...TORNADO AND SEVERE WEATHER AWARENESS WEEK IS APRIL 18-22... ...TODAY/S TOPIC IS...PART 2...MOST COMMON TORNADO MYTHS... ----------------------------------------------------------------- THERE ARE MANY MYTHS CIRCULATING AMONGST SOCIETY ABOUT TORNADOES... WHICH IN MANY CASES ARE FALSE AND COULD BE LIFE-THREATENING IF FOLLOWED CLOSELY. SEVERAL OF THESE MYTHS ARE LISTED BELOW ALONG WITH THE REASONS OF WHY THEY ARE FALSE... ----------------------------------------------------------------- ...WHEN TRAVELING BY CAR...SEEK SHELTER UNDER AN OVER-PASS... SEEKING SHELTER UNDER AN OVERPASS IS MORE DANGEROUS THAN STANDING IN AN OPEN FIELD WHILE A TORNADO IS APPROACHING. WHEN A TORNADO PASSES OVER AN OVERPASS...WINDS ARE FUNNELED UNDER THE BRIDGE THEREBY INCREASING THE VELOCITY. THE SAME PHENOMENA CAN BE EXPERIENCED BY STANDING BETWEEN TWO BUILDINGS ON A WINDY DAY. THE BEST PLACE TO SEEK SHELTER WHILE TRAVELING IS IN A STURDY BUILDING. IF NO BUILDING IS AVAILABLE...LIE FLAT ON THE GROUND AND COVER YOUR HEAD. TORNADOES DO NOT FOLLOW TERRAIN EXACTLY...SO CHANCES ARE IF THE TORNADO COMES DIRECTLY TOWARD YOUR LOCATION...IT WILL PASS RIGHT OVER YOU. BE WARY HOWEVER...DEBRIS TENDS TO COLLECT IN CULVERTS AND DITCHES...AND FLASH FLOODING MAY BE POSSIBLE AS WELL. ---------------------------------------------------------------- ...TORNADOES NEVER STRIKE TWICE... CORDELL KANSAS HAD A TORNADO HIT ON MAY 20TH THREE YEARS IN A ROW /1916...1917...1918/. IN GUY ARKANSAS...THREE TORNADOES HIT THE SAME CHURCH ON THE SAME DAY. ---------------------------------------------------------------- ...BIG CITIES AND THEIR TALL BUILDINGS ARE PROTECTED FROM TORNADOES... BIG CITIES AND THEIR IMMEDIATE SURROUNDING AREAS ARE NOT PROTECTED FROM TORNADOES. IN FACT...MANY CITIES ACROSS THE UNITED STATES HAVE BEEN HIT DIRECTLY WITHIN RECENT TIMES SUCH AS MIAMI... OKLAHOMA CITY...HOUSTON...FORT WORTH...AND NASHVILLE. EVEN SALT LAKE CITY HAS BEEN DIRECTLY HIT. UTAH ONLY EXPERIENCES A FEW TORNADOES PER YEAR...BUT THEY CAN STRIKE ANYWHERE. SINCE BIG CITIES COVER A RELATIVELY SMALL GEOGRAPHICAL AREA... THE CHANCES OF A TORNADO STRIKING THAT PARTICULAR AREA ARE RELATIVELY SMALL...BUT NOT IMPOSSIBLE. THE MYTH THAT TALL BUILDINGS PROTECT CITIES FROM TORNADOES IS FALSE SINCE TORNADOES ARE TYPICALLY 5 TO 10 MILES IN HEIGHT. A TALL BUILDING OF 500 TO 1000 FEET IN HEIGHT CAN NOT POSSIBLY DEFLECT OR DESTROY A TORNADO. ---------------------------------------------------------------- ...LARGE LAKES PROTECT NEARBY AREAS FROM TORNADOES... WHILE COLD WATER AND THE COOL AIR ON TOP OF THE LAKE CAN PROVIDE FOR A LOCALLY STABLE ENVIRONMENT AT TIMES...CHANCES ARE A THUNDERSTORM PRODUCING A TORNADO MOVING TOWARD A COLD LAKE HAS SOMETHING LARGER DRIVING IT THAN THAT COLD WATER CAN INHIBIT. IN ADDITION...TYPICAL LAKE BREEZES FOUND ALONG THE LAKE MICHIGAN SHORE ARE OFTEN SHALLOW AND ONLY AFFECT A SMALL