AEMO (and the BOM) warning about possible ‘Severe Space Weather’ (at G4, possible G5) in next ~24 hours

One of our keen readers has reminded us that on Monday evening 10th November 2025, the AEMO published MN130547 warning about possible ‘Severe Space Weather’

… with AEMO interested because of possible impacts on the electricity grid.

Here’s the full text of the Market Notice in the ez2view window:

Now, my initial comment to the reader was along the lines of these Market Notices becoming quite common in recent years, so me just tuning them out.  But the reader’s also highlighted specific wording on the BOM’s Space Weather Forecasting Centre site here (snapshot at 12:19 NEM time on Wednesday 12th November 2025):

The specific wording of the ‘Summary Forecast’ I’ll lift out here:

‘On UT day 12-Nov solar activity is expected to be R2-R3. A strong shock in the solar wind was detected at 11/2338UT. The solar wind speed is expected to be very strong. G4 geomagnetic storm conditions are currently being observed. G4 with a chance for G5 is expected on 12-Nov. Solar radiation storm conditions are currently at S2, expected to reach S3. Global HF radio propagation conditions are expected to become degraded. Maximum usable frequencies i the Australian region are expected to become depressed by 40-50%. Visible auroras are possible in mid to southern parts of Australia.’

Now, the bit that I’ve highlighted (remembering that times are in UTC, this was published at 11:17 NEM time on Wednesday 12th November 2025) is the particular bit of interest.

If we navigate through to this page of the NOAA Space Weather Prediction Center in the US, we see a useful table:

Again, I’ve copied out the highlighted bits, in relation to the possible effects on power systems:

1)  At G4 (i.e. Severe) levels, which the BOM says we are experiencing:

‘Power systems: Possible widespread voltage control problems and some protective systems will mistakenly trip out key assets from the grid.’

2)  At G5 (i.e. Extreme) levels, which the BOM says we might experience:

‘Power systems: Widespread voltage control problems and protective system problems can occur, some grid systems may experience complete collapse or blackouts. Transformers may experience damage.’

All in all, something readers might like to be aware of?