Particularly Dangerous Situation


Tornado near Walnut, MS (courtesy ABC News)

Two days before Christmas and for only the second time this year, the Storm Prediction Center (SPC) issued a Particularly Dangerous Situation (PDS) tornado watch. These kind of watches make up only 3 percent of all tornado watches issued in a given year. They are rare, so, what makes this watch so different?

Whenever the Storm Prediction Center believes there will be a risk of severe storms or tornadoes, they issue a Severe Thunderstorm or Tornado Watch, respectively. This means that they have assessed the environment in the atmosphere and believe the right conditions exist for storms to develop that may produce damaging wind, large hail or tornadoes. They usually issue this watch six to eight hours ahead of when storms are expected to develop. Usually, a large area is placed under a watch and includes dozens of counties and may span several states. While the conditions for storms may be favorable, it is not a guarantee that storms will form.

However, there are instances where some of the parameters exist at levels known to develop widespread tornadic storms in the past. In those cases, it seems like a “can’t miss” situation. To raise the confidence of the public and to elevate the expectation of widespread, long-lived intense tornadoes, SPC classifies the threat as a PDS. Here is what was issued on Wednesday, December 23rd:


One of the challenges of communicating the risk for severe weather is the sense of complacency that often develops from past events that weren’t as potent as advertised. Additionally, not all tornadoes are the same, but the mere mention of that seven-letter word conjures a variety of images. Some assume it will be a destructive mile-wide menacing cloud, leveling everything in its path. However, it could also be a quick burst of wind obscured by rain that just dents a roof.

In this case, the PDS was warranted as deadly tornadoes developed in northern Mississippi. As of this writing, there have been 7 fatalities and dozen injured from the storms that struck. That does indeed seem like a particularly dangerous situation.

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