Brenton Hills HOA

Weather Prevention

Lightning Safety

With the Spring weather here, please remember to practice good lightning safety. Lightning is the #2 weather killer in the U.S., killing more than hurricanes and tornadoes combined. Lightning also inflicts severe life-long injuries on many more. The vast majority of these casualties could be prevented if the public just practiced very simple lightning safety procedures. Don't let Memorial Weekend, the first "hurrah" of the summer vacation season, tempt you to stay outside longer than you should when thunderstorms threaten!

The '30-30 Rule' is excellent lightning safety guidance. If the time between lightning and thunder is 30 seconds or less, seek proper shelter. If the lightning can't be seen, just hearing thunder means the
thunderstorm is close enough to be dangerous. Wait at least 30 minutes after the last lightning before leaving proper shelter. The best shelter is a typical house, or other fully enclosed substantially
constructed building with plumbing and wiring. But stay away from corded telephones, plumbing, electrical appliances, or any electrical conducting path leading outside. A car with a solid metal roof and
metal sides is the second best place for lighting safety, but close the windows and don't touch any conducting path to the outside. Open picnic pavilions, or other rain shelters, provide absolutely no
protection from lightning.

Use the weather forecast to plan your outside activities to avoid thunderstorms. When outside, be aware of the locally changing weather and seek proper shelter if thunderstorms are
developing nearby, even before the first lightning occurs.

Enjoy your long weekend, recreating outside in America's great beauty. But remember that no place outside is safe near a thunderstorm--the life you save may be your own.

Tornado Safety Measures

Each year about a thousand tornadoes touch down in the US. Only a small percentage actually strike occupied buildings, but every year a number of people are killed or injured. The chances that a tornado will strike a building that you are in are very small, however, and you can greatly reduce the chance of injury by doing a few simple things.

One of the most important things you can do to prevent being injured in a tornado is to be ALERT to the onset of severe weather. Most deaths and injuries happen to people who are unaware and uninformed. Young children or the mentally challenged may not recognize a dangerous situation. The ill, elderly, or invalid may not be able to reach shelter in time. Those who ignore the weather because of indifference or overconfidence may not perceive the danger. Stay aware, and you will stay alive!

If you don't regularly watch or listen to the weather report, but strange clouds start moving in and the weather begins to look stormy, turn to the local radio or television station to get the weather forecast.
Check The Weather Channel for additional information, or if you have trouble getting up-to-the-minute forecasts on a regular radio, then a "NOAA weather radio" is a wise investment.


If a tornado "watch" is issued for your area, it means that a tornado is "possible."


If a tornado "warning" is issued, it means that a tornado has actually been spotted, or is strongly indicated on radar, and it is time to go to a safe shelter immediately.



Be alert to what is happening outside as well. Here are some of the things that people describe when they tell about a tornado experience:


A sickly greenish or greenish black color to the sky.
If there is a watch or warning posted, then the fall of hail should be considered as a real danger sign. Hail can be common in some areas, however, and usually has no tornadic activity along with it.
A strange quiet that occurs within or shortly after the thunderstorm.
Clouds moving by very fast, especially in a rotating pattern or converging toward one area of the sky.
A sound a little like a waterfall or rushing air at first, but turning into a roar as it comes closer. The sound of a tornado has been likened to that of both railroad trains and jets.
Debris dropping from the sky.
An obvious "funnel-shaped" cloud that is rotating, or debris such as branches or leaves being pulled upwards, even if no funnel cloud is visible.

If you see a tornado and it is not moving to the right or to the left relative to trees or power poles in the distance, it may be moving towards you! Remember that although tornadoes usually move from southwest to northeast, they also move towards the east, the southeast, the north, and even northwest.

Encourage your family members to plan for their own safety in many different locations. It is important to make decisions about the safest places well BEFORE you ever have to go to them.

IN HOMES OR OTHER SMALL BUILDINGS:
The best places are:
In a storm shelter specifically designed for that use--within the basement or outside the home entirely. Some companies manufacture pre-fab shelters that you drop into a hole in the ground, and that blends in with home landscaping(some more, some less).

In a basement, away from the west and south walls. Hiding under a heavy work-table or under the stairs will protect the family from crumbling walls, chimneys, and large airborne debris falling into the cellar. A family in the April 8th, 1998 tornado in the Birmingham, Alabama area survived because a hutch toppled and was held up by the dining room table they were under. That hutch helped deflect the debris that would have struck them. Old blankets, quilts and an unused mattress will protect against flying debris, but they should be stored in the shelter area. Precious time can be lost by trying to find these items at the last minute.

