Improving dynamical downscaling of thunderstorms in New England

This study aims to quantify the variability of wind speed and precipitation during summer storms events in New England by using standard verification metrics along with the Method For Object-Based Diagnostic Evaluation technique (MODE). Using WRF-ARW to dynamically downscale a set of storm events, the first approach investigates potential errors propagated from global analysis products used as initial and boundary conditions. The second approach evaluates the significance of applying a topographic wind parametrization scheme in order to obtain more realistic wind speeds. This fundamental study is born out of the necessity of developing a model for power outage prediction caused by severe storms. In New England, a densely forested region of the US, severe winds and precipitation are key weather factors that cause vulnerability in the power grid infrastructure. During storms, trees are uprooted and branches break, resulting in significant interruptions to electricity distribution. The power outage prediction framework utilizes simulated values of meteorological parameters from storms that have caused outages in the past; and the geographic coordinates of the trouble spots recorded by local utilities during these storms. These two components are used as input for a generalized multi-linear regression that estimate the coefficients for these meteorological parameters, which are then applied to weather forecasts of potential hazardous events, providing an estimate of the number and spatial distribution of power outages over the region for the approaching weather system. Given that the count and location of the predicted outages rely on the weather description of past events, the accuracy of spatial patterns and intensity of meteorological fields are crucial to developing an unbiased database for the regression. With that in mind, it is important to quantify the influence that a particular global analysis product can impose to the dynamical downscaling of precipitation and wind speed over the studied region. Additionally, a topographic wind parametrization scheme that includes enhanced drag coefficients and steep terrain corrections is used to quantify potential improvements in the wind speed fields over New England terrain. The comparisons are performed using standard verification metrics, along with the MODE object-based verification technique. The latter technique offering advantages over traditional approaches because it considers structural attributes of distributed events (area, centroid, axis angle, and intensity) instead of strictly point-wise comparisons, which are the main interest of our study into regionally-distributed likelihoods of power failure.