When Hurricane Irene passed over Brooklyn in 2011 I used our weather station to collect data on the storm. The time-series for atmospheric pressure (in purple) and wind direction (in tan) looked the most interesting. I decided to repeat the experiment for Hurricane Sandy, but given how much worse this storm was I extended the data collection from 24 hours to 3 days.
The first thing to notice are the dramatic drops in atmospheric pressure. Storms are always associated with low pressure. The drop is sharper for Hurricane Irene because the eye of the storm essentially passed right over Midwood. The drop for Sandy is softer since the eye of the storm made landfall near Atlantic City, New Jersey, 125 miles to the south. This means that the minimum pressure in the eye of Sandy must have been lower, which is true. (In fact, it may have set a record for lowest pressure ever recorded on the east coast of the US.)
The second thing to notice are the changes in wind direction. Winds swirl around low pressure systems counterclockwise in the northern hemisphere. As Hurricane Irene approached from the South it gave us east winds in New York. As it passed overhead and headed north, the winds switched to west. Hurricane Sandy, on the other hand, mostly stayed to our south. This meant the winds shifted gradually from the southeast to the southwest. The coastlines of New York and New Jersey meet at roughly a 90° angle. Seawater pushed by a southeast wind gets trapped in the vertex of this angle — New York City. It was the sustained winds from the southeast that made Sandy’s storm surge so unusually large.
|August 2011 — Hurricane Irene||October 2012 — Hurricane Sandy|