Fremantle Doctor
The Fremantle Doctor, the Freo Doctor, or simply The Doctor, is the Western Australia
Western Australia
Western Australia is a state of Australia, occupying the entire western third of the Australian continent. It is bounded by the Indian Ocean to the north and west, the Great Australian Bight and Indian Ocean to the south, the Northern Territory to the north-east and South Australia to the south-east...

n vernacular
A vernacular is the native language or native dialect of a specific population, as opposed to a language of wider communication that is not native to the population, such as a national language or lingua franca.- Etymology :The term is not a recent one...

 term for the cooling afternoon sea breeze
Sea breeze
A sea-breeze is a wind from the sea that develops over land near coasts. It is formed by increasing temperature differences between the land and water; these create a pressure minimum over the land due to its relative warmth, and forces higher pressure, cooler air from the sea to move inland...

 which occurs during summer months in south west
Southwest Australia
Southwest Australia is a biodiversity hotspot that includes the Mediterranean forests, woodlands, and scrub ecoregions of Western Australia. The region has a wet-winter, dry-summer Mediterranean climate, one of five such regions in the world...

 coastal areas
Coastal regions of Western Australia
Western Australia has the longest coastline of any state in Australia, at 10,194 km or 12,889 km.-Integrated Marine and Coastal Regionalisation of Australia:...

 of Western Australia. The sea breeze occurs because of the major temperature difference between the land and sea.

General trend

During summer months, it consistently blows from the southwest along the southern half of the west coast, starting between noon and 3 pm. It can penetrate as far inland as 100 kilometre, reaching York
York, Western Australia
York is the oldest inland town in Western Australia, situated 97 km east of Perth in the Avon Valley near Northam, and is the seat of the Shire of York...

 in the early evening.

In Perth
Perth, Western Australia
Perth is the capital and largest city of the Australian state of Western Australia and the fourth most populous city in Australia. The Perth metropolitan area has an estimated population of almost 1,700,000....

, the capital city of Western Australia, the wind is named the Fremantle Doctor because it appears to come from the nearby coastal city of Fremantle
Fremantle, Western Australia
Fremantle is a city in Western Australia, located at the mouth of the Swan River. Fremantle Harbour serves as the port of Perth, the state capital. Fremantle was the first area settled by the Swan River colonists in 1829...

, and it brings welcome relief from the summertime high temperatures.

The Fremantle Doctor often cools the Perth suburbs by several degrees, whilst nearer the coast the wind can be quite strong, often blowing between 15 and 20 knots and making afternoon beach visits unpleasant.

On days when the wind fails, the afternoon temperatures of Perth suburbs are considerably higher, often exceeding 40°C (104°F), although this is also attributable to the influence of a strong easterly wind blowing in hot desert air from the arid interior of the state.

Further analysis

The Fremantle Doctor is strongest in December and January, when the temperature differential between the land and ocean is greatest. In February and March the breeze is not as strong, because the ocean temperature is a bit warmer. Though October and November are not as warm, the ocean temperature is cooler resulting in the sea breeze in these months.

Other months have a weak or non-existent Fremantle Doctor. In the winter months, the land temperature is usually cooler than the ocean temperature, and this sometimes results in the weaker land breeze in the early morning.

When the Fremantle Doctor first arrives it is from the west-south-west (WSW) direction.
Later when it is at maximum strength, the direction is usually from the southwest or south-south-west. By the early evening, the direction is from the south. This change in wind direction is due to the Coriolis Effect
Coriolis effect
In physics, the Coriolis effect is a deflection of moving objects when they are viewed in a rotating reference frame. In a reference frame with clockwise rotation, the deflection is to the left of the motion of the object; in one with counter-clockwise rotation, the deflection is to the right...

. Other factors, like the prevailing wind of a particular day, can also have an effect on the direction.

A wind rose
Wind rose
A wind rose is a graphic tool used by meteorologists to give a succinct view of how wind speed and direction are typically distributed at a particular location. Historically, wind roses were predecessors of the compass rose , as there was no differentiation between a cardinal direction and the wind...

 showing the different wind directions for Perth can be found at the Bureau of Meteorology's website.

Further reading

  • "Origin of term for the sea breeze in Perth still unknown". Sunday Times: (Perth, W.A.), 23 Feb. 1986, p. 49,
  • Masselink, G. (1996). Sea breeze activity and its effect on coastal processes near Perth, Western Australia. Royal Society of Western Australia. Journal of the Royal Society of Western Australia, Vol. 79, part 3 (September 1996) p. 199-205.

External links

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