The British Met Office has confirmed that an active North Atlantic tropical storm season is expected this year.

The prediction of 20 tropical storms between July and November, with a 70 per cent chance that the number will be in the range 13 to 27, is well above the 1990-2005 long-term average of 12.4.

The Accumulated Cyclone Energy (ACE) index is a measure of the storm lifetimes and intensities as well as total numbers over a season. This year's most likely ACE index is 204, with a 70 per cent chance that the index will be in the range 90 to 319 - this is again well above the 1990-2005 average of 131.

This would make it one of the most active tropical storm seasons on record. In the past 40 years only 2005 has seen more storms in the July to November period with 25 recorded, and only three seasons (1995, 2004 and 2005) have recorded a higher ACE index than 204.

For the past three years, the Met Office forecast has given good indication of Atlantic tropical cyclone activity and was able to identify the relatively quiet seasons of 2007 and 2009 from the active season of 2008.

Matt Huddleston, Principal Consultant on climate change at the Met Office said: "North Atlantic tropical storms affect us all through fluctuating oil, food and insurance markets. The Met Office forecast has demonstrated its benefits over recent years through the accuracy of its predictions".

This year the Met Office has moved to a new prediction system called GloSea4. The new generation model has better representation of the complex physical processes that cause tropical storms and hurricanes to form.