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NOTE: Thanks to the proofreaders who caught my dyslexia ;-). Also added some information from another diary on the importance of heat stress on vegetation (i.e. crops!) and added a few clarifying words in other spots.

Drought condition as of 7/31/12.
The graphic is the headline.  I listened in on a webinar sponsored by NOAA and lead by the Midwest and Great Plains Regional Climate Centers, discussing the ongoing drought in the Midwest and Great Plains to see what the experts on the agricultural and economic impacts were saying.  We continue to live in interesting climatic times ... and from my atmospheric sciences background, I can tell you that it's unlikely that things will improve soon enough to stop what will become major crop failures over the next few weeks.

Here, have some corn ... :-(

Drought-stressed corn on 24 July 2012, likely in western KY.
More below.


Precipitation over the breadbasket of the US has been deficient for months, ever since we experienced the warmest March in the continental US (CONUS) on record.  The precipitation percentage departure from normal over the Great Plains Region for the last 90 days is below. Anything red or darker is less than 50% of normal. Those brick red colors you see in a few places are anywhere from 5-25% of normal. Keep in mind that this is the wettest time of year for many of these places.

Percent of normal precipitation, 5/4/12 through 8/1/12.
For the western part of the breadbasket, things have been more-or-less the same as farther east, particularly in MO, KS, and NE.
Percent of normal precipitation, 5/4/12 through 8/1/12.
For July alone, percentage of normal precipitation over the CONUS is shown below. The middle of the country is bathed in yellows, reds, and browns.  A couple of places had no measurable precipitation, including Norfolk NE. Some locations had record low July precipitation, with records that go back to before the Dust Bowl days of the 1930s.
% of normal July rainfall, July 2012
Heat and drought typically go together, since incoming solar radiation that would normally go to evaporation from the soil and evapotranspiration through vegetation goes instead to sensible heating of the land surface and the overlying air.  July 2012 was no different, as you can see below.
July 2012 temperature departure from normal, in degrees Celsius (1 degree C is 1.8 degrees Fahrenheit).
Temperature anomalies for July 2012 over the degrees Celsius. One degree Celsius equals 1.8 degrees Fahrenheit.
The heat also impacts agriculture in two ways:  
  1. Hot weather increases evaporation, and this year in particular, started the growing season (and the demand of vegetation for soil moisture) about three weeks early.  So that was three extra weeks of demand on soil water stores.
  2. Vegetation cannot take extreme heat, and will shut down at very high temperatures.. See 8ackgr0und N015e's diaryon that topic from late last month during one of the spikes in this summer's heat waves.


The percent of each state with short or very short soil moisture in the top 6" of soil is shown below.  Some states are almost completely deficient, including IL at 100%. IA, NE, KS, MO, IN, and OK are all at greater than 90% short or very short. With precipitation, this soil will have to be saturated for any water to effectively move further down into the vegetation root zone and to the ground water below.

Percent short top 6
% of state areas either short or very short on top 6" soil moisture, compared to normal for last 5 years. Yellow is drier than normal, green wetter than normal.
Groundwater is less well-observed than topsoil moisture. However, we can see that it is very deficient where observed in many areas in the center and eastern part of the country.  The map below shows the percentile (from 1% for lowest, to 100% for highest) of normal ground water over the CONUS.
Groundwater percentiles, compared to long-term normals.
Ground water percentiles over the CONUS (1% is lowest, 100% is highest).
Streamflow has a significant impact on commerce (especially agricultural), with barge traffic on the Mississippi, Missouri, and Ohio rivers impacted.  There have been stories in the news on this topic of late, particularly on the Mississippi.  And the graphic below tells the story very well.  Again, this is the percentile of streamflow over the CONUS, with again lots of red in the center of the country.
Streamflow percentiles, compared to long-term normals.
Streamflow percentile for CONUS, with 1% lowest and 100% largest.
How much rain is necessary in each climatological region to end the current drought?  The graphic below answers that question.
Additional precipitation (inches) required to bring Palmer Drought Severity index to -0.5 (normal range).
Additional precipitation (inches) required to bring Palmer Drought Severity index to -0.5 (bottom of the normal range).
Purple is 12-15", and dark blue over 15".  In some areas in the western part of the region, a full year of rainfall is needed to end the drought.


The following two graphics show the percentrage by state of corn and soybeans in poor and very poor condition as of 29 July 2012. In the case of corn, it's the largest area with such conditions since 1988, the last major drought, with 48% of the crop poor or very poor.  For soybeans, it's the largest area in the record at 37% poor or very poor.  For both crops, the area with these conditions increased from the previous week.


Corn % poor to very poor condition in drought area, 29 July 2012.
Percentage of each state with corn in poor or very poor condition as of 29 July 2012.
% of poor to very poor soybean cnodition, 29 July 2012.
Percentage of each state with soybeans in poor or very poor condition, 29 July 2012.
Additional crop condition data:

This graphic shows the percentage of the US corn, soybean, and pasture and range (for cattle feeding) conditions for all categories on 29 July 2012.  Very little of the crop is in good or very good condition.  Pasture and range conditions pretty much mirror those for corn and soybeans.  Some farmers are prematurely slaughtering their cows and pigs because they cannot afford to feed them, and/or the heat is increasing the risk that they will die before they can be brought to market.

Corn, soybeans, pasture and range crop conditions over the Midwest and High Plains, percentage area in excellent, good, fair, poor, and very poor condition, 29 July 2012..
Percentage of three crop types in excellent, good, fair, poor and very poor condition over the CONUS, 29 July 2012.

The Climate Prediction Center at the National Centers for Environmental Prediction have posted their usual week-2, monthly, and three-month outlooks. The graphics below show the probabilities of precipitation being above or below normal (green and brown shades, respectively) for those three periods.  No shading means equal chances of above or below normal precipitation.  Note the brown in the middle of the CONUS.

Week 2

Week 2 forecast for probability of above and below normal precipitation, 9-16 August 2012.
August 2012
Climate Prediction Center precipitation outlook for August 2012, with probabilities of above and below normal precipitation.
August - October 2012
Climate Prediction Center 3-month precipitation outlook, probability of above or below normal precipitation, August-October 2012.
November 2012 - January 2013

If El Niño occurs this winter, which now looks more likely than not, analogs to other El Niños tell us that it is more likely to be dry in the drought areas than wet, and more likely warm than dry.  The 2009-10 El Niño was an exception, with wet, cold weather over much of the country.  La Niñas are typically opposite in character from El Niños, and 2010-11 and 2011-12 were both La Niña seasons. 2010-11 mostly conformed to this rule though it was colder than normal, rather than warmer than normal, in the southern tier of the CONUS.  2011-12 was warm and dry almost everywhere.  

Whether climate change makes the usual equatorial Pacific/El Niño/La Niña relationships not work as well, or the last few years have been a random fluke of nature, we can't yet say with certainty. That being said, the following is a November through January precipitation composites for previous El Niño events  from the US National Centers for Environmental Prediction's Climate Prediction Center.

Climate Prediction Center composite of El Niño event precipitation anomalies, 1950-2011.
It doesn't look too promising for the drought regions, on the face of it. We can only hope that climate change means the usual relationship between El Niño and precipitation will not hold this time.

Originally posted to billlaurelMD on Fri Aug 03, 2012 at 08:20 AM PDT.

Also republished by SciTech.

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