How will extreme events impact New England in the future?The most reliable way to characterize the nature of extreme events and what may happen in the future is to look at the characteristics of these events in the past. By examining such events, we hope to learn how they may have varied in the past, and how they affected the various distinct regions within New England. We also need to examine past magnitudes of these events, their frequencies, and whether trends over time exist for particular types of events, for example, whether the number of exceptionally strong noreasters increased over the past few centuries. A knowledge of such events may allow us to answer the following general questions:
Did particular types of events occur more frequently in the past then they have in the last few years or even in the 1990s as a whole?
What type of trends do we see in the past that may have a bearing on what will happen in the future?
What is the significance of this general trend to decreasing small snow events in recent years?The average number of daily accumulations 5 inches, and thus the greatest number of snowfalls that probably originate from noreasters, is 3.5 snowfalls per year at both Durham and Hanover. In this case, the greater proximity of Durham to the coast actually results in an equal number of larger snows in the seacoast region of New Hampshire compared to further inland. This scenario reflects the tremendous importance of the track of coastal storms on New Hampshire and New England snowfall totals. A greater number of storms close to the coast will bring a higher number of 5 inch snows to the Hanover area and less to Durham because snow often will change to rain along the coast. If the main storm track is more frequently found farther offshore, there will be a greater number of 5 inch snowfalls in Durham and less in Hanover, since Hanover is farther from the center of such storms. We discuss the long-term trend in these larger snowfalls below. As for the total number of snowfall days, we conclude that there are a greater number of total snowfall events further inland in New Hampshire, but there appears to be an equal number of large storms per year across the region. Continued investigations may further support these initial findings or we may find that there are different trends along the New England coast as a function of latitude.
Is it a function of climate warming that has resulted in a greater number of rain events in the winter over the past two decades compared to the 1920s and 1930s or something else?
Is the frequency of these smaller snowstorms in a declining trend or are the trends more variable and fluctuating?
Is there a discernible cyclicity in the number of larger snowfalls across New Hampshire and New England?To answer this question more completely, it will be necessary to evaluate other snowfall records from around the region, especially at coastal sites such as Boston and Portland, for comparison with other inland sites. Information gathered from as many sites as possible will help us generate and then answer other questions such as:
How has the spatial variability in the number and magnitude of noreasters changed over time?Ice Storms
Could it be possible that tropical storms and hurricanes are becoming less intense and less frequent in New England?Given the dates presented in Table 1 (in addition to the time series in Figure 3.4), there is no suggestion that New England hurricanes and tropical storms are now getting more intense or frequent, which is in general agreement with the results of Henderson-Sellers et al. (1998) for the North Atlantic and North Pacific basins. In fact, four of the top five events this century occurred prior to 1955.
|Five most Intense New England Hurricanes, 1900-97.|
|Hurricane||Date||Pressure in Millibars|
|Gloria||27 September 1985||942|
|Number 4-1938||21 September 1938||946|
|Number 7-1944||15 September 1944||947|
|Edna||11 September 1954||954|
|Carol||31 August 1954||960|
|Source is the National Hurricane Center. Since accurate wind speed data are lacking for many hurricanes in the earlier decades examined, the central barometric pressure of the hurricanes are posted as an index for storm strength, with lower pressure relating to a stronger storm.|
|Largest 1-day Precipitation Events Recorded in New England, 1948-97.|
|Westfield, MA||19 August 1955||18.15|
|Portland, ME||21 October 1996||11.71|
|Cockaponset, RI||6 June 1982||10.47|
|Torrington, CT||31 December 1948||8.91|
|Middleton, MA||6 October 1962||8.64|
|Woods Hole, MA||3 September 1972||8.55|
|Norfolk, CT||16 October 1955||8.20|
|Brunswick, ME||11 September 1954||8.05|
|Source is the New Hampshire State Climate Office, University of New Hampshire.|
|Number of Documented Tornadoes for each N.E. State, 1950-96.|
|State||Tornado Reports||Average Per Year|
|Source is the National Severe Storms Laboratory.|
|Most Deadly New England Tornadoes, 1880-95.|
|County, State||Date||Strength||Est. Wind speed (mph)||Injured||Killed|
|Worcester, MA||9 June 1953||F4||207-260||1288||90|
|Essex, MA||26 July 1890||F3||158-206||63||8|
|28 August 1973||F4||207-260||31||4|
|Hampton, NH||4 July 1898||F1||73-112||120||3|
|3 October 1979||F4||207-260||500||3|
|Berkshire, MA||29 May 1995||F3||158-206||24||3|
|Sources are Grazulius (1991) and The Tornado Project, St Johnsbury, Vermont found on the world wide web at http://www.tornadoproject.com/.|