Forecaster summary - Issued 2023-08-16T00:29:22

In recent days the high energy (greater than 2 MeV) electron flux at GOES16 has been varying between Normal Background and diurnal peaks of High (above 1000pfu). However, on 16th August a diurnal peak of Moderate was observed and with the onset of two high-speed streams forecast on Day 1 and 2 (16th and 17th) any periods of High flux are considered very unlikely as electron counts at GEO are suppressed for a time.

Confidence in the intervening time period is perhaps a little lower relative to recent issues of this guidance - due to the uncertain timing and duration of the fast winds from CH33/+ and CH35/-. As stated, however, the chances of avoiding any high speed stream from trans-equatorial CH35 are considered very low. The extent of any rebound is therefore the main uncertainty for the forecast overall, rather than the timing, which is reasonably likely to take place later this working week. This should see fluence perhaps responding from late Day 3 (18th) and probably reaching diurnally High values once again. The coronal holes on the disc were present on last pass, but geometry changes serve to lower confidence in persistence, even in the absence of any complicating transient effects.

An overall and increasing Chance of Active electron fluence is indicated for late this UTC week, with an extremely low risk prior to this.