The Tropical Season is Right Around the Corner, Starting June 1st.

2:47 PM, May 9, 2013   |    comments
Even though Sandy had lost her tropical aspects, the storm still had hurricane-force winds and storm surge. After public outcry over mixed messages, the NHC has decided to reform its warning policies.
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There were some big announcements at the National Hurricane Center's off-season annual conference in New Orleans this past March. The NHC learned some important lessons from Hurricane Sandy last October, and they've made important changes based on what they've learned. At the same time, they're also introducing extended forecasts for tropical cyclones, and increasing the precision of the forecasts to give better better warnings to the people in the storm's path. Hurricane season begins on June 1st, so you might notice these changes as those first cyclones start developing in the Caribbean and the Atlantic Ocean! 

In a news release on the NHC's website, the conference's changes are outlined in detail. For meteorologists like myself, perhaps the most satisfying change is in the way tropical storms will be handled if they should lose their tropical characteristics during their life cycle. 

When Hurricane Sandy became an extratropical cyclone over the open waters of the Atlantic on October 29th, some people thought that this was a sign that the storm was weakening. The National Hurricane Center inadvertently reinforced this line of thinking by refusing to issue hurricane watches and warnings for areas in the storm's path. Tragically, not everyone evacuated Sandy's impact zone, despite an incredibly accurate forecast of where and when the storm would make landfall. 

From now on, the NHC will continue to issue Hurricane Watches and Warnings for storms, even if they are no longer classified as tropical systems, so long as "the system continues to pose a significant threat to life and property, and when the transfer of responsibility to another office would result in an 
unacceptable discontinuity in service". Systems will still be classified as post-tropical if the situation warrants it, but I am hopeful that a consistent message from the Hurricane Center will prevent people from letting their guard down. 

Now, some excellent news from the NHC's conference. Over the years, the forecasting service has become much more accurate in predicting the path of a tropical cyclone's movement. This year, they are confidently moving forward with their more accurate forecast products! The Tropical Weather Outlook, which discusses the possibility for tropical storms in a given area, is being extended from 48 hours to a full 5 days. This is obviously a huge improvement by more than doubling the forecast time! 

The "forecast cone" for tropical systems is also getting a lot better. The cone's size is based on the accuracy of previous hurricane forecasts from past years; it is a reflection of the margin for error in the forecast. During the 2013 season, the cone will only be 229nm (about 263mi) wide for the 120 hour forecast. That means when a storm is still 5 days away from landfall, the NHC will have its track pinned down to a segment of coastline about the same length as the distance between DC and New York City!

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