Articles | Volume 14
05 May 2017
 | 05 May 2017

Subseasonal-to-seasonal (S2S) forecasts with CNRM-CM: a case study on the July 2015 West-European heat wave

Constantin Ardilouze, Lauriane Batté, and Michel Déqué

Abstract. An intense heat wave struck West Europe in early July 2015. The degree of anticipation of that event is assessed through the new CNRM near-real time subseasonal to seasonal forecast system. A warm anomaly over France was detected for the first week of July in all the successive forecasts issued in June, even up to one month ahead. On the other hand, the positive 500 hPa geopotential anomaly observed during that period was little anticipated. Despite the limited skill of the forecast system beyond twelve days, the relatively successful anticipation of that event pleads for a predictability study based on a multi-system assessment.

Short summary
Was the July 2015 heat wave that struck Western Europe predictable more than 10 days ahead and to what extent? This article addresses the question by assessing forecasts from the CNRM-CM sub-seasonal forecast system. It is found that a warm anomaly was anticipated up to one month ahead despite the limited skill of the forecast system at such lead-time. The possible causes for this relative success are then discussed.