This report from KMOV TV aired yesterday illustrates the apparent gap between meteorologists and emergency managers on the topic of selectively warning of the path of tornadoes. Another example of the gap is here.
I don’t ever wish to sound like I am “picking” on emergency managers. They have a difficult, “darned if you do, darned if you don’t” job. That said, it does appear that there is a significant gap between meteorologists and emergency managers with regard to the the NWS “storm-based” (or path-based) warnings that became official more than five years ago.
Mr. Mark Diedrich, of St. Louis County Emergency Management, says in the report, “You never know what path the storm is going to take.” That is simply not true. To illustrate, below is the storm-based warning (purple) issued by the National Weather Service on the St. Louis Good Friday Tornado when it was approaching Lambert Airport (an earlier warning covered the tornado prior to this time). I have added the location of the tornado at the time of the image (circled) and the path it actually took (arrow).
|The tornado itself is just under the “rid” in Bridgeton Terrace and is
purple in color along I-70.
Note that the polygon is far, far wider than the path of the tornado itself so that a margin of safety is built in. Even with sounding the siren only in the areas covered by the polygon the sirens would be sounding far to the south in Clayton and downtown St. Louis. I don’t mind that because it is part of the “margin of safety” built-in by the National Weather Service. But to sound the sirens every time any part of a county (or adjacent county!) is threatened is unnecessary and breeds complacency.