Hurricane terms everyone should know as the season heats up
Keep these important terms in mind as you listen to hurricane forecasts throughout the season
Hurricane forecasts are a lifesaving tool for coastal residents during the summer and autumn months. Vast storms swirling around the Atlantic Ocean can turn toward shore with high winds, dangerous flooding, and torrential rains.
Keeping tabs on each forecast update is a critical step toward staying safe throughout this time of year.
Here’s a look at some of the most common terms you’ll hear throughout a typical hurricane season and why they matter for you.
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The basics of a hurricane season
Cyclone: All low-pressure systems are cyclones. Extratropical cyclones are our ‘everyday’ lows that feature cold and warm fronts. Tropical cyclones are lows powered by thunderstorms around the core of the storm. Subtropical cyclones exhibit characteristics of both.
Hurricane vs. Typhoon: Powerful tropical cyclones are called different names around the world. They’re hurricanes around North America, typhoons near eastern Asia, and simply cyclones in the Indian Ocean and the southern hemisphere.
Hurricane Season: A six-month stretch of the year during which tropical systems are most likely to develop. Hurricane season in the Atlantic Ocean runs between June 1 and November 30, though storms can (and have!) formed before and after those dates.
Cone of Uncertainty: The margin of error in a typical track forecast issued by the U.S. National Hurricane Center (NHC). Historically, the centre of a storm stays within the cone of uncertainty 66 per cent of the time. Cone don't show the extent of a storm's hazardous conditions—a system's rain, wind, and surge can extend far beyond its centre core.
A storm grows in the Atlantic
Disturbance: A tropical disturbance is a disorganized cluster of thunderstorms that hasn’t yet developed into a low-pressure system. A disturbance is the precursor to a tropical depression or tropical storm.
Invest: A special designation assigned to tropical disturbances that meteorologists want to gather more information on and run specialized computer models to track. Invests in the Atlantic are numbered 90L-99L (ex: Invest 99L) in order to keep track of them.
Spaghetti Models: A graphic that charts out a dozen or more weather model runs, showing the potential track and intensity of a given storm over the course of about a week’s time. The end result looks like spaghetti noodles drawn on the map.
Potential Tropical Cyclone: A tropical disturbance that’s expected to organize and hit land as a tropical storm or hurricane within the next 48 hours. This designation allows forecasters to issue forecast tracks, watches, and warnings for communities in harm’s way.
Tropical Depression: A weak tropical cyclone with maximum sustained winds of 62 km/h or less.
Tropical Storm: A tropical cyclone with maximum sustained winds between 63 and 118 km/h.
Hurricane: A strong tropical cyclone with maximum sustained winds of 119 km/h or greater.
Saffir-Simpson Hurricane Wind Scale: A five-category scale that conveys the severity of a hurricane’s maximum sustained winds. This scale only relates to wind speeds—it doesn’t take into account other deadly hazards such as flooding rains, storm surge, and tornadoes, which are common even in weak storms.
Rapid Intensification: Powerful systems sometimes strengthen very quickly. Rapid intensification occurs when a storm’s winds increase at least 55 km/h within 24 hours. The most extreme cases can see a Category 1 hurricane jump to Category 4 or 5 in less than a day.
The storm hits land
Tropical Storm/Hurricane Watch: High winds are possible within the next 48 hours. Make urgent preparations for dangerous conditions.
Tropical Storm/Hurricane Warning: High winds are likely within the next 36 hours. Act now to save life and property.
Landfall: The moment the precise centre of the storm crosses the coastline. Dangerous winds, rain, storm surge, and tornadoes begin long before a storm officially makes landfall.
Storm Surge: Seawater pushed inland by strong, persistent onshore winds. Storm surge can cause flooding up to several metres above ground level and sometimes extend far inland from the coast.
Rip Currents: Strong currents of water that pull from shore directly out to sea. Strong rip currents are possible even when a storm is thousands of kilometres offshore.
Remnants: The disorganized rain and thunderstorms associated with a former tropical cyclone. Tropical remnants can push far inland and cause gusty winds, flooding rains, and tornadoes.
Header image courtesy of NASA.