Nation Cut in Two by Drought

The latest US Drought Monitor map from May 14, 2013, shows a Dr. Jekyll/Mr. Hyde nation when it comes to drought. Much of the country to the west of the 96° longitude is in some stage of drought while the country to the east of that line is largely drought free for the moment. Hardest hit have been the Plains states which in some cases are in year 2 or 3 of this drought.
By the way, the US Drought Monitor began about 13 years ago to provide one, unified map of drought across the United States. It is produced in partnership between the National Drought Mitigation Center at the University of Nebraska-Lincoln, the United States Department of Agriculture, and the National Oceanic and Atmospheric Administration with lots of input from scientists, state climatologists, state and local agencies, university extension, landowners, farmers, etc.  Maps are updated weekly and released on Thursday mornings.

The precipitation pattern so far this year reflects these differences between east and west. The map is the current year to date departure from average precipitation produced by the NWS. Areas in green and blue are 2 to 8 inches above average and include much of the Midwest and Southeast. Areas in yellow are 2 to 6 inches below average. Hardest hit so far has been the West Coast with departures more than a foot below average.  There are large areas shaded gray which show near-average conditions. However, much of the west needs many more months of average precipitation or even above-average precipitation to start a recovery from their current drought situation.

The National Climatic Data Center has a product that gives a rough idea of the amount of precipitation needed over the next 6 months to recover from drought. I say “a rough idea” because the timing and intensity of the precipitation is important as well. The effect of getting 3 inches in 30 minutes is different than getting 3 inches over 3 days. The first will cause lots of runoff while the second will have a better chance of recharging soil moisture. As you can see, it will take a considerable amount of precipitation in the Plains states to get out of their current situation.