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Ida predicted to strike Louisiana as ‘extremely dangerous’ Category 4 hurricane late Sunday
Hurricane warning issued for New Orleans.
In its 5 p.m. advisory, the National Hurricane Center warned of “life-threatening inundation” due to the surge and “potentially catastrophic wind damage” near where Ida comes ashore, as it boosted the storm’s predicted landfall intensity a category, from 3 to 4.
New Orleans was placed under a hurricane warning, which stretches from Louisiana’s central coast to the border with Mississippi. Storm surge warnings, for the rise in ocean water above normally dry land, stretch from the Louisiana’s central coast to the Mississippi-Alabama border.
Anticipating flooding, New Orleans Mayor LaToy Cantrell issued a mandatory evacuation order for residents outside the city’s levee system Friday and called for voluntary evacuations elsewhere in the city.
“If you have any medical needs or wish to voluntarily evacuate on your own, now is the time to start that voluntary evacuation,” Cantrell said at a Friday morning news conference.
By her Friday evening news conference, Cantrell relayed a more urgent message. “The situation is much more serious than it was 6 hours ago,” she said. “Time is not on our side.”
Due to the storm’s predicted rapid strengthening, she said it was too late for a mandatory evacuation for areas inside the leveel protection system. Instead, Cantrell instructed people unable to evacuate to shelter in place. "People need to be in their safe spaces by and no later than midnight tomorrow [12 a.m. Sunday],” she said.
Two highway floodgates are expected to close Saturday afternoon, which will make it more difficult to travel through the area.
The forecast for Ida worsened throughout the day Friday. The Hurricane Center upgraded Ida from a tropical storm in the morning to a hurricane in the afternoon as it rapidly gained strength. Its peak winds had leaped 40 mph in 24 hours, reaching 80 mph, and they are forecast to climb much higher, to 140 mph by Sunday.
“Ida is expected to be an extremely dangerous major hurricane when it reaches the northern Gulf Coast on Sunday,” the Hurricane Center wrote, calling for hurricane-force winds to reach New Orleans Sunday.
In addition to inundation from the surge at the coast, abundant rainfall, topping a foot in some spots, could spell substantial flooding inland.
Exactly when and where Ida would cross the coast is still coming into focus, but the most reliable models predict landfall southwest of New Orleans and close to due south of Lafayette, La., between Sunday night and early Monday morning. Storm impacts from wind and flooding will expand far beyond where the storm’s center crosses the coastline.
“Being east of this storm’s track is not ideal,” said Collin Arnold, director of the New Orleans Office of Homeland Security and Emergency Preparedness. “We’re anticipating significant impacts including tropical-storm-force or stronger winds that could cause downed trees and prolonged power outages.”
He warned that even after most of the storm has passed, residents could still face severe winds and heavy rain on Monday.
Arnold encouraged residents to monitor the weather, gather their emergency supplies, check on loved ones and decide whether it’s time to evacuate.
“We will get through this like we’ve gotten through so many storms before,” he said.
Ida’s approach comes barely a year after Lake Charles, La., was slammed by back-to-back hurricanes, including Category 4 Laura in August 2020 and Delta in October. Zeta swept through New Orleans on Oct. 28 after striking Louisiana at Category 3 strength. The three storms caused roughly $27 billion in damage.
Cities such as New Orleans, Baton Rouge and Lafayette in Louisiana, Biloxi and Gulfport, Miss., and Mobile, Ala., are in line for potential direct impacts, with conditions deteriorating as early as late Saturday night. Ida’s remnants could even prove problematic far inland, dropping a swath of heavy rainfall across parts of the South, the Ohio Valley and Mid-Atlantic.
Louisiana Gov. John Bel Edwards (D) declared a state of emergency to free up state resources ahead of the approaching tempest.
“Now is the time for people to finalize their emergency game plan, which should take into account the ongoing covid-19 pandemic,” Edwards said in a news release issued Thursday.
In addition to New Orleans, several parishes in southeast Louisiana called for mandatory and voluntary evacuations Friday ahead of the storm.
Ida now
Ida was declared a hurricane at 1:15 p.m. Friday, with peak winds of 75 mph. By 5 p.m., the winds had ticked up to 80 mph but leveled off by 8 p.m. as Ida moved over western Cuba. Centered 90 miles southwest of Havana, Ida was moving steadily to northwest at 15 mph.
All day long, the storm became better organized, with towering thunderstorms wrapping around an increasingly well-defined center.
“Cuban radar data and reports from an earlier Air Force Reserve Hurricane Hunter mission indicate that Ida’s inner core structure continued to improve,” the Hurricane Center wrote at 5 p.m.
What’s next for Ida
Ida is forecast to cross over western Cuba on Friday night. Hurricane warnings are up there, with tropical storm warnings over central Cuba, where wind and rain squalls are expected through roughly midday Saturday.
A general 8 to 12 inches of rainfall with up to 20 inches in some areas is expected, which could spur a few landslides or mudslides in the higher terrain.
Even though Ida is set to pass over the Sierra del Rosario mountain range in western Cuba, which could briefly disrupt it, rapid intensification is already underway. It’s improbable that the growing storm will suffer more than a fleeting hiccup before emerging over the Gulf on Saturday morning.
