The astronomical autumn will start in about a month and a half, but for weather experts it starts on September 1st. Big question: what has winter got in store for us? The rule shows that October snowfall is often just too early, but that a snowy November guarantees the first real PowderAlerts.
The new forecasts of the ECMWF (European Center for Medium-Range Weather Forecasts) have recently been published. Their Seasonal Forecasting System (called S4) makes statements about the future on an experimental basis. They make experimental statements about temperature and precipitation in their maps, where they emphasize on deviations from the average.
This means that the regions that have a red glow on the temperature maps are expected to be warmer than normal, while in the blue zones it might become colder than normal. With the precipitation maps, a red glow means dryer weather than normal, while a blue glow means more precipitation than normal.
But what is normal? Francesco A. Isotta et al. have already done research on precipitation in the Alps in 2003. Especially extreme rainfall is most visible on the southern side of the Alps, with autumn and spring in particular guaranteeing days with extreme precipitation levels.
We can already regularly see lots of snow coming down in the high alpine of the southern Alps and the bordering areas in the main alpine ridge in November. If the Seasonal Forecasting System of the ECMWF is right, it could be like this again this winter. Up to and including January (according to their expectations), it is clearly warmer than normal with a lot of precipitation on the southern side of the main alpine ridge. This would indicate a south-western to southern current that often guarantees a lot of snow. Something that is in line with the seasonal forecast of Meteo France, but it also has a lot of similarities with the El Niño research that we wrote about earlier. The results: a mild start of the winter with lots of snow for the high alpine of the southern Alps.
Only from the middle of winter the temperature should drop significantly. But beware: seasonal forecasts are (still) a highly experimental product where you have to take into account that forecasts are increasingly less accurate in the future.
But experimental or not. These are nice reflections so by the end of summer and who knows we can ride powder in St. Moritz, the southern Ötztal or around the Ortler!