June 18, 2012 by Canadian Underwriter
The Canadian Hurricane Centre (CHC) has an improved handle on tracking hurricanes, and is now turning its eye towards decreasing errors in forecasting storm intensity, particularly for rapidly intensifying or weakening storms.
Error rates for tracking rapidly developing storms (those emerging in 24 or 48 hours) have been halved over 10 years, Bob Robichaud, warning preparedness meteorologist for the CHC, said in his presentation notes for the June installment of the Institute for Catastrophic Loss Reduction (ICLR)’s Friday Forum Series. Errors have also substantially reduced for tracking storms over 72-, 96- or 120-hour periods.
But “intensity forecasting is not as advanced as track forecasting,” Robichaud’s presentation notes indicate. “There is less skill for intensity forecasting than there is for track forecasting due to the many factors affecting storm intensity (water temperature, wind shear, pressure patterns, etc…).”
Partly for this reason, forecasters use entirely separate models to forecast storm intensity and storm tracking.
Robichaud’s presentation slides show that, for storms developing quickly during a 24-hour period, the rate of error for predicting storm intensity has increased from just under 10% to just over 10% between 1990 and 2010. “There is significant difficulty in forecasting rapidly intensifying and rapidly weakening storms,” the notes state.
In contrast, the error rates for forecasting the intensity of storms developing over longer periods (48, 72, 96 or 120 hours) have all decreased over time between 1990 and 2010.
Robichaud said the CHC is continuing to work on reducing track and intensity errors, from the first day of the storm through the fifth, aiming for a 50% reduction in the error rate over the next 10 years. It is also working on better forecasts of rapid intensity change.
The CHC plans to introduce some changes in how it presents its hurricane information. Currently, a map is available online that shows the current location and projected track of a hurricane, with a cone indicating where the storm might strike over a certain future period. The goal is to introduce a “cone of error” in 2013.
Also, the National Hurricane Centre, based in the United States, is planning to extend the lead time for its hurricane forecasts to seven days, Robichaud’s presentation notes say.