Characteristics of the top ten snowstorms at First-Order Stations in the U.S.
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- Houston, T.G. & Changnon, S.A. Nat Hazards (2009) 48: 101. doi:10.1007/s11069-008-9251-5
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Snowstorms can produce varying degrees of damage depending on the amount and intensity of the snowfall over a given amount of time. Concurrent weather conditions such as freezing rain and high winds often exacerbate the amount of damage received. In order to assess the frequency of potentially damaging conditions during climatologically significant snowstorms, the top ten snowstorms (TTS) at individual First-Order Stations in the eastern two-thirds of the conterminous U.S. were determined, and the hourly weather conditions during each event were analyzed. The results show that TTS have occurred as early as September and as late as June, with January being the peak month of occurrence. Hourly precipitation totals during TTS were 2.3 mm or less 88% of the time. Seven percent of TTS were classified as a blizzard with over half of the blizzards occurring in the West North Central region. The most common concurrent weather condition during a TTS was fog followed by blowing snow. Regionally, heavy snow events in the Northeast had relatively higher precipitation amounts, colder temperatures, higher winds, and more fog and blowing snow than any other region.
KeywordsSnowSnowstormsSnowfallConcurrent weather conditions
National Oceanic and Atmospheric Administration
National Climatic Data Center
National Weather Service
Northeast Snowfall Impact Scale
Top ten snowstorms
United States dollars
Snowstorms are one of the most damaging weather extremes (Changnon and Hewings 2001). Concurrent weather conditions, such as freezing rain and high winds often exacerbate these damages. Four percent of all weather related insured property losses in the U.S. are a result of snowstorms, averaging $408 million (USD) in insured property losses per year (Changnon and Changnon 2006). A report by Adams et al. (2004) found that the economic impact of snowfall on the U.S. economy, both positive and negative, range from $50 to $400 billion (USD) per year.
Previous snowstorm studies have typically focused on the synoptic conditions associated with snowstorms, the development of snowstorm climatologies, and case studies of particular events. In addition, studies by Branick (1997), Schwartz and Schmidlin (2002), Changnon and Changnon (2006), and Changnon et al. (2006) examined significant snowstorms and identified the spatial and temporal characteristics of damaging snowstorms and blizzards. This study builds on these previous studies by identifying the top ten 1- or 2-day snowfall totals at individual First-Order Stations (FOS) in the eastern two-thirds of the conterminous U.S. from 1948 to 2001. Concurrent weather conditions, such as low temperatures, high winds, and other weather conditions reported during top ten events were analyzed to examine the frequency of their occurrence. How these conditions contribute to the amount of damage produced by the storm are also noted. By knowing the types of conditions that can occur during a heavy snowstorm at a particular location, those impacted by these storms can be better prepared the next time a significant snowstorm threatens.
2 Data and analysis
In order to assess the frequency and types of potentially damaging conditions associated with locally significant snowfall events, hourly weather conditions during top ten snowstorms (TTS) at select FOS were analyzed. Daily observations of snowfall from FOS were used to identify the TTS at each station, and hourly observations of temperature, precipitation, wind speed, and other concurrent weather conditions were used to assess the characteristics of these storms.
A snowstorm was defined as an event in which snow fell over a 1- or 2-day period. This definition is consistent with the findings of Changnon (1969) and Changnon et al. (2006) who found that 84% of all 2-day snow events lasted less than 24 h but, due to a fixed once-a-day observation time, were reported over two observational days. Research has also shown that snowstorms begin to produce significant damages when heavy snowfall occurs within 48 h or less (Changnon 1969; Branick 1997).
The 1- or 2-day snowstorms were determined based on the following criteria. A subset of daily snowfall totals of 25.4 mm or greater at the chosen 121 National Weather Service (NWS) FOS from 1948 to 2001 was obtained from the National Climatic Data Center’s (NCDC) Cooperative Summary of the Day dataset (NOAA 2004a). From this subset, if one day reported snow with no snow reported on the day before or after, this snowstorm was considered for the TTS list. If two adjacent days reported snowfall, this 2-day total was considered for the TTS list. If three consecutive days reported snowfall, the two adjacent days with the greatest snowfall total were considered as a 2-day event. The remaining day was also considered, but as a separate event. If four or more consecutive days reported snowfall, the three consecutive days criterion was followed to identify the first snowstorm for consideration. Then if the next two adjacent days reported snowfall, or if only one day remained, then this snowstorm was also considered for the TTS list. Additional snowstorms were identified until snow was no longer reported. The snowstorms at each station were then ranked to determine the TTS at that station.
