The impact of targeted observations from 2011 Winter Storms Reconnaissance on deterministic forecast accuracy

Previous studies dating back ~1 decade have shown large positive impacts to mid-latitude weather forecasts from the assimilation of targeted observation data taken over relative data voids such as the central Pacific. During the last decade, however, assimilation and forecast systems have improved significantly and the observation network has become more dense. Accordingly, we have performed a test of the impact of targeted dropsonde observations, here from the 2011 Winter Storms Reconnaissance Program, in a modern data assimilation and forecast system (ECMWF, with their 4D-Var assimilation). We will demonstrate that there are generally modest positive impacts to the accuracy of forecasts in specific downstream target regions but that the impact is smaller when evaluated over larger regions. We consider how targeted observation concepts might be extended to help assimilation and forecast accuracy in the current era, where resources to provide extra in-situ data may be constrained.