Observed Trends in the Great Plains Low-Level Jet and Associated Precipitation Changes in Relation to Recent Droughts

Recent drought over the Great Plains has had significant impacts on agriculture and the economy, highlighting the need for better understanding of any ongoing changes in the regional hydroclimate. Trends in the Great Plains low-level jet (GPLLJ) during the months April-June (AMJ) and associated precipitation are analyzed using the North American Regional Reanalysis (NARR) for the period 1979-2012. Linear trends computed for meridional winds and precipitation intensity, frequency and total across the Great Plains show that (1) the GPLLJ has strengthened and expanded northward and (2) precipitation has decreased substantially in the Southern Plains while increasing in the Northern Plains. Particularly in May, the rainy season in the Oklahoma-Texas region, precipitation has migrated northward in correspondence to the shifted northern edge of the GPLLJ, leading to near 50% declines in precipitation since 1979. These observed changes are discussed in the context of recent droughts and projected climate for the region.