Better way to forecast winter weather a month in advance

Taking into account the unusual winds miles up in the stratosphere can lead to more accurate winter weather forecasts a month in advance, says new research led by an Indian-origin scientist.

"Forecasting the weather a full month ahead is a tough ask, but that is what businesses and emergency services really need to prepare for extreme winter weather," said lead researcher Om Tripathi from University of Reading in England.

"Our latest findings should give forecasters more confidence when issuing some winter weather forecasts up to a month in advance," Tripathi pointed out.

High up in the stratosphere is the polar night jet stream, at around 40 km above the surface of the Earth.

Winds in the polar night jet stream usually blow from the west and have speeds of around 70 mph.

The research team found that during conditions in which the polar night jet stream wind speeds exceed 90 mph, or reverse their direction to flow from the east, forecasts in both the stratosphere and troposphere (the layer of atmosphere closest to the ground), are more skilful.

The researchers examined 30 years' worth of past forecast data to see how the state of the stratosphere affected the accuracy of the forecast.

"We are only just beginning to learn how conditions in the stratosphere influence our weather several weeks later," study co-author Andrew Charlton-Perez from University of Reading noted.

"The more we learn about these links, along with other processes in the tropical atmosphere and links between the land surface and the atmosphere, the more we can improve weather forecasts" Charlton-Perez said.

The research was published in the journal Environmental Research Letters.