Future Changes in the Great Plains Low-Level Jet Governed by Seasonally Dependent Pattern Changes in the North Atlantic Subtropical High

This study investigates the response of the Great Plains low-level jet (GPLLJ) to global warming based on ensemble projections of the Coupled Model Intercomparison Project Phase 5 and 6. We show that the GPLLJ will intensify and extend northward in spring and autumn but change marginally in summer. This is governed by seasonally dependent pattern changes in the North Atlantic subtropical high (NASH), that are further linked to the poleward shift of the North America westerly jet (NAWJ). In spring and autumn, a substantial poleward NAWJ shift drives anomalous surface high poleward of the NASH and enhances the southerly GPLLJ to its west over the Central US. Among models, the NASH expansion and GPLLJ enhancement are correlated with the poleward NAWJ shift. In summer, the poleward NAWJ shift is weak and acts more northward. The NASH changes manifest a westward extension, which only affects the southerlies over the Gulf of Mexico.