The levees protecting New Orleans held off Hurricane Ida’s storm surge after its landfall near midday on Sunday, avoiding a repeat of the catastrophe that occurred exactly 16 years earlier when Hurricane Katrina breached multiple levees and flooded the city. Only one death has been reported as of 2 p.m. EDT Monday from Ida, the result of a falling tree. However, damage from the hurricane was widespread and severe, and a complete picture of the destruction the great hurricane has wrought is just beginning to be understood. Insurance broker Aon estimated Ida’s damage would be “well into the double-digit billions.”

Ida made landfall at the key oil industry hub of Port Fourchon, Louisiana, at 11:55 a.m. CDT August 29, with 150 mph winds and a central pressure of 930 mb. Wind and storm surge damage to the port was severe (see tweets below). Nearby Grand Isle suffered severe damage, as seen in footage from StormChasingVideo.com.

After landfall, Ida slowed down and turned to the north, delivering one of its harshest blows to Houma, Louisiana (population 33,000), while still a category 4 hurricane (see damage video by stormchasingtour.com). Weakening only slightly to a category 3 storm with 115-120 mph winds, Ida’s fierce right-front eyewall passed directly over the Port of South Louisiana between 8 and 9 p.m. EDT Sunday. Damage to this critical port, the largest bulk cargo port in the world, is unknown at this time, but is likely to be heavy.

The Waterford 3 Nuclear Generating Station, which is also located in this region, suffered minor damage to some of its non-nuclear buildings and is now on backup generators due to loss of electrical power from the grid.

Figure 1. The Port of South Louisiana, the largest bulk cargo port in the world, was in strong right front eyewall of category 3 Hurricane Ida at 8-9 p.m., when peak winds were estimated at 115-120 mph. (Image credit: Mark Nissenbaum, Florida State University)

Ida tracked just west of Lake Pontchartrain, bringing extreme rains and a dangerous storm surge to the west side of the lake that flooded the town of LaPlace, Louisiana (population 29,000). South of New Orleans, a levee in Braithwaite, which was not part of the levee system that protected the greater New Orleans area, was overtopped, flooding hundreds of homes (see tweet below). Nearby, the town of Lafitte was inundated with 10-12 feet of water, with reports of people trapped in their attics.

Over 1.2 million customers were without power in Mississippi and Louisiana at 11 a.m. EDT Monday, many of them in New Orleans, which suffered a city-wide power outage after a key transmission tower collapsed (see drone video of the collapsed tower and wires in the Mississippi River from Live Storms Media). Poweroutage.us documented 14 counties that had over 80% of their customers without power.

Officials are estimating that it will take at least six weeks to restore power to Jefferson Parish, the county that lies along the west side of New Orleans, and includes the city’s main airport. According to an email from Steve Bowen of Aon, “the current electrical grid issues are clearly a major catastrophe and is going to lead to a cascading effect of prolonged impacts. Beyond the consequence to people’s daily lives, the business interruption component is going to be something to closely watch as well. Katrina had its own unique set of massive challenges that it brought on the grid side, too. It’s honestly hard to compare. Both events stand on their own as case studies in how future adaptation/resilience planning should go to attempt to prevent this happening again.”

Ida remained a hurricane over land for about 15 hours before finally weakening to a tropical storm at 5 a.m. EDT Monday. The storm was able to maintain its strength unusually far inland after making landfall in part because of the ‘brown ocean’ effect – the land Ida traversed was mostly swampland that the storm surge has inundated, and Ida was able to draw energy from the shallow, warm waters.

Figure 2. Storm surge heights during Ida exceeded 10 feet at one station (upper left) and were approaching 10 feet at two other stations before they stopped transmitting data (bottom two panels). (Image credit: NOAA)

The highest wind gust reported from the hurricane was on a ship moored at Port Fourchon: 172 mph, according to a tweet by NWS New Orleans. This gust was measured at a non-standard height of 18 meters, and would be about 10% lower when reduced to an equivalent wind at the standard 10-meter wind measuring height. A sustained wind of 149 mph also measured by the ship was apparently a gust, according to a tweet by Philippe Papin.

