Storm Surge Not to be Ignored When it Comes to Hurricane Safety

by Jordanna Sheermohamed of Weather Forecast Solutions

With the 2019 Hurricane Season officially underway [June 1st – November 30th], many are actively keeping a wary eye on the Atlantic basin. While portions of the US were lucky to dodge direct impacts during the 2018 season, luck is never a repetitive guarantee with Mother Nature. All it takes is one system during that 6 month window, to change lives forever.
Hurricane prep often focuses on the comforts in the aftermath; purchasing days-to-weeks’ worth of food and water (general rule is 1 gallon per person per day), filling our vehicles’ gas tanks, or purchasing generators to maintain the power in the increasing modern lifestyle.

The direct impacts of a hurricane can be terrifying, from the elevated wind speeds of a Cat 1 (74-95 mph) to the extremely destructive power of Cat 5 winds (157+ mph). Substantial rains can produce flooding events such as which occurred with 2017’s Hurricane Harvey, which situated itself over SE Texas for several days as a result of a blocking high pressure to the north. Unfortunately, its position also allowed Harvey to access an infinite moisture feed from the nearby Gulf of Mexico, which in turn allowed the system to produce nearly 52 inches of rain over parts of the great Houston area. By comparison, this is nearly equal to the amount of precipitation that Houston receives over the span of an entire year, approximately 49 inches!

Even with the worries of the high winds, the endless rain, or the lack of general provisions, there’s another hurricane impact considered the worst of all; the storm surge. Many are unaware of how storm surges can exacerbate the destruction, especially if coupled with normal high tides. According to the National Hurricane Center (NHC), storm surge is defined as “an abnormal rise of water generated by a storm, over and above the predicted astronomical tides”. If astronomical tides and storm surge simultaneously occur, this produces a storm tide which can produce extreme flooding along coastal areas, “up to 20 feet or more in some cases” (NHC).

Surges are a combination of several factors; the storms intensity and size, its forward speed, its direction and angle of impact/proximity to the coastline, the topography and geography of the surrounding regions such as the presence of rivers, inlets, or bays, how far the winds have travelled across the ocean (fetch), and the changes the ocean floor depth as the system approaches the coast. “A Cat 4 storm hitting the Louisiana coastline, which has a very wide and shallow continental shelf, may produce a 20-foot storm surge, while the same hurricane in a place like Miami Beach, Florida, where the continental shelf drops off very quickly, might see an 8 or 9-foot surge” (NHC).

Those who live inland sometimes fall under the false pretenses that they are immune to the effects of the sea, but surges can reach tens of miles inland, especially in areas close to or below sea level. Hollywood theatrics often portrays storm surges to be the infamous “wall of water” that swallows up a coastal city, but in reality, the water may rise as quickly as several feet in just a few minutes. The storm surge itself travels with the same forward speed of the hurricane, which on average is 10-15 mph.

The National Weather Service (NWS) has produced a model to aid the meteorological community in better predicting storm surge affects, called the SLOSH model (Sea, Lake and Overland Surges from Hurricanes. This model considers a hurricane’s pressure, size, forward speed, and track for historical events, hypothetical scenarios, and predicted hurricanes, to produce a modeled wind field that would indicate the storm surge potentials.

There’s an old adage which highlights a general protocol when it comes to Mother Nature, “run from water, hide from wind”. This certainly underlines the state of mind one should apply when it comes to hurricane produced storm surge.