Most of us hate the stormy weather. It can cause disruption, and if they’re strong enough, even chaos.
Staying upright on your feet becomes a challenge, and if those winds are accompanied by heavy rainfall, well… you can kiss goodbye to your weekend plans.
Unfortunately, wherever you are in the world, you’ve probably experienced strong winds at least once in your lifetime.
Strong winds are often referred to as gale-force winds, and these formidable forces have the potential to bring plenty of destruction with them. But what exactly are gale force winds, how do they form, and what damage can they do?
What is a Gale?
First things first, let’s clear up any confusion. Strong winds are not uncommon, and they can occur in several major storm systems.
The persistent winds we’ll be discussing here though, are prolonged gale force winds, with gusts harsh enough to cause severe structural damage and quite literally blow you away.
A gale-force wind (often just called a gale) is a persistent, harsh, and incredibly strong wind with speeds between 31mph and 63mph. Gale force winds are usually seen in coastal regions.
Gale force winds can sometimes happen without the help of any strong weather system, and if conditions are optimal for them to occur, they can last all day.
These winds aren’t limited to major storm systems, so to understand more about gale-force winds and what creates them, we need to take a closer look at the Beaufort scale.
Understanding the Beaufort Scale
If you’ve never heard of the Beaufort scale, don’t worry, We’re here to walk you through the basics, so you can understand exactly what gale force winds are, and how they occur.
The Beaufort scale, or the Beaufort wind force scale, is a table that’s used to depict the force of wind through a range of numbers from 0 to 12.
Although the Beaufort scale can go up to 17, the final five numbers are only usually applied to tropical typhoons. For this reason, you’ll usually only see these numbers used to describe winds in areas around Taiwan and China.
The scale was named after British Royal Navy hydrographer Sir Francis Beaufort who, in 1805, created this method of describing the force of wind according to the procedures used to set sails on navy warships.
Essentially, the Beaufort scale can be a useful way to estimate wind power without using any specific wind instruments, and it can help us get a better idea of what a gale-force wind is, and how it’s characterized.
As you can see, the Beaufort scale does a great job at breaking down the different strengths of gale-force winds. Although this image includes numbers 0 – 12, we can see that the gale force winds are described in numbers 7 to 10. These gales are described as:
7: Moderate Gale/Near Gale
8: Gale/Fresh Gale
9: Strong/Severe Gale
10: Storm/Whole Gale
Not only is each gale clearly defined in a numbered category, but each category also gives a clear description of what conditions occur on the land and at sea when the described conditions are experienced.
The Beaufort scale also gives us a visual representation of where these gale-force winds sit when compared to other strengths of wind, giving us a clear idea of just how powerful these winds can be.
Let’s take a closer look at what conditions can occur with each strength of gale, according to the Beaufort scale.
7: Moderate Gale/Near Gale
With a moderate gale or a near gale, wave heights can reach anywhere between 13ft to 19ft. These heights can depend on the wind speed. According to the Beaufort scale, wind speeds in this category are between 32-38mph.
Compared to wind speeds in calm conditions (0) on the scale which are just 1mph, this is a significant difference.
With moderate gales to near gales, the sea may start to ‘heap up,’ and white foam from the ocean will blow downwind. On land, entire trees will be noticeably moving, and those walking on land may have a difficult time staying upright.
These gales are less severe than the others further up the scale.
8: Gale/Fresh Gale
A category eight gale or fresh gale is slightly more advanced than a category seven moderate gale or near gale. Wave heights on the water are usually between 18-25ft, and wind speeds are between 39 and 46mph.
This can determine the wave height seen on the water. The tallest wave height in a category eight gale is almost 10ft higher than the smallest waves seen with moderate gales to near gales.
If you’re out on the sea, you’ll notice tall waves that are medium-high, and clear foam streaks will be visible. On land, you may start to notice twigs breaking off trees, and as branches begin to snap, the movement of people on land becomes even more impeded.
This is a more significant gale, but it’s unlikely to cause as much structural damage as other gales.
9: Strong/Severe Gale
A category nine strong or severe gale is more powerful than a seven or eight gale. These gales can produce wave heights between 23ft to 32ft, and wind speeds can be anywhere between 47mph to 54mph.
On the waves, waves will be noticeably higher than those seen with category eight gales. It’s also likely that the waves will now impair your visibility on the water.
