Hurricanes
Characteristics
Hurricanes, coastal storms, and Nor’easter are all forms of cyclones. Hurricanes and coastal storms are tropical cyclones that are a rotating and organized system of clouds and thunderstorms that originate in tropical or subtropical waters and have closed low-level circulation.
Hurricane season runs from June 1 until November 30th each year. The peak period for named storms runs from around mid-August until late October.
Tropical Cyclones
Tropical cyclones in the northern hemisphere rotate counterclockwise. Tropical cyclones are warm-core, low-pressure systems that thrive on the warmer air and warmer waters. There are four primary types of tropical cyclones:
- Hurricane – max sustained winds of 74 mph and higher
- Major Hurricane – max sustained winds of 111 mph or higher (Category 3, 4, and 5)
- Tropical Depression – max sustained winds of 38 mph or less
- Tropical Storm – max sustained winds of 39-73 mph
Nor-easters
A Nor’easter is a form of a cyclone that forms, typically, along the upper East Coast of the United States and Canada. Nor’easters also rotate counterclockwise. Nor’easters differ from tropical cyclones in that nor’easters are cold-core, low-pressure systems, meaning they thrive on colder temperatures and waters.
The primary damaging forces associated with these types of storms include:
- Coastal erosion
- Flooding
- Heavy precipitation
- High-level sustained winds
- Storm surge
- Tornadoes
Nor’easters may also include snow and blizzard conditions due to the colder air temps.
Storm Development
Tropical cyclones can develop in the Gulf of Mexico, the Caribbean Sea, the Pacific Ocean, and the Atlantic Oceans. They are born in the moist tropical air.
About every four to five days, a tropical wave of low pressure moves along with westerly winds. In developing tropical cyclones, strong thunderstorms occur. Air pressure drops at the surface of these storms. This low pressure attracts warm moist air from the ocean's surface.
The Coriolis force causes the resulting low-level winds to spiral in a counterclockwise direction around the center of the low in the Northern Hemisphere. Sinking air at the center clears the tropical cyclone of clouds and forms the "eye”, but an eye is not necessary for a tropical cyclone to become a hurricane. Falling surface pressure can occur only if air mass is removed from the circulation center. This is accomplished by wind flowing away from the circulation in the upper atmosphere.
When maximum sustained winds reach or exceed 39 miles per hour, the system is designated a tropical storm, given a name, and is closely monitored by the National Hurricane Center in Miami, Florida.
When sustained winds reach or exceed 74 miles per hour the storm is classified as a hurricane. Hurricane intensity is further classified by the Saffir-Simpson Hurricane Wind Scale which rates hurricane intensity on a scale of 1 to 5, with 5 being the most intense. More information on intensity rating can be found on the Hurricane Wind Scale page.
Hurricane Wind Scales
Hurricane intensity is classified by the Saffir-Simpson Hurricane Wind Scale which rates hurricane intensity on a scale of 1 to 5, with 5 being the most intense.
MINIMAL
Very dangerous winds will produce some damage
: Well-constructed frame homes could have damage to roof, shingles, vinyl siding and gutters. Large branches of trees will snap and shallowly rooted trees may be toppled. Extensive damage to power lines and poles likely will result in power outages that could last a few to several days.Winds
- 74-95 mph
- 64-82 kt
MODERATE
Extremely dangerous winds will cause extensive damage
: Well-constructed frame homes could sustain major roof and siding damage. Many shallowly rooted trees will be snapped or uprooted and block numerous roads. Near-total power loss is expected with outages that could last from several days to weeks.Winds
- 96-110 mph
- 83-95 kts
EXTENSIVE
Devastating damage will occur
: Well-built framed homes may incur major damage or removal of roof decking and gable ends. Many trees will be snapped or uprooted, blocking numerous roads. Electricity and water will be unavailable for several days to weeks after the storm passesWinds
- 111-129 mph
- 96-112 kts
EXTREME
Catastrophic damage will occur
: Well-built framed homes can sustain severe damage with loss of most of the roof structure and/or some exterior walls. Most trees will be snapped or uprooted and power poles downed. Fallen trees and power poles will isolate residential areas. Power outages will last weeks to possibly months. Most of the area will be uninhabitable for weeks or monthsWinds
- 130-156 mph
- 113-136 kts
CATASTROPHIC
Catastrophic damage will occur
: A high percentage of framed homes will be destroyed, with total roof failure and wall collapse. Fallen trees and power poles will isolate residential areas. Power outages will last for weeks to possibly months. Most of the area will be uninhabitable for weeks or monthsWinds:
- 157 mph and higher
- 137 kts and higher
Hurricane Season
Summer is the best time to prepare for whatever tropical weather may affect Onslow County, and Emergency Management is urging residents to update their emergency plans and kits before storms strike.
The Atlantic hurricane season runs June 1 through November 30, but most hurricanes strike the East and Gulf Coasts between mid-August and mid-October. Summer is the best time to prepare for whatever tropical weather may affect Onslow County, and Emergency Management is urging residents to update their emergency plans and kits before storms strike.
Dangers
Tropical storms and hurricanes bring damaging winds, heavy rains, flooding, and even tornadoes. In coastal areas, hurricanes can cause rip currents and storm surges. In the foothills and mountains, these tropical storms can spur dangerous landslides and mudslides. Since hurricanes have impacted every part of North Carolina, it's important for everyone to have a plan in place before a storm threatens Onslow County.
Ready Your Emergency Kit
Onslow County Emergency Management urges residents to make a plan and put together an emergency supplies kit to provide the tools needed to survive the storm and recover from it.
