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Hurricane Dorian, How It Formed, And What It Means

cone graphic
This is the “cone of uncertainty,” which shows uncertainty on where the storm’s center – the eye – could go. The center of the storm, based on the cone, could land anywhere between Georgia and off the Florida Coast. Even so, however, Florida could still see some issues. Source: National Hurricane Center.

At around 2 pm EDT on August 28, the National Hurricane Center released a statement with important implications: Tropical Storm Dorian, a swirling mass of storms in the Atlantic, had reached hurricane status. 24 hours later, as of August 29, Hurricane Dorian has winds of 85 mph swirling around its center, with forecast models suggesting that it will be near the Central Florida coast by Labor Day. This does raise some questions though: What is Hurricane Dorian? How was she born? And what can we do about it?

Hurricane Dorian, as is important to remember, is like most other tropical cyclones. Tropical cyclones, also known as hurricanes in our corner of the world, are oceanic storms that form in the tropics, areas close to the equator. In our corner of the world (the Atlantic), they tend to form between June and November, with the most active month being September.

This is because hurricanes depend on several major conditions, including…

  • Warm water that extends deep. Sea surface temperatures need to be above 80*F (26.6*F), and the warm water needs to extend at least 150 feet deep, so that the hurricane will not stir up cooler waters in the ocean.
  • Sufficient moisture content in the atmosphere, which helps with thunderstorm development.
  • Low wind shear, which allows for the storm to grow without “toppling over” and disrupting circulation
  • A tropical disturbance of some kind, to cause these conditions to mix and “stir up” the atmosphere.

The reason that all these conditions are needed is that hurricanes are heat engines. They derive energy from water vapor. As the warm water evaporates, it rises and cools, forming clouds. Low pressure at the surface results in air rushing in, pulling more vapor and moisture into the storm and forming more clouds. This lowering of air pressure also increases wind speeds. If conditions are right, the wind can reach beyond 74 mph, of which we call a hurricane.

In Hurricane Dorian’s case, forecast models suggest that she will intensify into a major hurricane, with wind speeds beyond 111 mph. This is mainly due to its path through warm Atlantic waters. The hurricane’s direction, indicated by the black arrow, passes through waters with ocean temperatures around 29*C, or 84*F, as indicated by the map below. This means lots of fuel for Dorian.

Sea surface temperatures for the Atlantic Ocean. The white spot shows approximate hurricane position as of 2 pm EDT August 29, and the black arrow shows general direction for the hurricane. Source: NOAA Sea Surface Temperature (SST) Contour Charts

When (or if) Dorian reaches the coast, just like any other hurricane, she will come with an assortment of threats. Generally, most hurricanes cause destruction through the storm surge. When a low-pressure system, like a hurricane, approaches shore, its winds push ahead a bulge of water, which begins to pile onto shore. The surge can cause heavy inland flooding. Even if storm surge doesn’t become the biggest problem, hurricanes can also bring high winds and produce heavy rainfalls, which might mean lots of inland flooding and more damage. With Dorian expected to make landfall in the east coast of Central Florida as a major hurricane, this will mean lots of damage potential for those in its path.

Since Dorian is expected to hit Florida around Labor Day weekend, this will cause problems for those heading to the south at this time. For those who are in Florida, staying safe is of utmost importance. Before the storm arrives, make sure to be listening for updates on what the storm is doing and where it’s going, from NOAA or from weather forecasters. Make sure to have food supplies and medical kits stockpiled, and make sure you have sufficient power on phones and radios for updates. Make sure to have ways to contact relatives to tell them that you’re okay. If told to evacuated a low-lying area, do so to avoid storm problems. If doing so, make sure to know the best evacuation routes, in order to get out safely. If not told to evacuate, hunker down, make sure to tie down loose objects and cover window to mitigate damage. After the storm, make sure to be careful when cleaning up, and make sure to follow instructions from authorities. For more information on hurricane preparation, check out https://www.ready.gov/hurricanes.

Overall, Hurricane Dorian will be a major problem for those in the Southeastern US, and for those whose relatives are in the Southeastern US. For those in the path of the storm, stay safe.

-Weather Forecaster Joseph Williams

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