Hurricanes & Storms Information
A tropical depression is an organized system of clouds and thunderstorms with a defined surface circulation and maximum sustained winds of 38 mph (miles per hour) or less.
A tropical storm is an organized system of strong thunderstorms with a defined surface circulation and maximum sustained winds of 39 to 73 mph.
A hurricane is an intense tropical weather system of strong thunderstorms with a well-defined surface circulation and maximum sustained winds of 74 mph or higher. In other parts of the world, the term hurricane is synonymous with typhoons or cyclones.
Intensity & Damage for Hurricanes
The Saffir-Simpson Hurricane Scale breaks hurricanes into categories based on sustained wind speeds.
- Category 1: 74 to 95 mph
- Category 2: 96 to 110 mph
- Category 3: 111 to 129 mph
- Category 4: 130 to 157 mph
- Category 5: greater than 157 mph
Category 1 and 2 Hurricanes: Usually pose minor damage to stable structures but can do major damage to mobile homes, vegetation, and piers. Flooding will occur in some coastal areas and low-lying areas.
Category 3 Hurricanes: May cause some structural damage to small residences and utility buildings, but mobile homes are destroyed. Flooding near the coast destroys structures with floating debris. Low areas may be flooded inland 8 or more miles.
Category 4 and 5 Hurricanes: These storms are the most deadly and destructive. Both can create complete roof failure and building collapse of residences and industrial buildings. Major damage occurs in the lower floors of structures along the shoreline, and massive beach erosion is caused by the storm surge. Flooding of 15 feet or more may occur along the shoreline and up to 10 miles inland.
Four Main Concerns with Hurricanes & Tropical Storms
Wind ranks second behind storm surge, among the lethal components of a hurricane's destructive force, yet affects far more people due to the regional impact. High winds will impact inland as well as coastal areas causing problems such as structural failure, damage from wind blown debris, transportation and evacuation issues.
Flooding may be due to thunderstorms passing through an area dropping a considerable amount of rain or related heavy rains from a slow moving tropical storm or hurricane. Several areas in the city may be prone to flash flooding due to low land elevations and close proximity to the ocean. Nationally, flash floods are the number one cause of weather-related deaths.
Storm surge is considered the most destructive of the forces related to hurricanes and could present a major hazard in Northeast Florida coastal communities from the force and associated flooding. Storm surge is the result of wind driven water impacting the continental shelf and building up large waves of water reaching heights up to fifteen to twenty feet as it reaches the coast. Severe damage to any structure in the path can be expected as well as extensive beach erosion. Storm surge will also have an effect on the Intracoastal Waterway and adjoining property, backing up tidal waters and resulting in extremely high tides and possible flooding.
Tornadoes are described as violent rotating columns of air (100-300 mph) extending from a thunderstorm to the ground. This type of phenomenon will be associated with a thunderstorm or may form during a hurricane.