The cover image of this article is from westernrivers.org.

Unrelenting Rain and Unusual Heat Across US, California and Asia

The exceptionally wet weather across California has been caused by an “atmospheric river”, a long, narrow corridor of concentrated water vapour travelling through the atmosphere. This phenomenon has brought successive areas of low pressure, leading to more than 250mm (10 inches) of rain over a 10 day period ending on the 4th of January. Unfortunately, this heavy rain has already led to six fatalities. Although the majority of this precipitation has fallen in the form of snow in the Sierra Nevada mountains, there could be as much as 300mm of rain per week in the north-west of the state.

The rain is set to be accompanied by strong winds, with gusts as high as 70mph, while the snow levels in the mountains could accumulate up to several metres in depth by the end of the week.

Meanwhile, east Asia is in the grip of an unseasonably warm spell. Temperatures are already higher than normal throughout China and these high temperatures are forecast to spread to Japan and the Korean peninsula by the end of the week. This could lead to record temperatures in cities like Shanghai, with the January record of 22.1C potentially being broken. Other cities in the region, including Tokyo and Seoul, will see temperatures at least 10C higher than the seasonal average.

Skiers and snowboarders can take some solace in the Alps as the region has recently experienced some much-needed and consistent snowfall. After weeks of a near absence of snow, due to unseasonable warmth, 20-40cm of snow has fallen in recent days, with plenty more snow forecast until the end of the week. This should bring some welcome relief to skiing resorts that were suffering from a lack of snow.