This article was originally posted on RealClearScience.

Everybody in Seattle knows Jeff Renner. He’s the weather guy on KING5 News, the local NBC affiliate. Each night at around 11:15 p.m., he provides us with little nuggets of knowledge, from the extended forecast to the type of tires we should use when crossing the mountains.

Like all scientists, Mr. Renner has his own special lexicon. Meteorologists are known to use some phrases which may not make an awful lot of sense to the average person. For instance, you might very well hear your weather guy (or gal) say, “The barometic pressure is 30.2 inches and falling.” What on Earth does that mean? Well, it helps to know a little chemistry. Continue reading →