The Fremantle Doctor, the Freo Doctor, or simply The Doctor, is the Western Australian vernacular term for the cooling afternoon sea breeze that occurs during summer months in south west coastal areas of Western Australia. The sea breeze occurs because of the major temperature difference between the land and sea.
The name was in use as early as the 1870s and was similar to equivalent terms for winds that occurred in South Africa and the West Indies. [1]
During summer months, the Fremantle Doctor consistently blows from the southwest along the southern half of the west coast, starting between 10 am and 3 pm. It can penetrate as far inland as 100 kilometres (60 mi), reaching York in the early evening.
In Perth, 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, 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 (28 and 37 km/h; 17 and 23 mph).
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.
It was known to have an impact on cricket games being played at the WACA Ground, particularly helping fast and medium swing bowlers by making it hard for a batsman to play at the ball, while also providing a cooling breeze to the players on the field. [2]
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 is a bit warmer. Though October and November are not as warm, the ocean 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 is usually cooler than the ocean, 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 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. [3] Other factors, like the prevailing wind of a particular day, can also have an effect on the direction.
A wind rose showing the different wind directions for Perth can be found at the Bureau of Meteorology's website. [4]
The often intense Perth heat is famously eased in the afternoon by the Fremantle Doctor, a breeze which sweeps in along the Swan River.
The reason for the obliquely-onshore sea breeze system in Perth may be attributed to the interaction between the sea breeze and the geostrophic winds associated with the synoptic weather patterns. The Perth sea breeze system in sensu stricto is southwesterly due to a combination of pressure gradient flow (owing to differential heating) and the Coriolis force (Kepert and Smith, 1992). The Coriolis force has no influence on the wind direction at the start of the sea breeze, but may induce a small anti-clockwise shift in the wind direction of about 200 during the sea breeze.
Surface weather analysis is a special type of weather map that provides a view of weather elements over a geographical area at a specified time based on information from ground-based weather stations.
Upwelling is an oceanographic phenomenon that involves wind-driven motion of dense, cooler, and usually nutrient-rich water from deep water towards the ocean surface. It replaces the warmer and usually nutrient-depleted surface water. The nutrient-rich upwelled water stimulates the growth and reproduction of primary producers such as phytoplankton. The biomass of phytoplankton and the presence of cool water in those regions allow upwelling zones to be identified by cool sea surface temperatures (SST) and high concentrations of chlorophyll a.
Physical oceanography is the study of physical conditions and physical processes within the ocean, especially the motions and physical properties of ocean waters.
Atmospheric circulation is the large-scale movement of air and together with ocean circulation is the means by which thermal energy is redistributed on the surface of the Earth. The Earth's atmospheric circulation varies from year to year, but the large-scale structure of its circulation remains fairly constant. The smaller-scale weather systems – mid-latitude depressions, or tropical convective cells – occur chaotically, and long-range weather predictions of those cannot be made beyond ten days in practice, or a month in theory.
A sea breeze or onshore breeze is any wind that blows from a large body of water toward or onto a landmass. By contrast, a land breeze or offshore breeze is any wind that blows from a landmass toward or onto a large body of water. The term offshore wind may refer to any wind over open water. Sea breezes and land breezes are both important factors in coastal regions' prevailing winds.
A high-pressure area, high, or anticyclone, is an area near the surface of a planet where the atmospheric pressure is greater than the pressure in the surrounding regions. Highs are middle-scale meteorological features that result from interplays between the relatively larger-scale dynamics of an entire planet's atmospheric circulation.
In meteorology, a low-pressure area, low area or low is a region where the atmospheric pressure is lower than that of surrounding locations. Low-pressure areas are commonly associated with inclement weather, while high-pressure areas are associated with lighter winds and clear skies. Winds circle anti-clockwise around lows in the northern hemisphere, and clockwise in the southern hemisphere, due to opposing Coriolis forces. Low-pressure systems form under areas of wind divergence that occur in the upper levels of the atmosphere (aloft). The formation process of a low-pressure area is known as cyclogenesis. In meteorology, atmospheric divergence aloft occurs in two kinds of places:
In meteorology, prevailing wind in a region of the Earth's surface is a surface wind that blows predominantly from a particular direction. The dominant winds are the trends in direction of wind with the highest speed over a particular point on the Earth's surface at any given time. A region's prevailing and dominant winds are the result of global patterns of movement in the Earth's atmosphere. In general, winds are predominantly easterly at low latitudes globally. In the mid-latitudes, westerly winds are dominant, and their strength is largely determined by the polar cyclone. In areas where winds tend to be light, the sea breeze/land breeze cycle is the most important cause of the prevailing wind; in areas which have variable terrain, mountain and valley breezes dominate the wind pattern. Highly elevated surfaces can induce a thermal low, which then augments the environmental wind flow.
