Hurricane Milton made landfall along the western coast of Florida in the United States as a fierce Category 3 storm (peak wind speeds of 179 km/hr to 208 km/hr) around 8:30 pm on October 9.
The hurricane carried a lot of rainfall, similar to Hurricane Helene a couple of weeks ago, showcasing the role of increased moisture in the atmosphere due to warming oceans, especially in 2023 and 2024. The storm also produced a record number of tornadoes in certain regions of Florida before and during its landfall process.
Milton is the third hurricane to make landfall in Florida this year after Hurricane Debby in July and Hurricane Helene on September 26. It is the ninth hurricane in the 2024 Atlantic hurricane season and the second Category 5 (peak sustained wind speeds of >252 km/hr) hurricane after Hurricane Beryl in June.
Some places in the Tampa Bay area such as St. Petersburg received rainfall as high as 465 mm within 24 hours, which qualified as a once in a thousand-year rainfall event for the region.
Around 229 mm of the rainfall fell in just three hours. Sixteen people have lost their lives due to Hurricane Milton in Florida, mostly due to flash flooding and tornadoes that landed before the hurricane, according to media reports.
People on the ground reported 38 tornado events between the nights of October 9 and October 10, according to preliminary eyewitness reports received by the National Oceanic and Atmospheric Administration (NOAA). The total number of tornado warnings issued by the National Weather Service (NWS) ahead of Hurricane Milton was 126, the highest for Florida for one day.
The average annual number of tornadoes in Florida is 50. The actual final number of tornadoes can only be known after the NWS performs its ground surveys.
The impact of the tornadoes was higher on the Florida’s Atlantic coast where 10 deaths were reported, according to the Associated Press. Earlier in June, Category 5 Hurricane Beryl had produced 65 tornadoes in several regions of the United States over its entire lifespan on land. The highest number of tornadoes on record was 118 for Hurricane Ivan in 2004.
“Hurricanes and tropical storms can produce tornadoes. These tornadoes most often occur in thunderstorms embedded in rain bands well away from the center of the hurricane; however, they can also occur near the eye-wall. The majority of tornadoes associated with tropical systems occur in the right front quadrant of the storm. This area typically has the best wind shear and instability,” says NOAA on its website.
While atmospheric instability helped in generating the tornadoes the extraordinary rainfall came from the excessive moisture probably picked up by Hurricane Milton during its explosive rapid intensification (RI).
A tropical cyclone is said to have undergone RI if it gains peak sustained windspeed (one minute) of 56 km/hr in a period of 24 hours. Hurricane Milton gained 145 km/hr in a matter of 15 hours between the early hours of October 7 and evening of the same day, according to The Weather Channel.
A research paper published in the journal Tropical Cyclone Research and Review in June 2024, says that the moisture uptake by tropical cyclones (TCs) “mostly was from the regions where TCs underwent RI.”
The paper also identified that western and tropical North Atlantic Ocean, Caribbean Sea, the Gulf of Mexico, landmasses of Mexico and Central America contributed 85.4 per cent of all moisture that gets converted into rainfall in the North Atlantic Ocean. Hurricane Milton’s RI occurred exclusively off the coast of Mexico and Central America in the Gulf of Mexico.
Apart from the warm sea surface of the Gulf of Mexico which fuelled Hurricane Milton, as per NOAA, the other factor which powered it during landfall in Florida and its way forward was its interaction with a nearby jet stream.
“Hurricane Milton’s power across Florida didn’t just come from warm Gulf of Mexico water, but also from jet stream winds aloft and a boundary over the Atlantic. Milton began this transition of energy as it approached Florida’s west coast Wednesday evening and completed it Thursday afternoon. This transition helped Milton grow in size and also reoriented some of its threats as it came over the state,” said The Weather Channel on its website.