The National Hurricane Center will yet again improve their forecast and communication products with a number of changes for the upcoming hurricane season.
Their swiss army knife of products, including their well-known hurricane cone along with many lesser-known, but just as important tools, is updated each year based on the latest state of the science.
Here are a few ways that the National Hurricane Center (NHC) will be updating their products this year:
1. The cone of uncertainty will shrink
Each year, the NHC adjusts the size of its cone of uncertainty based on its average error over the previous five hurricane seasons. The cone of uncertainty refers to the projected path map you frequently see on the internet or television for a given storm.
The cone encapsulates 66 percent of the historical forecast track errors, and does not represent where impacts like surge, wind, flooding or tornadoes will be felt.
For the 2018 Atlantic hurricane season, the NHC will use the average track error for the 2013-2017 hurricane seasons.
Track errors have gone down over the last 10 years and forecasts have gotten better as well. In fact, since 2008, the size of the cone of uncertainty at 120 hours, or five days, has shrunk by 35 percent. Since last year, the size of the cone at five days has shrunk by more than 6 percent.
This cone does not encapsulate all impacts from a given storm or hurricane. In fact, most impacts will fall outside of the cone of uncertainty within a forecast out to a day or two.
For this reason, among others, the NHC and our meteorologists will be leaning more toward forecast impacts rather than this cone alone in the upcoming hurricane season.
2. Hazard information will be conveyed more than 48 hours in advance
The NHC’s formal advisory package includes a text statement that includes all hazards – storm surge, wind, inland flooding, tornadoes, increased surf – ahead of a tropical storm or hurricane.
Beginning in 2018, when the forecast confidence is high enough, a discussion of any applicable hazards will go well beyond two days in advance.
This will allow forecasters at the NHC to discuss high-impact high-confidence storms, like Hurricane Maria in 2017, as much as 5 days in advance.
3. Changes in forecast wind products
The NHC will make one of its trial run products from 2017 operational this year: a forecast for the time when it is too late to be making preparations for a tropical storm or hurricane outside.
This product shows when sustained winds could at the earliest reach 40 mph or make it dangerous to be outside doing anything, including preparedness activities. Winds of this intensity and higher gusts can cause damage to structures and can overturn and/or move some objects like ladders and plywood.
Generally, police, fire and ambulance support will stop answering requests for help when winds reach between 35 and 45 mph in a given area.
A similar graphic, not shown here, will show when sustained winds of 40 mph or greater will most likely reach a given area.
The NHC will also be making a 48-hour hurricane force wind radius forecast beginning this season.
Before 2018, these forecasts only went out to 36 hours. This improvement will allow forecasters to better communicate the risk of hurricane force winds for a given hurricane earlier before a hurricane arrives at a certain location.