Families should have their emergency kit ready to go at all times with enough non-perishable food and bottled water (1 gallon per person per day) to last 3 -7 days. Kits also should include:
- Bedding
- Cash or checkbook
- Changes of clothes
- Copies of insurance papers and identification sealed in a watertight plastic bag
- First-aid kit
- Hygiene items such as a toothbrush, toothpaste, soap, and deodorant
- Pet supplies including food, water, leashes, bedding, muzzle, and vaccination records
- Supply of prescription medicines
- Weather radio and batteries
Stay Informed
Stay informed during severe weather using a battery-powered radio for weather and evacuation information. Know evacuation routes in your community; heed the warnings of state and local officials and evacuate quickly when told to do so.
Be sure to review and update your homeowners' or renters' insurance policies to make sure they include coverage for accidental damage, natural disasters, and, if necessary, flood insurance.
More information on hurricanes and overall emergency preparedness can be found at the Ready.gov website and ReadyNC. Onslow County emergency officials also urge residents to get the free ReadyNC mobile app which provides real-time weather and traffic conditions for all parts of North Carolina.
Hurricane Safety
Before the Hurricane
- Closely watch/listen to the weather reports. Listening every hour as the storm nears.
- Put fuel in all vehicles and withdraw some cash from the bank. Gas stations and ATMs may be closed after a hurricane.
- If authorities ask you to leave, do so quickly.
- If you leave (evacuate), be alert to flooded or washed-out roads. Just a few inches of water can float a car. Think: Turn Around, Don't Drown.
- Keep a photo I.D. that shows your home address. You will need it when asking police if it is okay for you to re-enter your area or home.
- Secure your property.
- Bring inside all outdoor furniture, decorations, garbage cans and anything else that is not tied down.
- Cover windows with permanent storm shutters or board up windows with 5/8” plywood, cut and ready to install. Tape does not stop windows from breaking.
- Put in straps or extra clips to securely fasten your roof to the frame structure. This will lower roof damage.
- Trim trees and shrubs around your home, so they are more wind resistant.
- Clear clogged rain gutters and downspouts.
- Reinforce garage doors. If wind enters a garage it can cause dangerous and expensive structural damage.
During a Hurricane
If a hurricane is likely in your area, you should:
- Listen to the radio or television for information.
- Secure your home, close storm shutters and secure outdoor objects or bring them indoors.
- Turn off gas, water and power if you are told to do so. Otherwise, turn the refrigerator thermostat to its coldest setting and keep its doors closed.
- Turn off propane tanks.
- Try not to use the phone, except for serious emergencies.
- Moor your boat if time permits.
- Make sure you have a supply of water for sanitary purpose such as cleaning and flushing toilets. Fill the bathtub and other larger containers with water.
- Find out how to keep food safe during and after an emergency.
Leave your home or area if you are:
- Told to do so by local police.
- In a mobile home or temporary structure. Such structures are particularly dangerous during high wind events no matter how well fastened to the ground.
- In a high-rise building because hurricane winds are stronger at higher levels.
- On the coast, in a floodplain, near a river or on an island waterway.
If you are unable to leave, go to the safest room in your house.
- Stay indoors during the hurricane. Stay away from windows and glass doors.
- Close all interior doors – secure and brace external doors.
- Keep curtains and blinds closed.
- Do not be fooled if there is a lull; it could be the eye of the storm – winds will pick up again.
- Take shelter in a small interior room, closet or hallway on the lowest level.
- Lie on the floor under a table or another sturdy object.
After A Hurricane
- Listen to local officials for updates and instructions.
- Check-in with family and friends by texting or using social media.
- Return home only when authorities indicate it is safe.
- Watch out for debris and downed power lines.
- Avoid walking or driving through flood waters. Just 6 inches of moving water can knock you down, and fast-moving water can sweep your vehicle away.
- Avoid flood water as it may be electrically charged from underground or downed power lines and may hide dangerous debris or places where the ground is washed away.
- Do what you can to prevent further damage to your property, (e.g., putting a tarp on a damaged roof), as insurance may not cover additional damage that occurs after the storm.
- Walk carefully around the outside your home and check for loose power lines, gas leaks and structural damage before entering. Stay out of any building if you smell gas, if floodwaters remain around the building or your home was damaged by fire.
- Check your home for damage. Take pictures of damage, both of the building and its contents, for insurance purposes. If you have any doubts about safety, have your home check out by a trained building inspector or structural engineer before entering.
- Watch your pets closely and keep them under your direct control. Watch out for wild animals, especially poisonous snakes. Use a stick to poke through debris.
- Do not drink or make food with tap water until you are sure it’s not dirty.
- Check refrigerated food for spoilage. If in doubt, throw it out.
Wear protective clothing and be cautious when cleaning up to not get hurt. - NEVER use a generator inside homes, garages, crawlspaces, sheds, or other enclosed areas, even when using fans or opening doors and windows for airing. Deadly levels of carbon monoxide can quickly build up in these areas and can stay around for hours, even after the generator has shut off.
Additional Resources
Want to learn more about hurricanes and preparedness? Visit these site for additional information:
- NOAA-Weather Ready Nation: Hurricane Preparedness Week
- Ready.gov: Hurricanes
- ReadyNC.org: Hurricanes
- American Red Cross: Hurricane Preparedness
- Atlantic Tracking Chart (PDF)
- NC Dept. of Environmental Quality: Storm Season
- NC Dept. of Environmental Quality: Hurricane Recovery Checklist
- NC Dept. of Agriculture & Consumer Services: Emergency Programs