There was widespread media coverage in advance of of a predicted G3 storm on 2021-10-31 due to a CME. For instance, https://www.npr.org/2021/10/30/1050810514/northern-lights-halloween-2021:
A solar flare erupted on Thursday morning and is expected to reach Earth on Saturday. NOAA's Space Weather prediction center in Boulder, Colo., announced the possibility of increased visibility of the lights on Thursday when it issued a G3 geomagnetic storm watch for the weekend.
However, this storm never materialized.
The prediction from SWPC directly was as follows (available at ftp://ftp.swpc.noaa.gov/pub/forecasts/three_day/10310030three_day_forecast.txt):
:Product: 10310030three_day_forecast.txt
:Issued: 2021 Oct 31 0030 UTC
# Prepared by the U.S. Dept. of Commerce, NOAA, Space Weather Prediction Center
#
A. NOAA Geomagnetic Activity Observation and Forecast
The greatest observed 3 hr Kp over the past 24 hours was 4 (below NOAA
Scale levels).
The greatest expected 3 hr Kp for Oct 31-Nov 02 2021 is 7 (NOAA Scale
G3).
NOAA Kp index breakdown Oct 31-Nov 02 2021
Oct 31 Nov 01 Nov 02
00-03UT 5 (G1) 4 3
03-06UT 5 (G1) 5 (G1) 3
06-09UT 6 (G2) 4 2
09-12UT 7 (G3) 3 2
12-15UT 6 (G2) 3 1
15-18UT 5 (G1) 2 1
18-21UT 5 (G1) 2 1
21-00UT 4 3 2
Rationale: G1-G3 (Minor-Strong) geomagnetic storm conditions are likely
on 31 Oct due to the anticipated arrival of a CME from 28 Oct. G1
(Minor) storming is likely on 01 Nov as conditions persist.
B. NOAA Solar Radiation Activity Observation and Forecast
Solar radiation, as observed by NOAA GOES-16 over the past 24 hours, was
above S-scale storm level thresholds.
Solar Radiation Storm Forecast for Oct 31-Nov 02 2021
Oct 31 Nov 01 Nov 02
S1 or greater 99% 5% 5%
Rationale: S1 (Minor) solar radiation storm conditions are expected to
persist on 31 Oct.
C. NOAA Radio Blackout Activity and Forecast
No radio blackouts were observed over the past 24 hours.
Radio Blackout Forecast for Oct 31-Nov 02 2021
Oct 31 Nov 01 Nov 02
R1-R2 35% 35% 35%
R3 or greater 5% 5% 5%
Rationale: There is a chance for R1-R2 (Minor-Moderate) radio blackouts
on 31 Oct - 02 Nov due to the flare potential of Regions 2887 and 2891.
The actual levels over time are shown in this picture, taken from NOAA as well:
My question is, what happened? Did the CME miss the Earth? Or is there another explanation for the large difference between the prediction and reality?
