I spent some time yesterday looking for better measures than simple precipitation to describe the current drought situation in Northern Georgia. This is from a data set of Palmer Hydrologic Drought Index for north-central Georgia from the National Climatic Data Center. One of the problems with using precipitation alone, which I’ve been blogging about thus far, is that it doesn’t take temperature into consideration. The last year has been warmer than the long term average in northern Georgia, which can exacerbate drought conditions. The Palmer formula takes that into account. The Palmer hydrologic index is a variant of the classic Palmer index that takes into account longer term precipitation deficits, which seems to match most closely what we’re talking about in northern Georgia.
With that as a preface: Current PHDI for north-central Georgia is -4.59, which definitely qualifies as a badass drought. But if you look at the graph, you’ll see that Georgia has had lots of droughts this bad over the last century – seven that are at -4 or worse, which is the neighborhood we’re in right now.