A lull in activity, despite predictions of a hyperactive season, has surprised and confused scientists who make seasonal forecasts.
Tropical waves explained: How tropical waves affect the weather
Tropical waves do not refer to the storm surges seen during a tropical storm or hurricane. It is a purely meteorological term that describes the initial phase of a tropical storm’s development.
The outlook for the 2024 hurricane season was bleak, and its unprecedentedly early start with Category 5 Hurricane Beryl raised even greater fears than those predictions would be confirmed. And then…
No named storms have formed since August 12. There hasn’t been such a long stretch between August and September without hurricane formation since 1968, says Phil Klotzbach, chief hurricane researcher at Colorado State University, where Bill Gray pioneered seasonal hurricane forecasting 40 years ago.
This lull in activity has surprised and confused the scientists who make seasonal forecasts, despite predictions of a hyperactive season. Most forecasters expected up to 25 named storms. So far, however, only five have formed, including three hurricanes.
It could finally start.
The National Hurricane Center’s forecast map on Thursday showed five individual lemon-yellow circles for possible storm formation. However, none of these storms had a development potential of more than 30% for the next seven days, and meteorologists expect there to be no tropical storms or hurricanes for at least the next few days.
Although 2024 is becoming less likely to be a record year, experts still expect the season to be busier than usual. The season usually peaks around September 10, but there are still 12 weeks until it ends on December 1.
What happens next?
“From our current perspective, everything is still going according to plan,” said Dan Harnos, a meteorologist on the Climate Prediction Center team that produces the National Oceanic and Atmospheric Administration’s seasonal outlook.
Conditions are still favorable, with very warm and record-high sea temperatures across much of the Atlantic, Harnos said. “With all that warm water out there, there’s a lot of room for a tide turn. Things could change quickly.”
“I don’t think anyone expected a lull like this at the end of August,” Harnos said. “But we’ve had a decent amount of activity and I think it will pick up again at some point. It’s just a question of what the numbers will look like at the end.”
While there has been much talk about the lull, the average date for the 5th is…th The named storm formed on August 22, and Ernesto formed 10 days earlier. The average formation date of the third hurricane is September 7.
Hurricane Beryl Some Caribbean islands experienced almost “total destruction”
A typical hurricane season includes 14 named storms and seven hurricanes. Even if there are no named storms through Sept. 9 and activity is average for the rest of the season, the season would still be at the high end of average, according to an analysis released this week by Klotzbach’s team at Colorado State University.
While seasonal forecasts can predict what will happen overall during a hurricane season, we cannot predict at this point when activity will occur within that season, says Andrew Hazelton, a scientist at the University of Miami’s Cooperative Institute for Marine and Atmospheric Studies and NOAA’s Atlantic Oceanic Meteorological Laboratory.
“We won’t know for a few weeks if it was a lull or a long enough lull that the forecasts were a little below our expectations,” Hazelton said. “Water temperatures were well above normal, so it really seems like it’s only a matter of time before things settle back down.”
“There may be a phase in three or four weeks where everything lines up perfectly,” he said. “Maybe the peak is later than expected, but it’s still huge. We just don’t know.”
What happened to the August hurricane season?
A strong hurricane season cannot be attributed to just one thing or the other, says Craig Setzer, chief meteorologist for the Royal Caribbean Group. “Usually there are many different factors that work together to create a different weather pattern.”
Seasonal forecasts suggested that the key “ingredients” – record-breaking warm or very warm waters and an active monsoon season – appear to be in place this year to cause a repeat of the 27 named tropical systems of 2005 or even the 30 named storms of 2020.
Meteorologists said this week that temperatures on the surface and in the upper ocean were still extremely warm, or close to record highs.
However, changes in monsoon patterns, drier air, Saharan dust and higher temperatures in the upper atmosphere have messed up the ingredients, Setzer said.
Each of these factors will be examined as part of the seasonal assessment by scientists, Hazelton said.
Warmer upper air layer dampens storms
“When we saw Beryl, which became a Category 5 hurricane, everyone immediately thought, this is it, this is going to be the worst of all seasons,” said Setzer. But then the upper parts of the atmosphere began to warm.
For the clouds needed for tropical storms to form, the environment relies on the instability created by a layer of warm air at the Earth’s surface with a layer of cooler air above it. This summer, the warmer upper atmosphere created more stable conditions. According to Setzer, the instability needed for thunderstorms to form in a system simply wasn’t there.
These higher temperatures in the upper atmosphere were higher than in any other year and could be a sign that annual warming as a result of the El Niño phenomenon or human-induced climate change on a decadal basis could lead to additional stability problems in the coming years, according to the state of Colorado.
West African Monsoon
A typical trigger for hurricane activity in August is the West African monsoon trough. Monsoon waves originate from the west coast of Africa and often develop into storms on their way across the Atlantic. This year, the waves were driven from the continent to more northern latitudes and entered drier air from Europe, which hindered storm development.
“The African monsoon was so strong and these waves came so far north that they were almost too far north to develop,” Hazelton said.
“The low has moved northward enough in 2024 to cause easterly waves to emerge over the cold waters of the northeast Atlantic west of Mauritania,” the Colorado State analysis said. Extremely warm ocean temperatures in the Atlantic’s main storm development region, along with a pattern of cooler sea surface temperatures near the equator, may have helped drive the monsoon waves northward.
Sahara dust
Saharan dust was heavier than expected earlier in the season. Trade winds carried more dust than expected from Africa into and across the Atlantic. Sand and minerals help to weaken storms fueled by moisture.
According to Harnos, scientists are not yet able to predict exactly when the dust clouds will appear.
Is an active hurricane season still possible?
Yes. Will it be as active as predicted? Maybe not, meteorologists said. But given Beryl’s exceptional arrival so early in the season and the extreme water temperatures remaining in the Atlantic, Caribbean and Gulf of Mexico, they’re not ready to write off any possibilities for 2024.
As the air cools with the approach of fall, two things are expected. The Atlantic is still “extremely warm,” increasing the potential for instability that leads to storm formation. Cooler temperatures are also expected to help push monsoon waves south, where they will encounter more favorable conditions offshore.
Finally, conditions are expected to evolve toward La Niña, which produces cooler winds along the equator west of South America but reduces wind shear over the Atlantic, creating a more storm-friendly environment.
According to the state of Colorado, every season since 1900 that featured a tropical Atlantic hurricane before August 1 ended as an above-average season.
Dinah Voyles Pulver covers climate change and the environment for USA TODAY. She has covered hurricanes, tornadoes and severe weather for more than 30 years. Reach her at [email protected] or @dinahvp.
