Eye Wall
The ring of intense thunderstorms surrounding a hurricane's eye, containing the storm's strongest winds and heaviest rainfall. Eye wall replacement cycles can temporarily weaken a hurricane before it potentially re-intensifies.
More Tropical Weather Terms
Hurricane
A tropical cyclone with maximum one-minute sustained surface winds of 74 mph or greater in the Atlantic or eastern and central North Pacific. Hurricanes are categorized 1-5 on the Saffir-Simpson Hurricane Wind Scale, with Category 5 beginning at 157 mph.
Typhoon
A tropical cyclone with sustained winds of 74 mph or greater in the Western Pacific. Typhoons are meteorologically identical to hurricanes; the different name reflects only their geographic location.
Cyclone
A rotating low-pressure weather system. Tropical cyclone terminology and intensity categories vary by region: in Australia, a tropical cyclone has maximum sustained winds of at least 34 knots (63 km/h, about 39 mph), averaged over ten minutes. The term does not universally require hurricane-force winds of 74 mph.
Storm Surge
Storm surge is an abnormal rise in sea level during a hurricane or other intense storm, measured as the height of the water above the normal predicted tide. It is produced mainly by the storm's winds pushing water toward the shore. Storm surge is the leading cause of deaths from hurricanes.
Tropical Depression
An organized system of clouds and thunderstorms with defined circulation and maximum sustained winds of 38 mph or less. Tropical depressions can strengthen into tropical storms and eventually hurricanes.
Tropical Storm
A tropical cyclone with maximum sustained winds between 39-73 mph. At this stage, the storm receives a name. Tropical storms can produce dangerous flooding, winds, and tornadoes even without reaching hurricane strength.
Invest
A weather system designated for investigation by the National Hurricane Center. An Invest designation triggers enhanced data collection and model runs but does not indicate expected development. Many Invests never become tropical cyclones.
Saffir-Simpson Scale
The Saffir-Simpson Hurricane Wind Scale rates hurricanes from Category 1 to Category 5 by maximum sustained wind speed. Category 1 starts at 74 mph and Category 5 at 157 mph, and Category 3 and higher are called major hurricanes. The scale measures wind only: it does not account for storm surge, rainfall flooding, or tornadoes.
Post-Tropical Cyclone
A post-tropical cyclone is a former tropical cyclone that no longer has enough tropical characteristics to be classified as one. It can still bring heavy rain and strong winds. The two kinds are extratropical cyclones, which draw their energy from temperature contrasts between air masses, and remnant lows, which have winds below 34 knots (39 mph).
Eye Wall: Guides and Explainers
These explainers connect this definition to real-world forecasting and decision-making.
Weather Education
What Is Storm Surge? Surge vs Storm Tide, and Why Category Doesn't Predict It
Storm surge explained: how surge, storm tide, and inundation differ, what decides how high the water gets, why a Category 2 can flood worse than a Category 4, and which NHC products to act on.
Weather Education
Spaghetti Models Explained: What Those Tangled Hurricane Lines Actually Mean
Spaghetti models are a tangle of individual forecast tracks, not a forecast. Here is what each line is, what the labels like AVNO and EMX stand for, and how to read the spread instead of the scariest strand.
Weather Education
Typhoon vs Hurricane vs Cyclone: Same Storm, Three Names
A typhoon and a hurricane are the same kind of storm with the same 74 mph threshold. What changes is the ocean basin, the agency, and how the wind is measured. Here is the full naming map.
Helpful Tools and Hubs
Use these pages to apply the concept, compare conditions, or follow related weather workflows.
Guide
What Causes Thunder and Lightning?
How lightning forms through charge separation, what causes thunder, and how to stay safe.
Guide
Lightning Safety Guide
Know when lightning becomes dangerous, how far away it can strike, and when to move indoors.
Use Case
Weather App for Cyclists
Check wind, rain timing, and radar before a ride so conditions do not decide the route for you.
Guide
Hurricane Categories Explained
Understand what each Saffir-Simpson category says and what it does not say about a storm's risk.
Explore Other Terms
Epicenter
The point on Earth's surface directly above where a fault rupture begins. It is a single map location, not the whole earthquake: a large event can break hundreds of kilometers of fault, so severe shaking often extends far beyond the epicenter.
Tornado
A tornado is a violently rotating column of air in contact with the ground, extending from a thunderstorm. Tornadoes are rated from EF0 to EF5 on the Enhanced Fujita scale by the damage they cause. Most last less than 10 minutes, but the strongest can stay on the ground for more than an hour.
Snow Squall
An intense, short-lived burst of heavy snow accompanied by strong winds and often causing a sudden drop in visibility to near zero. Snow squalls can create extremely dangerous driving conditions despite lasting only 30-60 minutes.
Barometric Pressure
The weight of the atmosphere pressing down on a given point, measured in inches of mercury (inHg) or millibars (mb). Rising pressure typically indicates improving weather, while falling pressure suggests approaching storms or precipitation.
Velocity
Doppler radar measurement of how fast precipitation is moving toward or away from the radar. Velocity data reveals wind patterns, rotation in thunderstorms, and potential tornado signatures that reflectivity alone cannot show.
CAPE
CAPE (Convective Available Potential Energy) is the amount of energy a rising parcel of air can draw from the atmosphere, measured in joules per kilogram (J/kg). The higher the CAPE, the faster a storm's updraft can rise, and the stronger thunderstorms can become once something sets them off.
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