Date of Award

Spring 1-1-2017

Document Type

Thesis

Degree Name

Master of Science (MS)

First Advisor

Katja Friedrich

Second Advisor

Edward J. Szoke

Third Advisor

Matthias Steiner

Fourth Advisor

John Cassano

Abstract

The relationships between low-level convergence, vertical velocity, relative vorticity, and moderate-to-heavy precipitation indicate the significance of understanding both the meteorology and the topography of a given region. In this study, the three-dimensional winds, convergence, and relative vorticity associated with a terrain-induced low-level cyclonically-turning circulation (LLCC) are analyzed over the southern Colorado Palmer Divide on 9-10 October 2014 to diagnose the importance of complex topography in generating, enhancing, and distributing precipitation. Past studies show that the necessary ingredients for heavy precipitation over the Colorado Front Range (including the Palmer Divide) are: easterly upslope winds, a high water vapor environment, and an unstable or conditionally unstable atmosphere. Furthermore, many orographic precipitation mechanisms have been studied and identified across this region. However, few studies discuss the importance of the complex topography and its influence on both low-level circulations and precipitation over the Palmer Divide except for the Denver Cyclone.

The results of this study indicate that the LLCC formed near Colorado Springs, CO, and contained high moisture content traced back to Tropical Storm Simon, in conjunction with an easterly flow over the Palmer Divide. The circulation enhanced convective activity due to latent heat release, which strengthened convergence that led to heavy precipitation over the southern Palmer Divide. As the LLCC dissipated, a larger-scale upper-level induced circulation developed and extended convergence to the east, which produced significant mesoscale lifting and widespread precipitation that mirrored the shape of the Palmer Divide. Reflectivities dissipated as the circulation moved east and southeastward off the higher terrain. This movement led to a developing northeasterly flow initiated by high pressure to the north that weakened convergence over much of the Palmer Divide, which ended the event.

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