Once the TTS were determined for each station, hourly data for each event were obtained from NCDC’s Surface Airways Hourly and Airways Solar Radiation dataset (NOAA 2004b). This data included dry bulb, wet bulb, and dew point temperatures, wind speed and direction, visibility, and other concurrent weather conditions such as fog and freezing rain. Hourly precipitation was also obtained from NCDC’s Hourly Precipitation dataset (NOAA 2004c) in order to examine water equivalent totals during each event.
3 Characteristics of top ten snowstorms
Overall a total of 1,182 TTS were analyzed (28 TTS did not have hourly data available). The following sections describe the general characteristics of TTS, such as the frequency and timing of events, precipitation types and temperatures during TTS, the occurrence of blizzards and blowing snow during TTS, as well as the occurrence of other significant weather conditions.
3.1 Frequency and timing of TTS
The snowfall totals of the number one TTS at each station varied considerably depending on where the storm occurred. In general, there was a latitudinal increase in totals from south to north with higher totals downwind of the Great Lakes and in mountainous areas. The greatest TTS total was 1168.4 mm at Sault Ste Marie, MI on 9–10 December 1995. This event helped break the station’s all time record monthly snowfall total with a monthly total of 2507.0 mm. The smallest snowfall total for a number one storm on a TTS list was 139.7 mm at Jackson, MS from a storm that occurred on 13 January 1982.
Some snowstorms that occurred over a large geographic area were in the top ten list of multiple FOS. The snowstorm that generated the most TTS was the “Storm of the Century” that occurred on 12–13 March 1993. This storm was ranked among the top ten at 22 FOS stations throughout 15 states and was listed as the number one storm at seven stations. Overall, this storm produced maximum snowfall totals of over 1270.0 mm and caused over $1.8 billion (USD) in insured property losses throughout 21 states from Louisiana to Maine and was rated as a Category 5 storm (extreme, the largest value) on the Northeast Snowfall Impact Scale (NESIS) (Kocin and Uccellini 2004; Changnon and Changnon 2006). Other damaging conditions associated with this storm included high winds, tornadoes, flooding, and record low temperatures (Lott 1993; Kocin et al. 1995).
Call (2005) found that if two snowstorms occurred within several days of each other and the temperatures remained cold, the second storm tended to be more disruptive than the first due to the increased snow depth and snowfall mitigation equipment problems. Several TTS did occur within days of another TTS at several stations. One station reported three TTS which occurred over five consecutive days. During 24–28 December 2001, Buffalo, NY reported: (1) 645.2 mm of snow on 24–25 December which ranked fourth on the TTS list, (2) 759.5 mm on 26–27 December which ranked second, and (3) 665.5 mm on 28 December which ranked third. These events contributed to the 2100.6 mm of snow reported that month which became a new monthly snowfall record for Buffalo. While Buffalo is used to dealing with copious amounts of snow, help was needed to aid in the snow removal. Since these events occurred over a holiday, the impacts were less than what may have happened if they occurred even a week or two later (CNN 2007).
3.2 Damaging types of precipitation
The more water content snow contains the more damage the storm can cause. Light fluffy snow can easily be removed and driven on but heavy wet snow can strain snow removal equipment, break tree limbs, and cause building roofs to cave in under the added weight. Even in cities that have efficient snow mitigation capabilities, snow intensity can often have a greater impact than the amount of snowfall (Call 2005). At high intensities, snow falls too quickly for removal crews to keep up and visibility is reduced, as was the case during the Buffalo, NY events described in Sect. 3.1.
Relative frequencies (in percent) of hourly precipitation amounts during TTS in each region and across the eastern two-thirds of the nation
During TTS, heavy snowfall (i.e., visibility less than 400 m) occurred seven percent of the time while snowfall intensity was light (i.e., visibility greater than 805 m) approximately 75% of the time. These percentages were also true regionally except in the Northeast and Southeast where heavy intensities occurred 14% and 9% of the time, respectively, and light intensities occurred in both regions 65% of the time.
Dew point temperatures ranged from −7.8 to 0°C 67% of the time during TTS (Fig. 4). The warmest dew point temperature of 3.3°C occurred during the “Storm of the Century” in Atlanta, GA on 13 March 1993 where 106.7 mm of snow was reported. The coldest dew point temperature was −33.3°C which occurred during a snowstorm in Helena, MT on 10 January 1971 where a total of 307.3 mm of snow was reported.
3.4 Blizzards and blowing snow
Winds also contribute to the amount of damage received during a snowstorm. According to Changnon and Kunkel (2006), winds greater than 13.4 m/s increase damages by 25% compared to heavy snow alone. High winds blow falling snow and even pick up accumulated snow which can cause whiteout conditions and significant drifting. The NWS defines a blizzard as falling or blowing snow that reduces visibility to less than 400 m with sustained winds or frequent wind gusts 15.6 m/s or greater for a period of 3 h or more (NOAA 2007). A blowing snow advisory is issued when visibility is less than 400 m and sustained winds or frequent wind gusts are 15.6 m/s or less (NOAA 2007).
