Date of Award

Spring 5-2020

Document Type

Honors Thesis

Degree Name

Bachelor of Science

Department

Atmospheric and Environmental Sciences

Advisor/Committee Chair

Brian Tang, Ph.D.

Committee Member

Ross Lazear, M.S

Abstract

The region at the intersection of the Mohawk and Hudson valleys of New York is characterized by complex terrain. It has been hypothesized that this complex terrain may have an impact on the development and evolution of severe convection in the region. Specifically, previous research has hypothesized that terrain-channeled flow in the Hudson and Mohawk valleys contributed to increased low-level wind shear and instability in the valleys during past severe weather outbreaks. However, a lack of observations in the region prevented this hypothesis from being robustly tested.

The goal of this study is to further examine this hypothesis and complement existing observations by utilizing the Weather Research and Forecasting (WRF) model. High-resolution simulations were developed for a widespread severe weather outbreak that occurred on 31 May 1998. On this date, a strong (F3) tornado struck Mechanicville, New York, resulting in major damage. Results from the simulations suggest that terrain-channeled flow resulted in the formation of a robust moisture gradient at the intersection of the Mohawk and Hudson valleys during this case. East of this boundary, the environment was characterized by extreme low-level wind shear, and enhanced low-level moisture and instability, supporting tornadogenesis. A simulated supercell intensified after crossing the boundary.

These results suggest that terrain can drive mesoscale inhomogeneities that impact the evolution of severe convection. However, there remains a forecast challenge in anticipating the significance of terrain in advance of a given severe weather event. Identifying additional cases when terrain played an important role may be useful in improving the prediction of severe weather events in upstate New York.

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