Forecaster summary - Issued 2021-12-28T00:37:42

The diurnal oscillation in high energy (greater than 2MeV) electron flux, as observed by GOES-16 again showed an increase through the first half of the past UTC day, only to be attenuated by the arrival of a coronal hole high speed stream, perhaps that from CH37/+. Because the solar wind environment that Earth is encountering in this four-day period bears little resemblance to persistence, confidence is notably low for the period as a whole, with REFM's recent forecast trends markedly lower than observations and also proving very volatile.

There is a Chance of Active fluence being realised once geomagnetic activity eases from the current high speed stream, probably only to be interrupted once again after midweek by a further high speed stream from CH39/+. The onset of CH40/+ is of higher confidence, for bearing greater similarity to its past incarnation. This may mean that arrival is most likely on day four, Saturday 31 December, again potentially denting electron fluence levels for a time.

The forecast for fluence is therefore of low confidence throughout, but probably showing slightly higher chances of exceedence in the wake of the current coronal hole and CH39/+.