SECTION 4: RISK ASSESSMENT
portions of central North Carolina during the late afternoon into the evening. The storms produced multiple reports of wind damage, large hail and one measured wind gusts of 58 mile per hour. March 28, 2021 - A line of showers and embedded thunderstorms in the morning hours of March 28th over eastern Tennessee and western North Carolina pushed eastward ahead of a strong cold front. These storms intensified during the afternoon hours across portions of central North Carolina, producing several reports of trees down and quarter size hail. PROBABILITY OF FUTURE OCCURRENCE Based on historical occurrences recorded by NCEI for the 25-year period from 1998 through 2023, Wake County averages 21.6 thunderstorm wind events per year. Over this same period, 41 lightning events were reported as having caused death, injury, or property damage, which equates to an average of 1.64 damaging lightning strikes per year. The average hailstorm in Wake County occurs in late afternoon and has a hail stone with a diameter of an inch. Over the 25-year period from 1998 through 2023, Wake County experienced 298 reported hail incidents; this averages almost 12 reported incidents per year somewhere in the planning area, or a 100% chance that the County will experience a hail incident each year. Based on these historical occurrences, there is a 100% chance that the County will experience severe weather each year. The probability of a damaging impacts is highly likely.
Probability: 4 – Highly Likely CLIMATE CHANGE
Per the Fifth National Climate Assessment, “The complexes of thunderstorms that bring substantial precipitation to the central United States during the warm season have become more frequent and longer- lasting over the past two decades. ” As temperatures rise, the weather environments that give rise to severe thunderstorms in the spring and fall will increase. These changes are likely to lengthen the severe thunderstorm season throughout the Southeast during the cool-season months. Hail and lightning are often associated with thunderstorms and are predicted to follow a similar trend. Short-lived severe weather such as thunderstorm events are difficult to observe and the direct correlation of these events to climate change are still incomplete. NASA measures thunderstorm potential with an index called the Convective Available Potential Energy (CAPE) index. This measures how warm and moist the air is, which is a major contributing factor in thunderstorm/tornado formation. NASA projects that by the period of 2072-2099, the CAPE in the southeastern United States will increase dramatically. Parts of North Carolina are in an area that will likely experience the greatest increase in CAPE in the United States and all of the state is likely to experience at least some increase. VULNERABILITY ASSESSMENT
METHODOLOGIES AND ASSUMPTIONS
Population and property at risk to wind events was estimated using data from the NCEM IRISK database, which was compiled in NCEM’s Risk Management Tool.
PEOPLE People and populations exposed to the elements are most vulnerable to severe weather. A common hazard associated with wind events is falling trees and branches. Risk of being struck by lightning is greater in open areas, at higher elevations, and on the water.
Wake County, NC Multi-Jurisdictional Hazard Mitigation Plan
WSP June 2024 Page 200
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