How is a hurricane categorized? Those who follow changing weather events often wonder why and how hurricanes get those categories like “Category 1” or “Category 5?”
Well, these hurricane categories are all about estimating their destructive power. With a change in category, there is a change in how devastating a hurricane can be.
But the question is, “how a hurricane is categorized in the first place?
A hurricane is categorized using the Saffir-Simpson Hurricane scale and the sustained wind speed of a hurricane is the basis for these classifications.
Brief Explanation of Hurricane Formation
Hurricanes develop over the warm ocean waters of the equator. They begin life as tropical cyclones fueled by the warm, moist air.
Most cyclones dissipate but some are so charged with fuel they become hurricanes with the potential to cause damage if they make landfall.
As well as warm water, cyclones need wind to develop into a hurricane.
The wind passes over the ocean’s surface, causing the water to evaporate as water vapor.
The vapor is pushed up high where it cools to condense into water droplets forming the huge cumulonimbus clouds typical of thunderstorms.
How is a Hurricane Categorized?
Hurricanes have the potential to cause catastrophic damage and take lives.
Therefore, it is important that everyone understands the risk level and the storm’s expected severity so they can prepare for the worst and find safety.
No two hurricanes are the same but share certain characteristics in how they form and the factors that influence their behavior.
This allows meteorologists to give plenty of warning.
Even so, as witnessed with Hurricane Katrina in 2005, when large coastal settlements struggled to evacuate everyone, some people, perhaps ignorant of the true scale of the risk to property and life, chose to stay.
However, it is important to keep an eye on any storm warnings and act accordingly. This is when the Saffir-Simpson hurricane scale offers plenty of help.
The Saffir-Simpson Hurricane Wind Scale
The Saffir-Simpson Hurricane Wind Scale standardizes the language used to qualify the severity of a hurricane, ranking them in a 1 – 5 format everyone recognizes.
On this scale, hurricanes are categorized solely on the strength of their winds and the damage they have previously caused at that speed.
Overview of the Saffir-Simpson Scale
When the wind speed in a tropical cyclone reaches 74mph (119km) it is a hurricane.
Its sustained wind speed determines its category and helps meteorologists estimate the level of damage it is likely to cause.
Category 3 and over are rare major events, but even categories 1 and 2 can cause extensive damage.
The scale is similar to the Richter Scale for earthquakes, in that the damage caused by a category 2 is ten times that of a category 1.
Fact: All tropical storms have the potential to cause damage whether as a hurricane in the Atlantic or a typhoon in the Pacific.
Development and History of the Scale
Herbert Saffir and Robert Simpson devised the first wind-based version of the hurricane scale in the 1970s then added storm surge and air pressure estimates.
However, the storm surge values proved unreliable due to variations in the continental shelf along the coastlines.
In 2008, 112 people were lost in a storm surge when Hurricane Ike, a downgraded category 2 from the Gulf of Mexico hit Texas.
Many thought that as ‘only a 2’, it was no longer dangerous and didn’t evacuate, and that led to a catastrophe.
Fact: Katrina would have made landfall as a category 1 but was a category 5 according to the 30ft storm surge.
The Hurricane Scale and Details of Each Category
As mentioned already, the Saffir-Simpson scale takes many things into consideration when determining different categories.
But, you need to have a rough idea about what to expect from all these different categories.
Here is more about it:
A cyclone becomes a category 1 hurricane when it has a sustained wind speed of at least 74 mph.
The winds carry flying debris that is dangerous to both man and animal. Roof damage is likely and trees will lose larger limbs.
The fallen power lines will result in outages that could last several days.
Category 2 causes extensive damage with wind speeds from 96 to 110 m.p.h.
It has the power to uproot established trees and damage the roof and sidings of houses.
Most at risk are those sheltering in mobile homes. Power outages are more likely as is being seriously harmed by flying debris.
When the wind is between 111 and 129 mph, the hurricane is a category 3 with the potential to cause massive amounts of damage to even modern, well-built buildings.
In the immediate aftermath, there will be no power or fresh clean drinking water.
Uprooted trees and debris block the roads making movement difficult.
Category 4 hurricanes cause catastrophic structural damage that can render whole areas uninhabitable especially those nearer the coast although there will be extensive flooding inland.
Category 4 storms have wind speeds between 130 and 156 mph. In these high winds flying debris poses a significant risk to life.
A hurricane becomes a category 5 when sustained wind speeds reach 157mph. They are thankfully rare.
Many buildings suffer total roof failure and subsequently, collapsing walls. Roads are blocked with heavy debris, delaying help.
Power and fresh water will be off for weeks if not months.
Fact: During 2000 to 2009, the world witnessed the highest number of category 5 hurricanes, with eight of them occurring during this time.
Factors Influencing Hurricane Classification
To get a better idea about how a hurricane is categorized, it is of immense importance to understand more about factors having a direct impact on this classification.
The Saffir-Simpson scale is there to help, but it still pays to consider other factors when categorizing a hurricane.
The most common factors include the following:
- Central Pressure
- Storm Surge
- Size and Speed of the Hurricane
- Rainfall and Flooding Potential
These days, the Hurricane Scale takes central pressure into consideration.
Central pressure is the surface atmospheric pressure at the hurricane’s center.
Hurricane winds cycle around areas of low pressure and the lower the pressure, the faster the winds.
It is a firm symmetrical relationship that makes predicting storm severity much easier.
A hurricane with a central pressure of 892 millibars left 400 dead in 1935. Both Hurricane Gilbert 1988 and Hurricane Wilma 2005 had even lower.
During a hurricane, the greatest threat to life is a storm surge. Katrina is just one example of the extreme devastation they bring to an area.
Storm surges are generated by the storm and are abnormally high-water levels created by the force of the cyclonic winds pushing the water.
They are complicated phenomena, influenced by many factors such as:
- The storm’s intensity and central pressure
- Its angle to the coast
- The shape of the land
Size and Speed of the Hurricane
Hurricanes vary in size but about 300 miles wide is typical, with an eye diameter of 20 – 40 miles.
Rain bands are 10s of miles wide and can stretch out as far as 300 miles. The wind reach could be 25 or 150 miles depending on its size.
Its speed and direction are dictated by the interaction between the water and the atmosphere and nearby weather systems, or the lack of one.
Rainfall and Flooding Potential
One of the typical characteristics of a tropical storm is its torrential rains, its resultant flooding and the debris flow.
The rain can fall in short intense bursts as happened in the Virginias in 1969 when Hurricane Camille dumped 12 to 20 inches in a short time.
Fact: Flash flooding is the most immediate threat to life although the danger of flooding even far inland will persist as water drains off the land into swollen rivers.
How is a hurricane categorized? Categorizing hurricanes according to the Saffir-Simpson Scale is all about estimating their destructive potential.
The sustained wind speed is the basis for the ranking from 1 to 5. The greater the storm’s category, the greater its potential for destruction.
It is a vital resource for enabling meteorologists to foresee the effects of hurricanes and issue timely warnings to the public.
Do not dismiss reports of a Category 5 hurricane the next time you hear about one.