Hurricane season just shifted gears. After a rather mellow July, August is shaping up to have “above normal” hurricane activity, according to researchers at Colorado State University’s department of atmospheric science.
The National Oceanic and Atmospheric Administration echoed CSU’s prediction Thursday in their updated 2024 hurricane season forecast, calling for an “extremely active” remainder of the season, which runs from June 1 to November 30.
CSU said in their two-week forecast that there’s an 85% chance that the span of Aug. 6 to 19 will produce above-normal Accumulated Cyclone Energy (ACE) in the Atlantic. The norm is based on hurricane activity in the Atlantic from 1966–2023.
“We are quite confident that the next two weeks will be characterized by activity at above-normal levels. … We believe that the next two weeks will be quite active for Atlantic hurricane activity,” forecasters said in their report.
Their prediction is based on several factors. Firstly, there’s already been activity: Tropical Storm Debby, which strengthened into a Category 1 hurricane just before making landfall in the Big Bend region of Florida, maxed out the normal ACE for the time span, so any storm that follows vaults the status to above normal.
There is currently a tropical disturbance moving west across the tropical Atlantic that has a 60% chance of developing in the next seven days as it heads toward the Caribbean.
In their larger seasonal outlook, CSU said 2024 has been marked by unusually warm sea-surface temperatures in the tropical Atlantic. All that warm water can fuel storm formation. Additionally, the warm water tends to create lower atmospheric pressure and an unstable atmosphere, which also is favorable for storms.
A key force in inhibiting hurricane formation is wind shear. CSU analysis indicates that there will be very little, if any, wind shear in the coming weeks in the tropical Atlantic off Africa, where August storms usually form. “Vertical wind shear is generally forecast to be below normal (e.g., easterly anomalies) across the Atlantic Main Development Region for the next four weeks,” said the report.
That’s because a monthslong weather cycle called the Madden-Julian Oscillation is ramping up over the Indian Ocean. When it does, it reduces tropical Atlantic wind shear, and causes storminess over Africa, which can lead to storms over the Atlantic.
NOAA agrees
Additionally, NOAA updated their 2024 hurricane season forecast on Thursday, reiterating earlier outlooks by calling for a “highly active” remainder of the season.
“Atmospheric and oceanic conditions have set the stage for an extremely active hurricane season that could rank among the busiest on record,” said forecasters in a release.
The agency called for 17 to 24 named storms (the average is 14.4 between 1991 to 2020), 8-13 hurricanes (the average is 7.2) and 4 to 7 major hurricanes in the Atlantic Basin (the average is 3.2).
There have been four named storms thus far (Alberto, Beryl, Chris, Debby), leaving 20 more to go, if their worst-case prediction of 24 storms plays out.
NOAA called out similar atmospheric factors as CSU, but added that they expect the plums of dry Saharan dust, which travels off North Africa and over the Atlantic during summer, to dissipate. The dry air upon which the dust travels can halt hurricane formation.
The NOAA report also noted that in the coming months, La Niña is likely to kick in and reduce wind shear, thus enhancing hurricane formation.
