
| Long Island Hurricane Climatology |
| Epic Hurricanes
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Hurricane Frequency
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An empirical study of 20 past hurricanes that have impacted the New York City and Long Island coast regions by Scheffner and Butler (1996) found that the return period of a category 3 or greater hurricane is approximately 80 years. A strong category 3 or minimal category 4 hurricane has a return frequency of approximately 200 years. (Click graph to the right for larger image.) Therefore, it is not unlikely that another "epic" hurricane will strike the Long Island coastal region in the coming decades.
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Research done by hurricane experts at the National Center for Atmospheric Research (NCAR) reveals that hurricane frequency in the Atlantic Ocean and Caribbean Sea regions runs on a 20-30 year cycle. (Time, 1998) The graphic to the left (Risk Prediction Initiative, 1998) clearly illustrates this cycle. The last intense period was in the 1950's and 1960's with a lag between 1970 and 1994. The hurricane frequency is on the upswing once again which increases the chances for landfall everywhere along the east coast of the U.S. |
Climate Change and Hurricanes:
According to a review of the most recent literature, Vechi, Swanson, and Soden (2008) conclude that predicting the future of hurricane activity is at a crossroads. Vechi et al. compared the observed relation of the power dissipation index (PDI) vs. sea-surface temperatures (SST) in the main development region of Atalntic hurricanes. (PDI is the cube of the instantaneous tropical cyclone wind speed integrated over the life of all storms in a given season; more intense and frequent basinwide hurricane activity lead to higher PDI values.) There are two very different futures depending on whether absolute SST or relative SST controls PDI.
Figure 29b (ibid) shows PDI anomolies based on absolute SST.

By 2100, the lower end of the model projections shows a PDI comparable to that of 2005, when four major hurricanes (sustained winds of over 100 knots) struck the continental United States, causing more than $100 billion in damage. The upper end of the projections exceeds 2005 levels by more than a factor of two. Combined with rising sea levels, coastal communities face a bleak future if absolute SST determines hurricane activity and strength.
Figure 29c (ibid) shows PDI anomolies based on "relative SST" which is the SST in the tropical Atlantic main development region relative to the tropical mean SST.

A future where relative SST controls Atlantic hurricane activity is a future similar to the recent past, with periods of higher and lower hurricane activity relative to present-day conditions due to natural climate variability, but with little long-term trend.
Because the correlation of PDI vs. absolute SST and PDI vs. relative SST are equivalent, Vechi et al. conclude that more research is needed in this area.
The next section deals the future threat of New York hurrricanes and some worst-case scenario simulations of older events.
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| Scott A. Mandia, Professor -
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