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2024 Hennepin County All -Jurisdiction Hazard Mitigation Plan <br />Volume 2 — Hazard Inventory <br />Spotter reports, reports from emergency managers, and increasingly, reports from social media also help <br />forecasters in Chanhassen assess the severity of ongoing storms. <br />4.3.4.11. Critical values and thresholds <br />The National Weather Service considers hail to be <br />severe if it equals or exceeds one inch in diameter. <br />The NWS will issue a severe thunderstorm warning <br />with a "Considerable" tag when hail is expected to <br />be 1.75 inch in diameter or greater or will issue a <br />severe thunderstorm warning with a "Destructive" <br />tag when hail is expected to be 2.75 inches in <br />diameter or greater which would trigger a Wireless <br />Emergency Alert for those in the warning area. <br />Because impact increases exponentially with <br />incremental increases in hail size, larger hailstones <br />pose a significantly greater risk to safety and <br />property. Therefore, spotters are trained to use <br />common objects to make estimates about the size <br />of hailstones. It should be noted that few hailstones <br />are ever measured. Instead, they are often <br />observed, compared to the common objects, and <br />then the size is inferred from the size of the stated <br />objects. Thus, reported hail sizes are almost always <br />crude estimates. Table 4.3.411) summarizes the <br />common objects used as hail size references, along <br />with the approximate diameter. The diameters, and <br />often not the common objects, will be preserved in <br />the Storm Events Database. <br />4.3.4.12. Prevention <br />Table 4.3.4D <br />poi "Nii lmwslu 4� w,ei s a <br />bb <br />< 1A <br />< 0.64 <br />< 34 <br />< 39 <br />Pea, <br />IA <br />0.64 <br />24 <br />35 <br />marble <br />JJ2 <br />1.,3 <br />35 <br />56 <br />dime <br />V10 <br />1.6 <br />38 <br />6 <br />penny, <br />314 <br />13 <br />40 <br />64 <br />nickel <br />71' <br />.2 <br />46 <br />74 <br />quarter <br />1 <br />3.5 <br />49 <br />79 <br />half dollar <br />1 174 <br />3.3 <br />154 <br />67 <br />wainut <br />1 11 ' <br />3.6 <br />60 <br />97 <br />golf ball <br />1374 <br />4A <br />64 <br />103 <br />bon egg <br />2 <br />5.1 <br />60 <br />111 <br />teirnniis ball <br />2 V2 <br />6.4 <br />77 <br />124 <br />seball <br />3 314 <br />7.,0 <br />31 <br />13 <br />tea oup <br />3 <br />7.6 <br />34 <br />135 <br />grapefruit <br />4 <br />10,.1 <br />98 <br />153 <br />sottbamll <br />4112 <br />11A <br />103 <br />166 <br />Hailstorms cannot at present be prevented and should be considered an occasional risk within Hennepin <br />County. <br />4.3.4.13. Mitigation <br />Hailstone size comparisons of commonly reported <br />The risks of being killed or injured by hail are reference objects. <br />greatest when hail is very large and/or wind driven. Thus, awareness of conditions that could lead to severe <br />weather and hail, and having a plan of retreat if storms approach is of primary importance. <br />As with all storms, the safest place to be when it's hailing is inside, in a sturdy structure, away from <br />windows. Even though cars often lose windows and contain some flying glass, they may be safer than <br />being outside, if the travel distance to the vehicle is reasonable. If no shelter or vehicle is available, retreat <br />to lower ground, if possible, stay away from trees, which pose a lightning risk, and by covering the head <br />to avoid potentially lethal impacts from large hail. <br />106 <br />