Hurricane Angle of Attack

Angle of Attack is a very important aspect to consider when determining the potential damage from a hurricane storm surge. Remember that the Right-Front Quadrant (RFQ) is the stronger side of the storm and will deliver the highest storm surge. A powerful hurricane can be roaring up the coast at a good 20 mph and pass us by to the east by only 20 or 30 miles. Yes, we will have hurricane force winds and heavy rains but we would be spared the destructive RFQ and the storm surge that accompanies it.

Look at the diagrams below. Each one looks at different scenarios for different angles of attack. Notice that the Outer Banks are vulnerable to sound-side hurricanes as well as ocean-side hurricanes.

A hurricane striking the coast head on, or perpendicular, will do the most damage as far as storm surge is concerned. South facing beaches that are struck by a north moving hurricane would fit this profile. Also, east facing beaches that are struck by a westward moving hurricane would receive a perpendicular strike. Let's now look at a hurricane that parallels the coast:

As a hurricane parallels the coast, the dangerous RFQ stays offshore. There will be some surge and certainly some damaging winds and heavy rains. But this scenario does not offer the same direct hit that a perpendicular strike would yield.

The diagram above shows a scenario where a hurricane crosses the sounds of eastern North Carolina (Pamlico Sound) and then strikes the Outer Banks from a westerly direction. Note that even a hurricane paralleling the Outer Banks with the center just offshore could potentially produce a storm surge around the backside as hurricane Emily did in 1993.

This diagram shows that the Outer Banks are vulnerable to sound-side storm surge flooding even if the center of the hurricane or tropical storm remains several miles offshore.

Forward Speed:

The forward speed of the hurricane plays a critical role in the overall surge height.

Fast Moving Hurricane: (15.1mph to 35mph)

The surface wind stress is increased in the right-front quadrant thus creating a higher storm surge on the outer coast versus the storm surge from a slow moving hurricane.

Slow Moving Hurricane: (0 mph to 15.0mph)

However, a slow moving hurricane may produce the opposite effect inside of a bay, estuary or river system. This is because slow moving hurricanes have more time to pump water into inland water bodies than do fast moving hurricanes.

And:

There are also cases where neither rule mentioned above will apply