Snow and ice storms

Overview

Winter storms are a type of storm that forms in the transition zone between subtropical and polar climate regions. In late autumn and winter, when the ocean remains warm but polar regions are cold, bursts of cold polar air collide with warm subtropical air masses, leading to the development of large low-pressure systems. While the wind speeds of winter storms (typically 140-200 km/h) may not reach those of cyclones, they can be just as destructive due to their ability to sweep across much larger areas—sometimes up to 2,000 km wide—and bring additional perils such as heavy snow, freezing rain, and ice storms, all of which have significant impacts on society and human life.

Winter storms are among the seven disaster types that cause billion-dollar losses in the United States. They are also one of the most destructive natural disasters in Europe. For example, during the winters of 1990 and 1999, storm damages in Europe resulted in more than 10 billion euros in insurance payouts, with total economic losses estimated to be about twice that amount. The powerful winter storm Uri, which occurred in 2021, incurred overall losses of around 30 billion dollars, making it the most costly winter storm on record.

The damages from winter storms primarily arise from destruction to buildings, vehicles, and infrastructure. These storms can cause widespread power outages, road closures, supply chain disruptions, and significant health risks. Winter storms bring strong winds, heavy snowfall or freezing rain, and cold temperatures, which together create a range of impacts. As summarized by the IPCC AR6 as below:

"Heavy snowfall is a substantial concern for cities, settlements and key transportation and energy infrastructure. Heavy snowfall can interfere with transportation and cause a loss of both work and school days depending on local snow removal infrastructure. Freezing rain and ice storms can be treacherous for road and air travel, and can knock down power and telecommunication lines if ice accumulation is high. Rain-on-snow events can create a solid barrier that hinders wildlife and livestock grazing that is important to indigenous communities. Shifts in the frequency, seasonal timing and regions susceptible to ice storms alter risks for agriculture and infrastructure."

Data for Risk Analysis

Historical winter storm data

Dataset	Description	Data download link
Snowstorm database	A collection of over 500 snowstorms over the US dating back to 1900 and updated operationally. Only storms having large areas of heavy snowfall (10-20 inches or greater) are included. This data has been used to provide input for the calculation of the Regional Snowfall Index (RSI) and the Northeast Snowfall Impact Scale (NESIS) and for analyzing trends of large snowstorms. The data can also be used to make maps of historical snowstorms or for exploratory data analysis of historical storms. Archiving the data as shapefiles allows external users such as emergency managers, researchers, or anyone from snow sensitive entities to use the data directly in a GIS.	Access
Regional snowfall index (RSI)	NOAA's National Centers for Environmental Information is now producing the RSI for significant snowstorms that impact the eastern two thirds of the U.S. It is a regional index. The RSI ranks snowstorm impacts on a scale from 1 to 5, similar to the Fujita scale for tornadoes or the Saffir-Simpson scale for hurricanes. RSI is based on the spatial extent of the storm, the amount of snowfall, and the juxtaposition of these elements with population. Including population information ties the index to societal impacts.	View; Access
Northeast Snowfall Impact Scale (NESIS)	NESIS characterizes and ranks high-impact Northeast snowstorms, like Fujita and Saffir-Simpson Scales characterizing tornadoes and hurricanes respectively. The index differs from other meteorological indices in that it uses population information in addition to meteorological measurements. Thus NESIS gives an indication of a storm's societal impacts. This scale was developed because of the impact Northeast snowstorms can have on the rest of the country in terms of transportation and economic impact. Though it was developed aiming for the Northeast only, NESIS also ranks snow storms over the other regions of the US.
NOAA storm events database	A database that contains storm data (including winter storms) and other severe weather events (droughts, wildfires, etc.) from January 1950 to near present. Damage and fatalities are also provided.	Access
PRIMAVERA European winter windstorm event set	PRIMAVERA was a European Union Horizon 2020 project whose primary aim was to generate advanced and well-evaluated high-resolution global climate model datasets, for the benefit of governments, business and society in general.  Following consultation with members of the insurance industry, we have used a PRIMAVERA multi-model ensemble to generate a European winter windstorm event set for use in insurance risk analysis, containing approximately 1300 years of windstorm data. The uploaded dataset contains the model and re-analysis windstorm footprints in netcdf format and documentation of the data.  Further information is given in Lockwood et al., Using high-resolution global climate models from the PRIMAVERA project to create a European winter windstorm event set, Nat. Hazards Earth Syst. Sci. Discuss. [preprint], https://doi.org/10.5194/nhess-2022-12, in review, 2022.

Future projections under climate change

Winter storms are expected to be less frequent but more intense with climate change. Future climate projection and downscaled climate projection are used as input of risk assessment model to assess the potential risk of winter storms. Below are the data that are currently used.

Dataset	Description	Data download link
CMIP6	CMIP6 data refers to the vast collection of climate model outputs generated by the Coupled Model Intercomparison Project Phase 6 (CMIP6). This data is produced by various climate modeling groups around the world and is used to study past, present, and future climate conditions under different scenarios. It is the leading state-of-the-art resource for future climate projection.	Access (you may also refer to the Wildfire webpage of CRL wiki for guidance on downloading CMIP6 data )
CORDEX	The downscaled CMIP data created using regional climate modeling by Coordinated Regional Climate Downscaling Experiment (CORDEX).	Access
HighResMIP	Higher-resolution (25 km) CMIP6-like simulations (HighResMIP) that are provided by some CMIP6 models.	Access
NEX-GDDP-CMIP6	The downscaled dataset of CMIP6. This dataset includes downscaled projections from ScenarioMIP (i.e. different greenhouse gas emission scenarios) model runs for which daily scenarios were produced and distributed through the Earth System Grid Federation. The purpose of this dataset is to provide a set of global, high resolution, bias-corrected climate change projections that can be used to evaluate climate change impacts on processes that are sensitive to finer-scale climate gradients and the effects of local topography on climate conditions. Note that only a small number of CMIP6 variables (mainly precipitation, surface wind, surface temperature, and radiation) are provided.	AWS access

Risk assessment model

Munich Re’s NatCatSERVICE is one of the world’s most comprehensive databases for analysing and evaluating losses caused by natural disasters. For this service, Munich Re has for decades been systematically recording in detail all essential information on loss events worldwide. This is stored in a digital catalogue of events and damage. https://www.munichre.com/en/solutions/for-industry-clients/natcatservice.html

• G20 climate risk analysis: https://www.cmcc.it/g20
• climate related economic losses: https://www.eea.europa.eu/en/datahub/datahubitem-view/1fac8253-3df7-4408-b5fa-a6f2dc524182
• Economic losses from climate-related extremes in Europe https://www.eea.europa.eu/en/datahub/datahubitem-view/77389680-ecd2-4f56-926f-8106061a5570