On land, these winds may not start to produce minor structural damage, and people will be unlikely to travel anywhere on foot in these conditions. These gales can sometimes pose a threat to life, especially if structures are ill-fitted or weak.
10: Storm/Whole Gale
A category ten gale is the strongest gale force wind of them all. These gales can cause intense wave heights of between 29-41ft, and wind speeds of between 55mph and 63mph.
That’s a big difference compared to a category seven gale, with 13-19ft wave heights and 32-38mph winds.
On land and sea, conditions are even harsher. You will see incredibly high waves with dense white foam streaks at sea. Trees are likely to be uprooted on land, and you can expect considerable structural damage to your surroundings.
Although the Beaufort scale gives us a clear idea of what to expect from each category of gale, as with most weather phenomena, things are not always this clear-cut.
Conditions can be varied and complex, and there are several factors that can influence weather systems and the gale-force winds that occur from them. Let’s explore the causes of gale-force winds in more depth below.
Gale Force Winds: What Causes Them?
Wind, in general, is produced when gases start to move from high-pressure areas into low-pressure areas. The bigger the difference is between these pressures, the faster the air around you will move from high to low pressure.
This creates the rush of air or wind we experience in the atmosphere (also see ‘Everything You Need To Know About The Thermosphere‘). You’ll often find that winds around low-pressure systems will vary in strength.
Weather systems such as hurricanes, cyclones, and tropical storms are great examples of this point.
The strength of a low-pressure system will determine how quickly gale force winds are reached and whether or not they have the potential to build-up to the speeds of hurricanes.
As we’ve already established, though, gale force winds aren’t just caused by storm systems. Occasionally, they can develop without the presence of any major storm system, and occur in seemingly pleasant and clear conditions.
You’ll often find these winds along coastlines, where the coastline relief can play a pivotal role in the development of these winds. (Also see ‘The Top 10 Windiest Cities In The World‘).
In the summertime, the land and the ocean’s surface are warmed up by the sun, and the land can get warmer quicker than the ocean. When it hits the afternoon, the land can also cool down a lot quicker than the ocean does, contributing to these conditions.
This is because the conditions can also create a low-pressure system over land, and the warm air that sits over the ocean will move towards the system on land. It’s this movement that we usually describe as a sea breeze.
Sometimes though, this seemingly harmless sea breeze can develop into gale force winds, if the area and conditions around it are right. If gale-force winds develop on coastlines, it’s usually due to two factors:
- The Difference Between Low and High Pressure: The differences between low and high-pressure air over the sea and land is so large that a small breeze can quickly develop into something stronger, i.e. a gale.
- Mountainous Relief: If a region has mountainous relief, strong winds can be exacerbated through the creation of what’s known as a funnel effect. This happens when the winds are pushed through a narrow and low area, which in turn, strengthens the speed of the wind.
If either of these things occurs, gale force winds can develop. In areas along the Cape Peninsula, for example, winds can reach speeds of as high as 75mph.
There are also other coastal regions in the world that can experience this type of weather phenomenon, such as San Francisco, which is well known for its strong gales in the summertime.
It’s usually a combination of both of the above factors that causes these conditions to occur, especially in San Francisco. Wind tends to funnel through the infamous Golden Gate, which can cause gusts as high as 40mph. As we know from the Beaufort scale, this would be classified as a gale.
When we assess the development and classification of gale-force winds, it’s important to remember that classifications can vary by region. For example, in the US, gale force winds are described as any wind that reaches speeds between 39mph and 54mph.
So, although the Beaufort scale is a useful tool (and the most commonly used wind scale in the world), it may not always be applicable to the region you’re in.
However a gale is characterized, these strong winds are almost always dangerous and destructive. Even those gale-force winds at the lower end of the Beaufort scale can be dangerous, especially if structures in the surrounding areas are weak.
This is why weather forecasters will almost always issue warnings whenever a gale is predicted , even if it’s at the lower end of the scale.
The Bottom Line
Gale force winds are a common weather phenomenon at all corners of the globe, but they can be quite complex to understand. Not all gale-force winds occur with certain weather systems, and some can seemingly spring out of nowhere.
We hope this article has helped you to understand the nature of gale-force winds, how they’re categorized, and how their effects can vary according to region, environment, and classification.