US could see a record 25 named storms this year as experts predict 'extremely active' hurricane season
This is the highest number ever predicted by the agency in a single season, which on an average produces 12 named storms
The 2020 Atlantic hurricane season has had a tumultuous start with a record-setting nine named storms so far and it has the potential to be one of the busiest on record. Atmospheric and oceanic conditions are primed to fuel storm development in the Atlantic, leading to what could be an "extremely active" season, warned scientists from the National Oceanic and Atmospheric Administration or NOAA’s Climate Prediction Center.
The current season could bring up to 25 named storms with winds of at least 39 mph (63 km/h). This is the highest number ever predicted by the agency in a single season. "We’ve never forecast up to 25 storms. So this is the first time," says Dr Gerry Bell, lead seasonal hurricane forecaster at NOAA’s Climate Prediction Center.
Historically, only two named storms form on average by early August, and the ninth named storm typically does not form until October 4. An average season produces 12 named storms, including six hurricanes, of which three become major hurricanes (Category 3, 4 or 5). But this year there have already been nine named storms. The updated outlook covers the entire six-month hurricane season, which ends on November 30, and includes the nine named storms to date. "The updated outlook calls for 19-25 named storms (winds of 39 mph or greater), of which 7 to 11 will become hurricanes (winds of 74 mph or greater), including 3 to 6 major hurricanes (winds of 111 mph or greater)," explains the research team.
In May, the NOAA had forecasted that there is a 60% chance of an above-normal hurricane season this year, a 30% chance of a near-normal season and only a 10% chance of a below-normal season. Back then, the Center had predicted a likely range of 13 to 19 named storms, of which 6 to 10 could become hurricanes, with winds of 119 km/hour (74 mph) or higher, including 3 to 6 major hurricanes (category 3, 4 or 5, with winds of 178 km/hour (111 mph) or higher).
To determine whether a season is extremely active, the NOAA uses a measure of the overall hurricane season activity known as the Accumulated Cyclone Energy (ACE) index. This measures the combined intensity and duration of all named storms during the season. Based on the ACE projection, combined with the above-average numbers of named storms and hurricanes, the likelihood of an above-normal Atlantic hurricane season has increased to 85%, with only a 10% chance of a near-normal season and a 5% chance of a below-normal season, reveals the NOAA. "This year, we expect more, stronger, and longer-lived storms than average, and our predicted ACE range extends well above NOAA’s threshold for an extremely active season," writes Dr Bell.
The forecasters explain that current oceanic and atmospheric conditions that make an extremely active hurricane season possible are warmer-than-average sea surface temperatures in the tropical Atlantic Ocean and the Caribbean Sea, reduced vertical wind shear, weaker tropical Atlantic trade winds and an enhanced west African monsoon. These conditions are expected to continue for the next several months. "A main climate factor behind these conditions is the ongoing warm phase of the Atlantic Multi-Decadal Oscillation, which reappeared in 1995 and has been favoring more active hurricane seasons since that time," the findings suggest.
This year, another contributing climate factor is the possibility of La Nina developing in the months ahead. "Indicative of cooler-than-average sea surface temperatures in the equatorial regions of the eastern Pacific Ocean, La Nina can further weaken the wind shear over the Atlantic Basin, allowing storms to develop and intensify," say researchers.