- Tornadoes - What are they?
- Planning - Key to Tornado Survival
- Tornado Safety
- Safety After the Storm
- Thunderstorms and Lightning
- Lightning Safety Rules
- Flooding and Flash Flooding
- Types of Weather Bulletins
Tornadoes are violently rotating columns of air that descend from thunderstorms to come in contact with the ground. Tornadoes develop from thunderstorms when the wind variation with height supports rotation in the updraft. Severe thunderstorms and tornadoes occur most often in the spring months of March, April, and May. A secondary tornado season occurs in the Fall, typically in November. No month of the year is completely free from tornadoes.
Most tornadoes occur in the afternoon between noon and 6 pm. But tornadoes have occurred in every hour of the day and night, so no time of day is immune from tornado occurrences.
- Severe thunderstorms generally develop when the atmosphere provides the right conditions. These conditions include: a supply of warm, humid air flowing out of the Gulf of Mexico at ground level with cool, dry air flowing from the west or southwest at higher levels.
- a low pressure storm system to help lift the air and create thunderstorms;
- and an increase of wind speed with height.
When these conditions come together, severe thunderstorms form and with them the potential for tornadoes.
Springtime tornadoes have wind speeds that vary from as little as 65 miles an hour to as high as nearly 300 miles an hour. Tornadoes move with thunderstorms that produce them at forward motions varying from nearly a standstill to over 70 miles an hour.
Tornadoes develop very quickly; the violent ones, responsible for most deaths, tend to move very fast. In fact, forward speeds of over 60 mph have been observed! Once a tornado is underway, time for planning has passed and immediate action must be taken to protect ourselves. Our plan has to be ready to meet the test.
Preparedness plans come in all sizes as dictated by our individual and collective needs, but it always comes down to the individual. Betting that the storm will not strike you may be the most costly wager you ever make. Questions you should ask: Do you know the basic safety rules? How about your home shelter area; would your children know what to do if home alone? or what to do if they are away from home, Have planed check in point if something happens, Are plans ready to move elderly or disable people to shelter quickly? Do you know the best source for obtaining warning information?
Lets think about these things and PLAN AHEAD. Basic severe weather preparedness plans must include:
- A thorough knowledge of safety rules.
- Selection and designation of the best shelter that you have.
- Have reliable methods of receiving warning information.
- Instructions for every person in the proper procedures to follow when a watch or a warning is issued, or if threatening weather should develop without advance warning.
- Holding drills to test and practice the plan.
Your local Emergency Management Agency, the National Weather Service, or your local Red Cross Chapter can help you with your planning. Brochures on severe weather safety are available upon request. Some safety films are also available from National Weather Service Offices and are loaned without charge to schools and other organizations. It is especially important that school officials understand the severe local storm warning procedures and the importance of tornado drills. School plans must include procedures for buses to follow because they are vulnerable to overturning and high winds.
The primary mission of the National Weather Service is to warn of impending hazardous weather. But even with today's knowledge and technology, we simply cannot warn of every storm when we are dealing with something as volatile as tornado development or flash floods. Storm spotters, radar, and satellite reports all help, but tornadoes can and do develop without being detected. Advance warning time is often only a few minutes and may be only a few seconds. Preparedness is the other key in dealing with this threat.
The National Weather Service and your Emergency Management Agency urge you and your family to take time now to review tornado safety rules.
Knowing what to do means understanding terms used in the warning process.
TORNADO WATCH is issued by the National Weather Service when atmospheric conditions are favorable for tornado development. Listen to NOAA Weather Radio or commercial radio and television stations for the latest weather information. Stay informed! Review safety precautions wherever you are. Keep an eye out for threatening or rapidly changing weather conditions and be prepared to go to a safe place.
A TORNADO WATCH is normally issued for a large area covering a whole state or a large part of several states. The WATCH is intended to give you time to prepare, time to review safety rules. The sky may be blue, but weather changes could be just over the horizon. Begin preparing when you hear the watch.
