First posted on 10-15-2013
People in the Ozarks love to talk about the weather and how often it changes. However, the idea that Ozarks weather changes frequently also makes weather data collected since 1895 that much more interesting.
According to Pat Guinan, an associate professor of climatology with University of Missouri Extension Commercial Agriculture Program, southwest Missouri is in the middle of a warming trend. Guinan notes that data from several dozen National Weather Service Cooperative weather stations in the region show Southwest Missouri’s most recent warm annual temperature trend began in 1998 and 11 out of the past 15 years (73%) have been above normal.
“The 1930’s ranks as the warmest decade on record for southwest Missouri and according to the regional data, 2012 was the warmest year on record since 1895,” said Guinan.
Seasonally, southwest Missouri winters have experienced the greatest warming trend, with 16 out of the past 24 winters (67%) being above normal. Following winter, the longest seasonal warming trend in Missouri has been during the spring period (March to May), with 10 out of the past 14 springs (71%) being above normal.
“We have also seen the median last spring frost date in Missouri occurring about three to four days earlier over the past 30 years compared to the long-term average,” said Guinan.
Guinan gave a presentation entitled, “Historical and Recent Climate Trends in Southwest Missouri” to members of the Southwest Region Extension Council on Sept. 24 at the Greene County Extension Center in Springfield, Mo.
According to Guinan, the cooperative weather station network was established in 1890 and now includes over 8,000 weather stations. These stations form the backbone of the nation’s climate records and can provide a perspective on regional weather trends.
“At most stations, the volunteer observer mostly sees it as their civic duty to report their high and low temperature and precipitation every day,” said Guinan. “There are fewer than 200 sites in Missouri and 28 of those are what I like to call pioneer stations, meaning they’ve been continuously active since the late 1800’s.”
The southwest Missouri climate division has four pioneer stations: one in Neosho, one in Lamar, one at the Springfield weather office and one in Lebanon. Two MU Extension automated weather stations exist in the region, one in Lamar and one in Mountain Grove. There are just over 40 cooperative stations in southwest Missouri that provide information that make it possible to monitor precipitation and temperature.
Data collected at these stations shows a number of trends and patterns.
“We have seen a warming trend in the last 15 years, but the 1930s and 1950s were hotter. Still, we are in a warming pattern right now,” said Guinan. “Likewise, our winters have been mild, and our snowfall has decreased.”
The late 1970s provided three bone cold winters, but southwest Missouri seems to be in a mild pattern again. At the same time, the 2013 spring was the coolest spring since 1993.
“Prior to 2010 I was thinking we were due for a hot summer. In much of the 1980s and 1990s, summers were seasonably mild with no extended extreme heat periods. The only exception was 1980, which was the fourth hottest summer on record. The years of 2010, 2011 and 2012 were a reality check on what summers can be like in southwest Missouri,” said Guinan.
The five hottest summers on record are 1934, 1936, 1954, 1980 and 2011. Some locations in southwest Missouri reported more than 60 days with triple digit heat in 1936 alone.
Recent winters and springs have had the biggest temperature variance since 1895. Southwest Missouri’s most recent warm annual temperature trend began in 1998. Since that time, 11 out of the past 15 years have been above normal, and because of that, we are seeing an earlier start to growing seasons.
Beginning in the early 1980’s, an unprecedented wet period has evolved in southwest Missouri. Three out of the top five wettest years since 1895 are 1985, 1990 and 2008.
“Over the past few decades, winter, spring and autumn have witnessed more above normal precipitation years in southwest Missouri. Most notably in winter where only four out the past 32 winters have been unusually dry,” said Guinan. “Three of the top five wettest winters have occurred since 1984 even though snowfall trends have been declining.”
Since the 1970s, there has also been an upward trend in heavy rainfall events.
“Southwest Missouri winters have been wet since the 1980s. The year 2008 was the wettest spring on record since 1895. Even though summer precipitation patterns have shown a trend toward being slightly drier, this has been the wettest summer since 1958,” said Guinan.
Drought has been and always will be part of the Missouri landscape. As an example, we see that the drought of 2012 was the worst in decades.
“Last year was the warmest on record for southwestern Missouri, and we had a climate of central Louisiana, more than 12 degrees above normal, during March of 2012,” said Guinan. “But the 1950s were the mother of all droughts for this region.
Between 1952 and 1956, southwest Missouri accumulated a deficit of 60 inches of precipitation. Extended dry and wet patterns can change abruptly. There are numerous occasions, both in temperature and precipitation, where southwest Missouri quickly transitioned from one extreme to another according to Guinan.
Recent historical trends for southwest Missouri indicate an unprecedented multi-decadal wet period beginning in the early 1980’s. Conversely, there have been multi-decadal dry periods like in the 1950’s and 1960’s.
“An important question we all need to consider is how prepared are we when the next 1950’s drought impacts southwest Missouri,” said Guinan. “The idea of an extended drought is even more concerning now because water use has gone up in both agriculture and urban areas. We have had a wet trend over the past 30 years, but I have a hard time believing that pattern will sustain itself. Another multi-year drought is not out of the realm of possibility again.”
A copy of the presentation given by Patrick Guinan is available for download on the Greene County Extension website: http://extension.missouri.edu/greene. This publication includes all of the graphics and slides used in the presentation.
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