PORTION OF THE LOWER ATMOSPHERE. WARM AND UNSTABLE AIR ABOVE THIS MARINE LAYER/LAKE BREEZE COULD VERY WELL SUSTAIN A THUNDERSTORM/S STRENGTH. FOR EXAMPLE...ON MARCH 8 2000...MILWAUKEE COUNTY EXPERIENCED ITS EARLIEST TORNADO ON RECORD AT A TIME WHEN LAKE MICHIGAN IS CLIMATOLOGICALLY COLDEST. ------------------------------------------------------------------ ...MOUNTAINS...RIDGES...RIVER VALLEYS...AND LARGE LAKES INHIBIT TORNADO DEVELOPMENT AND/OR SPLIT STORMS... TORNADOES ARE POSSIBLE IN EVERY CORNER OF THE UNITED STATES... INCLUDING MOUNTAINS...RIDGES...AND RIVER VALLEYS. WHILE CONDITIONS AREN/T OPTIMAL FOR TORNADO DEVELOPMENT ON TOP OF MOUNTAINS OR DIRECTLY OVER LAKE MICHIGAN...TORNADOES HAVE BEEN DOCUMENTED TO CROSS THE APPALACHIAN MOUNTAINS....GO UP AND DOWN A 10 THOUSAND FOOT TALL MOUNTAIN IN YELLOWSTONE NATIONAL PARK. STRONG TORNADOES HAVE ALSO BEEN KNOWN TO CROSS THE MISSISSIPPI RIVER AND OTHER LARGE RIVERS OR LARGE LAKES. ----------------------------------------------------------------- ...SEEKING SHELTER IN THE SOUTHWEST CORNER OF YOUR HOUSE WILL PROTECT YOU FROM BEING HIT BY DEBRIS... THIS MYTH WAS DEVISED SOLELY BY THE MIS-CONCEPTION THAT ALL TORNADOES PROPAGATE IN A NORTHEAST DIRECTION. THEREFORE AS THE TORNADO HITS YOUR HOUSE...ALL THE DEBRIS WILL BE BROUGHT WITH IT TO THE NORTHEAST AND AWAY FROM YOU. SINCE TORNADOES CAN MOVE FROM ANY DIRECTION...THIS MYTH IS OBVIOUSLY FALSE. DEBRIS SUCH AS PICKUP TRUCKS AND CARS CAN ALSO BE SHOVED INTO THE BASEMENT BY A TORNADO. OBVIOUSLY ONE CAN BE CRUSHED BY A VEHICLE THAT IS DEPOSITED INTO A BASEMENT. ONE SHOULD POSITION THEMSELVES UNDER THE I-BEAM OR A HEAVY WORK BENCH TO INCREASE THEIR CHANCES OF SURVIVAL. DURING A TORNADO WARNING...PEOPLE WILL WANT TO SEEK SHELTER IN AN INTERIOR ROOM ON THE LOWEST LEVEL OF THE BUILDING...AWAY FROM WINDOWS...AND UNDER A STEADY PIECE OF FURNITURE OR STAIRCASE. ---------------------------------------------------------------- ...TO MINIMIZE DAMAGE TO YOUR HOUSE...OPEN ALL THE WINDOWS PRIOR TO A TORNADO STRIKING IT TO EQUALIZE THE PRESSURE INSIDE AND PREVENT IT FROM EXPLODING... WHILE TORNADOES DO HAVE INCREDIBLE PRESSURE CHANGES ASSOCIATED WITHIN THEM...IF A TORNADO STRIKES YOUR HOUSE DIRECTLY...THE WINDS ALONE WILL DAMAGE IT SEVERELY ANYWAY. ALL HOMES HAVE THE ABILITY TO EQUALIZE ITS PRESSURE INSIDE...SINCE NO HOUSE IS 100 PERCENT COMPLETELY SEALED. FURTHERMORE...BY OPENING WINDOWS YOU ALLOW NO CHANCE OF THE WINDOW SHIELDING YOU FROM DEBRIS OUTSIDE WHICH MAY CAUSE BODILY HARM...AND IT WASTES PRECIOUS TIME YOU NEED TO TAKE COVER. ---------------------------------------------------------------- ...TORNADOES ONLY OCCUR IN THE LATE SPRING AND SUMMER ACROSS WISCONSIN... WHILE THE OPTIMAL TIME FOR TORNADO DEVELOPMENT OCCURS DURING MAY THROUGH JULY ACROSS WISCONSIN...TORNADOES MAY DEVELOP AT ANY TIME OF DAY AND ON ANY DAY OF THE YEAR. SINCE 1950...TORNADOES