▁on ▁the ▁ground ▁has ▁been ▁sp otted ▁or ▁confirmed , ▁or ▁a ▁significant ▁torn ado ▁is ▁expected ▁based ▁on ▁rad ar ▁sign atures . ▁While ▁the ▁intention ▁of ▁this ▁experimental ▁warning ▁may ▁be ▁to ▁replace ▁the ▁lo os ely ▁defined ▁torn ado ▁emer gency , ▁P DS ▁torn ado ▁warnings ▁are ▁struct ured ▁as ▁the ▁second ▁highest ▁level ▁of ▁torn ado ▁warning ▁within ▁the ▁Imp act ▁Based ▁Warning ▁system ▁( an ▁experiment ▁– ▁which ▁also ▁includes ▁tags ▁within ▁warning ▁products ▁illustr ating ▁rad ar ▁indic ations ▁or ▁physical ▁observations ▁of ▁torn ado es , ▁and ▁damage ▁potential ▁– ▁participated ▁by ▁the ▁ 3 3 ▁We ather ▁Fore cast ▁Off ices ▁within ▁the ▁Central ▁Region , ▁as ▁well ▁as ▁eight ▁additional ▁offices ▁within ▁the ▁Western , ▁Eastern ▁and ▁Southern ▁regions ▁that ▁began ▁util izing ▁the ▁system ▁in ▁the ▁spring ▁of ▁ 2 0 1 4 ); ▁a ▁torn ado ▁emer gency , ▁the ▁highest ▁warning ▁level , ▁is ▁used ▁within ▁the ▁United ▁States ▁for ▁destruct ive ▁torn ado es ▁approaching ▁more ▁dens ely ▁populated ▁areas . ▁These ▁are ▁the ▁first ▁warnings ▁issued ▁with ▁P DS ▁word ing , ▁and ▁like ▁P DS ▁flash ▁flo od ▁watch es , ▁are ▁issued ▁by ▁local ▁forec ast ▁offices . ▁ ▁Below ▁is ▁an ▁example ▁of ▁a ▁P DS ▁T orn ado ▁Warning ▁from ▁the ▁Ro ch elle / F air dale , ▁IL ▁T orn ado ▁on ▁April ▁ 9 , ▁ 2 0 1 5 ▁ ▁P DS ▁Wind ▁Ch ill ▁Warning ▁P DS ▁wind ▁ch