A southerly buster is the colloquial name of an abrupt southerly wind change in the southern regions of New South Wales and Victoria, Australia, which approaches from the southeast, mainly on a hot day, bringing in cool, usually severe weather and a dramatic temperature drop, thus ultimately replacing and relieving the prior hot conditions. Marking the boundary between hot and cool air masses, a southerly buster is sometimes represented by a roll-up cloud perpendicular to the coast, which appears from the south and coexists with the wind change, though sometimes there is little visual signal of the southerly's arrival.
Swanbourne is a western coastal suburb of Perth, Western Australia, located within the City of Nedlands. It is an affluent, upper middle class residential area with older Federation style homes, many being renovated. The suburb was established in the late 19th century. New housing estates have been built recently through the redevelopment of areas such as the Swanbourne Senior High School, Swanbourne Primary School and Lakeway Drive-In Cinema sites.
Berg wind is the South African name for a katabatic wind: a hot dry wind blowing down the Great Escarpment from the high central plateau to the coast.
The climate of Sydney, Australia is humid subtropical, shifting from mild and cool in winter to warm and hot in the summer, with no extreme seasonal differences as the weather is moderated by proximity to the ocean, although more contrasting temperatures are recorded in the inland western suburbs. Despite the fact that there is no distinct dry or wet season, rainfall peaks in the first few months of the year and is at its lowest just around the middle of the year, though precipitation can be erratic throughout the year. Precipitation varies across the region, with areas adjacent to the coast being the wettest. According to the Bureau of Meteorology, Sydney falls in the temperate climate zone which has warm to hot summers and no dry season. Sydney's plant hardiness zone ranges from zone 11a to 9b throughout the metropolitan area. Under the Holdridge Life Zones classification, eastern Sydney falls in the Subtropical Moist Forest zone and the western suburbs in the Subtropical Dry Forest zone.
Wind is the natural movement of air or other gases relative to a planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few hours, to global winds resulting from the difference in absorption of solar energy between the climate zones on Earth. The two main causes of large-scale atmospheric circulation are the differential heating between the equator and the poles, and the rotation of the planet. Within the tropics and subtropics, thermal low circulations over terrain and high plateaus can drive monsoon circulations. In coastal areas the sea breeze/land breeze cycle can define local winds; in areas that have variable terrain, mountain and valley breezes can prevail.
Thermal lows, or heat lows, are non-frontal low-pressure areas that occur over the continents in the subtropics during the warm season, as the result of intense heating when compared to their surrounding environments. Thermal lows occur near the Sonoran Desert, on the Mexican plateau, in California's Great Central Valley, in the Sahara, in the Kalahari, over north-west Argentina, in South America, over the Kimberley region of north-west Australia, over the Iberian peninsula, and over the Tibetan plateau.
Tasmania has a cool temperate climate with four distinct seasons. The highest recorded maximum temperature in Tasmania is 42.2 °C (108.0 °F) at Scamander on 30 January 2009, during the 2009 southeastern Australia heat wave. Tasmania's lowest recorded minimum temperature is −14.2 °C (6.4 °F) on 7 August 2020, at Central Plateau.
The Monsoon of South Asia is among several geographically distributed global monsoons. It affects the Indian subcontinent, where it is one of the oldest and most anticipated weather phenomena and an economically important pattern every year from June through September, but it is only partly understood and notoriously difficult to predict. Several theories have been proposed to explain the origin, process, strength, variability, distribution, and general vagaries of the monsoon, but understanding and predictability are still evolving.
Perth, the capital city of the state of Western Australia, has a Mediterranean climate, with hot, dry summers and mild, wet winters. February is the hottest month of the year, with an average high of 31.6 °C (88.9 °F), and July is the coldest month of the year, with an average low of 7.9 °C (46.2 °F). 77% of rain in Perth falls between May and September. Perth has an average of 8.8 hours of sunshine per day, which equates to around 3,200 hours of annual sunshine, and 138.7 clear days annually, making it the sunniest capital city in Australia.
This glossary of meteorology is a list of terms and concepts relevant to meteorology and atmospheric science, their sub-disciplines, and related fields.
A Wind generated current is a flow in a body of water that is generated by wind friction on its surface. Wind can generate surface currents on water bodies of any size. The depth and strength of the current depend on the wind strength and duration, and on friction and viscosity losses, but are limited to about 400 m depth by the mechanism, and to lesser depths where the water is shallower. The direction of flow is influenced by the Coriolis effect, and is offset to the right of the wind direction in the Northern Hemisphere, and to the left in the Southern Hemisphere. A wind current can induce secondary water flow in the form of upwelling and downwelling, geostrophic flow, and western boundary currents.