Superstorm Sandy packed more total energy than Hurricane Katrina at landfall – Capital Weather Gang – The Washington Post

We spend a lot of time talking about flood zones, 100 year (1%) storms, hurricane categories and similar information. We throw a lot of maps out there, try to explain each in their own way, and hope all the information correlates. When they don’t we act befuddled.

This Washington Post article approaches Hurricane Sandy in a manner that explains why a Category 1 hurricane can pack a larger punch than almost any hurricane in modern times, including Hurricane Katrina.

Taking this from a Town of Dennis point of view, the following three maps illustrate storm impact areas from differing perspectives. First is the new flood maps. These illustrate the impacts of the 1% storm. Traditionally thought of as a 100 year storm, but is really the 1 storm out of 100 storms (1%) storm. For reference, I recently saw a projection that Dennis could expect a storm like 1954’s Hurricane Edna once every 63 years. Hurricane Edna being a local storm impact reference point.


The second map illustrates storm surge expected from “normal” Category 1 through Category 4 hurricanes. The 1% storm equates closely to a Category 2 hurricane. This level of impact, and flooding, could be expected if such a storm hit at the correct tide cycle (high tide). Hurricane Bob came ashore during a low tide, minimizing flood impacts.


The final map illustrates possible impacts of storm surge if everything came together at one time: high tide; full moon high tide perhaps; a multi-high tide storm that keeps pushing water in with little opportunity to recede; etc. The end result could be flooding, at significant depths well beyond the noted flood zones.


Bottom line, if a storm is coming, be prepared.

To learn more about your flood risk, come to our August 7th Workshop with FEMA staff and at the Dennis Senior Center between 3 pm and 8 pm.


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