In a small, windowless, first floor, interior room like a closet or bathroom. The bathtub and commode are anchored directly into the ground, and sometimes are the only thing left in place after the tornado. Getting into the bathtub with a couch cushion over you gives you protection on all sides, as well as an extra anchor to the foundation. Plumbing pipes may or may not help hold the walls together, but all the extra framing that it takes to put a bathroom together may make a big difference. If there is no downstairs bathroom and the closets are all packed with "stuff," a hall may be the best shelter. Put as many walls as you can between yourself and the tornado. In a pinch, put a metal trash over as much of you as you can. It will keep some flying debris from injuring you. Even that may make the difference between life and death.

Wherever it is, the shelter should be well known by each member of the family. Also, you can register your shelter with a local emergency service like Oklahoma City Fire Department. If you and your family will conduct annual emergency drills(fire, tornado, etc), everyone will remember what to do and where to go when a tornado is approaching--automatically and without panic. Choose a friend or family member in another part of town or elsewhere to be a "contact person" that will be called by everyone should the family members become separated.

The Red Cross suggests that you assemble a "disaster supplies kit" that you keep in your shelter area. It should contain:
A first aid kit with essential medication in addition to the usual items.
A battery powered radio, flashlight, and extra batteries.
Canned and other non-perishable food and a hand operated can opener.
Bottled water.
Sturdy shoes and work gloves.
Written instructions on how to turn off your homes utilities.

IN SCHOOLS
Leave auditoriums, gyms, and other free-span rooms, exiting in an orderly fashion. Go to interior rooms and halls on the lowest floor, but avoid halls that open to the outside in any direction. If there are no interior hallways, avoid those that open to the southwest, south, or west, since that is the usually the direction the tornado will come. Stay away from glass, both in windows and doors. Crouch down, and make as small a "target" as possible. If you have something to cover your head, do so, otherwise, use your hands. Don't assume that there will always be a teacher or other adult there to tell you what to do--if there is, you should follow their direction, but you need to know these things too.
Peak time for tornadoes to strike varies from region to region. In some southeastern states, early morning tornadoes are almost as common as late afternoon ones. In Oklahoma the peak hours are from 3 to 7 PM, just at the end of the school, but including the hours of afterschool activities.

TO AND FROM SCHOOL, WORK, OR AFTERSCHOOL ACTIVITIES:
If really severe weather is expected, your school may be dismissed early in order that you can reach home before the worst of the weather reaches the area.
If you are on foot or riding a bike, it is doubly important that you go home immediately, and not linger with your friends. If caught in the open, you should seek a safe place immediately. The chances of encountering falling trees, power lines, and lightning is greater than encountering the tornado itself. The basement of a sturdy building would be best, but lying flat in a ditch or low-lying area may be the only thing available. A culvert in a ditch MAY be a good choice if there is no rain, but if there IS rain, flash flooding may be more dangerous and likely than the tornado.

If you are in a car, and you can see a tornado forming or approaching, you should leave the car and take shelter as above. You may think you can escape from the tornado by driving away from it, but you can't know what you may be driving into! A tornado can blow a car off a road, pick a car up and hurl it, or tumble a car over and over. Many people have been killed in cars while they were trying to outrun the tornado, and although it is sometimes possible to escape, it is generally not a good idea.

A few years ago a fellow contacted us and tell us his experiences with the Wichita Falls tornado of 1979. When he was a young man, he outran the Wichita Falls, Texas tornado in a car. He survived, but many people that day tried the same thing and were killed.

An underpass may seem like a safe place, but may not be. While videos show people surviving under an underpass, those tornadoes have been weak. No one knows how survivable an underpass is in a strong or violent tornado. The debris flying under the underpass could be very deadly... head for a ditch.

IN HIGH-RISE BUILDINGS:
Interior rooms and halls are the best locations in large buildings. Central stairwells are good, but elevators are not. If the building loses power, you may be in the elevator for a long time. Stay away from glass walls and windows, no matter how small.

MOBILE HOMES:
Most tornado deaths occur in cars and mobile homes. If you visit a mobile home park, you should find out from a resident where you should go in the event of a tornado--but don't wait until you really need the information--ask him/her on a nice day! Mobile home parks may have a designated tornado shelter, or a steel reinforced concrete laundry room. If they don't, you need to find another substantial structure that you can reach very quickly. You may have only seconds to get to it.