TORNADO WARNING is broadcast when a tornado has been detected by radar or a tornado has been reported. A TORNADO WARNING is usually issued for one or two counties. If the tornado warning is for your county, you should seek a safe shelter immediately.
Before a watch or warning is issued, National Weather Service meteorologists may issue special outlooks and/or place wording within forecasts to alert you to possible severe weather ahead. The intent is to keep people informed and aware.
Remember, tornadoes form quickly! You may have only a few seconds to react and find shelter. When a tornado threatens, your immediate action can save your life! Seconds do save lives! Know what to do.
In general, get as low as you can. A basement below ground level or at least the lowest floor of a building offers the greatest safety. And, put as many walls between yourself and the outside as possible. Avoid windows at all cost!
Homes or small buildings: go to the basement or to a small interior room such as a closet or bathroom or an interior hall on the lowest level. If available, get under something sturdy like a heavy table. Protect yourself from flying debris with pillows, heavy coats, blankets, or quilts.
Schools, nursing homes, hospitals, factories, and shopping centers: go to a pre-designated shelter area. Basements are the best, but interior hallways on the lowest floor usually offer protection. Close all doors to the hallway for greater protection.
Mobile homes or vehicles: leave them and go to a strong building. If there is no shelter nearby, get into the nearest ditch and lie flat with your hands shielding your head.
Stay away from windows! Don't bother opening or closing them. It won't protect the structure anyway. You'll just waste time and put yourself, and possibly others, at greater risk. Use those valuable seconds to find a place of safety.
Stay away from doors, windows, and outside walls. Protect your head!
Safety does not stop after the storm has passed. Everyone should be aware of the many dangers that might exist after bad weather has moved out of the area.
- Remain calm and try to deal with immediate problems such as care for injured people until professional help can arrive.
- Do not light matches or turn on electrical switches if you suspect damage to your home or business.
- Carefully check for damage around your home or business. If you smell gas or suspect a leak, turn off the main gas valve, open windows, and get everyone out of the structure quickly.
- Stay away from downed lines. Do not attempt to touch or move them. Keep children and pets away from downed lines. Report downed wires to your local power company.
- People should know where to find the main electrical fuse or breaker box, water service main, and natural gas meters. Learn how and when to turn these utilities off. Have a professional turn utility service back on.
- Clean up or rope off dangerous areas such as near broken glass.
- Trees and tree limbs may be weakened and could fall unexpectedly, so use caution when walking through treed areas where high wind or tornadoes have gone.
- Locate your emergency supply kit with essential documents and materials for taking care of yourself after a storm damages your home.
- Avoid using candles. While inexpensive, candles are open flames that can start fires. And in a disaster, response agencies are already overloaded.
- Be sure not to forget about caring for pets after a disaster has occurred.
Thunderstorm wind reached damaging force in Pennsylvania at least 267 times during 1998 and caused millions of dollars worth of damage. Damaging thunderstorm wind events remain much more common than tornadoes in Pennsylvania. In a typical year, Pennsylvania is likely to experience 10 to 20 times as many wind events as tornado events. Not only can severe thunderstorms produce injury and damage from violent straight-line winds & hail, but tornadoes can and sometimes do develop very quickly from these storms. Severe thunderstorms will continue to take their toll on lives and property but we can lessen their impact by taking severe thunderstorm warnings seriously.
A severe thunderstorm is defined as having wind of at least 58 mph and/or hail ¾ of an inch in diameter or larger. Severe thunderstorm winds can gust to more than 100 mph, overturning trailers, un-roofing homes, and toppling trees and power lines. While dime size hail denotes a severe thunderstorm, hail as large as grapefruit has occurred. The danger to serious injury from hail is not hard to imagine when you consider that a good-sized hailstone may fall at speeds near 110 mph.
Severe thunderstorms can strike any time of the year, but, like tornadoes, are much more frequent in the spring months of March, April, May and June. Severe storms that develop on a summer day are usually more isolated. However, some of the most dangerous and intense lightning may occur with summer storms. This is a fact well worth our attention since summer is the time of the year when outdoor actives are at a maximum.
