edu.ucar.opensky::articles:21553 UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact 2025-12-25T16:05:25.878190 ISO 19115-2 Geographic Information - Metadata - Part 2: Extensions for Imagery and Gridded Data ISO 19115-2:2009(E) https://n2t.org/ark:/85065/d7qj7m1q On the anomalous counterclockwise turning of the surface wind with time in the plains of the United States 2018-02-01T00:00:00Z publication https://n2t.org/ark:/85065/d7qj7m1q https://doi.org/10.1175/MWR-D-17-0297.1 Bluestein, H. B. author Romine, Glen author Rotunno, Richard author Reif, D. W. author Weiss, C. C. author UCAR/NCAR - Library publisher Vertical shear in the boundary layer affects the mode of convective storms that can exist if they are triggered. In western portions of the southern Great Plains of the United States, vertical shear, in the absence of any transient features, changes diurnally in a systematic way, thus leading to a preferred time of day for the more intense modes of convection when the shear, particularly at low levels, is greatest. In this study, yearly and seasonally averaged wind observations for each time of day are used to document the diurnal variations in wind at the surface and in the boundary layer, with synoptic and mesoscale features effectively filtered out. Data from surface mesonets in Oklahoma and Texas, Doppler wind profilers, instrumented tower data, and seasonally averaged wind data for each time of day from convection-allowing numerical model forecasts are used. It is shown through analysis of observations and model data that the perturbation wind above anemometer level turns in a clockwise manner with time, in a manner consistent with prior studies, yet the perturbation wind at anemometer level turns in an anomalous, counterclockwise manner with time. Evidence is presented based on diagnosis of the model forecasts that the dynamics during the early evening boundary layer transition are, in large part, responsible for the behavior of the hodographs at that time: as vertical mixing in the boundary layer diminishes, the drag on the wind at anemometer level persists, leading to rapid deceleration of the meridional component of the wind. This deceleration acts to turn the wind to the left rather than to the right, as would be expected from the Coriolis force alone. UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact PDF Text theme Resource Type 2016-01-01T00:00:00Z publication Copyright 2018 American Meteorological Society (AMS). None eng geoscientificInformation