top of page

Tropical Cyclones

Tropical cyclones (tropical depressions, tropical storms, or hurricanes) are among the most destructive weather phenomena.  They are intense circular storms that originate over warm tropical oceans, have maximum sustained wind speeds exceeding 74 miles per hour, and produce heavy rain.  To learn how tropical cyclones and hurricanes form, Click HERE.  

​

A hurricane can be up to 600 miles across and have strong winds spiraling inward and upward at speeds of 75 to 200 mph.  Each hurricane usually lasts over a week, moving 10-20 miles per hour over the open ocean.  In the Northern Hemisphere, these tropical systems rotate in a counter-clockwise direction around a calm "eye" gathering energy; evaporation from the seawater increases their power. 

Graphic illustrating the rising humid air above the ocean feeding the developing hurricane and the cloudless eye of the storm.
Graphic illustrating the first phases of a thunderstorm forming into a hurricane over very warm ocean water, humid air rising and rotation of the earth causing the air to spin.

Once a tropical cyclone has formed, the National Hurricane Center (NHC) provides wind speed updates and track forecasts at least every six hours.  They give the tropical system a name and assign it a "Category" number on the Saffir-Simpson wind speed scale.  The strong winds coupled with heavy rain, large waves, and storm surge can damage buildings, roads, cars, and trees; so, as it approaches land, the NHC issues Watches and Warnings for the areas that are likely to be impacted.  

  • A Watch means that impacts from the system are possible within 48 hours and preparations should be made. 

  • A Warning means you can expect the system to impact the area in less than 36 hours; finish preparations and get to safe shelter. 

The primary hazards from tropical cyclones are powerful winds and tornadoes, heavy rainfall, coastal and inland flooding, rip currents, high surf, and storm surge.

Graphic of cross-section of a hurricane indicating its layered structure.
FEMA info-graphic indicating hurricanes are most active in September but can happen in any ocean water with temperature over 79 degrees and can have impacts more than 100 miles inland.

Click HERE for the FEMA Ready Business Hurricane Toolkit.

Graphic heading says Prepare Now surrounded by a Blue Circle

Before

Graphic heading says Survive During the Hazard surrounded by Orange Circle

During

Graphic heading says Be Safe After the Hazard surrounded by Green Circle

After

  • Be aware that the Atlantic Hurricane Season is six months long, June 1st through November 30th.  

  • When a Hurricane Watch is issued, it is time to complete pre-storm preparations.

  • "Hide from the wind; Run from the water."  Nine out of 10 direct hurricane deaths are related to storm surge and flood water.  

  • If told to evacuate, do so immediately.  Let friends and loved ones know where you are going.  If you live in a mobile home, get to a safe, site-built structure for shelter.  Do not drive around barricades. 

  • Stay on high ground.  When sheltering in place during high winds, go to a small, interior, windowless room or hallway on the lowest floor. 

  • As the storm approaches, fill the bathtub with water to be used for toilet flushing during a loss of power. 

  • If the power does go out: 

    • use flashlights; avoid using open flames.  

    • turn off fans and other electrical appliances; unplug computers and televisions - power sometimes comes back in surges, which can damage sensitive electronics; circuits could overload when power returns if all your electrical items are on

    • do not unplug refrigerators and freezers; keep their doors closed as much as possible

    • check to see if elderly neighbors are able to navigate when the lights aren’t on, and if they want or need your help.

  • If trapped in a building by flooding, go to the highest level of the building; but do not climb into an enclosed attic - you can easily become trapped by rising flood water.  

  • Save phone calls for emergencies. Phone systems are often down (or at least, very busy) during and after a disaster.  Use text messages or social media to communicate with family and friends. 

National Weather Service info-graphic showing a Hurricane Watch is issued when hurricane-force winds are possible within 48 hours and a Hurricane Warning is issued when hurricane-force winds are expected in less than 36 hours.

  • Listen to authorities for information and special instructions.  Stay somewhere safe.  Don't try to return to evacuated areas until officials announce that it is safe to do so. 

  • Do not walk, wade, swim, or drive through flood waters.

  • Refrain from sight-seeing.  Many people are injured or killed walking or driving around after the storm.  Live power lines, gas leaks, dangling tree branches, flooding, damaged roadways, and dangerous wildlife (e.g. snakes, alligators) can be life-threatening.

  • Turn Around.  Don’t Drown.  Just six inches of fast-moving water can knock down an adult, and one foot of moving water can sweep a vehicle away.  Stay off bridges over fast-moving water.

