Hurricane Hazards: more than high wind and heavy
Veterans of 2003’s Hurricane Isabel have a good idea of what to expect from hurricane-force weather. But for readers who didn’t experience this event or similar natural disasters directly, the memories may be of intrepid newscasters trying to report through tree-bending winds and heavy rains just before or during a hurricane landfall.
These are the kinds of conditions that rip up shingles, tear off sections of roof, knock down limbs, weaken and eventually fall whole trees, break windows and set pieces of debris flying. And these are the kind of possibilities that get much of the attention regarding hurricane preparation, particularly when it comes to residential dwellings and commercial buildings.
But in fact, some of the most dangerous aspects of a hurricane or tropical storm are by-products of the initial wind, rain and very low barometric pressures – namely storm surges, inland flooding and tornados.
For people living in coastal areas, storm surge, the water that’s pushed toward the shore by the force of a hurricane, represents the greatest potential for loss of life. The wind and wave driven surge combines with the normal tides to significantly raise water levels and cause severe coastal flooding.
During Isabel for example, storm surge caused significant damage on Virginia’s eastern shore and on both shores of the Bay. But it also affected areas at some distance from the coast when local rivers carried the high storm surge inland. See Inland Flooding. More than any other hurricane hazard, storm surge is the basis for evacuation. So in addition to standard hurricane preparation, specific protection against storm surge includes:
- Select the nearest possible evacuation destination, preferably within your local area, and map out your route. Do not get on the road without a planned route, or a place to go.
- Choose the home of the closest friend or relative outside a designated evacuation zone and discuss your plan with them before hurricane season.
- You may also want to choose a hotel/motel outside of the vulnerable area.
- If neither of these options is available, consider the closest possible public shelter.
- Use the evacuation routes designated by authorities and, if possible, become familiar with your route by driving it before an evacuation order is issued.
- Prepare your home prior to leaving by boarding up doors and windows, securing or moving indoors all yard objects, and turning off all utilities.
- Before leaving, fill your car with gas and withdraw extra money from the ATM.
- If your family evacuation plan includes an RV, boat or trailer, leave early. Do not wait until the evacuation order or exodus is well underway to start your trip.
- If you are ordered to evacuate by state or local officials, act as quickly as possible. Delaying your departure can increase your chances of being stuck in traffic, or even worse, not being able to get out at all.
- Expect traffic congestion and delays during evacuations. Expect and plan for significantly longer travel times than normal to reach your intended destination.
In the past 35 years, most hurricane-related fatalities have been caused by inland flooding. The intense rainfall associated with hurricanes is not directly related to the wind speed of the storm. In fact, some of the greatest rainfall amounts occur from weaker storms that drift slowly or stall over an area. As a result, inland flooding can be a major threat to communities many miles from the hurricane’s initial landfall.
Keep these recommendations in mind in the event of a hurricane and remember: when you hear hurricane, think inland flooding.
- If you are relatively new to an area, determine whether you live in a potential flood zone.
- If advised to evacuate, do so immediately. Be aware of streams, drainage channels and areas known to flood, so you or your evacuation routes are not cut off.
- Keep abreast of road conditions through the news media.
- Move to a safe area before access is cut off by flood water.
- The rule of thumb when driving is: If you cannot see the road or its line markings, do not drive through the water. Fatalities can occur when people are in their cars or attempting to abandon them. Do not attempt to cross flowing water. As little as six inches of water may cause you to lose control of your vehicle.
- Have flood insurance.Flood damage is not usually covered by homeowners insurance. Do not make assumptions. Check your policy. Note that the National Flood Insurance Program makes federally backed flood insurance available to residents and business
- Keep materials on hand like sandbags, plywood, plastic sheeting, plastic garbage bags, lumber, shovels, work boots and gloves.
- Test drinking water for potability; wells should be pumped out and the water tested before drinking.
- Do not use fresh food that has come in contact with floodwaters. Wash canned goods that come in contact with floodwaters with soap and hot water.
Hurricanes can also produce tornadoes that add to the original storm's destructive power. Research and experience show that tornadoes are most likely to occur in the right-front quadrant of the hurricane. However, they are also often found elsewhere embedded in the rain bands, well away from the center of the hurricane.
Some hurricanes seem to produce no tornadoes, while others develop multiple ones. Studies have shown that more than half of the landfalling hurricanes produce at least one tornado. In general, tornadoes associated with hurricanes are less intense than those that occur in the Great Plains but they can still produce substantial damage.
It’s important to know that a tornado or multiple tornadoes can occur for days after landfall when the hurricane or severe tropical storm maintains a low pressure circulation. In addition, they can take place at any time of the day or night – however, by 12 hours after landfall, tornadoes tend to occur mainly during daylight hours.
We have no way at present to predict exactly which storms will spawn tornadoes or where they will touch down. The newest generation of Doppler radar systems has greatly improved the forecaster's warning capability, but the technology usually provides lead times from only a few minutes up to about 30 minutes. Consequently, preparedness is critical and the following steps should be taken:
- When a tornado warning is issued, or a tornado is imminent, move to a small interior room away from windows.
- Have a plan of where to go during a tornado threat—a nearby pre-identified safe structure within walking distance.
- If you live in a mobile or manufactured home park, get together with other residents and the park owner/manager to designate safe shelter areas in the park or community.
- Monitor local newscasts and NOAA weather radio for updates on tornado watches or warnings.
Helpful Information on Hurricane Preparation
In addition to the specific information on storm surge, inland flooding and tornadoes provided here, the following web sites provide excellent resources for the kind of general hurricane preparation that will help keep you and your family as safe as possible:
- The National Oceanic and Atmospheric Administration
- The American Red Cross
- Hurricane Preparation Links (From the U.S. Coast Guard)