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Storm Tracker Documents: Forecast Errors

The track forecast error bounds shown on the TSR Storm Tracker represent the mean distance between forecast and actual tropical cyclone positions at all lead times over a number of previous years. These errors are calculated by each tropical cyclone forecasting centre (see the Data document for more about these centres) during the post tropical cyclone season assessment of their forecast performance. The errors represent the average performance of tropical cyclone track forecasts at given lead times in a particular region during previous years. As such they do not indicate a definitive bound on the actual future cyclone position and serve as an indication only.

The table below shows the error values (in nautical miles) used by the TSR Storm Tracker. Note that the 96 h and 120 h lead forecasts for the North Indian and Southern Hemisphere have only been introduced in 2010. The error figures used for these lead times and basins (marked * in the table) represent average errors over the period 2010-2012.

The table below provides a summary of the data available for each tropical cyclone region:

RegionMean Position Error for each Forecast Lead Time (nm)Data Period
0 h 12 hrs 24 hrs 36 hrs 48 hrs 72 hrs 96 hrs 120 hrs
North Atlantic 10.1 28.8 45.5 61.2 77.8 114.5 158.4 208.2 2009-2013
North East Pacific 10.1 25.9 41.7 55.3 68.9 98.1 134.6 167.1 2009-2013
North West Pacific 13 38 60 81 104 155 178 243 2008-2012
North Indian 15 42 64 83 101 137 197* 274* 2008-2012
Southern Hemisphere 15 41 62 82 105 134 197* 274* 2008-2012



Researched and Developed by Mark Saunders and Frank Roberts
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