2013 Hurricane Awareness Week - With a Special Focus on Storm Surge

National Hurricane Preparedness Week runs this year from May 26th to June 1st, and it is a good time to review information on the hazards that hurricanes pose, the possible threats to you and your family or business, and replenish or create any emergency supply kits. The National Hurricane Center has a good webpage with preparedness information that you can access by clicking here. You can also access more preparedness materials on the Ready.gov website.

Each day of Hurricane Preparedness Week has a theme. They are as follows. Click on a link to see a YouTube video from the National Hurricane Center about that particular topic.

We also prepared a one-and-a-half minute video with three basic things you can do to be more prepared before a tropical cyclone even forms.

The Atlantic Hurricane Season runs from June 1st to November 30th each year. The vast majority of tropical cyclones occur in those six months, with the peak of the season from mid-August to late October. The 2013 outlook for the hurricane season from NOAA calls for "an active or extremely active season this year". The forecast calls for a 70% chance of 13-20 named storms, of which 7 to 11 could become hurricanes.

 

Special Focus On Storm Surge

This year, we have prepared some extra educational graphics and materials related to storm surge. We encourage you to share some of these facts and graphics to raise awareness. To get yourself oriented, here is a 5-page pamphlet on storm surge from the National Hurricane Center. Storm surge is an abnormal rise of water generated by a storm, over and above the predicted astronomical tides. Along the coast, storm surge is often the greatest threat to life and property from a hurricane.

A common myth is that storm surge will automatically be weaker with lower category storms. This is FALSE. The Saffir-Simpson Hurricane Scale is based on the peak wind speeds in a tropical cyclone, not the height of the storm surge. Although storm surge is related somewhat to wind speed, there are many other factors that affect how significant the storm surge will be such as the size of the storm, the shape and characteristics of the coastline, and the angle the storm approaches the coastline - to name a few.

There have been numerous examples in recent years of lower category hurricanes producing significant, deadly storm surge. This includes: Isaac (2012), Sandy (2012), and Ike (2008) - none of which struck the US coastline as a Category 3-5 on the Saffir-Simpson scale. Every storm is different. Just like it is important not to focus on the center of the storm as impacts can spread out hundreds of miles, it is also important to not just focus on the category. Pay attention to the forecast information, and if you live in a coastal area, be aware that even lower category storms can produce deadly storm surge.

Storm surge awareness is especially important in our section of coastline, which is particularly susceptible to storm surge and can actually amplify the surge. Apalachee Bay, in particular, is one of the most surge-prone areas in the United States. The shape of the coastline near the "bend" in Florida acts to funnel the water in, and the shallow shelf waters extend many miles offshore. A coastline that has a gradual slope is more prone to storm surge, and the slope of the coast around Apalachee bay is very gradual.

Past storms have shown that there can be substantial storm surge effects from north or northeastward moving hurricanes that approach the Florida Panhandle, as water becomes trapped and pushed into Apalachee Bay. Numerous hurricanes in the late 19th century and early 20th century made landfall along the "Forgotten Coast" of Florida, producing major storm surges. In the 1800s, several small towns along the coast, like St. Joseph and Port Leon, were destroyed by surge and never rebuilt.

Because of the hazards posed by storm surge to our coastline, it is important that you know which evacuation zone you live in if you are in a coastal county. You can find information on that at the Florida SERT website, or by contacting your local emergency management.

 

It Doesn't Take A "Major Hurricane"

There are several other risks that can be posed by tropical cyclones, even with tropical storms or Category 1 or 2 hurricanes. Again, it is important to treat each storm differently and individually, and pay attention to the specific forecast.

A major hazard that storms with lower wind speeds can still pose is heavy rainfall and significant inland flooding. In fact, it is sometimes the weaker storms that move very slowly or stall - producing extreme rainfall totals.

One quarter of hurricane fatalities in the last 50 years are a direct result of inland flooding.

A couple of tropical storms (top wind speeds 39 to 73 mph) have affected the NWS Tallahassee area of responsibility in the past decade and produced exceptional rainfall amounts - Tropical Storm Fay in 2008, and Tropical Storm Debby in 2012. Below are graphics showing rainfall total estimates across the area from those tropical storms - Fay on the left, Debby on the right. Both Fay and Debby led to significant flash flooding across the area.

Another hazard that we are always concerned about in our area is the potential for wind damage, even from storms with lower wind speeds - including tropical storms. The area of north Florida from near the Apalachicola River eastward is one of the more densely forested sections of coastline along the entire Gulf coast. There are numerous canopy roads around the area - including in Tallahassee - where the tree canopy covers a roadway. This is shown below on a map produced by NASA, below.

As a result, even tropical storm force winds across our area can produce a considerable amount of damage. Winds during Hurricane Kate in 1985 were only measured at tropical storm force in Tallahassee, with a few hurricane force gusts. However, the damage to trees and power lines was substantial. Therefore, a tropical storm or hurricane of any intensity will be a concern for damage across our forecast area.

 

Summary

The important message to take away from this is that you should treat each storm individually, and that storms with lower wind speeds can still pose a significant hazard. In fact, our section of coastline is particularly susceptible to some of these hazards, including storm surge.

It only takes a small amount of time to create or maintain an emergency supply kit and to look up your evacuation zone. Now is the time to do that, well before a tropical cyclone ever threatens our area.



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