Live-updating widgets in the blog's right-hand column now display the daily and hourly S&P 500 (ES) against NOAA's Ap and Kp forecasts. In the daily chart, the historical and forecast Ap is shifted forward by 4 calendar days. This 4-day shift is an averaged compromise. Historically, the optimal shift fluctuates continuously between 2.8 and 6.2 days and currently stands at 5.12 days, as shown in the SWAV chart below, which also updates live.
Exhaustive tests of Kp/ap lags from 0 to 120 hours against the hourly S&P 500 identified a 45-hour forward shift of the Kp/ap as producing the strongest and most stable negative correlation with price.
Assumptions and methodology: