AUSTIN (KXAN) — The Atlantic hurricane season begins on June 1 — and given our proximity to the Gulf of Mexico, it’s important to know the differences between different types of tropical cyclones we can experience in Texas.
First, according to the National Hurricane Center (NHC) a tropical cyclone is a generic term for a low-pressure system that formed over tropical waters (25°S to 25°N) with thunderstorm activity near the center of its closed, cyclonic winds. Tropical cyclones derive their energy from vertical temperature differences, are symmetrical, and have a warm core.
If a tropical cyclone lacks a closed circulation, it is called a tropical disturbance. If it contains a closed circulation with wind speeds less than 39 mph it is a tropical depression. While tropical depressions have a closed circulation, they are typically very unorganized around it. Tropical depressions are assigned a number instead of a name by the NHC and are generally heavy rain producers.
If a tropical depression moves into a favorable environment for strengthening (i.e. warm ocean waters and low wind shear) it can strengthen into a tropical storm. Tropical storms contain stronger winds, on the the range of 39 to 73 mph, and have more thunderstorm development around its center of circulation. A name is assigned to the system by the NHC when it strengthens from a tropical depression into tropical storm.
If further strengthening occurs to a tropical storm, it will then become a hurricane. A hurricane has winds of at least 74 mph, but can increase to over 200 mph. Once a storm becomes a hurricane, they are categorized by maximum sustained winds according to the Saffir-Simpson scale.
Hurricanes contain an “eye” which is where the strongest winds and thunderstorm activity is located at. However, in some of the strongest hurricanes, hurricane force winds can be felt 90 to 100 miles from the eye of the storm.
Storm surge is also associated with hurricanes and occurs when the strong winds near the eye push oceanwater on shore. Storm surge can push water on shore up to 20 feet high and destroy everything in its path, and is also the leading cause of death among hurricane fatalities.
In addition to hurricane force winds and storm surge, inland flooding from torrential downpours and tornadoes can happen from a landfalling hurricane.