Forecaster summary - Issued 2020-10-19T00:15:04

Recent changes to the geometry of upcoming coronal holes discussed in the 'geomagnetic' section will have a significant impact on the electron forecast in the coming four days, with persistence likely to offer relatively limited guidance. This means that the day four (Thursday 22 October) rises in probability of Active fluence suggested by the recurrence-persistence model are not favoured. REFM is thought to be doing better, with its suggested flat trend looking more realistic.

Should Earth experience the 400-450km/s high speed stream(s) suggested by STEREO A PLASTIC measurements of late, this should not significantly trouble the Active threshold, although probabilities do rise in the four days, partly a result of uncertainty. The once-a-rotation major player coronal hole appears to be CH90 on this pass, and even this ought to have a more limited impact on electrons this time around for being smaller and having disconnected from the northern crown.