- Hurricane Ida has made landfall on Cuba's Isle of Youth.
- It's expected to rapidly strengthen over the Gulf of Mexico, then strike Louisiana and Mississippi as a Category 4 storm on Sunday.
Climate change is causing more storms to strengthen rapidly.
Forecasters at the National Hurricane Center expect Ida to hit Louisiana and Mississippi as a Category 4 storm with winds of 140 mph on Sunday. Ida is expected to make landfall on the same date that Hurricane Katrina struck the area catastrophically 16 years ago.
"Ida is expected to be an extremely dangerous major hurricane when it reaches the coast of Louisiana," the NHC forecast warned on Friday evening.
Ida was still a tropical storm early on Friday but it strengthened into a hurricane by the afternoon. As of 11 p.m. ET, the storm entered the Gulf of Mexico and is forecast to rapidly intensify before its projected landfall late Sunday.
Cuba has issued a hurricane warning for its Pinar del Rio and Artemisa provinces. Up to 20 inches of rainfall from the storm may cause dangerous flash floods and mudslides across western Cuba, Jamaica, and the Cayman Islands.
A hurricane warning is also in place for the Louisiana coast from Intracoastal City to the mouth of the Pearl River - an area that includes metropolitan New Orleans. The city has issued a mandatory evacuation order for all areas outside its levee system. The Friday announcement included voluntary evacuations for the rest of the city.
Ida may bring "extremely life-threatening" storm surge - a wall of water as high as 10 to 15 feet - along the coast from Morgan City, Louisiana, to the mouth of the Mississippi River. Smaller surges are expected across the rest of Louisiana, Mississippi, and Alabama.
As the cyclone moves through the Gulf of Mexico, NHC forecasters say it will encounter "very favorable" conditions - warm water and air, a moist atmosphere, and very little wind shear to disrupt the storm. This will likely fuel a process called rapid intensification, in which a storm's wind speeds increase by at least 35 mph in just 24 hours.
The NHC initially expected Ida to strike the Gulf Coast as a Category 3 storm but the agency now projects a Category 4, since the cyclone is entering the Gulf with higher wind speeds than expected. Forecasters also expect Ida to grow in size, expanding its wind field to affect a larger area.
"There is higher-than-normal confidence that a large and powerful hurricane will impact portions of the northern Gulf coast by late this weekend and early next week," the NHC said.
Miami
A hurricane watch extends west to Cameron, Louisiana, and east to the border of Mississippi and Alabama. The entire Alabama coast is under a tropical storm watch.
NOAA predicts up to a dozen more named storms this season
By definition, any cyclone-shaped storm with winds faster than 39 mph is a tropical storm. Storms get named once their winds reach that speed. After winds hit 74 mph, a storm becomes a Category 1 hurricane on the Saffir-Simpson scale.
Ida is the year's ninth named storm; three other storms - Elsa, Grace, and Henri - also became hurricanes. Hurricane season runs from June 1 to November 30, with activity peaking around September 10.
The National Oceanic and Atmospheric Administration predicted that there will be a total of seven to 10 hurricanes in 2021, and up to 21 named storms. That includes three to five major hurricanes. A major hurricane is a Category 3, 4, or 5, with sustained wind speeds of at least 111 mph. Grace - which made landfall in Mexico as a Category 3 hurricane - has been the only major hurricane so far this year.
Overall, the average number of storms per season has increased, so NOAA recently updated the baseline numbers it uses to make seasonal hurricane predictions. The agency now defines an average season based on data from 1991 to 2010, when the average was 14 named storms, seven of which were hurricanes. Previously, NOAA considered an average season to have 12 storms in total, with six being hurricanes.
Climate change is making cyclones stronger, slower, and wetter
Earth's warming increases the chance that a hurricane will be more devastating. Rising ocean temperatures in particular play a major role, since the temperature of the water below a storm influences its wind speed. A 1-degree-Fahrenheit rise in ocean temperature can increase a storm's wind speed by up to 20 miles per hour.
That also enables storms to intensify in less time, so rapid intensification events have gotten more frequent over the last 40 years. One study found that the chance a hurricane will undergo rapid intensification went from 1 in 100 in the early 1980s to 1 in 20 by 2005.
Over the past 70 years or so, the speed at which hurricanes and tropical storms travel has also dropped about 10%. That's a problem, since it means any given storm has more time to pummel an area with wind and rain. To make matters worse, a warmer atmosphere can hold more moisture, so a 10% slowdown in a storm's pace could double the amount of rainfall and flooding that an area experiences. Peak rain rates of storms have increased by 30% over the past 60 years.
That increased rainfall, paired with rising sea levels, means cyclones will likely bring increasingly devastating flooding in the coming years and decades.