Weather Blog: NOAA Updates “Average” Atlantic Hurricane Season Numbers

Weather Blog

NOAA Increases The Number Of Storms For An Average Season From 12 To 14.

Updated average hurricane season for the Atlantic Basin. Image: NOAA

NOAA (National Oceanic & Atmospheric Administration) has announced an update to the “average” hurricane season for the Atlantic Basin.

Waves crash near a pier, at Gulf State Park, Tuesday, Sept. 15, 2020, in Gulf Shores, Ala. Hurricane Sally is crawling toward the northern Gulf Coast at just 2 mph, a pace that’s enabling the storm to gather huge amounts of water to eventually dump on land. (AP Photo/Gerald Herbert)

Beginning this year, the Climate Prediction Center (CPC) & National Hurricane Center will use 1991-2020 as the new 30-year average baseline for average hurricane seasons.

The new update increases the number of named storms (tropical storm or hurricanes) from 12 storms per year to 14 named storms.

Tropical cyclones are classified based on their maximum sustained wind speed. Tropical cyclones with maximum sustained winds 38 mph or less are considered a tropical depression. Tropical storms have sustained winds between 39-73 mph. Storms become a hurricane when sustained winds reach 74 mph or greater. If a storm has sustained winds 111 mph or greater, it becomes a major hurricane.

The average number of hurricanes (storms with sustained winds 74mph or greater) for a given season in the Atlantic has also increased from 6 to 7 per year.

The number of major hurricanes (hurricanes with sustained winds of 111mph or greater) on average remains the same at 3 storms per year.

NOAA updates the numbers for an “average” hurricane season every 10-years to reflect the past 30 years of data. The previous update was done in 2011 and used data from the 1981-2010 seasons.

“This update allows our meteorologist to make forecasts for the hurricane season with most relevant climate statistics taken into consideration,” said Michael Farrar, director of NOAA’s National Centers for Environmental Prediction.

Visible satellite of Hurricane Laura’s eye upon final approach to the SW Louisiana coastline on August 26, 2020. Laura made landfall in Cameron, LA in the early morning of August 27, 2020.

Seasonal hurricane forecaster Matt Rosencrans said, “These updated averages better reflect our collective experience of the past 10 years, which included some very active hurricane seasons”.

With the increase in numbers, many wonder if climate change is responsible. Research has determined warmer ocean temperatures can influence cyclone intensity, but additional research is needed to understand how climate change may impact the frequency of storms.

Trendline showing percentage of all hurricanes as major storms. NOAA scientists have determined impacts from climate change can influence tropical cyclone intensity. Image: Climate Change

Rosencrans states “NOAA scientists have evaluated the impacts of climate change on tropical cyclones and determined that it can influence storm intensity. Further research is needed to better understand and attribute the impacts of anthropogenic (human-caused) forcing and natural variability on tropical storm activity”.

NOAA will release their official forecast for the 2021 season in late May. You can read the full news release from NOAA here:

Keep it here with your Weather Authority team for the latest update on the tropics.

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