Hurricane Beryl's dramatic strengthening was a result of record warm surface water temperatures that fueled it, scientists say, creating a powerful storm at an unprecedented date that has so far wrecked parts of the Caribbean and Mexico.
New instruments deployed into the path of Beryl over the past nine days helped document – and predict – its intensification from tropical storm to Category 5 hurricane in the eastern Atlantic Ocean in only 42 hours. They also followed its course as a deadly storm through the Caribbean, across the Yucatan Peninsula and into the Gulf of Mexico.
Extremely warm waters drove it, helping make it the earliest Category 5 storm on record. The warm water acts as an energy source that, combined with a lack of upper atmospheric wind shear, allows thunderstorms to grow and intensify, creating tropical storms and hurricanes.
Comparison of sea surface temperatures on June 29, 2024 with July 1, 2000, which NOAA says was a typical view of surface temperatures near the same date 24 years ago. (NOAA)
Researchers say the warmer water has a good chance of being linked to global warming, but the creation of one major storm like Beryl may also be the result of an oddly timed combination of still unclear seasonal ocean changes. Those include 20- to 40-year patterns of warmer or cooler water temperatures and changes in regional ocean currents.
"The really unusual aspects of Beryl are how early in the season and how far east it formed and rapidly intensified, and that it reached Category 5 in early July, about 2 weeks before any other hurricane reached Category 5 in the Atlantic in recorded history," said Gregory Foltz, an oceanographer with NOAA’s Atlantic Oceanographic and Meteorological Laboratory who is overseeing the use of drones to collect information at the ocean's surface.
"These are due to the exceptionally warm water in the central-western Atlantic and Caribbean, which we normally see in September, not June-July," he said. "Clearly the warm waters in the Atlantic and Caribbean are part of larger-scale longer-term warming caused by climate change, but attribution of conditions during a particular season or year to natural variability vs. climate change is difficult and will require more study."
This graphic shows how information about Hurricane Beryl was captured from a variety of new collection tools, including a Saildrone glider, and radar aboard NOAA and Air Force Reserve Hurricane Hunters. (Courtesy of Saildrone and NOAA)
Beryl reached tropical depression strength, with winds of 35 mph, at 5 p.m. on June 28, south of the Cape Verde Islands off the coast of Africa. Just 24 hours later, it had rapidly intensified to hurricane strength, with winds of 75 mph. The National Hurricane Center defines rapid intensification as a storm that has strengthened by 35 mph or more in 24 hours.
Beryl accomplished that feat again at 11:35 a.m. on Sunday, June 30, when the National Hurricane Center declared it a major hurricane with 130 mph winds. That meant the storm had reached major hurricane strength in only 42 hours after forming, the earliest that had happened in recent hurricane history.
“Beryl is rewriting the history books in all the wrong ways,” Eric Blake, a senior hurricane specialist at the National Hurricane Center and a Metairie native, posted on X after that record was hit.
View from aboard a Saildrone on the edge of Hurricane Beryl on July 2, looking at wave estimated at 24.6 feet high. (Courtesy of Saildrone and NOAA)
The storm dropped a bit in intensity by 5 a.m. on July 1, with winds dropping to 120 mph, Category 3, as an eyewall replacement occurred. But by 8 a.m., it was again back at 130 mph as it was approaching the Windward Islands into the Caribbean Sea.
But even as the storm was making landfall on Carricacou Island, it had already again rapidly jumped to a Category 5, with 150 mph winds, in just two hours.
That rapid intensification is in part blamed for the severe damage the storm caused as it barreled through the islands, killing at least three there and another four along the nearby coast of Venezuela.
By 2 a.m. Tuesday, Beryl had intensified again to a top wind speed of 165 mph as it began a trek that would result in a bit of weakening by 5 p.m. on Wednesday, to about 140 mph, as its eye moved along the south coast of Jamaica, again causing significant damage and storm surge flooding.
Forecasters blamed the slight reduction in power at that time on the increase in westerly wind shear, but pointed out that the storm remained aligned in a way that allowed it to stay strong.
By 11 p.m. Wednesday, the shear seemed to have begun taking a greater toll on the storm’s structure, and hurricane hunter aircraft reported the storm’s eyewall was open – no thunderstorms – on its southwest side.
But Beryl remained a Category 3 storm, with 130 mph winds for another 12 hours.
