Published: 3:00 PM GMT on February 21, 2013
The largest snowstorm of the winter for the Midwest drought region is winding up, and promises to bring more than a foot of snow to portions of Kansas and Nebraska. Rain and snow from the storm--dubbed Winter Storm "Q"--will put a noticeable dent in the Great Drought of 2012 - 2013 over the Midwest. A second storm due to move through the region on Monday will provide a bit of additional help. The twin storms promise to drop more than an inch of rain (or liquid equivalent rain, for regions like Kansas and Nebraska getting heavy snow.) Many areas of the drought region should enjoy their their wettest day in months on Thursday. The core drought region in the Midwest needs 3 - 9 inches of precipitation to end the drought, so the 1" of precipitation expected from the two storms will merely dent the drought, not end it. Still, the economic value of the rain and snow from the two storms is in the billions of dollars. In addition, runoff from the storms will insure that barge traffic on the Mississippi River will be able to operate well into summer. The Mississippi River at St. Louis is currently about 7' above the lowest water level on record, up over six feet from the near record-low levels of early January.
Figure 1. Predicted precipitation for the 5-day period ending Monday, February 25 at 7 pm EST. The core Midwest drought region is expected to get about an inch of precipitation. Since this region needs 3 - 9 inches of precipitation to end the drought, this coming week's rain and snow will take them at least 10% towards that goal. Image credit: NOAA/HPC.
Figure 2. The amount of precipitation needed to bring the contiguous U.S. out of long-term drought conditions (raise the long-term Palmer Drought Severity Index, PDSI, above -0.5) shows that the core drought region in the Midwest needs 3 - 9 inches of precipitation to end the drought. Image credit: NOAA/Climate Prediction Center.
Drought-busting rains coming for Georgia and Alabama; flooding now a concern
Heavy rains last week in Alabama and Georgia helped give that region no areas of exceptional drought for the first time since January 10, 2012. Another 3 - 8 inches of rain is expected during the next five days, which will help bust the multi-year drought that has affected the area. Flash flooding will even be a concern, particularly on Tuesday. However, as noted in the latest NOAA seasonal drought outlook, "any recovery will occur very slowly, as it will take time for any increased rainfall to chip away at the large moisture deficits that have accumulated over the course of a multi-year drought."
Figure 3. NOAA's February 21 Seasonal Drought Outlook calls for drought to persist over at least 60% of the U.S. drought area through the end of May, with new areas of drought developing over the Southwest U.S. and Florida. However, significant improvement is expected in the Southeast and Upper Midwest.
Drought expected to continue into the summer
The area of the contiguous U.S. covered by drought remained unchanged this week at 56%, according to the latest U.S. Drought Monitor report. NOAA's February 21 Seasonal Drought Outlook calls for drought to persist over at least 60% of the U.S. drought area through the end of May, with new areas of drought developing over the Southwest U.S. and Florida; significant improvement is expected in the Southeast and Upper Midwest, though. After Monday's storm, the GFS and European (ECMWF) models predict that the jet stream will return to the pattern it was in for the first six weeks of 2013, meaning that precipitation-bearing storms will continue to miss the Midwest through at least the first week of March. Given that this jet stream pattern has been very persistent for many months, it's a good bet that drought will be a huge concern as we enter summer. NOAA's Climate Prediction Center predicts an increased chance of drier than average conditions over southwestern portions of the drought region during the coming three months. In general, droughts are more likely in the Midwest U.S. when warmer than average ocean temperatures prevail in the tropical Atlantic, with cooler than average ocean temperatures in the tropical Eastern Pacific (La Niña-like conditions.) This is what we have had so far in 2013. The equatorial tropical Pacific was about 0.3°C below average (as of February 18). This is similar to the ocean temperatures seen in the spring of 2012, just before the Great Drought of 2012 began.
My post on Lessons from 2012: Droughts, not Hurricanes, are the Greater Danger discussed how drought is our greatest threat from climate change.
Ricky Rood blogs about the Dust Bowl
Southern Arizona, USA