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BEPA Severe Weather Safety

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  • 1. SEVEREWEATHER SAFETY
  • 2. BACKGROUND Between 04 April and 22 June 2011, over 800 tornadoes werereported across the Midwest, southeast, and Ohio Valley. These storms killed over 500 people and caused more than 27 Billion dollars in damages. Source NOAA.gov
  • 3. Severe Weather SafetyAGENDA: Severe weather definitions What to do in the event of a tornadoTornado myths and facts Lightning myths and factsSummary
  • 4. Severe Thunderstorm Watch & WarningA National Weather Service (NWS) Severe Thunderstorm Watch is defined as:This is issued by the National Weather Service when conditions are favorable for thedevelopment of severe thunderstorms in and close to the watch area. The size of thewatch can vary depending on the weather situation. They are usually issued for aduration of 4 to 8 hours. They are normally issued well in advance of the actualoccurrence of severe weather.A National Weather Service (NWS) Severe Thunderstorm Warning is defined as:This is issued when either a severe thunderstorm is indicated by radar or a spotterreports a thunderstorm producing hail one inch or larger in diameter and/or winds equalor exceed 58 miles an hour; therefore, people in the affected area should seek safeshelter immediately. Severe thunderstorms can produce tornadoes with little or noadvance warning.
  • 5. Tornado Watch & WarningA National Weather Service (NWS) Tornado Watch is defined as:This is issued by the National Weather Service when conditions are favorable for thedevelopment of tornadoes in and close to the watch area. Their size can vary dependingon the weather situation. They are usually issued for a duration of 4 to 8 hours. Theynormally are issued well in advance of the actual occurrence of severe weather. Duringthe watch, people should review tornado safety rules and be prepared to move a placeof safety if threatening weather approaches.A National Weather Service (NWS) Tornado Warning is defined as:This is issued when a tornado is indicated by radar or sighted by spotters; therefore,people in the affected area should seek safe shelter immediately. They can be issuedwithout a Tornado Watch being already in effect. They are usually issued for a durationof around 30 minutes.
  • 6. NWS “Particularly Dangerous Situation”A National Weather Service (NWS) “Particularly Dangerous Situation”is definedas:A PDS is a term used to describe a Particularly Dangerous Situation arising from theissue of a severe weather watch or warning. The addition of a PDS watch means theremay be some very large hail, severe winds, intense lightning, or other severe weatherdangers. Typically a PDS watch is rare. Forecasters issuing a PDS must feel there is animminent threat to life or property. Tornadoes are expected to be either intense, or long-lived. Aka potentially dangerous situation
  • 7. WHAT TO DO IF A TORNADO WARNING IS ISSUED Source NOAA.gov Have a plan in place  Know where you will go when at home or at work. Don’t wait until the last minute to go to your storm shelter. In a house with no basement, a dorm, or an apartment  Avoid windows. Go to the lowest floor, small center room (bathroom or closet), under a stairwell, or interior hallway.  Crouch as low as possible facing down and cover your head with your hands.  Get into a bathtub if possible  Cover yourself with padding (blankets or mattress) to protect from debris. In a mobile home  Get out! Even if your home is tied down, it is not as safe as an underground shelter or permanent, sturdy building. Evacuate to a permanent structure. In a car or truck  If the tornado is visible and far away and traffic allows, drive out of the area.  Seek shelter underground or in a sturdy shelter if possible.  If no flying debris and OBVIOUSLY lower ground is available, leave your car and lie face down covering your head with your hands.
  • 8. Tornado Myths/Facts (Slide 1)1. “When traveling by car seek shelter under an overpass."FALSE: The number one priority in tornado safety right now is to discourage peoplefrom seeking shelter under overpasses. Wind Currents are concentrated as they aresqueeze under the overpasses and are increased in speed. This increase in speed withflying debris INCREASES the risk of injury or death.2. “Mobile homes attract tornadoes."FALSE: Mobile homes are not more likely to be hit, it just seems that way. There aretens of thousands of mobile homes spread across tornado alley. Mobile homes offer littleto no protection against even the weakest tornadoes, so when a tornado does strike amobile park, the damage is more likely to be significant.3. “Hills / Rivers / Cities deflect or inhibit tornadoes."FALSE: Tornadoes have been observered crossing the Appalachian Mountains, 30significant tornadoes have crossed the Mississippi river, and major tornadoes haveplowed right through Dallas, Kansas City, Omaha, ect. In August 1999 a tornado wentright through downtown Salt Lake City. In fact, an urban tornado will have a lot moredebris to toss around than a rural twister.
