17 June 2010
Our latest forecast confirms the North Atlantic tropical storm season looks set to be active this year.
The Met Office prediction of 20 tropical storms between July and November, with a 70% 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% 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 last 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, which should further improve the accuracy of the forecast.
The forecast also uses information from the seasonal prediction system of the European Centre for Medium Range Weather Forecasts (ECMWF).
One of the key indicators for a tropical storm season is the El Niño Southern Oscillation (ENSO), which affects sea surface temperatures in the tropical Pacific and, remotely, conditions in the North Atlantic.
Therefore, it is vital to be able to accurately predict the ENSO cycle and GloSea4 has shown good skill in such predictions.
Forecasts and background information on tropical storms can be found on our tropical cyclones pages.
Our Climate Services for Reinsurance provide expert advice on tropical storms.
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Last updated: 5 August 2011