By the morning of July 4, Beryl’s round shape seemed to be disrupted, elongated, with a section of the eyewall still missing, but sustained winds were still 120 mph, or Category 3, as it rolled through the Cayman Islands.
Wind shear helped reduce Beryl’s strength on Thursday after it moved into the Yucatan Straits towards landfall on the Mexican southern peninsula. On Thursday night, it had again regained minimal Category 3 strength, but dropped to 110 mph when it made landfall at about 5 a.m. Central time.
The Yucatan Peninsula dramatically reduced Beryl’s intensity to tropical storm strength, just 70 mph, at 1 p.m. Friday.
In a Friday afternoon discussion message, Senior Hurricane Specialist Jack Beven warned that it could a full day before Beryl’s structure recovers from the Yucatan landfall, but then reintensification will begin in earnest, with the storm having top winds of 90 mph, at the top of Category 1, before making landfall on the Texas coast, somewhere between the mouth of the Rio Grande river and Sargent, Texas.
The role of human-caused climate change is still under debate, and scientists like David Nolan, an atmospheric scientist at the University of Miami’s Rosenstiel School of School of Marine, Atmospheric, and Earth Science, are still trying to understand the connections.
"The time being so early here, there's just no other way to explain that than the extremely warm temperatures, which you have to relate to global warming," Nolan said.
Louisiana State Climatologist Jay Grymes thinks natural variability is a more likely answer. He said it may also be linked to a reduction in easterly winds in that part of the Atlantic, which could reduce evaporation at the ocean's surface, which releases heat into the air. The result would be warmer water temperatures, he said.
Other researchers point out that warmer temperatures resulting from climate change also can result in the atmosphere over the Atlantic holding more water droplets, which also supports tropical storm formation. That may influence recent trends toward rapid intensifications and in storms like 2017's Hurricane Harvey delivering dramatically more rainfall.
Andrew Hazelton, an associate scientist at the University of Miami’s Cooperative Institute of Marine and Atmospheric Sciences and NOAA’s Hurricane Research Division, said recent studies also have linked it to a reduction in sulfate aerosol pollution over the ocean, the result of more strict rules limiting sulfur dioxide in ship fuels. The reduction in those tiny particles in the air means more sun getting through and warmer water temperatures.
The lack of upper atmospheric wind shear is in part the result of a shift from El Nino to La Nina conditions in the easternmost Pacific Ocean, from warmer than normal to cooler than normal water temperatures. While still only in a neutral phase between the two, the reduction in Pacific water temperatures has resulted in reduced high winds in the upper atmosphere over the Atlantic that increase the ability of thunderstorms to grow and form tropical depressions.
The lack of those winds when Beryl moved over the warmer than normal water helped speed the growth of its central eye, and its quick rise in wind speeds.
Grymes points out that conditions also were assisted above Beryl by what's known as "divergence aloft," a combination of lower pressure and winds above the storm that pull air upward from its eye and out into the atmosphere around it, helping to increase the storm's intensity.
Some of the intensification has been linked to the layering of freshwater flowing from the Amazon River in Brazil atop Atlantic salt water in the area where Beryl formed, slowing the mixing of deeper, cooler water to the surface where it could disrupt the intensification process.
Julio Morell, executive director of the Caribbean Coastal Ocean Observing System, and Leah Hopson, a Rutgers University graduate student, preparing an underwater glider for release into the Atlantic Ocean. Rutgers is working with CARICOOS in underwater research aimed at better understanding hurricane formation. (Courtesy of Rutgers University)
That's one of the patterns that seem to have been confirmed by readings taken by a torpedo-like underwater glider deployed by scientists at Rutgers University for other research just south of the Dominican Republic. On Tuesday, it was redirected to pass within 20 nautical miles of Beryl as it moved over the central Caribbean.
Other new instruments also are being used to help understand Beryl's intensification process.
A Saildrone, a surface autonomous vessel, edged close enough to Beryl on Tuesday as it approached Jamaica to measure its wind speeds outside its central eye, the 25 ½-foot waves it was creating, the decrease in pressure supporting its intensity, and several rapid decreases in air temperature caused as the storm’s rain bands, according to Foltz.
Atop the storm, Air Force Reserve and NOAA Hurricane Hunter aircraft were using sophisticated tail-mounted Doppler radars to capture a three-dimensional view of Beryl as it intensified, said Hazelton.
Information provided by these new instruments are helping researchers improve models forecasters use to determine the direction and intensity of tropical systems, said Nolan.