HAVE BEEN DOCUMENTED IN THE BADGER STATE DURING EVERY MONTH OF THE YEAR EXCEPT FEBRUARY. BECAUSE A FEW TORNADOES HAVE OCCURRED EVEN IN JANUARY...IT IS NOT IMPOSSIBLE FOR THEM TO DEVELOP IN FEBRUARY....IT/S JUST A MATTER OF TIME. ----------------------------------------------------------------- ...THE SHAPE AND SIZE OF THE TORNADO DETERMINES HOW STRONG IT IS... TORNADOES COME IN ALL SHAPES AND SIZES AND ONE SHOULD NOT DEPEND ON HOW LARGE THEY ARE OR THEIR SHAPE TO DETERMINE STRENGTH. THE ONLY WAY TO DETERMINE THE STRENGTH OF THE TORNADO IS THROUGH DAMAGE ASSESSMENTS CONDUCTED BY THE NATIONAL WEATHER SERVICE...OR BY TAKING A DIRECT MEASUREMENT OF WIND. DURING DAMAGE ASSESSMENTS...NWS EMPLOYEES LOOK FOR CLUES THAT WILL TELL THEM HOW STRONG THE WINDS WERE. THE WIND ESTIMATE /OR MEASUREMENT/ IS THEN RELATED TO THE FUJITA TORNADO SCALE AND A TORNADO INTENSITY LEVEL WILL BE ASSIGNED. MERELY BY LOOKING AT THE TORNADO/S SHAPE DOES NOT TELL THE WHOLE STORY. THE VISIBLE FUNNEL IS CREATED BY CONDENSATION OR DIRT AND DEBRIS. CONDITIONS THAT CREATE THE VISIBLE FUNNEL WILL CHANGE EACH TIME A TORNADO DEVELOPS...AND THEREFORE ONE CAN NOT USE THIS METHOD RELIABLY. -------------------------------------------------------------- ...SIGNIFICANT PROPERTY OR CROP DAMAGE IS ALWAYS A RESULT OF A TORNADO... TORNADOES DO PRODUCE SIGNIFICANT DAMAGE...HOWEVER STRAIGHT-LINE WINDS CAN BE JUST AS DESTRUCTIVE. DOWN-BURST WINDS ASSOCIATED WITH SEVERE THUNDERSTORMS ARE CAPABLE OF REACHING WIND SPEEDS OF 100 TO 150 MPH...OR THE EQUIVALENT OF AN F1 OR F2 TORNADO. SIGNIFICANT DAMAGE DOES NOT ALWAYS IMPLY A TORNADO. SEVERAL...LESS OBVIOUS... CLUES WILL TELL NWS EMPLOYEES WHETHER A TORNADO OR STRAIGHT-LINE WINDS CAUSED THE DAMAGE. --------------------------------------------------------------- ...MOBILE HOMES ATTRACT TORNADOES... NOTHING ATTRACTS TORNADOES. TORNADOES FORM AND TRAVEL AT THEIR OWN LEISURE. IT SEEMS AS THOUGH MOBILE HOMES ATTRACT TORNADOES BECAUSE THEY ARE MORE SUSCEPTIBLE TO DAMAGE. HOWEVER...ON A PRO- RATED BASIS...HIGHER NUMBERS OF FATALITIES AND INJURIES OCCUR WITH MOBILE-TRAILER HOMES. --------------------------------------------------------------- ...THE NUMBER OF TORNADOES PER YEAR HAVE BEEN INCREASING DUE TO MORE FAVORABLE WEATHER CONDITIONS... THE NUMBER OF TORNADOES IN THE U.S. HAS INCREASED SINCE THE PRE-1950 YEARS. HOWEVER...THIS INCREASE IS MOSTLY LIKELY DUE TO THE GENERAL INCREASE IN THE POPULATION...MORE TRAINED STORM SPOTTERS... BETTER RADAR DETECTION TECHNOLOGY...AND BETTER FOLLOW-UP DAMAGE SURVEYS. TORNADOES HAVE NOT BECOME MORE COMMON DUE TO MORE FAVORABLE WEATHER CONDITIONS. --------------------------------------------------------------- FOR INFORMATION ABOUT TORNADOES...PLEASE REFER TO: http://spc.noaa.gov/faq/tornado/index.html FOR INFORMATION ABOUT WISCONSIN SEVERE WEATHER...PLEASE REFER TO: http://weather.gov/mkx $$ KAPELA/BORGHOFF