SHOPPING CENTERS, HOSPITALS, AND FACTORIES:
Go to interior rooms and halls on the lowest floor. Stay away from glass enclosed places or areas with wide-span roofs such as auditoriums, theaters, and warehouses. Crouch down and cover your head. Deaths have occurred in large, single story department stores. They have occurred inside the building when the roof or wide span brick walls, which collapsed. A corner would be safer than the middle of the wall. A bathroom, closet, office, or maintainance room with short walls would be the safest area, especially if it was on the north or east side of the building.

Is it likely that a tornado will strike your home or school? No. But being ready for the possibility will keep you safer!

Deaths and injuries from tornadoes have dropped dramatically in the past 50 years. Casualties numbers are holding steady as scientists learn more about tornadoes and develop the technologies that detect them sooner. Forecasters must continue to improve techniques because the population is increasing. The National Weather Service, Storm Prediction Center, and television and radio weather people have taken full advantage of the advancements in tornado prediction to improve warnings.
In addition, many people generously donate their time and expertise to help protect their neighbors and communities in another way--by tornado and severe storm "spotting." "Spotters" combine an interest in the weather, a willingness to serve and often, ham radio experience to make tornado prone areas safer for all. Spotting can provide a focus to a person's interest in the weather, and ham radio helps you meet other like-minded people. It is not often that something that starts out as a hobby can potentially do so much good.

Hail Safety

In an average year, hail causes more than $1.6 billion worth of damage to residential roofs in the United States, making it, year in and year out, one of the most costly natural disasters. Hailstorms are most frequent in the southern and central plains states, where warm moist air off of the Gulf of Mexico and cold dry air from Canada collide, thereby spawning violent thunderstorms. This region, known as hail alley, lies predominantly within the states of Texas, Oklahoma, Colorado, Kansas, Nebraska, and Wyoming. While their domain of greatest frequency is in the plains states, hailstorms have been observed just about everywhere thunderstorms occur.

The combination of gravity and a downward wind known as a downburst (a common occurrence during severe thunderstorms) can propel a hailstone at speeds upwards of 90 mph. At such excessive speeds, large hailstones have been known to penetrate straight through roof coverings and the deck to which they are attached. Although the majority of hailstorms are not quite so severe, even moderate hailstorms can damage buildings, automobiles, crops, and other personal property.

Hailstones usually form in severe thunderstorms where there are updrafts of warm air and downdrafts of cold air. The birth of a hailstone usually occurs when a drop of rain is carried above the freezing level in a thunderstorm by an updraft. With temperatures below 32ºF the raindrop freezes. Hailstones can also be formed from pebbles, twigs, insects and other debris carried in the updraft. As the frozen raindrop begins to fall or is carried by a downdraft, some thawing may occur as it travels into warmer air toward the bottom of the thunderstorm. This frozen raindrop may get carried above the freezing level again by another updraft. As the frozen raindrop travels in the updraft it collects more water (accretion) and re-freezes. Each trip above and below the freezing level the frozen raindrop (now a hailstone) adds another layer of ice. Eventually, the weight of the hailstone exceeds the force of the updraft and falls to earth, or the hailstone gets caught in a downdraft and is hurled toward earth.The presence of hail is often a precursor for a far more serious weather event?a tornado. Large hailstones often indicate very strong updrafts and downdrafts within a thunderstorm. Strong updrafts and downdrafts are indicators of possible tornadic activity.

As mentioned previously, hailstorms are most frequent in the southern and central plains states, where warm moist air off of the Gulf of Mexico and cold dry air from Canada collide, producing violent thunderstorms. The highest frequency of large hail events occurs in the months of April through June, with the highest frequency of large hail occurring in May.

Many factors will determine the type, distribution, and level of hail damage. Although the occurrence of a hailstorm can potentially damage any exposed objects such as vehicles, crops, and other personal property, the item of particular concern focused on here is the potential damage to roofs of residential buildings. Hail can cause damage to building walls: however, the roof is the most exposed element because of its sloping profile.

Factors that affect the level of hail damage can be attributed to properties of the hailstone in addition to properties of the roof covering and climate in which the structure is located.

Hailstones factors:
• Size
• Density
• Velocity
• Distribution

Other factors:
• Roof slope
• Deck stiffness
• Age of roof covering
• Number of roof coverings
• Climate

Hailstone factors

The amount and severity of damage that a hailstone can inflict on a roof system are primarily dependent upon the impact energy imparted by the hailstone on the roof system. The magnitude of the impact energy is directly related to the size, density, and falling velocity of the hailstone.

Hailstones have been reported to range from ¼ inch in diameter (very little roof damage to none) up to 4 ½ inches in diameter (severe roof damage). The threshold size for causing damage to roofing systems is ¾ inch in diameter and larger. Hailstone sizes with common descriptors are shown below.

