Canadian Underwriter

Winter storm could become first billion-dollar weather event of 2016 for U.S.

January 26, 2016   by Canadian Underwriter

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The winter storm that delivered record-breaking snow totals and hurricane-force wind gusts – affecting 20 states in the eastern United States and paralyzing a number of major cities – could represent the first billion-dollar weather event of 2016 for the United States.

Winter storm hits U.S. hard, causes damage and disrupts services

Noting it is too early to provide a specific economic or insured loss estimate, Impact Forecasting LLC, a catastrophe model development centre of excellence within Aon Benfield, is reported to have said the substantial damage and business interruption resulting from the storm could make the event the U.S.’s first billion-dollar weather event of the year.

“It is still too early to estimate damage totals, but this event could rank as one of the more significant events in recent history,” comments Jeff Waters, a meteorologist at RMS, who reports RMS does not plan on issuing an industry loss estimate for this event at this time.

That said, “economic and insured loss will likely be driven by a combination of factors, including roof collapse from high snow loads, coastal flooding, and business interruption claims as a result of travel delays, widespread power outages, and closed businesses,” Waters explains.

“A historic winter storm brought prodigious snowfall, high winds, coastal flooding, freezing rain, ice, sleet and severe thunderstorms to the Eastern United States from January 21-24, killing at least 29 people and injuring dozens of others,” notes an overview from Impact Forecasting. States of emergency were declared in Washington, D.C., Virginia, Maryland, Pennsylvania, New York, New Jersey, Tennessee, Kentucky, Delaware, West Virginia, Georgia and North Carolina.

“With a strong ridge of high pressure established between northeast Canada and Greenland, this prevented much northward motion of the storm system on January 23, which largely spared the majority of New England,” the overview explains. “However, the slow motion of the storm allowed for nearly 48 straight hours of very heavy snowfall that exceeded 2.0 inches (5.1 cm) per hour that included Washington, D.C., Baltimore, Philadelphia, and New York City,” Impact Forecasting notes, adding the storm “strengthened due to sharp temperature and moisture differences (or gradients) across a relatively short distance.”

Heavy snowfall, high winds and coastal flooding started to gradually subside before the event finally ended in the early morning hours of Jan. 24.

Related: Icy roads, spotty transit service follow East Coast blizzard

There have only been 13 winter storms in the Northeast and Mid-Atlantic that have been rated either Category 4 or 5 since 1900, Impact Forecasting points out, reporting that it expects the recent storm will become the 14th such event.

“The storm shut down the nation’s capital and New York City over the weekend, forcing flight cancellations at major airports and causing power outages, roof collapses and severe flooding in several states,” notes a statement Monday from AIR Worldwide.

More than a foot of snow fell in 20 states, with West Virginia receiving the most, 42 inches (107 cm) in Glengary. There was also 39 inches (99 cm) in Philomont, Virginia; 38.3 inches (97 cm) in Greencastle, Pennsylvania; 30.5 inches (78 cm) at New York John F. Kennedy Airport; 29.2 inches (74 cm) at the Baltimore-Washington International Airport; 22 inches (56 cm) in eastern Kentucky; 22.4 inches (57 cm) in Philadelphia; 17.8 inches (45 cm) at Reagan National Airport in Washington, D.C.; and 8 inches (20 cm) in Nashville, where “thundersnow” was also observed, AIR Worldwide reports.

Waters notes that multiple cities – New York City, Baltimore and Harrisburg, Pennsylvanis – broke their all-time snowfall accumulations. “Jonas is the first winterstorm on record to bring more than 18 inches of snow to Washington D.C., Baltimore, Philadelphia, and New York City,” he adds.

Beyond roof buckling and collapses caused by the accumulation of heavy, wet, snow, snow accumulation has also increased the risk of ice damming, as snow melts on the roofs of homes and refreezes, AIR Worldwide reports.

“This has caused damage due to water leakage under roof shingles and over flashing, and has blocked gutters and drainage pipes. The weight of the dams can cause cracks and deformation in the wall/roof interface, allowing water to infiltrate ceilings and walls,” notes the AIR Worldwide statement.

The company explains that damage caused by snowfall is primarily the result of the weight of the accumulated snowpack, rather than to its depth. “Therefore, property damage is determined by snow load, which is the estimated weight of a snowpack. The snow load depends on the amount of water in the snow that is absorbed by the snowpack, increasing its density,” the statement notes.

Water-equivalent snow totals in this storm would result in snow loads of 10 to 20 pounds per square foot on flat roofs, but this calculation does not account for snow drift, which can significantly increase loads, AIR Worldwide explains.

“The risk of roof collapse is particularly acute for light metal, long-span roofs (such as on warehouses or hangars),” the company notes. “The roofs of marginally engineered structures (such as small businesses and convenience stores) can collapse under large accumulations of snow, particularly if their roofs have not been well-maintained,” it states. Many old buildings, however, may not meet the current code requirements, which can increase their vulnerability.

Waters points out, however, that pipe freeze and burst, which is a common driver of insured losses during winter, is not expected to be material in this event because there is a lack of sufficient Arctic air to warrant such a deep freeze.

Eric Robinson, senior scientist at AIR Worldwide, reports that “wind gusts from the storm reached hurricane strength in several areas early Saturday,” with gusts of 85 mph (137 km/h) recorded on Assateague Island, Maryland.

There were also storm surges that exceeded those from Hurricane Sandy occurred in several areas, AIR Worldwide reports. “The storm coincided with a full moon and high tide, which increased the tidal effects of coastal flooding from Delaware to New Jersey,” Robinson explains. “One of the hardest-hit places was Cape May, New Jersey, where water levels reached 4 to 5 feet (1.2 to 1.5 m) above normal tide levels.”

Flood damage has been reported in several residential houses and commercial buildings in Ocean City and other areas of Cape May, AIR Worldwide notes. Damage is also reported in many areas of Long Beach Island.

“The storm surge and pounding waves caused considerable water damage to homes, businesses, beaches and coastal infrastructure. In many instances, there were large chunks of ice floating in the floodwaters,” notes the overview from Impact Forecasting. “Some of the hardest-hit New Jersey communities included Ocean City, Atlantic City, Sea Bright, Long Beach, Hazlet, Sea Isle City and Manasquan,” the company adds.

AIR Worldwide further reports that travel was greatly hampered because of the treacherous road conditions and shuttered rail, bus, and subway systems. Disruptions affected, among others, the Washington Metropolitan Area Transit Authority and the Southeastern Pennsylvania Transportation Authority.It also led to flight cancellations, mostly in North Carolina, Washington and Philadelphia.

In addition, power outages were widespread as wind and heavy snow downed power lines, notes AIR Worldwide.

Impact Forecasting reports that “at the peak of the event, there were more nearly 500,000 power outages across the U.S. as power lines and poles collapsed due to the weight of heavy snow and ice. Outages included North Carolina (150,000); Georgia (125,000); New Jersey (90,000); Maryland, Virginia & Washington, D.C. (50,000); Philadelphia (2,000); South Carolina (1,000).”

Comparable historical events include the Blizzard of 1996, which caused approximately $1.5 billion in economic losses, and $740 million insured losses (1996 dollars), notes Waters.

Related: U.S. insurers paid out US$2.9 billion in winter-related insured losses in 2015: Insurance Information Institute