Some scientists see stronger storms in the weather-related hurricane season


Like death and taxes, the annual hurricane season is a sure thing. The number and intensity of named storms can vary each year, as well as where they occur and whether or not they hit land. But there’s no doubt that these storms will evolve annually – it’s a matter of when, not if – and some scientists see increasingly intense and wetter storms in the future as the climate continues to warm.

A report – Preventing the next Katrina – published by Munich RE in 2020 and written by Mark C. Bove, meteorologist and natural disaster solutions manager, states that when Hurricane Katrina hit land in southeast Louisiana in 2005, “the impact of climate change on tropical “cyclones has been the subject of intense debate in the meteorological community.” Aside from Katrina, still considered the most catastrophic and costly hurricane in US history, 2005 was a stormy year in which the country fell within 15 months Experienced 12 hurricane landings. At that time, some scientists attributed the increased intensities of tropical cyclones to climate change. Others argued that the historical records of hurricanes prior to the satellite era were not reliable enough to reach this conclusion.

“Since then, significant progress has been made in understanding the complex interplay between tropical cyclones and the climate,” says the Munich RE report. A scientific review of the latest climate models “has shown that tropical cyclone precipitation rates will increase worldwide as climate change continues, the proportion of Saffir-Simpson category 4-5 storms will increase worldwide, and the frequency of category 4-5 storms will increase.” becomes”. worldwide, among other possible changes (Knutson et al. 2020). “

According to meteorologists, heavier rainfall can be expected in a warmer world, the report said. The recent experiences of the residents of southwest Louisiana can be seen as a prime example of climate-related higher rainfall, with or without a tropical cyclone. With the area still struggling to recover from last year’s successive Hurricanes Laura and Delta, southwest Louisiana experienced day-to-day rains in May. According to the Associated Press, an estimated 400 to 500 structures in Lake Charles were flooded in just one day.

Munich RE’s report also notes that “tropical cyclones seem to move more slowly today than in the past, possibly as a result of declining atmospheric currents in summer, which may be linked to climate change (Kossin 2018). Slower or slower storms, like Harvey 2017 or Dorian in the Bahamas, keep torrential rain, wind and / or flooding in one place for long periods of time, causing more damage and disruption than if the storm had passed, albeit quickly. “

Rising seas, which are also associated with warmer climates, also exacerbate storm surges generated by tropical cyclones. Munich RE’s Katrina report cites Hurricane Donna, which hit New York City in September 1960, as an example. Back then, “the flood levels in the Inner Harbor were only six inches to flood subway tunnels in Lower Manhattan. If an exact repetition of Donna [had] Happened in September 2020, its storm surge would hit another seven centimeters of sea level, flood the subway and have a far greater impact on the city and its daily life than 60 years ago. “

CoreLogic’s Hurricane Report 2021 examines the potential impact of hurricane-driven wind and storm surges on homes in the United States.

When assessing the storm surge and hurricane wind risk for single-family (SFR) and multi-family (MFR) dwellings along the Gulf and Atlantic coasts for the 2021 hurricane season, CoreLogic identified more than 31 million single-family homes and nearly one million additional single-family homes in multi-family homes that make up a medium-sized or at greater risk from harmful hurricane winds. It was found that around eight million were directly or indirectly at risk from coastal storm surges.

With regard to salvage, damage and compensation expenses from coastal storm events in 2021, the “significant price increases for lumber and other building materials in recent months”, as Moody’s Investors Service has pointed out, could be particularly affected.

Current projections

The Atlantic hurricane season officially runs from June 1 to November 30, although Tropical Storm Ana turned into a Tropical Storm on May 23. Ana made 2021 the seventh straight year that a named storm formed before the start of hurricane season, according to the Insurance Information Institute (III).

Moody’s Investors Service states in its report Weak La Nina and Warm Waters Point to Active Atlantic Hurricane Season 2021 that eight weather research organizations have predicted an above-average hurricane season for this year. “These projections assume that tropical storm activity this year will be well above the long-term average of 12 named storms, six hurricanes and three major hurricanes per season between 1950 and 2020,” noted Moody’s. No one predicts a season like 2020, with its record-breaking 30 named storms, but 11 of them landed on the US mainland.

Early predictions predict between 14 and 19 named storms in 2021, with seven to eleven potentially developing into hurricanes, and the potential for three to five hurricanes taking the status of a major (category 3, 4, or 5) hurricane with wind speeds can reach more than 180 mph, Moody said.

Factors influencing forecasts for 2021 include current La Nina conditions, which “are causing an increase in the number of Atlantic hurricanes that develop and allow more intense hurricanes to form”.

As mentioned earlier, Hurricane Katrina, which devastated New Orleans and the Mississippi coast in August 2005, remains the most expensive hurricane to land in the United States. Including losses from the National Flood Insurance Program (NFIP), Katrina had $ 65 billion in insured losses. In terms of $ 2020, that amount would swell to $ 86.6 billion, according to Aon.

But as Munich RE stated in its report: “Hurricane Katrina was the first natural disaster in the 21st century that forced a lengthy, complete shutdown of a major US city and metropolitan area, and it will probably not be the last.”

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