Weathering Hurricane Ida

How forensic meteorologists and structural engineers are helping insurers pay claims and resolve lawsuits

October 06, 2021 Photo

Hurricane Ida made landfall on Sunday, Aug. 29, 2021, near Port Fourchon, Louisiana as a powerful Category 4 hurricane with maximum sustained winds of near 150 miles per hour. High winds, wind damage, storm-surge flooding, and flash floods occurred in many areas.

Hurricane Ida affected many of the same areas of the northern Gulf Coast that had already been affected by other tropical storms and hurricanes over the past few years, leading to many questions about causation and the correct date of loss. As the remnants of Hurricane Ida moved toward the East Coast, a unique combination of weather features caused horrific flooding damage and numerous deaths in the New York City metropolitan area.

With so many different types of claims and lawsuits already filed, insurance carriers and attorneys must seek out reliable sources of weather information and qualified experts. Carriers strive to provide good customer service quickly and efficiently, with the goal of paying the claims that are owed. Forensic weather consultants can provide companies and residents alike with accurate and reliable weather information for each address to help make those decisions.

The insurance industry is quickly adapting to the new trend of combining the expertise of forensic meteorologists and structural engineers during the claims stage to create the perfect team. This combination helps adjusters and attorneys make informed claims coverage decisions on whether to settle or defend lawsuits. Having the right experts with the right qualifications and reliable information for cases that go to trial is also important because of the Daubert and Frye standards, which can get experts giving opinions outside of their areas of expertise removed from a case.

Site-Specific Weather Reports

Adjusters, engineers, and attorneys have traditionally used the weather records from the closest airport or the closest National Oceanic and Atmospheric Administration (NOAA) storm report to show what occurred at a given property. The problem is that these weather stations are often far apart and not representative of what occurred at a specific incident location. Many weather stations fail during powerful storms, leading to inaccurate peak wind reports by non-meteorologists. The weather conditions often change over short distances, especially during tropical storms and hurricanes.

Around the time Hurricane Ida made landfall, sustained hurricane-force winds of 74 mph or higher extended outward 20-35 miles from the eye of the storm, depending on which side of the storm was being looked at. This suggests that the winds ranged between 74 and 150 mph within that 20-35 mile wide annular area. All of that is to say, the exact location of a loss in relation to the mesoscale features of a hurricane can cause the weather conditions to vary greatly. Even a few miles can make a big difference.

Weather Analysis Investigation

Whether an assignment is in the claims stage or in litigation, experienced forensic meteorologists use numerous types of weather records from different sources to provide reliable information for each specific property. Weather records typically include Doppler radar imagery, wind velocity data, local mesonet weather observations, local storm reports, high water mark and storm surge sensor data, and hurricane hunter dropsonde data, among other things, to help determine what occurred at a specific property. Analysis of the information can show how strong the winds were at the property and at different elevations of a building, the directions the winds came from, how high the storm surge was, how much rain fell, and if the rain represented a 10-, 25-, 100-, or even a 1,000-year storm.

Historical weather studies of other high-wind events and rainstorms prior to Hurricane Ida will also prove to be very important in many of these claims. When conducting these analyses, some things that must be taken into consideration include: the height of the wind sensor equipment above the ground; the locations of the weather stations; the wind reporting periods; comparisons of ground-truth rainfall measurements versus the Doppler radar precipitation imagery estimation; the elevation of a property above North American Vertical Datum of 1988 (NAVD88) and how that compares to storm surge and wave height levels; and how the movement of the hurricane’s outer bands and eyewall caused different wind speeds to occur over short distances.

Understanding the Forensic Engineer

The primary role of a forensic engineer is to apply accepted engineering principles and reliable scientific methodologies to provide answers to questions of fact. The questions that forensic engineers are often asked to answer include the probable cause of a component or system failure and any contributing factors, the extent of damage associated with the failure, and when the failure occurred. To answer these questions, a thorough root-cause analysis must be performed. Ultimately, the work product provided by a forensic engineer is an expert opinion. In some cases, a forensic engineer will serve as an expert witness in legal matters and must assist the court by explaining complex technical issues in a manner that is understandable to a layperson familiar with the matter at hand.