The best defense against thunderstorms is to stay inside a substantial building. Thunderstorms do not usually last for a long time and will generally pass in less than an hour. When thunderstorms are expected, be sure to pick up loose objects around your home or business. Small items can become deadly in strong wind, and flying debris can cause serious damage to other property.
Lightning - The Underrated Killer
Lightning was responsible for only one death and three injuries in Pennsylvania in 1998, about the same as the previous year. Since 1990, lightning has killed 14 people and injured 175 in the state. Lightning has been rightfully called "the underrated killer" since it does not usually get headline attention. Nationally, the average toll is around 80 deaths and 500 injuries. In an average year, lightning will claim more victims than tornadoes or hurricanes.
Every thunderstorm contains this potential killer. Whether it is the large spring-time severe storm or a more common afternoon variety, that electrical charge, which may reach 100 million volts, is always present and searching for the path of least resistance to complete the circuit. It might strike you, an isolated tree, or an object out in the open. Keep in mind that you do not have to be standing directly beneath a cloud to be hit.
Take some time now to learn or refresh your memory on lightning safety rules. That quick dash out in the open when a thunderstorm is in the area may unnecessarily expose you to the possibility of being struck. Is it worth the risk?
- Inside a home, avoid using the telephone except for emergencies. Also, stay away from windows.
- If you're outside, get into a building or in an all-metal (not convertible) vehicle
- DO NOT stand beneath a tall isolated tree, or in an open area.
- AVOID projecting above the surrounding landscape as on a hilltop, in an open field, or a beach, or fishing from a boat.
- Move away from open water or from tractors or other farm equipment.
- Get off and away from motorcycles, scooters, golf carts, riding lawn mowers, and bicycles. Put down golf clubs.
- Stay away from wire fences, clotheslines, metal pipes, rails or other metallic paths which could carry lightning to you from some other distance away.
- Avoid standing in small isolated sheds or other small structures in open areas.
- In a forest seek shelter in a low area under a thick growth of small trees. In open area, go to a low place such as a ravine or valley. Be alert for flash floods.
- If you feel your hair stand on end, this indicates that lightning is about to strike. Drop to your knees and bend forward putting your hands on your knees. Do not lie flat on the ground.
- Remember, there is no truth to the old myth that "lightning never strikes twice."
On average, flooding and flash flooding account for about as many deaths nationally each year as lightning, tornadoes, and hurricanes combined! We must ensure that our preparedness plans include every possible step that can be taken to prevent the tragic loss of life that can occur during floods.
Advanced planning is important, but obvious dangers should not be under estimated. These include such activities as allowing children to play near a swollen drainage ditch or small stream, or attempting to drive or walk across flooded roadways or bridges. Such acts take a needless toll because the powerful force of moving water is easily underestimated.
Floods, similar to tornadoes and severe thunderstorms, are generally most frequent and intense during the late winter and spring, but can develop at any time of the year when conditions are right. The flooding that occurred during March and April of 1979 claimed 15 lives in Alabama. Also, the flooding of February and March of 1990 claimed 16 lives in Alabama.
While flooding can be divided into two general categories, flash floods and mainstream flooding along rivers and streams, both hold the potential for causing death, injury, and the destruction of property. Our safety plan must include ways to deal with each type.
River flooding along major streams is generally slower to develop than flash flooding. There are exceptions to this, especially near headwater areas of smaller rivers where the time lag between the runoff from heavy rain and the onset of flooding can be very short. On the other hand, it make take several days or maybe a week for a flood crest to pass downstream points on major rivers.
The National Weather Service issues River Flood Warnings when rivers are expected to rise above flood stage. Crest forecasts for specific points downstream are given along with known flood stages for each point. It is important that everyone living near a river know how to react to the various flood crest forecasts that may be issued. While there is more warning lead time in most cases than with flash floods, advanced planning and preparation is essential to safeguard life and property from the dangers of mainstream flooding.
