Atlantic hurricane season 2013: What's in a name?
Since 1950, tropical cyclones in the Atlantic Ocean have been given names to help quickly and uniquely identify current and past storms. From 1950-1952, storms were given names from the Royal Air Force's phonetic alphabet. For the following 26 years, all storm names were female names. Then in 1979, the current system of alternating male and female names was introduced, and the same six lists are rotated through in six years. So unless a name is retired, it will be used again six years later. For example, Ana has been used in 1979, 1985, 1991, 1997, 2003, 2009, and will be used again in 2015. But occasionally, the first time a name is used is also the last. The most recent example is Igor; Igor was introduced to the list when Ivan was retired in 2004. But, Igor was then retired after its one and only use in 2010.
According to the National Hurricane Centre, names get retired "if a storm is so deadly or costly that the future use of its name on a different storm would be inappropriate for reasons of sensitivity". This year, we have three new names in the list. In 2007, Dean, Felix, and Noel were retired; they are replaced by Dorian, Fernand, and Nestor.
2013 Atlantic Storm Names:
Melissa, Nestor, Olga, Pablo, Rebekah, Sebastien, Tanya, Van, Wendy,
A shrinking cone
Another noteworthy update for 2013 is a smaller "forecast cone" (also referred to as the "cone of uncertainty") for tropical systems. The National Hurricane Centre (NHC) uses a cone on its forecast track graphics to convey typical forecast errors. While a centre line is drawn for clarity, forecasters stress not to focus too much on it because there are likely to be errors in the forecast, and the storm will affect areas far away from the centre.
The cone is designed to enclose two-thirds of the recent forecast errors meaning, that on average, there is still a one-third probability that the centre of the storm could track outside of the cone.
Of course, the centre of the storm is just a small part of the story. Since any given storm expands well beyond its centre, the impacts of a storm can be felt a substantial distance away. Thus, the forecast cone is NOT an impacts cone. Presently, the same cone size is used for an entire season and for all storms. The 2013 cone size is determined by NHC's track errors from the 2008-2012 seasons. As track forecasts improve, the cone gets smaller!
New tropical weather impacts-based graphics
Also in the spirit of improved visual communication of forecasts, there is an experimental web-based product that has been in development for over ten years, and has undergone several iterations of public feedback and inter-agency collaboration.
When an active storm threatens the American coast, the Tropical Cyclone Impact Graphics (TCIG) website lets users view detailed maps showing potential impacts from wind, storm surge, inland flooding, and tornadoes. Impacts in each of those categories are ranked and colour coded from "None" up through "Extreme".
This impacts communication product is expected to transition to fully operational in the 2014 or possibly 2015 hurricane season, but it is being supported on an experimental basis for this season.