Discrete Air Masses www assignmentpoint com Location of
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Discrete Air Masses www. assignmentpoint. com
Location of high or low pressure centers provides information about: Wind direction Wind speed Cloud cover Precipitation www. assignmentpoint. com
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Differences in pressure from one location to another causes: 1) Horizontal motions (wind) 2) Vertical motions (convection and subsidence) www. assignmentpoint. com
The change in pressure measured across a given distance is called a "pressure gradient". www. assignmentpoint. com
05 Jan 2009 500 mb Northern Hemisphere Winds blow clockwise out of a high pressure center. www. assignmentpoint. com Winds blow counterclockwise into a low pressure system
High Pressure Centers A high pressure center is where the pressure has been measured to be the highest relative to its surroundings. That means, moving in any direction away from the "High" will result in a decrease in pressure. A high pressure center is indicated on a weather map by a blue "H". www. assignmentpoint. com
Low Pressure Centers A low pressure center is where the pressure has been measured to be the lowest relative to its surroundings. A low pressure center is indicated on a weather map by a red "L" and winds flow counterclockwise around a low in the northern hemisphere. www. assignmentpoint. com
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As air flows out of a high pressure center, air from higher in the atmosphere sinks to replace it. This subsidence produces warming, dissipation of clouds and precipitation As air converges in a low pressure center, it rises and cools. If moist, cooling will cause moisture to condense and form clouds. www. assignmentpoint. com
Pressure level maps (rather than heights) § Surface maps, at Earth surface § 850 mb - available moisture for precipitation, ~1500 m level § 500 mb - middle of atmosphere, troughs (lows) and ridges (highs), ~5500 m level § 300 mb - jet streams at ~9100 m level [The average atmospheric pressure at sea level is ~1000 mb] www. assignmentpoint. com
A line connecting points of equal pressure is called an isobar. www. assignmentpoint. com At every point along a given isobar, the values of pressure are the same.
Pressure reports in Washington are between 1004 mb and 1020 mb. An area of relatively high pressure is centered in western S Pacific, while the pressure increases outward from this region. www. assignmentpoint. com An area of lower pressure is located in western B. C. & Ak.
Troughs: Elongated low pressure centers Ridges: Elongated high pressure centers. The small green numbers are contour labels, which identify the value of an www. assignmentpoint. com isobar.
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Small wave length waves or ripples are called shortwave troughs or ridges. 500 mb forecast for 1/21/1999. Troughs = red; solid lines = 500 mb height contours. www. assignmentpoint. com
Surface Maps Uses available surface data Shows: § Temperature § Weather § Dew point temperature § Cloud cover § Pressure § Wind direction and speed (wind barb) www. assignmentpoint. com
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Observed Temperature station reporting symbol Observed Dew Point Temperature www. assignmentpoint. com
Cloud Cover: The amount of cloud cover at the time the observation. In this case, broken clouds were reported. Surface Maps Sea Level Pressure: The last three digits of the sea level pressure reading in millibars (mb). Wind Barb: The wind barb indicates wind direction and wind speed. www. assignmentpoint. com
Surface Maps Use available surface data Shows: Temperature Weather Dew point temperature Cloud cover Pressure Wind direction and speed (wind barb) www. assignmentpoint. com