Agri News, MN
12-04-07
Taylor says indicators point to possible drought in 2008
By Jean Caspers-Simmet
Agri News staff writer
AMES, Iowa -- Elwynn Taylor, Iowa State University Extension climatologist,
can't say with complete certainty that there will be a widespread drought in the
Corn Belt in 2008, he can say that many indicators are pointing in that direction.
Taylor clicked off his checklist of signs at last week's Integrated Crop
Management Conference in Ames.
Sea surface temperatures in the equatorial Pacific are like those observed in
1987 in the months leading up to the last widespread drought in 1988. Midwest
weather extremes throughout 2007 have been apparent, also often the case
before major drought events.
The 19-year wet-dry climate cycle is in its high risk drought phase. Global
warming is compounding the risk.
The Southern Oscillation Index, an indicator of El Nino/La Nina events, is moving
toward La Nina, Taylor said. La Nina is likely to occur when the 5-month SOI
averages 0.80. The SOI is currently .64 and Taylor expects it to be at 0.80 by
Christmas
"The weather conditions typical of a La Nina event are forecast through spring of
2008, according to the National Weather Service," Taylor said. "It looks like La
Nina will be here, and that mean a 70 percent chance of below trend line yields in
the Corn Belt."
Semi-permanent pressure centers that develop seasonally at high latitudes
together with polar air flow that gives rise to the "jet stream winds" over North
America, the 19-year and 60-year moisture cycles and global warming appear to
be the cause of erratic weather in the Corn Belt and elsewhere in the world in the
past 18 months, Taylor said.
"There is some historical indication that such anomalies culminate in widespread
Midwest drought events," he said.
During the first 10 months of 2007, a 50-year record of heavy rainfall was set with
eight separate events of 4-inch plus rainfall at multiple sites in Iowa. The previous
record of six was set in 1977, a year of serious drought in central Iowa.
Also contributing to greater 2008 drought risk is the 2007 drought in Georgia and
South Carolina. Although widespread drought doesn't always follow drought in
the southeast United States, the record shows that 16 of the previous 17 major
Corn Belt droughts were preceded by drought in the South Carolina area, Taylor
said.
There is one sign that he sees as positive for 2008 crops. Subsoil moisture
should be near normal by spring.
"This is not the year to not buy crop insurance," Taylor said. "It's a time for
management. For you crop advisors, it's a year to give good advice. Everyone
needs it."