First thunderstorm of the season in the Anchorage, Alaska area

May 4th, 2022 |

GOES-17 “Red” Visible (0.64 µm) images [click to play animated GIF | MP4]

1-minute Mesoscale Domain Sector GOES-17 (GOES-West) “Red” Visible (0.64 µm) images (above) showed these isolated thunderstorms as they moved north-northwestward up the Susitna Valley (northwest of Anchorage).

In the corresponding 1-minute GOES-17 “Clean” Infrared Window (10.35 µm) images (below), the coldest cloud-top infrared brightness temperatures of the thunderstorms were around -35ºC (darker blue enhancement).

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

A toggle between Suomi-NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images around 2201 UTC (below) included a plot of available NUCAPS sounding points from NOAA-20.

Suomi-NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images and 2201 UTC [click to enlarge]

The NOAA-20 NUCAPS profile for the green (infrared + microwave) sounding point 25 miles WSW of Big Lake (below) diagnosed a surface parcel CAPE value of 616 J/kg, with a Lifted Index of -3.  

NOAA-20 NUCAPS profile for the sounding point 25 miles WSW of Big Lake [click to enlarge]

A later toggle between Suomi-NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images and 2345 UTC is shown below; the coldest cloud-top infrared brightness temperature of the thunderstorms was -38ºC (near Big Lake), which closely corresponded to the altitude of the Equilibrium Level on the NUCAPS profile.

Suomi-NPP VIIRS Visible (0.64 µm) and Infrared Window (11.45 µm) images and 2345 UTC [click to enlarge]

Comparisons of LIS and GLM Lightning observations

May 4th, 2022 |
GOES-16 5-minute Flash Extent Density (updated every minute) and ISS LIS Flash Events, 1318-1320 UTC on 4 May 2022 (Click to enlarge)

The Geostationary Lightning Mapper (GLM) on GOES-16 and the Lightning Imaging Sensor (LIS, additional information here) on the International Space Station (ISS) both observe lightning. The GLM has nadir resolution of approximately 8 km, and is in geostationary orbit, about 36000 km above the Earth’s surface. In contrast, the LIS has a resolution of approximately 4 km, and it’s on the ISS, only 400 km above the Earth’s surface. Both sensors detect the optical signal of the lightning. The animation above shows 2 minutes of LIS Flash Events plotted (in yellow) on top of 5-minute aggregates of GLM Flash Extent Density (updated at 1-minute time-steps). The animation below shows the same LIS observations, but plotted in black, on top of GOES-16 ABI Band 13 imagery. Many of the LIS flash events are colocated with cold cloud top as defined by the GOES-16 Band 13 (10.3 µm) brightness temperatures — meaning that the optical signal is strongest there. That’s not always the case though, as shown in this image with LIS data from 13:19:48.

GOES-16 Band 13 Infrared (10.3 µm) imagery and LIS Flash Events, 1318-1320 UTC on 4 May 2022 (Click to enlarge)