Post-Tropical Cyclone
Also called: remnant low, extratropical 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).
Key Points
- Post-tropical does not mean weak. An extratropical cyclone can keep hurricane-force or tropical-storm-force winds after it loses its tropical structure.
- A remnant low has lost the organized thunderstorm activity a tropical cyclone needs and has maximum sustained winds below 34 knots.
- The change is in how the storm is powered. A tropical cyclone runs on heat released by condensation over warm water, and an extratropical cyclone runs on the contrast between warm and cold air masses.
Related 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.
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.
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.
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.
Nor'easter
A storm along the East Coast with winds blowing from the northeast. Nor'easters can bring heavy snow, rain, and coastal flooding, especially from Virginia to New England. The most powerful nor'easters rival hurricanes in intensity.
Bomb Cyclone
A bomb cyclone is a midlatitude storm that intensifies rapidly through a process called bombogenesis: its central pressure falls by at least 24 millibars in 24 hours, measured at 60° latitude. The threshold shrinks toward the equator, to about 17.8 millibars at the latitude of New York City.
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: 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.
Tool
Wind Speed Converter
Convert between mph, km/h, knots, and m/s for wind reports and forecasts.
Guide
Hurricane Categories Explained
Understand what each Saffir-Simpson category says and what it does not say about a storm's risk.
Seasonal Hub
Hurricane Season Guide
Track tropical risk, categories, and preparedness advice in one place.
Feature
Hurricane Tracker
Track cones, watches, warnings, and tropical systems from formation through landfall.
Sources
Explore Other Terms
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.
Sleet
Frozen raindrops that bounce when hitting the ground. Sleet forms when snowflakes partially melt falling through a warm layer, then refreeze in a cold layer near the surface. Unlike freezing rain, sleet is frozen before it hits the ground.
Heat Index
The heat index is how hot it feels when relative humidity is combined with the air temperature. Humid air slows the evaporation of sweat, so the body cools less efficiently and feels hotter than the thermometer reads. At 100°F with 55% relative humidity, the heat index is 124°F.
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.
Probability of Precipitation
Probability of precipitation (PoP) is the chance that a given point receives measurable precipitation, at least 0.01 inch, during the forecast period. A 40% chance of rain means a 4 in 10 chance of at least 0.01 inch at your location. It does not mean rain over 40% of the area or for 40% of the time.
VFR
Visual Flight Rules allow flight using visual references when the applicable visibility and cloud-clearance minimums are met. Those minimums vary by airspace class, altitude, and day or night under 14 CFR 91.155. Separately, the VFR weather category means a ceiling above 3,000 feet and visibility greater than 5 statute miles.
Browse by Category
In the WeatherAI App
Optional Tropical Storm News notifications in WeatherAI cover new named storms, each category climb, and post-tropical transitions in the Atlantic and Pacific.
Availability, coverage, update frequency, and alert delivery vary by data source, region, subscription plan, device permissions, and service conditions. WeatherAI supplements official sources and is not an emergency notification service. For life-safety decisions, rely on your national weather service, local emergency management, and official warning channels.