My son read this in the 2006 Guinness Book of Records - "Most freakish temperature rise - The temperature rose from -4 degrees F to 44 degrees F in two minutes at Spearfish, South Dakota on January 22, 1943." Would you explain meteorologically how this could have happened? Thanks.
Posted August 29, 2007
MIKE MOSS SAYS: Neal, This is an extreme example of what can happen when a Foehn wind (often called a Chinook in the western U.S. and Canada) occurs. These winds flow down the lee side of substantial mountain chains and in rapidly descending can both bring very strong winds to the surface downstream, and also can rapidly warm due to something called adiabatic heating (essentially, warming through compression as they rapidly descend from lower pressure aloft to higher pressure near the surface). When the occurence of the Chinook winds happens to coincide with especially cold antecedent conditions in the lowland communities in the lee of the mountains, usually involving a strong temperature inversion near the surface and a shallow, very cold airmass, the resulting jump in temperatures can be dramatic indeed. This is what happened at Spearfish in the episode you cited. Of course, if the Chinook comes along at a time when the downstream communities are already under a mild airmass, the temperature change is not such a big jump and doesn't make the record books. For a little more reading on the subject, there is a pretty nice explanation, along with a listing of some other names given to Foehn winds around the world, provided at