Forecasters at the National Oceanic and Atmospheric Administration (NOAA) have increased the number of named storms they expect to form in the Atlantic basin in the 2021 hurricane season.
The revised forecast was released on Thursday 20 May, less than two weeks from the official start date of the Atlantic hurricane season.
It calls for 20 named storms, three more than its initial forecast last month.
The new forecast anticipates six to 10 hurricanes, five of which could become major hurricanes.
During a virtual press briefing Thursday 20 May, Matthew Rosencrans, head of NOAA’s hurricane season outlook team, said the Atlantic basin is still experiencing a period of high activity, and current weather conditions support the call for an above average season.
“As we look forward to the 2021 hurricane season, there are several factors that we took into consideration when developing the May outlook,” said Rosencrands. “Last year’s busy season was a clear reflection of the ongoing high activity era which began in 1995 and continues to be a factor in our outlook for 2021.”
Rosencrans said indicators of high activity include warmer than average sea surface temperatures, weaker trade winds in the Atlantic hurricane basin, weaker vertical wind shears, and the development of an El Nino Southern Oscillation (ENSO).
Weather Roundup
- April one of the hottest in 142 years
NOAA said April 2021 was the ninth warmest April since 1879. That coincided with a 5.8% reduction in arctic sea ice, or a decrease of 267,000 square miles.
- 2020 hurricane season continues to be record-setting
Last year’s Hurricane Zeta has been reclassified to Category 3, making it a major storm. The reclassification brings the number of major storms to seven, tying 2005 for the most on record.
- Active storm season prompts early outlook
Forecasters at the NHC in Miami, Florida, released their Atlantic tropical outlook two weeks early, on 15 May, due to the early development of storms in recent years. The tropical outlook is currently live.
“We are currently experiencing ENSO natural conditions which do not largely inhibit hurricane formation or suppress the features of the ongoing high activity era,” he said.
“Based on our current data and analysis, we do not expect the 2021 hurricane season to be as active as 2020.”
The 2020 hurricane season was the most active season in recorded history. Thirty named storms developed, 13 of which became hurricanes, and seven became major hurricanes.
Forecasters were forced to use the Greek alphabet after they ran out of preapproved storm names. The Greek alphabet has since been retired.
The seasonal average has also increased following a shift in the climatological range, which previously spanned from 1980 to 2010. During that time, the season average was 12 named storms and six hurricanes, three of which were expected to become major hurricanes.
“The climatological average was changed in January, so it now runs from 1991 to 2020,” said Kerry Powery, the chief meteorologist at the Cayman Islands National Weather Service.
Powery told the Cayman Compass, “The change in the range has also resulted in an increase in the season average, which is now 14 named storms, seven hurricanes and three major hurricanes.”
Each year the Atlantic Hurricane season runs from 1 June to 30 Nov.
However, this does not mean storms cannot develop outside this period.
On Saturday, 22 May, subtropical storm Ana formed off the coast of Bermuda, making it the first named storm of the 2021 Atlantic Hurricane season.
Ana’s formation makes the 2021 hurricane season the seventh consecutive season that a storm has formed prior to the official 1 June start date.
The increased activity storm activity over the course of the past seven years has resulted in calls to shift the official start date of the season. However, Powery said this idea was voted down.
“There were talks about changing the official start date of the Atlantic hurricane season, during our last regional hurricane conference, which was held online because of the COVID situation,” said Powery.
“Those discussions were shut down, but as a fall back they moved the start date of the tropical outlook to May 15.”
Related Videos
