GLM and low-topped convection in the Midwest

In glancing over the weather this morning at the TCF desk within the Summer Experiment, participants caught sight of some interesting happenings with the GLM lightning.

Below is the 1557 UTC display of gridded GLM Event density.

20170810 1557 UTC GLM gridded event density - 10 minute average every 2 minutes. THIS DATA IS PRELIMINARY AND NON-OPERAITONAL!

An area of low-topped convection was beginning to develop over SE Missouri, with the GLM picking up some associated lightning activity. Particularly interesting was the southern area of GLM lighting near Branson. Though not overlaid here, there were no NLDN strikes in the same area at this time.

Now the 1617 UTC gridded GLM Event density with NLDN overlaid:

20170810 1617 UTC GLM event density and NLDN strikes. THIS DATA IS PRELIMINARY AND NON-OPERAITONAL!

Note now, about 15 minutes after the first GLM activity was noted, the NLDN finally saw some strikes in the convection over SW Missouri. Additionally, there was more GLM activity within this area that still wasn't not showing NLDN strikes. Earth Networks was also not picking up this activity:

20170810 1557 Earth Networks gridded density - 10 minute average every 2-minutes.

So, from a first glance, it does appear that the GLM has some skill in picking up lightning activity earlier than current ground-based networks.

All that said, caution must be used when looking at ground-based vs. satellite-based. Comparing Earth Networks to GLM is not apples to apples given the inherent differences in the sensor platforms. For that reason, participants have been exploring this data at a more general scale. Instead of examining intensity and number of strikes, they have been examining areas where GLM might be picking up lightning activity more quickly as noted above, and also areas in which GLM is simply detecting lightning where other networks are not. An example of the latter is shown below:

20170810 1337 Earth Networks and NLDN lightning over the tropics. Note the activity over Florida and the Bahamas and also out towards Bermuda.

20170810 1337 GLM lightning density. Note the activity over Florida and the Bahamas and also out towards Bermuda. THIS DATA IS PRELIMINARY AND NON-OPERAITONAL!

GLM showed lightning in convective activity over Florida and the Bahamas that the other networks did not. Additionally, it also detected lightning in convection further out into the Atlantic that the other networks did not. If data quality is accurate, this has a lot of potential for Tropical forecasters at the AWC. Observations off shore are very hard to come by, particularly for Convective SIGMET issuance and GLM will provide a lot of value.