Hurricanes

What is the difference between a tropical storm and hurricane?

With Hurricane Milton strengthening on its path towards Florida, here's how storms are classified from a tropical depression to a Category 5.

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Editor's note: The original version of this story was published on Aug. 18, 2023.

Hurricane Milton has strengthened to a Category 5 storm just days before it is expected to make landfall in Florida.

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The storm, which is projected to come ashore Wednesday and bring dangerous storm surge to Tampa Bay, comes less than two weeks after Hurricane Helene battered the coastline and killed more than 230 people.

Milton intensified over the eastern Gulf of Mexico on Monday, with maximum sustained winds of 175 mph, the National Hurricane Center said.

Scientists expect the system to weaken slightly before landfall, though it could retain hurricane strength as it churns across central Florida toward the Atlantic Ocean. As evacuation orders were issued, forecasters warned of a possible 8- to 12-foot storm surge in Tampa Bay and widespread flooding from 5 to 10 inches of rain in mainland Florida and the Keys. As much as 15 inches could fall in places.

The Tampa area was last hit by the eye of a major hurricane on Oct. 25, 1921. The Category 3 storm, with winds of up to 129 mph and an 11-foot storm surge, left at least eight people dead and caused an estimated $5 million in damage.

With Milton approaching, storm surge and hurricane warnings were issued for Florida’s Gulf Coast, while a tropical storm warning was issued for the Florida Keys. The storm is expected to make landfall as a Category 3, still a major hurricane.

Here's how hurricanes are classified from a tropical depression to a Category 5.

What is the difference between a tropical storm and hurricane?

Storms are classified by their strength and intensity, which include hazards like coastal storm surge, high winds and heavy rainfall. 

Here's the difference between the types of categorized tropical cyclones, according to the National Hurricane Center

What is a tropical depression? 

A tropical depression is a cyclone with maximum sustained winds of 38 mph or less.

Tropical depressions are not as strong or threatening as tropical storms or hurricanes, with wind gusts that are less likely to cause damage or destruction. The intense rain and inland flooding produced by the storm can still be catastrophic.

In 2004, Tropical Depression Winnie was a weak cyclone with peaks of 35 mph wind gusts, but its torrential rainfall led to widespread flooding in the Philippines, killing more than 1,000 people.  

What is a tropical storm?

A tropical storm is a cyclone with maximum sustained winds of 39 to 73 mph.

While classified just below a hurricane, tropical storms can have similar damaging effects, particularly with flooding. Tropical Storm Allison in 2001 never reached hurricane-level winds but the slow-moving storm caused billions of dollars in damage, with particular devastation in Texas after five days of heavy rainfall.

It became the costliest tropical storm in history, and the first to have its name retired, after damaging 73,000 homes and flooding 95,000 cars. There were 41 fatalities.

Life-threatening storm surges are expected to hit Florida's gulf coast this week with the arrival of Hurricane Milton, which was upgraded Monday morning into a Category 5 hurricane.

What is a hurricane?

A hurricane is a tropical cyclone with maximum sustained winds of 74 mph or higher that typically registers as a Category 1 or 2 on the Saffir-Simpson Hurricane Wind Scale. 

A Category 1 storm has sustained wind speeds between 74 mph and 95 mph, and a Category 2 storm is between 96 mph and 110 mph.

Hurricanes typically cause the most widespread damage of all classified storms, with capabilities of causing extensive destruction to homes and property. In 2022, hurricane damage cost the U.S. $165 billion in damages.

Hurricane Sandy, a Category 2 storm in 2012, caused $50 billion in damage over 24 states. When the storm made landfall in the Northeast, its winds extended 1,000 miles end to end, producing a devastating storm surge that flooded houses along the coast. 

What is a major hurricane? 

A major hurricane is a tropical cyclone with maximum sustained winds of 111 mph or higher that is classified as Category 3, 4 or 5.

Here are the classifications provided by the Saffir-Simpson Hurricane Wind Scale:

Category 3: Sustained winds of 111 mph to 129 mph.

Extensive damage from dangerous winds. Some structural damage to small residences and utility buildings with minor amount of wall failures. Mobile homes destroyed. Many trees uprooted or snapped. Power outages lasting several days or weeks.

Category 4: Sustained winds of 130 mph to 156 mph. 

Devastating damage from extremely dangerous winds. Some wall failures with complete house roof structure failures. Extensive damage to doors, windows, and trees. Electricity unavailable for weeks.

Category 5: Sustained winds of 157 mph and higher.

Catastrophic damage. Complete roof failure on many residences and industrial buildings. Some complete building failures with small buildings blown over or away. Power outages for weeks or months.

Hurricane Katrina in 2005 intensified to a Category 5 storm over the Gulf of Mexico before making landfall in Louisiana as a Category 3 with wind speeds of 140 miles per hour. It was one of the deadliest hurricanes to ever hit the United States, with more than 1,800 people estimated to have been killed. It caused roughly $161 billion in damage, leaving millions homeless and becoming the costliest hurricane on record.

The Associated Press contributed to this story

The Saffir-Simpson scale is used to measure the speed of hurricanes. Why does it stop at Category 5?
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