Forecasts were largely accurate

The National Hurricane Center track forecasts for the location of Ida’s landfall were brilliant, though the timing of landfall was less so (Ida was originally predicted to hit Sunday night/Monday morning but ended up hitting near noon on Sunday).

Kudos also go to the National Hurricane Center for their intensity forecasts. Beginning with the first advisory for Ida on Thursday morning as a tropical depression, it was clear that the National Hurricane Center expected this storm was going to rapidly intensify and threaten the northern Gulf coast on Sunday as a major hurricane. Confidence in this forecast was high and unwavering through all their advisories.

Here’s a statement from their first advisory on TD 9: “This system is forecast to approach the northern Gulf Coast at or near major hurricane intensity on Sunday.” In fact, the 72-hour intensity forecast for that first advisory was tied for being the most aggressive intensity forecast they had ever made. The final explosion of Ida to 150-mph winds was not anticipated, though, as the National Hurricane Center was calling for landfall as a 130-mph Cat 4 in their Saturday forecasts.

Figure 3. Areas of greatest risk for flash flooding from Ida August 30 – September 2, 2021. (Image credit: NOAA/NWS THE NATIONAL HURRICANE CENTER & WPC)

More flooding rains from Ida to sweep across the eastern U.S.

For millions of people from the Tennessee Valley to New England, Ida will only add to the troubles of an already soggy summer. Vast amounts of moisture from Ida will be hauled northeastward as the storm decays, leading to potentially flooding rains over an unusually large area. The National Weather Service Weather Prediction Center has tagged large areas of the U.S. at moderate risk of excessive rains leading to flash flooding for each day from Monday through Wednesday (see Figure 3).

The areas of most concern will shift from Mississippi and Alabama on Monday into Tennessee and Kentucky by Tuesday, including areas already deluged over the past few days by Tropical Storm Fred and hammered by a catastrophic flash flood in middle Tennessee. Widespread rains of 2-4 inches can be expected, with some 4–to-6-inch amounts. Well in advance of Ida’s remnants, locally heavy showers and thunderstorms can be expected on Monday and Tuesday along a pre-existing frontal zone from Kentucky to southern Pennsylvania. Flash flood watches already extend across this area.

By late Tuesday into Wednesday, Ida’s remnant low will be merging with a mid-latitude storm system and the pre-existing frontal zone. This process will likely intensify rainfall from West Virginia and northern Virginia into Pennsylvania, the mid-Atlantic, and southern New England, especially on Wednesday and Wednesday night. Pockets of 6-10 inches of rain can be expected over the rugged terrain of the central Appalachians, which may pose a substantial risk for flash flooding and mudslides. Heavy rains from Fred and Hurricane Henri have left soils saturated in much of the Northeast, which will heighten the flood risk in some areas. As noted by the National Weather Service Storm Prediction Center, there will also be some threat of tornadoes in rainbands associated with Ida’s remnants, particularly on Tuesday across Alabama and Georgia and on Wednesday across parts of the mid-Atlantic.

Figure 4. Infrared satellite image of Tropical Storm Kate at 1545Z (11:45 a.m. EDT) Monday, August 30, 2021. Kate’s showers and thunderstorms (lower right) were being blown well east of the storm’s central circulation, faintly visible at center. (Image credit: tropicaltidbits.com)

Tropical Storm Kate cruising north over the central Atlantic

The eleventh tropical storm of the hyperactive 2021 Atlantic season was born on Monday, August 30, as Tropical Depression Ten became Tropical Storm Kate at 9:30 a.m. EDT. Kate was located far out in the central tropical Atlantic, about halfway between Florida and Africa, with top sustained winds of 45 mph.

