Importance of Grasping a Tropical Cyclone’s Storm Surge

By Meteorologist Jordan Rabinowitz, GWCC

DISCUSSION: As we get deeper into the 2018 tropical Atlantic hurricane season, many people living both across the United States and around the world often have many questions regarding various aspects and dangers both directly and indirectly related to tropical cyclones. Among such questions, often includes a curiosity for a what the definition of storm surge is and why it is so important to understand what a storm surge physically is. It is so important understand what a tropical cyclone’s storm surge physically is because a storm surge is typically the most destructive force tied to a landfalling tropical cyclone both across the tropical Atlantic Ocean (and often in any tropical cyclone-producing basin around the world).

A storm surge is best characterized as the above-normal rise in sea-level height both in advance, during the potential landfall of, and during the aftermath of a given tropical cyclone due to a nasty combination of both stronger regional atmosphere pressure differential and strong onshore winds.  This destructive combination of factors (especially in stronger tropical cyclones with maximum sustained winds of at least 100 miles per hour or 44.7 meters per second) often will lead to an increase in the localized sea-level in the immediate vicinity of the storm.  This localized increase in the average sea-level height near and within the tropical cyclone region is due to the presence of the substantially lower atmospheric pressure tied to the core of the given tropical cyclone.  This notably lower minimum central pressure creates a stronger pressure gradient between the inner-most parts and the outer-most parts of the given tropical cyclone; thereby creating larger wave actions and swells.  As a consequence of this large wave and swell production by a more intense tropical cyclone and a potential landfall situation characterized by a higher mean sea-level height along with anomalously larger waves/swells, this creates the infamous aspect of tropical cyclones which is observed as the tropical cyclone’s storm surge.

When in the path of an intensifying tropical cyclone (and especially if you or family/friends live and/or are visiting a vulnerable coastal region), it is imperative to always communicate such tropical cyclone threats well ahead of time so there is adequate time for action.  The reason for this is because in cases involving much larger tropical cyclones (i.e., in terms of their total spatial coverage in terms of square miles and total diameter from side-to-side), such as Hurricane Katrina (2005) or Hurricane Ike (2008), a substantial storm surge began impacting many coastal towns/cities well ahead of the core of each respective tropical cyclone landfall.  Therefore, in these such cases, waiting until there was a sense of greater reactive urgency made it too late for any action to do any real good.  Thus, it is always critical to respect the natural power of tropical cyclones the natural imposing threat created by an increasing storm surge both prior to, during, and sometimes even after landfall due to the wrap-around the tropical cyclone’s wind field.

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© 2018 Meteorologist Jordan Rabinowitz