Date of Award

2026

Degree Type

Thesis

Degree Name

Master of Science in Biological and Environmental Sciences (MSBES)

Specialization

Earth and Environmental Sciences

Department

Biological Sciences

First Advisor

Ambarish Karmalkar

Abstract

Extreme surface winds pose an important risk to infrastructure, utilities, and coastal communities in the northeastern United States, yet their magnitude, spatial extent, seasonal behavior, and large-scale controls remain underexplored. This thesis examines how wind speed, wind gust behavior, and extreme wind-event footprints varied across the northeastern and mid-Atlantic United States from 1950 to 2024. The primary goal is to determine whether extreme winds are changing in magnitude, frequency, or spatial extent, with particular attention to utility-relevant service territories and the atmospheric processes associated with widespread events.

ERA5 reanalysis data, produced by the European Centre for Medium-Range Weather Forecasts (ECMWF), are used to analyze 10 m wind speed, daily maximum 10 m wind gusts, and upper-level wind fields. Chapter 1 evaluates long-term wind speed and gust behavior across PPL-relevant service territories in Kentucky and Virginia, Pennsylvania, and Rhode Island. Seasonal and annual trends, distributional shifts, threshold-exceedance counts, and service-territory maximum gust statistics are used to assess changes relevant to energy infrastructure risk. Chapter 1 also includes a preliminary event-based extension using spatiotemporal clustering to identify coherent extreme wind footprints and describe differences in event area and duration. Chapter 2 extends the analysis to the broader northeastern United States using seasonal extreme wind area anomalies, defined as the area exceeding local high-percentile gust thresholds relative to a 1950-1980 baseline. These wind area anomalies are compared with 250 hPa eddy kinetic energy, used as an indicator of the jet stream strength and upper-level storm-track activity, as well as with the natural modes of climate variability describing the large-scale oceanic and atmospheric circulation patterns.

Results show that extreme winds are not changing uniformly across the study region. Long-term trends in average wind speed and typical gust magnitude are generally weak, but important seasonal and regional differences exist. The Kentucky (+VA) service territory shows a modest but statistically significant increase in winter mean maximum gusts, while Rhode Island shows consistently high gust exposure, substantial winter variability, and an increase in winter mean monthly maximum gusts. Across all three service territories, exposure to gusts exceeding 20 m/s (44.7 mph) is highest during winter and lowest during summer. The intensity of extreme gusts, represented by the 95th and 99th percentile daily maximum gusts, has also increased during fall across all three territories, while changes in other seasons are mixed.

The preliminary clustering analysis shows that storms with similar peak gust magnitudes can differ substantially in spatial extent and duration. This event-based perspective complements conventional trend and exceedance metrics by distinguishing localized extremes from storms that affect multiple states or service territories. It also demonstrates that changes in wind hazard may occur through larger or longer-lasting event footprints even when trends in average or maximum gust magnitude remain limited.

At the broader northeastern U.S. scale, extreme wind area variability is strongly seasonally dependent. Fall shows the clearest relationship between warm Atlantic Multidecadal Variability conditions and larger extreme wind footprints. This relationship is consistent with a background environment favorable for tropical or post-tropical systems that can produce widespread surface wind extremes. Pacific-linked relationships are weaker and more uncertain, although summer results suggest a possible pathway involving Pacific sea-surface temperature variability, Rossby-wave activity, PNA-like circulation, and downstream jet stream variability. Eddy kinetic energy is more strongly related to seasonal mean surface wind behavior than to extreme wind area anomalies, indicating that upper-level storm-track activity helps shape the regional wind environment but does not, by itself, determine the spatial extent of damaging gust events.

Overall, this thesis supports a layered interpretation of northeastern U.S. extreme wind risk. Low-frequency climate modes help shape the background atmospheric environment, jet stream and storm-track activity provide an important dynamical pathway, and individual storms determine whether those conditions are expressed as localized or widespread surface-wind extremes. These results show that wind risk cannot be fully understood through annual averages, single-location gust records, or event counts alone. A more complete assessment must consider changes in gust magnitude, exceedance frequency, event duration, and spatial extent.

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Available for download on Wednesday, April 07, 2027

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