Nightly News | March 26, 2013
>>> the start of spring means after a violent year last year, here we go again. the start of tornado season . and in the aftermath of such a large outbreak in the southeast, one woman responded by trying to connect people with some of the property they lost, when it became airborne. and it turns out what started as an act of kindness genuinely is having another effect. it's teaching forecasters more about how tornados behave. our report tonight from nbc's kerry sanders .
>> reporter: when a tornado touches down.
>> i can't believe it hit that.
>> reporter: nothing, not even an 18 wheeler is safe.
>> this is something i've never seen before.
>> reporter: meteorologists can predict with some accuracy where wind in excess of 200 miles an hour will form twisters and strike.
>> you need to be taking shelter right away.
>> reporter: they're only just beginning to understand what happens to debris sucked into the tornado's vortex.
>> the house is coming apart.
>> reporter: the science has come from the most unlikely of places, facebook .
>> this is one of the things that was found.
>> reporter: patty created a lost and found page after she picked up an ultrasound image in her front yard.
>> it broke my heart that it was at my house and i didn't know where it belonged.
>> reporter: 120 twisters ripped through the southern u.s. in 2011 . keepsakes were eventually reunited with their owners.
>> that's where the debris went.
>> reporter: scientists realized for the first time they had hard data of where items started and ended up.
>> the wizard of oz with dorothy going up and the house spinning around and around may not have been quite as crazy as we think, except it's not entire houses that's been around, it's the debris from houses.
>> reporter: the facebook page connected a cheerleading jacket with its owner 66 miles away . and this five foot high memorial from the football field in smithfield, mississippi found 69 miles away in russellville, alabama. and this photo landing more than 220 miles away in east tennessee .
>> if a tornado is coming but it misses you, you might still be in danger of having debris fall on your property or on your house.
>> reporter: tornados with facebook converging to better understand mother nature . kerrien sadders, nbc news, miami.