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Forensic Meteorology and the North American Monsoon

As we head into monsoon season, the potential for flash flooding, hail, and damaging winds from thunderstorms is a concern for New Mexico. Each year, the North American Monsoon is responsible for deaths, injuries and property damage that can range from the millions to tens of millions of dollars across New Mexico. That translates to a lot of insurance claims for losses caused by monsoon weather, and a lot of lawsuits arising from claims being denied.

A couple of cases that I've worked as a forensic meteorologist stemmed from lawsuits arising from monsoon weather. In one case, a homeowner filed a lawsuit against the previous owners of the home and the real estate broker who worked the sale after the home flooded during a monsoon storm. The plaintiff claimed the defendants failed to disclose that the property was improperly graded so that rainwater would drain away from the home. The defendants countered that the storm that caused the house to flood was an unprecedented event that could have not reasonably been foreseen. I was retained by the defendant's counsel to conduct a precipitation analysis for the time and location of the event that contributed to the flooding. After reviewing radar storm total precipitation data, rainfall data from nearby reporting stations, and historical rainfall data for those sites, I concluded that the thunderstorm event that contributed to the home flooding was a typical monsoon storm that produced brief heavy rain. However, the statistical analysis indicated that while the storm produced intense rainfall in a short amount of time, rainfall and rain rate from the storm was not unprecedented in any way, thereby defeating the defendant's argument that the storm was an unprecedented event that could not reasonably be foreseen.

The second case I was retained for involved a building owner filing a lawsuit against a roofing contractor to compel the contractor to honor the warranty for a roof that had been recently installed on the building. When the roof system failed within one year of installation, the roofing contractor denied the warranty claim, stating the roof failed because of "hail damage," which was not covered under the warranty. In this case, I was retained by the plaintiff's counsel, who argued the roof failed due to shoddy workmanship. The plaintiff also retained a forensic civil engineer with knowledge of the material behavior when exposed to different conditions. My forensic research in this case involved examining hail reports and radar imagery spanning three years. Combined with 50-year climatology for the county in which the case was located, it was evident that severe hail was quite common during the summer monsoon period. The plaintiff's counsel added to her argument that the contractor should have designed the roof system to withstand severe hail, given how common severe hail is in the area where the building was located. Furthermore, with hail damage, one would expect to see the roof system filled with pockmarks, but pictures of the failed roof system in this case suggested decay (splitting and cracking) of the roofing materials due to the ponding of water--a sign of poor roof design that wasn't allowing rainwater to properly drain. Armed with this information, and materials test results provided by the forensic engineer, the defendant ultimately decided to settle the claim to avoid the risk a lengthy and costly trial.

The moral of the story: First, make sure that your insurance policy or warranty covers weather-related losses, and remember that homeowner's policies typically don't cover floods. If you're in a flood-prone area, consider purchasing flood insurance to give you extra peace of mind when the monsoon season comes around. Regardless, don't be surprised that a seller, contractor, or insurer will try to find a way to denying your claim for repairs to your home or business. When your claim gets denied because of "extreme weather," they say is not covered in your warranty or insurance policy, give me a call or send me an e-mail and we'll figure out exactly what the weather was doing when the loss occurred.

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