Lab 12: Revisiting the real-time midterm case (Jack Zweifel)

Introduction

For our final lab and blog post of radar and satellite meteorology, I decided to revisit the case presented in our real-time forecasting midterm. On August 14th, 2020, severe weather including thunderstorms with damaging winds, flooding precipitation, and multiple tornadoes were prevalent over Minnesota, especially near its border with North and South Dakota. While localized sounding and radar data were analyzed to investigate the mesoscale environment in the buildup and climax of the event, viewing the case through the lens of satellite imagery will further help to paint a complete picture of the atmosphere that day. To better understand the synoptic scale environment an investigation into worldview data from the Suomi and Aqua instruments was conducted via NASA Worldview.

Worldview Analysis

Figure 1: Gif of Suomi Corrected Reflectance Imagery; Dissipating Convective Conditions over MN (8/14/20 - 8/18/20)

One of the first investigations done using the Suomi corrected reflectance was to analyze the broader region of the Minnesota event and study is propagation and presence with time. Though the real-time midterm focused primarily near individual cities and counties affected by the storm, viewing satellite imagery allows for a big picture of the event. In Figure one, corrected reflectance from the event day of the 14th to full dissipation on the 18th is captured. In the beginning of the loop on the 14th, the entire state of Minnesota is seen blanketed in clouds that have propagated Northward carrying high levels of moisture and instability from the Southern United States. During this great cloud cover was the storm event itself, but just as quickly as storm environment was set up, Westerly winds carried it away as deep convective cloud cover begins to disappear and form smaller pockets of clouds or horizontal convective rolls leaving much of the state uncovered.

Figure 2: Gif of Corrected Reflectance to Cloud Top Temperatures (8/14/20)

Figure 3: Gif of Corrected Reflectance to Cloud Top Heights (8/14/20)

Further investigating the cloud cover, using tools like AQUA's cloud top temperature and height algorithms allow one greater insight into the event itself. As the imaging can be coarse, gifs toggling back and forth between the two instruments' respective field of view and corrected reflectance background provide details on the cloud cover anatomy (figures 2 & 3). As expected with deep convective cloud cover, a majority of the clouds are extremely cold recording temperatures as low as 150 Kelvin. These areas are also associated with the highest cloud tops reaching greater than 13-15 kilometers in depth. The association of "the higher the clouds the colder the tops" holds true in our imagery as temperatures are known to decrease with height in the troposphere. Inversely, clouds recording the warmest temperatures can be seen to have the areas of lowest altitudes, this makes sense as earth's surface is the warmest object so closer proximity to it should result in higher temperatures.  

Figure 4: ISS Lightning Flash Count overlaid on Corrected Reflectance (8/14/20)

Lastly, while storms were reported during the live midterm reports, detection of lighting was unavailable due to limitations in our analysis tools. Wanting to investigate this further, using the International Space Station's Lightning Flash counter overlaid on Suomi corrected reflectance details pinpointed locations of intense convective weather as seen in Figure 4. The ISS LIS Flash Count layer on NASA Worldview provides the number of lightning flashes recorded by the lightning imaging sensor (LIS) on board the International Space Station. By providing total lightning measurements between +/- 48 degrees latitude the tool is able to capture a geographic range mapping nearly all global lightning. As said previously, the concentration of the most severe weather over the border area between North and South Dakota with Minnesota is well seen under this lens. Capturing the highest density of flashes seen over this exact area and parts of North/Central Minnesota adds another layer of information to our storm.

Note: somewhat surprisingly, viewing the event under instrumentation detailing flooding threats and cyclone presence revealed data not-indicative of the reported levels of flooding and damage recorded from on the ground measurements. Interestingly, this may support the idea that while satellites are great for studying the over-arching themes and variables present during a severe weather event, true mesoscale and microscale analysis is best left to radar and trained spotter detection.