagery above from 1521 UTC on 20 May.  Of special note are the dark pixels very close to Midland MI in the 0.86 µm imagery (shown here with a map)   Water is more reflective in the visible (0.64 µm) than in the near-infrared (0.86 µm) (Compare the darkness of Lake Huron in those two channels) so when areas are flooded, they acquire a darker reflectance value.  A more zoomed-in toggle, below, between Visible (0.64 µm) and 0.86 µm imagery highlights the reflectance differences near Midland where flooding is occurring.  Flooded regions are also apparent south of Saginaw, to the south and east of Midland County.

GOES-16 VIsible (0.64 µm) and Near-Infrared (0.86 µm) at 1521 UTC on 20 May 2020. Midland County is outlined. (Click to enlarge)

Real Earth includes Flood Products that are derived from ABI and from the VIIRS Instrument (the Visible-Infrared Imaging Radiometer Suite) on NOAA-20 and Suomi NPP. The ABI-only product, below, taken from that site, shows the regions of flooding.

ABI Flood Product, 1400 UTC on 20 May 2020 (Click to enlarge)

This link (courtesy Tim Schmit, NOAA/CIMSS) compares Band 3 (0.86 µm) imagery from before and during the flood (13 and 20 May 2020).  VIIRS true-color imagery, below, processed at the Direct Broadcast antenna at CIMSS, also show the changes from 13 May to 20 May.

VIIRS True Color Imagery over and near Saginaw Bay in lower Michigan on 13 and 20 May 2020 (click to enlarge)

The Flood Areal Extent processed from VIIRS data is shown below.  Both ABI and VIIRS products are available via LDM feed (in addition to being available in Real Earth and in GeoNETCAST). The Project Website is here. Tim Schmit has created a slider between the ABI and VIIRS flood product here.

VIIRS Flood Areal Extent product, 20 May 2020 (Click to enlarge)

The National Weather Service in Detroit is issuing flood warnings for this event. Midland County is in their County Warning Area.


Shane Hubbard at UW-Madison/CIMSS has created an arcGIS website that shows the areal extent of the flooding.  That site is here.  A screen capture is shown below.

Arcgis view of flooded regions near Midland and Saginaw MI from the 20 May 2020 Dam Break.

Satellite detection of this event is also discussed here.