At midday Monday, fierce wind shear of 35-40 knots was shoving most of Kate’s sparse thunderstorms well east of the storm’s mid-level center. The shear was also pushing fairly dry mid-level air (relative humidity around 50%) into Kate’s circulation, further hampering the storm. The shear is expected to ease to around 30 knots by Tuesday and to 10-15 knots by Wednesday, and sea surface temperatures along Kate’s path will rise from around 27 degrees Celsius (81°F) to 28-29°C (82-84°F) by midweek, so Kate may manage to hold its own despite the continued presence of dry air. If it survives, there is strong model agreement that Kate will move mainly north through the week, eventually recurving to the northeast by late week as it encounters a strong upper-level trough that will also incorporate the remnants of Ida.

Kate the sixth-earliest 11th storm since 1966

Kate’s formation date of August 30 is very early for the appearance of the season’s 11th named storm; during the 1991-2020 period, the average arrival date of the season’s 11th storm was October 1. The record earliest appearance of the season’s 11th storm was on August 14, 2020 (Kyle). According to Phil Klotzbach of Colorado State University, only five other seasons since accurate satellite records began in 1966 have had as many as 11 named storms by August 30: 2020, 2012, 2011, 2005, and 1995.

Hello and goodbye to Julian

While we were busy with Ida this weekend, Tropical Storm Julian came and went. Julian developed from TD 11 at 11 a.m. Sunday, August 29, in the central Atlantic at latitude 35.1°N, well north of where tropical storms usually take shape. By Monday morning, Julian had encountered a trough in the polar jet stream and quickly evolved into a post-tropical cyclone, less than 24 hours after its birth. Julian is an example of a weak, short-lived named storm that might have been missed before the advent of satellites.

Julian’s formation date of August 29 was unusually early for the appearance of the season’s 10th named storm; during the 1991-2020 period, the average arrival date of the season’s 10th storm was September 21. The record earliest appearance of the season’s 10th storm was on August 13, 2020 (Josephine).

Figure 5. Visible satellite image of a large tropical disturbance near the west coast of Africa at 1515Z (11:15 a.m. EDT) Monday, August 30, 2021. (Image credit: RAMMB/CIRA/CSU)

A strong tropical wave in the eastern Atlantic likely to develop

There’s no rest for those weary of tropical activity in the Atlantic, as a strong wave moving off the coast of Africa on Monday designated 90L appears destined to become the next named storm. There is strong support in the GFS and European model ensembles for this potent wave to develop as it moves west-northwest, and it may well become a hurricane by week’s end. The vast majority of model ensemble members indicate this system will continue northwest into the central Atlantic late this week and this weekend, well away from the Caribbean or the U.S. East Coast. In its 2 p.m. EDT Monday Tropical Weather Outlook, the National Hurricane Center gave this system 70% odds of becoming at least a tropical depression by Wednesday and 80% odds by Saturday. The next name on the Atlantic list is Larry.

Less likely, but more problematic if it did occur, would be development in the southwest Caribbean, where low pressure is expected to take shape later this week. There is only modest model support for any development in this area, and any such low could move inland over Central America before any serious strengthening. In its 2 p.m. EDT Monday Tropical Weather Outlook, the National Hurricane Center gave the system a near-zero percent chance of any development here before Thursday, but a 20% chance by Saturday.

How to help hurricane recovery efforts

The Partnership for Inclusive Disaster Strategies (formerly portlight.org), co-founded by members of the Weather Underground community, is responding to the Hurricane Ida disaster. Also, the Weather Channel has put together a list of many excellent charities that will be active in Hurricane Ida recovery.

Editor’s note: Just this month, the new IPCC Sixth Assessment Report announced that “it is likely that the global proportion of major (Category 3-5) tropical cyclone occurrence has increased over the last four decades.” Also see: How climate change is making hurricanes more dangerous, by meteorologist Jeff Berardelli

Also see: Safety tips: How to clean up after a hurricane

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Jeff Masters

Jeff Masters, Ph.D., worked as a hurricane scientist with the NOAA Hurricane Hunters from 1986-1990. After a near-fatal flight into category 5 Hurricane Hugo, he left the Hurricane Hunters to pursue a...

Bob Henson

Bob Henson is a meteorologist and journalist based in Boulder, Colorado. He has written on weather and climate for the National Center for Atmospheric Research, Weather Underground, and many freelance...