• Pea = ¼ inch diameter
• Marble/mothball = ½ inch diameter
• Dime/Penny = ¾ inch
• Nickel = 7/8 inch
• Quarter = 1 inch
• Ping-Pong Ball = 1 ½ inches
• Golf Ball = 1 ¾ inches
• Tennis Ball = 2 ½ inches
• Baseball = 2 ¾ inches
• Tea cup = 3 inches
• Grapefruit = 4 inches
• Softball = 4 ½ inches

Another factor affecting the impact energy is the density of the hailstone. It would seem reasonable to assume that the density of hail would approximate the density of ice. However, studies have shown that hail-producing thunderstorms occurring in periods of cold weather generate small hail with a relatively low density. Hail-producing thunderstorms occurring during periods of warm weather generate larger hail with a higher density. The damage inflicted by larger hailstones is further exacerbated by the increase in density.

As objects fall from the sky and head toward earth, the effect of earth’s gravitational forces causes the objects to accelerate at a rate of 32.2 ft/sec2. However, falling objects reach what is called a terminal velocity – a point at which they stop accelerating and travel at a constant speed. A number of factors affect the terminal velocity. The terminal velocity of a 3-inch hailstone is around 90 mph. Now consider that often hail is propelled at even greater velocities aided by the downdraft from the associated thunderstorm. Under this scenario, even small hail, combined with a strong downdraft, can inflict serious damage on a roof system. However, the presence of a downdraft is not the only factor that can intensify the speed of a hailstone. Horizontal (straight line) winds will also significantly impact the falling speed of a hailstone. The same 3-inch stone with a free-falling terminal velocity of 90 mph combined with a 40 mph horizontal wind will increase the resultant velocity to 99 mph.

Factors attributed to the roof covering system itself will have a significant impact on the level of damage to a roof during a hailstorm aside from the properties of hailstones themselves. The slope of the roof has a considerable effect on the outcome of the hailstone impacting the roof. Hailstones striking the roof at a 90-degree angle are more likely to cause damage than those striking a glancing blow.
Wind effects and the nature of the thunderstorm may influence the trajectory of the hailstone, which could also change the impact angle (for better or worse) of the hailstone on the roof. For most conditions though, steeper roof slopes (6:12 and greater) will improve the impact resistance of the roof covering.

Newer roof coverings are more impact resistant than older coverings. The effects of the sun and weathering often result in the covering becoming more brittle over time, and thus reducing its impact resistance. Newer coverings are more ductile and are more capable of absorbing the impact energy. Along the same lines, roof coverings on buildings in colder climates are often more brittle than those in warmer climates.

The stiffness of the roof deck plays an important role in hail resistance. Too much flexibility in the system reduces the effectiveness of the system impact resistance. Solid roof decks, using tongue and groove decking or plywood on moderately spaced trusses, greatly improve the impact resistance of the roof.

Re-covering over an existing roof system significantly reduces the impact resistance of the roof. A roof with two or more layers of asphalt shingles exhibits a “sponge” effect, resulting in the top layer being more susceptible to penetration by impacting hailstones.

Hailstones impacting a roof result in primarily two types of damage – aesthetic and functional. Aesthetic damage, which affects only the appearance of the roof, is by far the most common type of damage from hailstorms. For asphalt shingles, this is usually in the form of negligible loss of granules, which will have minimal impact on the life of the shingle. For other roof coverings, the aesthetic damage may include discolorations and/or dimples. While neither of these scenarios is very attractive to building owners, the result is minimal to no impact on the life expectancy of the roof covering.

Functional damage affects the expected performance characteristics of the roof. This type of damage is defined as the loss of water-shedding ability or a reduction in the expected service life of the roof. Functional damage levels will vary from roof to roof depending on the type and age of the roof covering material.

Identifying Hail Damaged Roofs

The majority of roof coverings for residential roofs are asphalt shingles, wood shingles and shakes, and roof tiles. In fact, asphalt shingles are used on more than 80% of residential roofs. The following sections examine hail damage to various types of roof coverings that has been documented from field observations.

Asphalt Shingles

Although standard asphalt shingles generally perform well under a variety of weather conditions, hailstones impacting an asphalt shingle roof covering influence the expected performance of this roof covering more than any other roof covering. Damage to asphalt shingles from hailstones is typically one of two modes – rupturing of the reinforcing mat and loss of granules that exposes the underlying bitumen. Rupturing of the reinforcing mat represents a potential loss in the shingle’s water-shedding ability in that a ply of roof covering is removed by the rupture. The loss in water-shedding ability increases the potential for water to reach the roof fasteners, causing corrosion, or the butted joints in the sheathing, permitting water to enter the interior of the building. The loss of granules represents the potential for a reduction in the expected service life of the shingle.