Out of the 1,182 TTS, 80 TTS from 56 separate storms were considered blizzards by the NWS definition. Thirty TTS blizzards were from storms that caused catastrophic damage (based on insured property losses of $1 million (USD) or greater (Changnon 2005)). TTS blizzards were reported in each month between October and April and occurred most frequently (25% of the time) in the month of March. Fifty-five percent of the TTS blizzards occurred in the West North Central region which includes the nation’s maximum blizzard zone states of North Dakota and South Dakota, as well as the western part of Minnesota (Schwartz and Schmidlin 2002).
Ninety percent of the time hourly wind speeds were 11.2 m/s or less during TTS. Only three percent of the time did winds during a TTS exceed 15.6 m/s, the threshold for defining a blizzard. The highest hourly wind speed reported during a TTS was 26.4 m/s at Rapid City, SD on 30 April 1967 where a total of 345.4 mm of snow was reported. Approximately 54% of the time, the prevailing wind direction during a TTS was from the northern quadrant.
3.5 Other significant weather conditions
Many types of weather conditions occurred at the same time as snowfall during the TTS. These conditions included: thunderstorms, rain, freezing rain, fog, smoke, haze, and blowing snow and included the various types of precipitation (rain, rain showers, drizzle, ice crystals, ice pellets, etc.) and intensities (light, moderate, and heavy). Sixty percent of hours reporting snow also reported one additional concurrent weather condition, 6% reported two additional concurrent weather conditions, and less than 0.5% reported three additional concurrent weather conditions. Regionally, the South had the highest percentage of additional concurrent weather conditions with one or more condition occurring 76% of the time, while in the Southwest, one or more concurrent weather conditions were reported 52% of the time.
Types and frequency of occurrence of concurrent weather conditions during TTS
Concurrent weather type
Frequency of occurrence (%)
Smoke, haze, dust
This study assessed the frequency of various weather conditions that occurred during hours when heavy snowfalls occurred. Data from 121 FOS across the eastern two-thirds of the U.S. and for 1948–2001 were used to identify the TTS at each station. The results revealed that TTS have occurred as early as September and as late as June, with January being the peak month of occurrence. The year 1978 had the greatest number of TTS.
The most frequent hourly liquid equivalent precipitation total during a TTS was 0.3 mm with 88% of all hours having values of 2.3 mm or less. Seven percent of the time, snowfall intensity was heavy.
An assessment of temperatures showed that dry bulb temperatures during TTS ranged from −27.2 to 7.2°C and most frequently occurred near the freezing point. Fifty-one percent of all values were from −4.4 to 0.6°C. Sixty-seven percent of all snow hours during TTS had dew point values between −7.8 and 0°C.
Approximately, 54% of the snow hours had winds from the northern quadrant. Wind speeds less than 11.2 m/s prevailed 90% of the time. Seven percent of TTS were classified as a blizzard with over half of the blizzards occurring in the West North Central region.
Weather conditions occurring during the hours when heavy snow fell were assessed, and the most frequent conditions in the U.S. were fog (52% of the time) and blowing snow (40% of the hours), both of which reduce visibility. These two conditions were more frequent in the Northeast, and fog was also frequent with snows in the Central, Southwest, South, and Southeast regions. Freezing rain, rain, and haze also occurred during TTS, further increasing damages and limiting visibility.
The regional results revealed that heavy snow events in the Northeast had relatively higher precipitation amounts, colder temperatures, higher winds, and more fog and blowing snow than any other region. The East North Central region had relatively high frequencies of relatively low temperatures, high winds, and blowing snow. Thus, heavy snows are more dangerous in these two regions of the U.S.
A listing of the TTS at each station and their concurrent weather conditions along with additional snowfall data and information found in Changnon (2005), Changnon and Changnon (2006), and Changnon et al. (2006) can be obtained from two products available from NCDC. A CD-ROM titled “Snowstorm Data: Long-Term Data Sets about Snowstorms in the United States” and a publication titled “Snowstorms Across the Nation: An Atlas about Storms and Their Damages” can be obtained from the NCDC web site at http://www.ncdc.noaa.gov or by calling NCDC Customer Service at +1-828-271-4800.
The authors would like to thank Imke Durre and Mike Squires of NCDC and two anonymous reviewers for their helpful comments and suggestions. Portions of this research were funded by a grant from the National Oceanic and Atmospheric Administration (NOAA) and the National Aeronautics and Space Administration (NASA), as part of the Climate Change Enhanced Data Set Project, under Grant No. NA16GP1585 as well as by a grant from the Office of Biological and Environmental Research, U.S. Department of Energy, under Grant No. DE-AI02-96ER62276.