DISCUSSION: A trajectory is the path followed by an object moving under certain forces and can explain where something came from or where it is going. Modeled trajectories can be applied directly to particles of air in the atmosphere and answer the questions, why is it so cool today, or vice versa. Using the HYSPLIT model from NOAA, which shows a backwards trajectory of air molecules, can tell the story. This model, which uses the GFS ensembles, can be used to explain the atmospheric pattern showing where air molecules originate in Kansas, as in this example.
The type of air-mass over much of the eastern half of the United States is shown well in this backwards trajectory. The air-mass that ends up in Kansas originated in central Canada which can be chilly even for late May. As the air-mass progressed south and east from Canada, it interacted with the upper level counterclockwise circulation in the eastern half of the country and progressed from around southeastern Quebec to Manitoba and into the central United States. Because of this, the Great Plains experienced the brunt of the below normal temperatures on May 24th as shown in the image above from the Climate Prediction Center.
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©2017 Forecaster Joseph DeLizio