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]

Derecho in South Dakota

June 7th, 2020 |


GOES-16 ABI Band 13 (10.3 µm) infrared imagery, 1901 6 June 2020 – 0656 7 June 2020 (Click to play mp4 animation)

 

Portions of the High Plains and intermountain states experienced a climatologically rare Derecho event oni 6-7 June 2020. (Here is a preliminary write-up on this event from the National Weather Service in Rapid City SD;  the forecast office in Boulder discussed the event here.). The GOES-16 Clean window infrared (10.3 µm) animation, above, (Click here for the same animation as an animated gif) shows rapid development over western South Dakota late in the afternoon of 6 June. The swath of wind reports is shown in this graphic from the Storm Prediction Center.

Several satellite-based thermodynamic estimates keyed in on South Dakota as a region where instability was noteworthy. The GOES-16 All-Sky Convective Available Potential Energy (available here), shown below from 2026 UTC on 6 June when values were greatest, for example, showed a persistent corridor of instability across South Dakota.

GOES-16 ‘All-Sky’ estimates of Convective Available Potential Energy, 2026 UTC on 6 June 2020 (Click to enlarge)

NUCAPS estimates of 700-500 mb lapse rates, below (from this site), show pronounced instability upstream of South Dakota at 1945 UTC, when Suomi-NPP overflew the region. (Most of the soundings used to produce the lapse rate information were from successful infrared retrievals as shown in this graphic).

700-500 mb Lapse Rates derived from Suomi NPP NUCAPS soundings, 1945 UTC on 6 June 2020 (Click to enlarge)

Surface moisture had pooled over western South Dakota. That is shown in the plot below of surface dewpoints showing very unusual (for South Dakota) mid-60s dewpoints! Further evidence of the unusual moisture amounts over the high Plains (for early June) is in this sounding from Rapid City at 0000 UTC on 7 June (source); Precipitable Water is at 1.2″! This value is unusual for the location and time of year, as shown here (Source).

Surface Dewpoints, 2100 UTC on 6 June 2020 over South Dakota and surrounding states (Click to enlarge)

GOES-17 Full-Disk imagery (at 10-minute time-steps) captured an oblique view of the developing convection. (The ‘PACUS’ sector with 5-minute imagery terminates in west-central South Dakota so is not used here; A GOES-17 Mesoscale sector was not in place for this event, although a GOES-16 one was).

GOES-17 Visible Imagery (0.64 µm) on 7 June 2020, 0000 – 0220 UTC (Click to animate)

1-minute Mesoscale Domain Sector GOES-16 “Red” Visible images with time-matched plots of SPC Storm Reports are shown below.

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]