AGS-PRF: Antecedent Remote and Local Synoptic Environments Most Conducive to North American Polar/Subtropical Jet Superpositions

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The jet stream is a well-known atmospheric phenomena, but the public is generally unaware that there are two main jet streams in each hemisphere, the polar jet stream and the subtropical jet stream. These jets are typically separated by a significant distance, but in certain circumstances can end up in the same geographic location, known as a jet stream superposition. These superposition occurrences can be tied to very high-impact weather events, so learning more about their causes and characteristics is important for improving weather forecasts. The researcher funded under this award will use 35 years of atmospheric data to identify, classify, and analyze an estimated 700 superposition events over North America. The main societal impact will be the development and testing of an operational forecast product that would provide a first alert to high-impact weather events in the 8-10 day forecast range. The early career researcher also plans to continue his education and outreach activities by mentoring an undergraduate student and communicating scientific results to the public.The researcher plans to study the topic of jet superposition events, wherein the polar jet and the subtropical jet meet in a vertical superposition of initially distinct jet streams. The NCEP CFSR dataset will be used to identify superposition events over North America and then various analyses will be run to answer the following research questions: 1) What is the nature of the large-scale interactions between polar cyclonic and tropical anticyclonic PV anomalies throughout the production of a jet superposition and does the polar or tropical component consistently dominate those interactions? 2) What are the antecedent remote and local synoptic environments that are most conducive to the production of a superposition for each type of PV anomaly interaction and what influence does a superposition have on the downstream midlatitude flow pattern? 3) What environmental discriminators exist between jet superposition events and "null cases", or instances in which the PJ and STJ closely approach one another but do not superpose, for each type of PV anomaly interaction?