Historical Hurricanes

Sixty-seven hurricanes during the period 1620-1997 were selected for detailed analysis, including all hurricanes since 1851 that tracked within 200 km of New England according to HURDAT, and all earlier hurricanes for which Ludlum (1963) presented evidence of F1+ wind damage in the study region. Newspapers were often the best source of information for later hurricanes, especially the Boston Globe and the New York Times for storms since 1871, and various local newspapers, depending on the area of impact, for the period 1700-1870. Evidence for earlier storms (1620-1699) was drawn mainly from personal diaries and town histories (especially at the American Antiquarian Society, Worcester, Mass.). Primary sources cited in Ludlum (1963) were consulted wherever possible.

Our analysis of temporal variation in New England hurricanes was based on 52 hurricanes whose maximum actual wind damage in the study region equaled or exceeded F1. At a seasonal scale, 90% of such hurricanes (and all hurricanes that caused F3 damage) occurred during the months of August, September, and October. About 30% of these storms occurred in October and November, during or after leaf senescence in New England, when deciduous trees are much less likely to suffer wind damage. At an annual scale, there were 4 years with two hurricanes in the same year; in two of these years both storms caused F2 damage, whereas in one year both storms caused F3 damage, suggesting a higher than average hurricane intensity during these exceptionally active years. At a decadal scale, the number of hurricanes since 1851 varied from a minimum of 0 storms in the 1910s to a maximum of 4 storms in the 1950s, and evidence suggests that such multidecadal variation was present during the entire historical period (figure 2.2a). At a centennial scale, there was no clear trend in the timing of hurricanes causing F3 damage; the greatest number occurred in the nineteenth century. At lower levels of damage, fewer storms were recorded in the seventeenth and eighteenth centuries than in the nineteenth and twentieth centuries, probably because of improvements in meteorological observations and records since the early nineteenth century.

Our analysis of spatial variation in hurricane impacts was based on meteorological reconstructions of each storm using the HURRECON model. Results for F0+, F1+, and F2 damage were based on the periods 1871-1997, 1800-1997, and 1620-1997, respectively, to maximize the observation period while minimizing the likelihood that storms of a given magnitude escaped historical notice. The frequency of F0 events was probably underestimated, because F0 damage could result from storms not covered in this study. At a regional scale, the frequency and

(a) New England

(a) New England

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Figure 2.2 Number of hurricanes by decade with maximum reported damage equal to F1-F2 (white) or F3 (black). (a) New England, 1620-1997. (b) Puerto Rico, 1508-1997 (adapted from Boose et al. 2001, in press). Adapted and reprinted with permission from Ecological Monographs and Ecology, respectively.

intensity of hurricane wind damage decreased from southeast to northwest across New England (figure 2.3a). These gradients result from the consistent direction of the storm tracks, the shape of the coastline, and the tendency for hurricanes to weaken rapidly over land or over cold ocean water north of the Gulf Stream. At a site scale, estimated mean return intervals for F0+, F1+, and F2 damage at the Harvard Forest were 10 years, 20 years, and 125 years, respectively (figure 2.4a), with the highest winds from the southeast. At a landscape scale, there was a gradient of hurricane impacts across the town of Petersham, Massachusetts (the location of Harvard Forest), with reduced impacts in protected valleys and scattered lee hill slopes, though most of the gently rolling terrain was fully exposed to all storms.

(b) Puerto Rico

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