Hurricane Sandy-Like Tropical Cyclones in the Historical Record

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Sunday, 4 January 2015
Reginald Johnson, Cornell University, Ithaca, NY

Handout (8.2 MB)

After it re-curved away from the East Coast, Hurricane Sandy (2012) turned northwestward and made landfall in southern New Jersey. The NOAA 20th Century Reanalysis and NCEP/NCAR Reanalysis datasets were searched for tropical cyclones that similarly took a northwestward turn after re-curving over the North Atlantic basin. A total of nine such storms (including Sandy) were found from 1889 to 2012. Storms similar to Sandy tended to occur in either June-July or September-November. There were no such storms during August. A subset of eight storms (including Sandy) was selected for closer study. The average northwestward “turning point” in these storms was located around 30N, 74W or about 500 miles off the coast of the FL-GA border. Composites were constructed, before and after the turning point, of the four storms in the modern era (after 1948) using the NCEP/NCAR reanalysis data, and four storms in the historical era (1871-1947) using the 20th Century Reanalysis. Composites were also constructed of long-term daily mean data from the NCEP/NCAR Reanalysis corresponding to the dates of the storms so that anomalies could be calculated. The calculations reveal that, in the upper troposphere prior to the storm's turning point, there were composite negative geopotential height anomalies (an anomalous trough) west of the storm and positive anomalies (an anomalous ridge) to the storm's north. Additionally, the storm was modeled as if there was no latent heat release (using the WRF model). The purpose of conducting the model runs was to see what would have happened to Sandy had latent heating not been there. A hypothesis is that the latent heat release caused divergent outflow that helped modify the storm's track. The result was that the hurricane dies out relatively quickly when the model was initiated early in Sandy's life. However, when the model was initiated when Sandy was near land, Sandy could survive without latent heating, but follows different tracks depending on the initial time. Future investigations will see if Sandy helped cause the concurrent high pressure ridge over Newfoundland.