Fig 7. Log scores from training and out-of-sample retrospective forecast using the baseline and perturbed SIRS-EAKF systems.

Results are averaged for weekly forecasts for a randomly chosen half (training) and the rest (validation) of historical outbreaks in 95 US cities during the 2003–2004 through 2013–2014 seasons, excluding the 2008–2009 and 2009–2010 pandemic seasons. The perturbation procedure improves log scores for all four targets, predominantly at the predicted leads between 0 to 6 weeks.