FAST WARNING 'PRESTO' MESSAGE  from the SIDC (RWC-Belgium) 2021 May 12
16:14:01

The fast forward shock that reach Earth at 05:49 UT caused NOAA Kp index
value of 7 (strong geomagnetic storm) for the synoptic period of 12:00 -
15:00UT. For the synoptic period of 15:00 - 18:00 UT the index value
dropped to 6 (moderate geomagnetic storm). The local K Dourbes index value
was 6 (moderate geomagnetic storm) between 14:00-16:00 UT. The geomagnetic
activity is expected to decline significantly in the next 24 hours.