Published: 2007-10-10 10:04:22
Updated: 2007-10-10 10:04:22
Posted October 10, 2007 10:04 a.m. EDT
By Carole Gelston
MIKE MOSS SAYS: Carole, You make a good observation about the relatively lower rainfall defecit at RDU. Sometimes, these kinds of variations can be microclimate-related, as you mentioned about the mountains. In other cases, there is simply a component of chance involved, wherein various atmospheric features involving localized upward vertical motions and unevenly distributed moisture combine in a way that produces locally significant rainfall, but not much over a widespread area. We've had a couple of episodes this year in which some fairly heavy rain in the vicinity of RDU (especially Spring and early Summer) pushed totals up there while many surrounding areas received considerably less. For that reason, the folks assessing drought intensity look at a large number of rainfall measurement sites, radar rainfall estimates, and data on reservoir levels, evaporation rates, groundwater and stremflow trends, and water demand, in order to establish whether drought exists and how it should be classified.