  • 9. Tornado Myths/Facts (Slide 2)4. “We should open windows if a tornado is approaching."FALSE: STAY AWAY from all windows. It won’t make any difference whether thewindows are open or closed IF your home is struck by a tornado. Getting everyone to aplace of safety should be your only priority.5. “The southwest corner of the house is the safest location during a tornado."FALSE: Always go to the lowest level and center of the house as far as possible fromexterior walls and windows during a warning and cover youself.6. “Deaths from tornadoes are more likely in the Southeastern U.S. than in the GreatPlains."TRUE: Partly due to: Population concentration, lack of basements, time of day, and ahigher concentration of mobile homes.
  • 10. Tornado Myths/Facts (Slide 3)7. “There are small U.S. regions of unexpected high tornado frequency and areas withunexpected low frequency of tornadoes."TRUE: There are several “holes” in the map of tornado distributions and small regions ofextreme concentration. Hall County has a tornado density of 124.5 tornadoes per 1000sq. miles. However, Lancaster County only has 35.8 tornadoes per 1000 sq. miles andDodge County only has 35.5 tornadoes per 10,000 sq. miles.8. “Tornadoes, like lightning never strike twice."FALSE: Guy, Arkansas has been hit 3 times by a tornado damaging the same churcheach time. Cordell, KS had a tornado hit it on May 20th >>> 3 years in a row! –1916,1917, & 1918.9. “Tornadoes are the number one weather killer in the U.S."FALSE: 1960-1996 total fatalities: for Flash Floods: 4629; Lightning: 3221; Tornadoes2734; Hurricanes 1104.
  • 11. Tornado Myths/Facts (Slide 4)10. “The “clash of the seasons” causes tornadoes."FALSE: A temperature contrast is important, but circulation dynamics (shear), upperlevel support (jet stream), and high moisture content are more important than atemperature contrast.11. “Reported tornadoes are increasing in frequency."TRUE: but, is it real? It is assumed that since the number of days with tornadoes is NOTincreasing nor are the larger tornadoes increasing in number, just the smaller ones, thatthe increase might be the result of better reporting of the smaller tornadoes (morereported than previously).12. “Annual tornado deaths are decreasing in number."FALSE: Early on – in the data record – it was true, but during the last decade the fatalityrate has leveled off and stopped decreasing. But, when taking into account theincreasing population, while the rate remains static, overall it is actually becoming safer.
  • 12. Tornado Myths/Facts (Slide 5)13. “Tornadoes can rotate clockwise as well as anti-clockwise."TRUE: A few small F-0 and F-1 tornadoes can rotate “anti-cyclonically” (especially latesummer, NW flow tornadoes). Also, though rare, small tornadoes can change (morph)from anti-cyclonic to cyclonic.14. “Most tornadoes are the large size that you see on the evening news."FALSE: Most tornadoes are small 50-100 feet wide, travel less than 1 mile, and last justa few minutes. The large F-4 and F-5 tornadoes combined represent less than 5% of alltornadoes.15. "Tornado damage is caused by rapid reduction in pressure. (You should leavewindows open as a tornado approaches."FALSE: Damage is caused by wind gusts and flying debris. Don’t worry about equalizingthe pressure, the roof ripping off and a pickup truck smashing through any wall willequalize the pressure for you. Dr. Ted Fujita showed that an open garage causes MOREdamage to a house.
