Weather Maps Flashcards
Define isobar and explain its use on a weather map.
The isobar is a feature on a weather map which denotes a line connecting places with equal pressure. Isobars define many of the other features on weather maps. If an isobar is labeled 1022 hPa, the pressure at MSL is 1012 hPa along its entire length. The pressure will be higher or lower on either side of this line. Denoted by a black line.
What is the symbol for wind in the southern hemisphere on a weather map?
A dashed red arrow.
Define anticyclone and explain its use on a weather map.
An anticyclone or a high, is a region of relatively high pressure shown by at least one or more enclosed isobars surrounding the centre where pressures are highest. There is no minimum pressure assigned to regions of high pressure. In theory, a high pressure of 980 hPa could exist if the surrounding pressures were even lower.
Define depression and explain its use on a weather map.
Depressions, also referred to as lows or cyclones, are regions of relatively low pressure shown by more-or-less circular and concentric isobars surrounding the central ‘L’
where pressures are lowest. There is no maximum pressure assigned to a region of low pressure. In theory, a low with a central pressure of 1030 hPa could exist if surrounding pressures were higher.
Define a ridge of high pressure and explain its use on a weather map.
A ridge of high pressure is an extension of the isobars away from the parent high in any direction. Often a high may have several ridges extending from it. Ridges are never marked on a weather map.
Define a trough of low pressure and explain its use on a weather map.
A trough of low pressure is an extension of the isobars away from the parent low such that the pressure at any point along the trough is lower than the pressure on either side. The isobars change direction at the axis of the trough, indicating a sharp change in wind direction. All fronts of any kind mark troughs. Other troughs may be marked by a bold solid black line or on rare occasions, not at all.
Define a col.
A col is a region of almost even pressure between two opposing highs and two opposing lows. It can be likened to a pass or saddle in a mountain range.
What do fronts mark?
Fronts mark the boundaries between airbuses with different temp and moisture characteristics.
List the types of fronts. (4)
Cold front.
Warm front.
Occluded front.
Stationary front (weak).
What is a tropical cyclone?
In the tropics, a different set of terms is used to describe low pressure systems (though direction of circulation is the same). With the right conditions, weak low pressure areas and/or tropical disturbances may develop and deepen to become tropical depressions and with further development, they may become tropical cyclones.
What are the weather characteristics associated with isobars?
Isobars denote both the wind speed and direction on a weather map, although both may be modified significantly. when the isobars cross a land mass.
What is pressure gradient?
Pressure gradient is a measure of the rate of change of pressure over distance.
What is the pressure gradient principle?
The greater the pressure difference between two places, the closer the isobars and the stronger the wind blows.
Describe the weather characteristics associated with anticyclones. Why should you not assume this is always the case?
In an anticyclone, the isobars are more widely spaced than in a low, particularly near the centre, therefore highs are generally associated with light winds and the weather is often described as ‘fine with light winds’.
However, there may be regions within an anticyclone that contains showers and others where you may experience extremely low cloud and/or poor visibility in fog or drizzle.
Define a bomb low and describe the weather associated with it.
A bomb low is a low which has formed very quickly. In these lows, the pressure drops so fast that the wether deteriorates very quickly. They are associated with storm force winds, very low cloud, extremely poor visibility and storm surges on exposed coasts.
