Why Hurricane Freddy could redefine fundamental basics of meteorology

Hurricane Freddy may be remembered as the longest surviving one

Why Hurricane Freddy could redefine fundamental basics of meteorology

Hurricane Freddy may be remembered as the longest surviving one. It's up to scientists to decide, the world's leading expert on weather extremes told AFP. Freddy, formed in early February off Australia, twice ravaged southern Africa. An international panel of experts will now spend months reviewing the data to decide whether it can be listed in the UN's World Meteorological Organization (WMO) extreme weather records as the longest cyclone on record.

According to Randall Cerveny, WMO rapporteur for weather and climate extremes, the verdict will be based on an assessment of the phases during which Freddy descended below 34 knots (nearly 63 km / h), before picking up speed. “The fundamental question will be whether we count the time during which Freddy did not reach the stage of a tropical storm,” the professor of geographical sciences at Arizona State University told AFP. , which launched the WMO Records of Extreme Weather Events in 2007. The current record for duration is held by Typhoon John, which lasted 31 days in 1994. Freddy passed it but it will take months of deliberation to determine if a new record has in fact been set.

The WMO Archives of Extreme Weather Events contains data on a multitude of phenomena, including temperatures, wind speeds and lightning. In the event of a possible record, Randall Cerveny gathers around 10 to 20 experts online to review the data. For Freddy, he notably called on scientists from the National Hurricane Center in the United States, experts in hurricane monitoring by satellite imagery and meteorologists specializing in the Indian Ocean, including Météo-France.

"These scientists are the best of the best, and once they make a decision, I think everyone can accept it," Randall Cerveny said. “These talks can be really amazing. In previous discussions, we rewrote some fundamental definitions of meteorology,” he said, quoting the definition of lightning.

Hurricanes get their energy from warm ocean water. Born in the southeast Indian Ocean, Freddy was named on February 6 by the Australian Meteorological Service, and dissipated around mid-March. "What saved him and allowed him to last so long was the fact that he was continuously moving over warm waters," said Randall Cerveny.

The cyclone crossed the entire Indian Ocean from east to west, affecting Mauritius and Reunion on its long way to Madagascar and then Mozambique, causing heavy rains and flooding. It then made a loop to return to strike in early March these last two countries as well as Malawi, where it killed around 500 people. Once he has obtained all the raw data from the Indian Ocean weather monitoring stations, Randall Cerveny will write a report that will allow the expert group to begin discussions.

The current record holder, Typhoon John, had been determined using aerial reconnaissance. "Looking at the data, you can see it had dropped below tropical storm status," Randall Cerveny said. "I'm in discussion with the people who made this decision and trying to understand how they made it. Freddy could also be in contention for other records, as the cyclone has traveled more than 8,000 kilometres.

According to Randall Cerveny, the most important reason for setting the records is "climate change". "If we want to see how things are changing, we need to have a good baseline of what's happening right now," the scientist says, pointing out that tropical cyclones seem to be causing more and more rain. Data on weather extremes is also used by civil engineering, such as knowing the maximum wind speed a bridge must be able to withstand. Not to mention, he slips, that "people generally like to know the records".