A “Level 4 storm” is a designation used across meteorological classification systems to signal extreme danger and catastrophic potential. This classification signifies a major event, carrying a life-threatening risk to any area in its path. While the specific scale and the type of weather phenomenon differ, the number four uniformly represents a high-end classification demanding immediate public action. This category of storm is capable of widespread destruction that can render communities uninhabitable for extended periods.
Why Storms Are Classified by Severity
Meteorological classification systems, such as the widely used 1-to-5 scales, serve as a standardized language for communicating the threat of severe weather. These scales allow meteorologists and emergency management officials to quickly convey the expected severity and potential impact of a storm. By assigning a numerical rating, authorities can standardize response protocols, triggering specific actions like mandatory evacuations and resource staging.
The ratings are based on measurable physical characteristics of the storm, such as wind speed or the resulting damage to structures. This standardization helps in predicting the potential scale of destruction, which is crucial for planning effective disaster mitigation and recovery efforts.
Level 4 on the Saffir-Simpson Hurricane Scale
A Category 4 storm on the Saffir-Simpson Hurricane Wind Scale (SSHWS) is defined as a major hurricane, characterized by extremely dangerous winds that cause devastating damage. Sustained wind speeds range from 130 to 156 miles per hour (209 to 251 kilometers per hour). The force of these winds is sufficient to cause complete failure of the roof structure on many smaller residences and extensive damage to windows and doors on well-built homes.
The impact extends beyond structural damage to buildings. Most trees and power poles will be downed, leading to widespread power outages that can last for weeks or months. Extensive damage is expected to well-constructed frame homes, including total roof loss and some wall failures. Complete destruction of mobile homes is also expected.
Although the current SSHWS focuses solely on wind speed, a hurricane of this intensity produces a life-threatening storm surge. This surge can flood areas up to six miles inland on flat terrain. The combination of intense wind and water can isolate residential areas due to impassable roads blocked by debris and flooding.
Level 4 on the Enhanced Fujita Scale
A Level 4 storm on the Enhanced Fujita (EF) Scale refers to an EF4 tornado, which causes devastating damage. The EF Scale is a damage-based system; the rating is assigned after a storm based on observed destruction, which is correlated to estimated wind speeds. An EF4 tornado is estimated to have three-second wind gusts ranging from 166 to 200 miles per hour (267 to 322 kilometers per hour).
The damage indicators for an EF4 focus on the destruction of well-built structures. A defining characteristic is the leveling of well-constructed, whole frame houses; structures with weak foundations are often blown away entirely. Cars can be thrown significant distances, and large debris are transformed into high-speed projectiles capable of being embedded into concrete.
Essential Public Safety During Level 4 Alerts
Immediate and decisive action is paramount when a Level 4 alert is issued for either a hurricane or a tornado. For a Category 4 hurricane, the primary focus must be on following mandatory evacuation orders without delay, due to the threat of storm surge and prolonged isolation. Individuals should focus on reaching a designated shelter or a safe location well inland, rather than attempting to secure property.
In the case of an EF4 tornado alert, the response must be instantaneous and focused on seeking immediate, reinforced shelter. The safest location is an underground space, such as a basement or storm cellar. If no underground shelter is available, the best alternative is an interior room on the lowest floor of a building, away from windows. Protecting the head and neck from flying debris is necessary for survival against the tornado’s intense, localized winds.