  • Floodwater can hide large holes, sharp objects, downed power lines that can electrify the water, and contaminants (chemicals, human and animal waste.) 
    It also chases wild and stray animals, rodents, reptiles, and insects such as fire ants out of their normal habitats, and provides a breeding ground for mosquitos.

  • Do not touch electrical equipment if it is wet or if you are standing in water.  Turn off electricity at the main breaker or fuse box to prevent electric shock.

  • Be careful during clean-up.  Wear protective clothing and work with someone else.  One third of indirect hurricane fatalities are from heart failure, when people overexert themselves.  Other indirect fatalities are related to car accidents, electrocution, and fires. 

  • Only use a generator or other gasoline-powered machinery outdoors and well away from open windows.  Take special safeguards while using a chainsaw.  

  • If your well is flooded or damaged by the hurricane, assume that it is contaminated and do not use it until it has been flushed, disinfected, tested, and found clear of bacteria.

  • Make sure food and water supplies are safe to consume.  Wash your hands well with soap and water, especially if you touch floodwater.  If you don’t have soap or water, use alcohol-based wipes or sanitizer that will kill bacteria and viruses. 

  • Document any property damage with photographs.  Contact your insurance agent for assistance with claims.  

Info-graphic stating that the only hurricane feature covered by the Saffir-Simpson scale is Maximum Sustained Wind Speed.
Info-graphic showing that the Saffir-Simpson scale category does not indicate maximum wind gusts, size or speed of storm, symmetry of storm, duration of storm, landfall approach angle, potential rainfall, threat of flooding or storm surge, or threat of tornadoes.
Graphic illustrating the categories of hurricanes based upon wind speeds and the potential damage those wind speeds can cause to structures, trees, and power infrastructure.
Info-graphic illustrating approaching tropical cyclone generating storm surge above the normal sea level and high tide wave action.
2-Pre-season-Prep.png
4-When-Storm-Threatens.png
5-During-Storms.png
6-After-Storms.png
Info-graphic listing 5 things to know about hurricane hazard risks: storm surge, winds, inland flooding, tornadoes, and rip currents.
Info-graphic listing 5 things to know about an evacuation plan: know your zone, plan where to go, plan to host others, leave immediately when told to do so, don't forget pets.
Info-graphic listing 5 things to know about preparing for hurricanes: write it down, document property with a camera, gather vital documents, include all members of the family, it only takes one.
Info-graphic listing 5 things to know about insurance: have annual insurance check-ups, get flood insurance early because there is a 30-day waiting period for it to take effect, visit floodsmart.gov, take the mitigation actions required by insurance, know where your insurance documents are and how to contact your agent.
Info-graphic listing 5 things to know about hurricane supplies: have a week's worth of food and water for each person and pet, have a 30-day supply of medications on-hand, have extra batteries and ways to charge phones and radios, fill your vehicle with fuel, have cash on hand.
Info-graphic listing 5 things to know about strengthening the home: keep trees trimmed away from the house, get approved window coverings, bring in loose objects, secure all doors, move your car into the garage.
How to Prepare Your Property for a Hurricane
Graphic of a residence with preparedness measures highlighted for each feature. Brace gabled roofs, use CO monitors, protect windows, prepare the yard by removing loose items that could blow around, photograph the home and property, check seals around windows and doors, brace the garage door, prepare your vehicle, make a survival supply kit, take action to prepare boats on land or in the water. Anchor, Brace, Cover, and Strap items to secure them from the storm.
Info-graphic with a home floorplan indicating things that can be done to prepare in each room. Designate an interior safe-room, take down framed objects, fill the bathtub for extra water for cleaning and flushing, locate utility cutoffs and know how to turn them off, elevate furniture and cover expensive items with plastic sheeting, place a spare set of clothing in the dryer, clean out gutters, clear off window sills, organize food and water supplies, set refrigerator and freezer to coldest settings and make extra ice, park car in the garage close to the door to help brace it from the wind, cover windows with specialty shutters or 3/4" plywood, bring in tools and power equipment, take photographs or video of all property and contents and keep it in a secure place.
Prepare Pre-Hurricane
Clickable Facebook logo link to Nassau County Florida Emergency Management's Facebook page
Clickable Twitter Logo Link to Nassau County Florida Emergency Management on x, formerly known as twitter

Nassau County Emergency Operations Center
77150 Citizens Circle  |  Yulee, FL  32097

Clickable link to WebEOC
Clickable image of Nassau County is Storm Ready linking to National Weather Service storm ready program webpage

Nassau County Emergency Management is committed to a continued effort to enhance and improve our website's accessibility for all audiences. 

If there are changes we can implement to make our website easier to use, or if you encounter material or services you cannot use, please email us at NCEM@nassauso.com

bottom of page