Latest Analysis on the Impacts of Drought on U.S. Agriculture

The USDA has produced some interesting slides for the World Agricultural Outlook Board, showing the current drought overlaid on production areas. The first two are about the U.S. corn production areas, then the soybean areas, and finally the cattle areas. Each pair of slides shows a map of the overlay, and a time series of the area affected by drought.
By July 24, about 89 percent of the corn production area was in drought. That percentage has been climbing steadily since early June. It’s the same story with 88 percent of the soybean production area and 73 percent of the cattle production area in drought.

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Drought Intensifies in Illinois

The latest U.S. Drought Monitor has expanded D3 “extreme” drought across Illinois. It went from 8 percent of the state last week to 71 percent this week. This major shift was based on a number of short-term drought indicators based on rainfall, streamflow, and temperature, as well as from widespread reports of significant crop and pasture losses.
According to the USDA

The streamlined process provides for nearly an automatic designation for any county in which drought conditions, as reported in the U.S. Drought Monitor … when any portion of a county meets the D2 (Severe Drought) drought intensity value for eight consecutive weeks. A county that has a portion of its area in a drought intensity value of D3 (Extreme Drought) or higher at any time during the growing season also would be designated as a disaster area.

Earlier this week, the USDA NASS reported that 66 percent of the corn crop, 49 percent of the soybean crop, and 91 percent of pasture was rated poor to very poor. Topsoil was rated at 91 percent poor to very poor and subsoil was rated 97 percent poor to very poor. More details can be found in the weekly Illinois Weather and Crops report.

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Near Record Heat and Dryness in July

Based on data through yesterday, this July is shaping up to be one of the warmest and driest on record. Based on the forecast, this July is likely to remain as one of the warmest on record. My hope is that we get so much rain in the next week that we are not even close to the driest July on record.
Statewide Average Temperature Rankings for July in Illinois

  1. 1936:  83.1 ºF
  2. 2012:  81.8 ºF (as of July 30)
  3. 1901:  81.7 ºF
  4. 1934:  81.3 ºF
  5. 1916:  80.4 ºF

Statewide Average Rainfall Rankings for July in Illinois

  1. 1930:  1.02 inches
  2. 1916:  1.23 inches
  3. 1936:  1.24 inches
  4. 2012:  1.44 inches (as of July 30)
  5. 1914:  1.51 inches

Drought Expands in Illinois

The U.S. Drought Monitor released the latest drought map, showing that the “severe” D2 drought has expanded across much of northern Illinois. Only an area in the northeast part of the state remains in moderate drought (first figure).
The Climate Prediction Center also released their drought outlook today. They expect the drought in the central U.S. to persist over the next 3 months (second figure).

U.S. Drought Monitor map for Illinois, released on July 19, 2012. Click to enlarge.

Climate Prediction Center drought outlook, released on July 19, 2012. Click to enlarge.

Short-Term Weather Lore Holds a Kernel of Truth

Before the Internet, The Weather Channel, and NOAA radios, our ancestors relied on nature to tell its tale of upcoming weather. Moss growing on the south side of trees and squirrels hiding their nuts deep underground were thought to foretell a severe winter ahead.
Some natural prognostications like these are grounded in truth, given our current knowledge of meteorology, but others are purely fiction, according to State Climatologist Jim Angel of the Illinois State Water Survey at the University of Illinois at Urbana-Champaign.
Short-term weather forecasts based on nature observations are more likely to be accurate than long-term seasonal predictions.  In fact, there may be some merit to the notion that bad weather is coming when cattle lie down in the pasture and birds fly low.
“Many animals have a better sense of hearing and smell than we do, so when humidity, air pressure and wind direction change right before a storm, as well as the distant rumble of thunder, some animals may become restless,” Angel said.  “They can pick up on weather changes hours before we can.”
Predictions based on the appearance of the sky are thought to be particularly valuable, since certain clouds are associated with certain weather conditions, according to Angel.  Clouds described as mare’s tails and mackerel scales are very high-level cirrus and cirrocumulus clouds that can precede an approaching warm front, with rain not far behind.
Likewise, a halo around the moon is actually the refraction of moonlight through the ice crystals that make up high-level cirrus clouds, indicating an approaching low-pressure system bringing rain or snow.
Long-term forecasts, such as winter weather predictions, are much more uncertain.
“Centuries ago, it was important to determine how severe the winter would be so that adequate wood and supplies would be stored for the duration,” Angel said.  “The early settlers’ lives may have depended on their predictions, so they were grasping at anything to forecast the coming weather.  However, the size of the brown band on woolly worms, the groundhog seeing its shadow, or spoon-shaped persimmon seeds are just happenstance.”
Even with today’s modern technology, the theoretical limit of daily weather forecasts is about two weeks. Within the 6- to 14-day range, forecast errors can be large enough to limit their usefulness.
That is why forecasters typically only discuss general patterns of weather behavior beyond five days, usually in terms of probability or odds. For example, the 8- to 14-day forecast may show the eastern U.S. with an increased chance of below-normal temperatures.
The same is true for seasonal forecasts that are driven by both long-term trends and specific weather patterns such as El Niño.
For the upcoming winter, forecasters look at historical records to decipher a pattern.  The Midwest is under the La Niña effect, which is characterized by unusually cold waters in the eastern tropical Pacific Ocean.
The National Weather Service’s winter forecast for Illinois is an increased chance for above normal temperatures in the southern two-thirds of Illinois, and equal chances of above, below, and normal temperatures in the northern third of Illinois. All of Illinois has an increased chance of above normal precipitation.
What does the woolly worm predict?
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Source: Jim Angel, Ph.D. (217) 333-0729, Fax: (217) 244-0220, jimangel@illinois.edu
Editor: Lisa Sheppard (217) 244-7270, sheppard@illinois.edu
The Illinois State Water Survey at the University of Illinois at Urbana-Champaign, a division of the Institute of Natural Resource Sustainability, is the primary agency in Illinois concerned with water and atmospheric resources.