Likelihood of additional rapid intensification
All signs are pointing toward Ida continuing to strengthen rapidly. Water temperatures are in the upper 80s in the Gulf of Mexico, providing Ida a seemingly limitless bathtub of fuel to gobble up as air pressures plummet and winds quickly ramp up. Some of the warmest waters are found immediately along the coastline, meaning Ida will probably continue strengthening up until the point of landfall.
Studies have shown that warming sea surface temperatures because of human-caused climate change have increased the likelihood of such rapid strengthening.
Added to the equation is a lack of disruptive wind shear, or change of wind speed and/or direction with height. That means Ida won’t be knocked off-kilter, the atmosphere largely leaving it alone to fester and spin up undisturbed.
At the upper levels, a zone of high pressure and clockwise-spinning air will help with Ida’s “outflow,” or the evacuation of exhaust-air exiting the storm. That removal of spent air will allow Ida to ingest more warm, humid air in contact with the sea surface, fueling explosive intensification.
The Hurricane Center noted that the bulk of computer models project Ida to reach Category 4 over the Gulf of Mexico and increase in size.
“As a result, 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,” it wrote.
#Ida has me very concerned this morning for Louisiana- you can’t ask for a worse recipe for a destructive hurricane. Not much shear, and a track right up the deepest, very warm water (using ocean heat content). There is extremely serious high-end #hurricane potential here! pic.twitter.com/89XFMnsikg
— Eric Blake 🌀 (@EricBlake12) August 27, 2021
What to expect: Wind speeds
The National Hurricane Center is forecasting Ida to make landfall late Sunday at major hurricane strength with winds in the eyewall gusting over 140 mph. The eyewall is a ring of strong thunderstorms that forms a destructive doughnut around the calm eye.
The harshest and most extreme conditions are found where the eyewall intercepts the coast. In this zone, the National Weather Service warns of “[s]tructural damage to sturdy buildings, some with complete roof and wall failure,” and “[m]any roads impassable from large debris.”
While the eyewall is a relatively narrow zone of destructive winds, damaging winds exceeding tropical-storm-force (39 mph) will cover a much larger area, probably extending more than 100 miles from the center, while hurricane-force winds (topping 74 mph) could extend 50 miles away.
Even if Ida’s eyewall avoids downtown New Orleans and tracks to its west, the Big Easy could still see wind gusts to hurricane force.
Tropical storm-force winds may arrive in coastal Louisiana as early as Saturday evening in any spiral rain bands that work ashore.
Widespread power outages and tree damage are possible where the core moves ashore; there will be a drop-off in wind away from the center. Winds will still be fierce, but magnitude and impacts will decay well away from the coast as Ida penetrates inland and begins to weaken Monday.
Storm surge
A destructive and potentially deadly storm surge is possible near the coast where strong winds push water ashore. The Hurricane Center is referring to the anticipated surge as “extremely life-threatening,” noting that a 10- to 15-foot storm surge is possible if a worst-case scenario is realized across the Mississippi River Delta from roughly Fort Morgan, La., to the mouth of the Mississippi River.
Lake Pontchartrain, La., is slated to see 4 to 7 feet of storm surge, and a dangerous surge up to several feet is likely all the way east to the Florida Panhandle. The most serious surge will occur east of where the center makes landfall.
Much of New Orleans is protected from surge by the Hurricane Storm Damage Risk Reduction System, a system of levees, pumps and flood gates, that was constructed after Katrina at a cost of $14.5 billion. But outside this system, the Weather Service warns the surge could bring “[w]idespread deep inundation,” “structural damage to buildings, many washing away,” “roads washed out or severely flooded,” “extreme beach erosion,” and “massive damage to marinas.”
Furthermore, the system is only designed to protect New Orleans from a 100-year storm. Ida could test the system if the maximum surge of 15 feet reaches as far east as New Orleans.
“[A] storm surge of 15 feet could threaten New Orleans’ levees,” wrote meteorologists Jeff Masters and Bob Henson at Yale Climate Connections. “A surge of that magnitude is close to the system’s design limits, and will be higher than any observed since the levee system was rebuilt.”
It’s important to note that surge can vary significantly over short distances and is largely dependent on wind direction, local topography and tidal cycles at the time of landfall.
Heavy rainfall and flooding
Flooding because of anticipated rainfall is probable both along the coast and far inland. “[T]otal rainfall accumulations of 8 to 16 inches with isolated maximum amounts of 20 inches are possible from southeast Louisiana to coastal Mississippi and Alabama through Monday morning,” the Hurricane Center predicts.
There will be a sharp west to east cutoff of rainfall on the left side of the system toward western Louisiana and Texas, but rainfall rates could top three inches per hour as the heaviest rain bands work through.
New Orleans is likely to see 10 to 15 inches of rain, and it’s not out of the question that a few isolated communities could approach 20 inches. This amount of rain will test the city’s network of 99 pumps, 96 of which are currently functional.
Making matters worse, the Weather Service is predicting heavy rain and flash flooding in southeast Louisiana through Friday night, ahead of the storm because of a separate tropical weather disturbance, prompting a flash flood watch. Several inches of rain could fall, saturating soils ahead of the deluge from Ida. Moreover, many parts of southern Louisiana have seen much above-normal precipitation since the spring.
Heavy rainfall with amounts topping four inches could continue all the way through the Midwest and Mid-Atlantic or Northeast midweek as Ida’s remnants weaken and unleash considerable moisture. “This is likely to result in considerable flash, urban, small stream, and riverine flooding,” the Hurricane Center cautioned.
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