Date of Award

2013

Document Type

Thesis

First Advisor

Lin, Yuh-Lang

Abstract

This study explores in detail the meteorological factors that contributed to the 2011 April 16 (Mid-April 2011) Tornado Outbreak by performing numerical simulations using the WRF model and performing analyses of observational and RUC-Reanalysis data. The synoptic pattern resembles Barnes and Newton’s (1986) diagram for a significant severe weather outbreak with the exception of a noticeable subtropical jet. Early in the day on April 16, the air mass was stable in central NC. However, the presence of an exceptionally strong low level jet in the warm sector, leading to extreme 0 to 1 km helicity values, strong 0 to 6 km layer shear, a negatively tilted trough, and a strong cold front favored a squall line initially. WRF-D3 (1-km) and RUC-Reanalysis results verified with observations and were able to provide additional synoptic and mesoscale analysis that led to the severe weather outbreak that day. One of the main distinct features WRF-D3 depicted was that surface based CAPEs increased at least 500-1000 J/kg in 3 hours across Eastern NC as the weather system approached east. Despite the WRF-D3 revealing that instability was higher than what the observations reflected, especially in Eastern NC, it still matched the observed evolution of the squall line on that day. The increased instability environment depicted by WRF-D3 led to the maintenance and intensification of the squall line where peak updraft speeds in simulated squall line was at 30 m/s.

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