03/20/2021
Atlantic hurricane season 2021: Named storms coming earlier, in warmer waters due to climate change.
With named storms coming earlier and more often in warmer waters, some assumptions about the Atlantic hurricane season are being rethought.
For six straight years, Atlantic storms have been named in May, before the season even begins. On Wednesday, a special World Meteorological Organization committee will discuss whether the hurricane season should be moved a couple of weeks earlier. The National Hurricane Center has already decided to start issuing its routine tropical weather outlooks for the Atlantic on May 15.
Meanwhile, the National Oceanic Atmospheric Administration is recalculating just what constitutes an average hurricane season. If it follows the usual 30-year update model, the new “normal” season would have 19% more named storms and major hurricanes. And prominent hurricane experts want meteorologists to rethink how they warn people about wetter, nastier storms in a warming world.
“Climate change is real, and it is having an impact on tropical cyclones,” University of Albany atmospheric scientist Kristen Corbosiero said.
STARTING EARLIER
MIT hurricane researcher Kerry Emanuel said “this whole idea of hurricane season should be revisited.”
During the past nine Atlantic hurricane seasons, seven tropical storms have formed between May 15 and the official June 1 start date. Those have killed at least 20 people, causing about $200 million in damage, according to the WMO. So the organization will discuss an earlier starting season and likely commission a study to figure out how to adopt one.
Last year, the hurricane center issued 36 “special” tropical weather outlooks before June 1, according to center spokesman Dennis Feltgen. Tropical Storms Arthur and Bertha both formed before June 1 near the Carolinas.
“The Atlantic hurricane season has changed quite a few times in the past since the concept of a hurricane season came about,” but not since 1965, said University of Miami hurricane researcher Brian McNoldy. “I don’t think there’s any harm in including the May 15 start date.”
The early systems are generally weaker tropical storms, said Colorado State University hurricane researcher Phil Klotzbach. If the season begins earlier, he worries that people will lose interest by mid-August when hurricanes get more frequent and nastier.
Storms seem to be forming earlier because climate change is making the ocean warmer, McNoldy and Corbosiero said. Storms need warm water as fuel — at least 79 degrees (26 degrees Celsius). Also, better technology and monitoring are identifying and naming weaker storms that may not have been spotted in years past, Feltgen said.
CHANGING NORMALS
Meteorologists calculate climate averages based on 30-year periods to account for variations in daily weather.
Over the next few weeks, the 30-year average for Atlantic hurricanes is being recalculated by NOAA. That means changing the benchmark for normal from the 1981-2010 period to the much busier 1991-2020 period.
University of Miami’s McNoldy did his own calculations based on NOAA data and found that the average number of named storms a year would jump from 12.1 to 14.4 if the benchmark is changed. Thirty years ago, the average was 10 named storms.
With more storms, risks for people and property go up and that’s likely to continue, McNoldy said. Last year’s record of 30 storms was like two seasons crammed into one, he said.