  • 13. Tornado Myths/Facts (Slide 6)16. “Tornadic thunderstorms produce an above average amount of lightning and a largerthan normal amount of hail compared to non-tornadic thunderstorms."TRUE: Intense updrafts amplify charge separation and electrical build-up as well asincreased lifting to freeze layers of super cooled water drops.17. “Doppler radar will observe ALL tornadoes."FALSE: Doppler radar, although much more accurate than earlier radar, cannot see thevery smallest of tornadoes that are “rope-like” in size. Plus, due to the curvature of theearth, Doppler radar can only see the upper portions of storms that are more than 60miles away from the radar.18. “The movie “TWISTER” with Helen Hunt and Bill Paxton was based on the NationalSevere Storms Laboratory and University of Oklahoma storm chasers and wastherefore, very factual."FALSE: Hollywood produces fantasy For reality, check out the many documentariesshown by the Weather Channel, Discovery Channel, and the IMAX movie: “STORMCHASERS”.
  • 14. Tornado Myths/Facts (Slide 7)19. “Tornado chasing looks like its fun. Should I try it."FALSE: It may look like fun, but it is extremely dangerous. Leave the chasing to theprofessionals and watch their photographs from the safety of your home.20. “Tornadoes have picked people and items up, carried them some distance and thenset them down without injury or damage."FACT: People and animals have been transported up to a quarter mile or more withoutserious injury. Fragile items, such as sets of fine china, or glass-ware have been blownfrom houses and recovered, miles away, without any damage. However, given thequantity of airborne debris, these occurrences are the exception, rather than the norm.21. “Cars are safer than mobile homes during a tornado (with no other shelteravailable)."TRUE-FALSE-MAYBE: BOTH are DEADLY locations, but cars might be marginallysafer according to researchers. However, the best advice is to abandon both for shelter.
  • 15. Tornado Myths/Facts (Slide 8)22. "I can outrun a tornado, especially in a vehicle."FALSE: Tornadoes can move at up to 70 mph or more and shift directions erraticallyand without warning. It is unwise to try to outrace a tornado. It is better to abandon yourvehicle and seek shelter immediately.23. “A tornado is not coming directly at me, I am safe."FALSE: Tornadoes have been known to act erratically, often suddenly changingdirection very quickly. Sturdy shelter is the only safe place to be during a tornado.
  • 16. Lightning Myths/Facts“Lightning never strikes the same place twice.”MYTH: Lightning often strikes the same place repeatedly, especially if it’s a tall, pointy,isolated object. The Empire State Building is hit nearly 100 times a year.“If it’s not raining or there aren’t clouds overhead, you’re safe from lightning.”MYTH: Lightning often strikes more than three miles from the center of thethunderstorm, far outside the rain or thunderstorm cloud. “Bolts from the blue” can strike10-15 miles from the thunderstorm.“If you are in a house, you are 100% safe from lightning.”FACT: A house is a safe place to be during a thunderstorm as long as you avoidanything that conducts electricity. This means staying off corded phones, electricalappliances, wires, TV cables, computers, plumbing, metal doors and windows. Windowsare hazardous for two reasons: wind generated during a thunderstorm can blow objectsinto the window, breaking it and causing glass to shatter and second, in older homes, inrare instances, lightning can come in cracks in the sides of windows.
  • 17. Lightning Myths/Facts Continued"If outside in a thunderstorm, you should seek shelter under a tree tostay dry.”MYTH: Being underneath a tree is the second leading cause of lightning casualties.Better to get wet than fried!“Structures with metal, or metal on the body (jewelry, cell phones,Mp3 players, watches,etc), attract lightning.”MYTH: Height, pointy shape, and isolation are the dominant factors controlling where alightning bolt will strike. The presence of metal makes absolutely no difference on wherelightning strikes. Mountains are made of stone but get struck by lightning many times ayear. When lightning threatens, take proper protective action immediately by seeking asafe shelter & don’t waste time removing metal. While metal does not attract lightning, itdoes conduct it so stay away from metal fences, railing, bleachers, etc.
  • 18. SUMMARY Know the difference between a watch and a warning Know where you’ll go Flying debris is the greatest danger in High Wind Conditions Have a NOAA weather radio that will wake you up at night Not all tornadoes will have a warning issued before they hit