A method for determining the historical climatology of East Coast Winter Storms

East Coast Winter Storms (ECWS) are among the most severe weather phenomena to impact the Northeastern United States. Hirsch et. al. (2001) and subsequent data keeping has provided an accurate history of ECWS for the past 60 years. Climatology of storms prior to this period, however, is less readily available.

Due to the lack of surface datasets for historical periods prior to 1949, a way of using strictly NCDC Climate Database Modernization Program (CDMP) data to find ECWS was sought. The method indicated the presence of a storm when a given hourly observation had a wind direction between 330 and 60 degrees, sea level pressure of 30.00 inches of mercury or lower, and a pressure fall or rise of at least 0.04 inches of mercury in the past hour, and when at least two of these observations occurred on a given day (or 24-hour period).

Validation of this technique using data from LaGuardia Airport showed that 336 of the 352 storm identified by the method corresponded to storm in the Hirsch climatology.

Using pre-1949 data from the Washington Naval Observatory, LaGuardia, and Providence showed that on average 6 to 7 ECWS occurred per season, with maximum frequency in January and February, in agreement with Hirsch. Annually frequency of ECWS could vary considerably, with no distinct trend during the period.

Developing a climatology of East Coast Winter Storms using single station data is not a perfect science. No one station can detect all ECWS, or is immune from being affected by a comparable storm system which the computer program counts as an ECWS. Nevertheless, a very good picture of the trends and occurrences of ECWS can be gleaned by using CDMP data from several stations around the Northeast, especially New York and New England.

REFERENCES

Hirsch, DeGaetano, and Colucci, 2000: An East Coast Winter Storm Climatology, Journal of Climate, 882-899

Jones, Osborn, and Briffa, 2001: The Evolution of Climate Over the Last Millennium, Science, v.292(5517), pp. 662, April 27, 2001.