Richard Steever writes from Abingdon: "Why does the hurricane center report pressure in 'millibars,' and the weather centers [use] 'inches of mercury?' " Millibars (Mb) have been the standard international unit for atmospheric pressure since 1929. But the U.S. public is more familiar with "inches" (inHg), derived from old (1643) mercury barometers. Here's a conversion table: pcwp.com/mb_conversion.html.