...TORNADO AND SEVERE WEATHER AWARENESS WEEK IS APRIL 18-22... ...TODAY/S TOPIC IS..PART 6..STRAIGHT-LINE WINDS IN SEVERE STORMS... ------------------------------------------------------------------- ...SIGNATURE OF STRAIGHT-LINE WINDS... STRAIGHT-LINE WINDS ARE OFTEN RESPONSIBLE FOR MOST OF THE WIND DAMAGE ASSOCIATED WITH A THUNDERSTORM. THESE WINDS ARE OFTEN CONFUSED WITH TORNADOES BECAUSE OF SIMILAR DAMAGE AND WIND SPEEDS. HOWEVER THE STRONG GUSTY WINDS ASSOCIATED WITH STRAIGHT-LINE WINDS ARE UNLIKE THE ROTATING WINDS OF A TORNADO. IF YOU WERE TO SURVEY THE DAMAGE PATTERN LEFT BY STRAIGHT-LINE WINDS...YOU WOULD SEE DEBRIS...SUCH AS UPROOTED TREES...LAID OUT IN NEARLY PARALLEL ROWS. ...DOWN-BURST BASICS... DOWN-BURSTS ARE ONE EXAMPLE OF DAMAGING STRAIGHT LINE WINDS. A DOWN-BURST IS A SMALL AREA OF RAPIDLY DESCENDING RAIN AND RAIN-COOLED AIR BENEATH A THUNDERSTORM. WIND SPEEDS IN SOME OF THE STRONGER DOWN-BURSTS CAN REACH 100 TO 150 MILES PER HOUR WHICH IS SIMILAR TO THAT OF A STRONG TORNADO. THE WINDS PRODUCED FROM A DOWN-BURST OFTEN TRAVEL IN ONE DIRECTION...AND THE WORST DAMAGE IS USUALLY ON THE FORWARD SIDE OF THE DOWN-BURST. ...DERECHOS... ANOTHER CATEGORY OF STRAIGHT-LINE WINDS COMMON TO THE MIDWEST ARE KNOWN AS DERECHOS. DERECHOS USUALLY OCCUR IN THE MIDWESTERN STATES IN THE LATE SPRING AND SUMMER. DERECHOS ARE CREATED BY THE MERGING OF MANY THUNDERSTORM CELLS INTO A CLUSTER OR SOLID LINE EXTENDING FOR MANY MILES. THE WIDTH OF SUCH A STORM CAN RANGE FROM 20 TO 65 MILES...AND THE LENGTH CAN REACH 100 MILES OR MORE. IN EXTREME CASES THESE STORMS CAN CREATE MAXIMUM WIND GUSTS OF 150 MPH. NOT ONLY CAN A DERECHO CONTAIN INCREDIBLY STRONG STRAIGHT-LINE WINDS...IT IS ALSO CAPABLE OF PRODUCING SMALL TORNADOES. AS A RESULT THESE TYPES OF STORMS CAN BE EXTREMELY DANGEROUS AND INCREDIBLY DAMAGING. ...HURRICANE-FORCE THUNDERSTORM WIND FREQUENCY... ON AVERAGE...WISCONSIN EXPERIENCES HURRICANE-FORCE THUNDERSTORMS ON 4.5 DAYS PER YEAR. ON AVERAGE...WISCONSIN EXPERIENCES A 100 MPH THUNDERSTORM WIND EVENT ON ONE DAY EVERY OTHER YEAR. ...EXAMPLES OF POWERFUL DOWNBURSTS... IN 2002 ON AUGUST 21...NUMEROUS OCCURRENCES OF THUNDERSTORM WINDS BLEW THROUGH PRIMARILY SOUTHEAST WISCONSIN...INCLUDING A POWERFUL 100 MPH MACRO-BURST THAT TORE THROUGH BROOKFIELD WISCONSIN. MANY LARGE TREES AND STREET SIGNS TOPPLED...AND IN NEARBY MILWAUKEE WISCONSIN...AN 80 MPH GUST RIPPED A 100 FOOT LONG BLIMP FROM IT/S MOORING AND BLEW IT SIX BLOCKS THROUGH THE DOWNTOWN AREA. DAMAGE TOTALED IN THE MILLIONS OF DOLLARS. THANKFULLY...NO ONE WAS INJURED OR KILLED IN THIS EVENT. ALWAYS KEEP IN MIND THAT MAJOR DAMAGE TO A HOME...BUILDING OR ANY PERSONAL PROPERTY CAN BE CAUSED BY A VARIETY OF DIFFERENT STRAIGHT- LINE WIND EVENTS. ALWAYS TAKE COVER WHEN STRONG THUNDERSTORM WINDS THREATEN. AS WITH ANY SEVERE WEATHER STAY TUNED TO NOAA WEATHER RADIO ALL-HAZARDS OR YOUR LOCAL TV OR RADIO STATIONS FOR THE LATEST FORECAST AND SEVERE WEATHER WARNINGS. FOR ADDITIONAL SEVERE WEATHER INFORMATION AND UP TO DATE FORECASTS AND WARNINGS PLEASE VISIT OUR WEB SITE AT: http://weather.gov/mkx $$ KAPELA/KONOP