The Saffir-Simpson Hurricane Wind Scale Explained

When a hurricane is approaching land, you might hear a meteorologist refer to its "dirty side", which is a reference to the storm's counterclockwise swirling nature helping to create some of the most severe impacts in the so-called right-front quadrant.

Here's a closer look at why hurricanes aren't uniform throughout and what gives this sector of a storm an extra boost of ferocity.

Big Picture

• What We Mean By Right-Front Quadrant: If you divide up the circular shape of a hurricane into four quadrants, you first look to the right side of whatever forward direction it's tracking. The most forward part of that side in relation to the circulation center is the right-front quadrant.
• Tracking Direction Matters For How To Find It: In the case of a hurricane moving due north, the right-front quadrant is on the upper east side, as shown in the example below from Hurricane Michael approaching the Florida Panhandle in October 2018. A hurricane moving due west would have its right side north of the storm's center, while for one moving east that side would be located south of the storm's center.
• Multiple Impacts Are Usually Worse Here: The entire hurricane packs dangerous impacts, but the right side, particularly the right-front quadrant, usually contains the most severe storm surge, often the strongest winds and the biggest tornado threat. Rainfall flooding can happen anywhere in a hurricane, but the right side can be more prone to bands of rain hammering the same areas for a longer period of time.

Deeper Dive

• Why Winds Are Worse: Wind speeds in the right-front quadrant are enhanced since the counterclockwise circulation in this part of the hurricane is moving in the same general direction as the storm's movement. As an example, a hurricane that contains 90 mph winds and is moving at 10 mph would see a bump to 100 mph winds on its right side, which is then what you would see listed as the top wind speed in advisories. Winds on the back, or left side of the hurricane, are moving opposite of its forward motion, so they are usually reduced on that side to some degree.
• Storm Surge Piles Up: Counterclockwise rotating winds in the right-front quadrant are constantly pushing ocean water forward with a hurricane. When a hurricane nears landfall, that surge of water arrives along the coast and produces the worst, most damaging inundation near and to the right of where the center crosses the coast. This is shown clearly in the analysis below of the storm surge Hurricane Helene's right-front quadrant produced in Florida in September 2024.
• Extra Spin Produces Tornadoes: While any part of the hurricane can have tornadoes, there's an extra boost to that threat in the right-front quadrant. That's because the wind shear that's required to make individual storms rotate and produce tornadoes is enhanced in this part of a hurricane.

More To Know

• It's All Reversed South Of The Equator: Tropical cyclones in the Southern Hemisphere rotate clockwise. That means the "dirty side" is on the left side of tropical cyclones in places like the southern Pacific and southern Indian Oceans. The left-front quadrant is therefore the worst for winds, storm surge and tornadoes when these storms make landfall in those regions of the world.

Chris Dolce has been a senior digital meteorologist with weather.com for 15 years after beginning his career with The Weather Channel in the early 2000s.

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