This is more a curiosity question: On the noon news today, The rainfall for Raleigh was a bit over 8" below normal, but locations all around Raleigh, particularly Wilmington, were considerably further behind than Raleigh. We hear so much that any rain will be south and east of the Triangle. Why are other locations so much further behind than us? I know the mountains have some micro-climates where the annual rainfall can vary greatly from one location to the other. Is this also the case south and east of here?
Posted October 10, 2007
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.