Forensic engineers are generally responsible for the identification and analysis of pertinent data and the development of conclusions and professional opinions that are supported by the facts. As part of the forensic investigation, an engineer generally performs one or more site visits to thoroughly document the failure, note any specific failure modes and mechanisms, and obtain field measurements prior to the spoliation of evidence. In some cases, evidence will be retained.

Subsequent investigation steps often include interviewing witnesses, examining construction and design documents, reviewing photographs obtained during the course of construction, developing computer models and performing structural analyses, and evaluating available weather data. Once the relevant data has been identified, the investigator develops hypotheses, tests the hypotheses through the analysis and correlation of the data, and potentially refines hypotheses in order to determine the probable cause, or causes, of the failure.

Putting the Pieces Together

When a forensic engineer performs hurricane and other wind-related damage assessments, obtaining reliable weather data can be critical to the investigation. Reliable weather data is particularly important when questions regarding construction, design, or material defects arise and the potential for subrogation recovery exists.

An example of this scenario is the structural failure and complete removal of the roof framing system from a building during a Category 4 hurricane with peak wind gusts of 150 mph at a building site, even though the framing system was required by local building codes to have the capacity to resist peak wind gusts of 165 mph.

At first glance, it may seem relatively reasonable to expect the failure to have occurred given that the demand placed on the roof framing system during the storm was roughly 91% of the required design capacity. However, the pressures that the exterior surfaces of a building structure experience during a wind event are not directly proportional to the wind velocity. Rather, the wind pressures are equal to the wind velocity squared. Thus, the demand placed on the roof framing system during this hypothetical scenario was closer to 83% of the required design capacity. Such conditions suggest that defects should be investigated.

It is also imperative that forensic engineers understand how any reported wind speeds were recorded and obtained when relying upon government sources, such as NOAA. More specifically, and as previously discussed, considerations must be made for both the height of the wind sensor equipment above ground and the wind reporting periods. The design wind-speed values prescribed by the International Building Code (IBC) and ASCE 7, “Minimum Design Loads and Associated Criteria for Buildings and Other Structures,” (the structural design standard referenced by the IBC) are noted as three-second gust wind speeds at 33 feet above ground. Therefore, wind reports obtained via public sources may not necessarily provide an absolute comparison of wind speeds. Given that wind speeds can vary greatly across relatively short distances during a tropical storm, obtaining a site-specific weather report is often necessary to ensure reliable data.

With such high-quality information available for any property, in-depth written expert reports can be prepared that adhere to Federal Rule 702. Insurance carriers and structural engineers can use these reports with confidence to answer many different questions, including if damage occurred as a result of Hurricane Ida or a prior storm; how much rain accumulated; the timing of wind versus storm surge; and the recurrence interval of the rainfall that occurred at each property. Making informed claims coverage decisions and determining how to resolve a case requires reliable information, and having a reliable team of experts in their respective fields is essential to the accuracy and effectiveness of the process. 


Damage Figures for Ida

Hurricane Ida brought destruction in many forms to different parts of the U.S., with catastrophe modelers estimating that insured losses will fall between $20 billion and $44 billion.

AIR Worldwide estimates losses of between $20 billion and $30 billion. Its estimate includes wind and storm surge losses of between $17 billion and $25 billion, and private-market inland flooding losses of between $2.5 billion and $5 billion.

Catastrophe modeler RMS estimates losses of between $31 billion and $44 billion. RMS’ estimate includes $25 billion to $35 billion in expected losses for the Gulf of Mexico region and $6 billion to $9 billion in insured losses from precipitation-induced flooding in Atlantic states.

“The majority of the insured flood losses in the Ohio Valley, Mid-Atlantic, and Northeast U.S.—between $4.5 billion and $7 billion—will be to the private market, with an additional $1.5 billion to $2 billion to the National Flood Insurance Program,” states RMS.

Hurricane Ida was the ninth named storm of the 2021 Atlantic hurricane season.

About The Authors
Multiple Contributors
Howard Altschule

Howard Altschule is a certified consulting meteorologist and CEO of Forensic Weather Consultants, LLC.

Jason C. Johnston

Jason C. Johnston is a senior structural engineer from EFI Global.

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