Geography in the News

The new Met Office model, better at predicting extreme winters?
The met office is now able to predict cold winter weather a season ahead with more confidence, according to analysis of a new computer model.
Scientists say that the new model is better at simulating indications known as sudden stratospheric warming’s (SSWs).These happen when the usual westerly winds at 10-50km altitude break down, causing cold weather on the surface.
The seasonal forecasting model is still in the early stages, but the Met Office says that improving their ability to represent sudden stratospheric warming is a help.
When the stratospheric westerly winds break down, it generates a signal that typically burrows down to the Earth's surface over following weeks. This obstructs surface westerly winds that bring mild air to northern Europe from the Atlantic and allows Europe to get blocked in a cold state.

'High-top' modelling

The model, known as GloSea4, simulates winds, humidity and temperatures from the Earth's surface to 50 miles high. Data points on the old low-top model were capped at around 30 miles.

The high-top model was not available to the Met Office before the bitter winter of 2009/10, and they could not forecast sufficiently far ahead the arrival of the cold that resulted in the UK grinding to an unprepared halt in the snow and ice.

If we had had the high-top model with its atmospheric data available from autumn 2009, the Met Office could have seen the cold coming farther ahead if they had been able to use the new model.

Using its data, the Met Office forecast in autumn 2010 that there was a 40% chance of a cold start to the winter, with a 30% chance of a mild start and a 30% chance of an average start.
The Met Office's current long-range forecasting system, GloSea4, is able to simulate weather conditions in higher parts of the atmosphere. This was not a feature available in the forecast system used for the 2009/10 long-range outlook....