Flash flooding can occur almost anywhere in Pennsylvania. Flash flooding can but does not necessarily occur in the classic "wall--of-water" concept. Simply stated, it is too much water in too short a time. Whether it occurs from excessive rainfall or possibly a dam failure, flooding develops very quickly. Rapidly rising water in a low area or near a drainage ditch or small stream may not be as spectacular as a rushing wall of water down a canyon, but it can be just as deadly. And with our changeable weather, we have gone from drought conditions to flash flooding within a few hours.
The National Weather Service issues a Flash Flood Watch when conditions are detected that could result in flash flooding within the designated watch area. A Flash Flood Warning is issued when flash flooding has been reported or is imminent. Preparedness plans must include being familiar with these items as well as all flood safety rules.
Also, you should be familiar with the land features where you live, work, or frequently visit. Is it in a low area, near a drainage ditch, or small stream, or below a dam?
Flash flooding sometimes develops with no advance warning. During periods of heavy rain, it is best to think flash flooding and be ready to respond quickly if flooding is observed or a warning is issued. Planning now with proper response should one of these events occur in your area can save your life. Remember that floods come in varying degrees of intensity. Although the ones you may have experienced in the past may have caused little concern, that major event could still be ahead,.
Flash Flood Safety Rules
- During periods of heavy rain, stay away from streambeds, drainage ditches, and culverts.
- Water runs off of streets and parking lots very rapidly causing natural and man-made drainage systems to overflow with rushing flood waters. These flood waters carry rocks, trees, trash, and other debris that can be deadly to someone in their path.
- Move to high ground should flooding threaten your area. Heavy rain should be a signal to alert you to possible flooding danger. If you live or work in a flood-prone area, or near streams or drainage ditches, remain alert during periods of heavy rain.
- Stay out of flooded areas. The water may still be rising, and the water is usually swift. A rapidly flowing stream or ditch can sweep you off your feet or even sweep your car downstream.
- Be especially cautious at night, when it is harder to recognize flood dangers.
- If your vehicle stalls, abandon it if possible because flood waters could cover it or sweep it away.
SEVERE THUNDERSTORM WATCH
|Conditions are favorable for the development or approach of severe thunderstorms in and close to the watch area. Stay tuned to NOAA Weather Radio or local media and be prepared to take cover indoors.|
|Conditions are favorable for the development or approach of severe thunderstorms and tornadoes in and close to the watch area. Stay tuned to NOAA Weather Radio or local media and be prepared to take cover indoors.|
SEVERE THUNDERSTORM WARNING
A severe thunderstorm (a storm with winds in excess of 58 miles per hour or with 3/4" or larger hail, or both) is indicated on radar or has been reported by a Skywarn spotter. Take cover immediately in a sturdy building. Stay away from windows and do not use the telephone or appliances unless it is a life threatening emergency. To keep informed until the storm passes and the warning expires, use a battery powered radio tuned to:
A tornado (violently rotating column of air in contact with the ground) or funnel cloud (developing tornado) approaching the ground surface has been indicated on radar or has been reported by a Skywarn spotter. Take cover immediately in a sturdy building. Go to the lowest level of the structure preferably into a small windowless room and crouch under a sturdy desk or table. Stay away from windows and do not use the telephone or appliances unless it is a life threatening emergency. To keep informed until the storm passes and the warning expires, use a battery powered radio tuned to:
FLOOD AND FLASH FLOOD WATCH
|Conditions are favorable for flooding and flash flooding (inundation of flooding waters within 6 hours) in and close to the watch area. Stay tuned to NOAA Weather Radio and local media. Be aware of current conditions, especially if you live or work near a flood prone area or are near a river, creek or stream. Prepare to take immediate action to protect life and property.|
FLOOD AND FLASH FLOOD WARNING
Flooding or flash flooding is imminent or is occurring now. If rising water nears, immediately evacuate to higher ground. Do not attempt to drive through flooded roadways or underpasses. To keep informed until the flooding subsides and the warning expires, use a battery powered radio tuned to:
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