Visible identification of rupture of the mat includes bruising or puncturing. More substantial damage of asphalt shingles where significant loss of granules has occurred, exposing much of the underlying bitumenField observations and some laboratory experiments tend to indicate that for bruising or puncturing of asphalt shingles to occur, hailstones must be 1 inch in diameter or larger. However, for older shingles that show some deterioration or weathering, or those that are not effectively supported (flexible deck), hailstone sizes as small as ¾ inch in diameter have been documented to cause damage. These are general ranges, and as discussed previously, there are factors other than hail size that also affect the level of damage to the roof covering.

When analyzing a roof for hail damage, it is important to differentiate between damage caused by hail and damage caused by natural weathering. Additionally, manufacturing defects, damage during construction, and/or damage occurring during transportation can often look much like hail damage. A detailed description distinguishing between hail-induced and natural weathering damage is outlined in the paper titled Protocol for Assessment of Hail-Damaged Roofing, by Haag Engineering.

A roof should be inspected in a manner that permits an intimate and careful examination of the roof system. It will also be beneficial to diagram the roof and damaged areas, in addition to taking photographs and written notes concerning the observations.

To quantify the extent of hail damage to a roof it has been suggested [Haag Engineering] that a test area on each slope of the roof be used. Test areas should measure approximately 100 ft2 (equivalent to one roofing square). The roof covering should be examined thoroughly within the test area. The amount of damage in a test area will typically suffice for determining the extent of the hail damage and may also be used to determine whether repairing or replacing the roof covering is the more economical choice.

Clearly, the most effective way to minimize hail damage is to use roofing materials that are resistant to hail impacts. In 1996, the first test standard was developed to assess the impact resistance of roof coverings – UL 2218 Impact Resistance of Prepared Roof Covering Materials. Subsequently, an additional test standard, FM 4473, Specification Test Protocol for Impact Resistant Testing of Rigid Roofing Materials by Impacting with Freezer Ice Balls, was developed. UL 2218 is intended primarily for testing flexible roof coverings, but has also been used to test rigid roofing materials. FM 4473 was developed specifically for testing rigid roof coverings. FM 4473 defines rigid roofing materials as those manufactured as tiles or planks from slate, concrete, or clay materials.

The UL 2218 test standard uses steel balls ranging from 1.25 inches to 2.0 inches in diameter. The steel balls are dropped from heights of 12 feet for the 1.25 inch ball to 20 feet for the 2 inch ball. Although this apparatus tests for impact resistance, not hail resistance, the impact of the steel ball simulates the impact energy of free-falling hailstones. The test assembly is struck with the steel ball twice in the same location on the assembly. To meet the acceptance criteria of UL 2218, the roof covering material exposed surface, back surface and underneath layers must show no evidence of tearing, fracturing, cracking, splitting, rupture, crazing or other evidence of opening of the roof covering layer. Qualifying assemblies are given a class rating depending upon successful performance of the assembly under impacts from the varying sized steel balls.
Even though most of the common roofing systems used today can be altered or modified for increased impact resistance, the features that make a roofing product impact resistant vary depending upon its material type. Wood shingles and shakes can be made more impact resistant by increasing their thickness and density. Such alterations make them less prone to splitting, which is the primary mode of failure after an impact. Metal roofing can be made more impact resistant by increasing the thickness or the stiffness of the material. Metal 26 gage and thicker will pass the UL 2218 impact test at a Class 4 level. In addition to thickness, metal becomes much stiffer when it is bent or seamed. The fact that some of the metal products are made to look like wood shakes, tile, or slate means the metal has been stiffened considerably just through the forming process. Alternative products, such as synthetic tiles, are generally made of either flexible material, such as rubber, or more rigid materials such as plastic, wood fiber, urethane, and recycled resins. These alternative materials can usually be manufactured to attain a Class 3 or 4 UL 2218 rating. Asphalt shingles manufactured with polymer-modified styrene-butadiene-styrene (SBS) or atactic polypropylene (APP) are more impact resistant than typical composition shingles manufactured using a glass fiber base mat or organic felt. The SBS or APP is blended into the asphalt to enhance flexibility, durability, crack resistance, impact resistance, and resistance to ultraviolet light. These and other modifications have enabled asphalt shingles to make the transition from being one of the most vulnerable roofing systems to one of the strongest choices available.