Presentation on theme: "Regents Earth Science HIGH AND LOW PRESSURE SYSTEMS WEATHER SYSTEMS UNIT By the end of this class, you will be able to: *Compare and contrast high and."— Presentation transcript:
Regents Earth Science HIGH AND LOW PRESSURE SYSTEMS WEATHER SYSTEMS UNIT By the end of this class, you will be able to: *Compare and contrast high and low pressure systems *Identify areas of high and low pressure on a weather map
DO NOW: What’s in a letter? Take a moment to think about what each letter stands for when used on a weather map
High PressureLow Pressure Type of phenomenon Weather system Determined by… Changes in air pressure Moving inward on isobars… Pressure IncreasesPressure Decreases Density of air Higher (increases)Lower (decreases) Representation on a map H (typically blue)L (typically red) Motion of air Clockwise, air sinksCounterclockwise, air rises Also known as… AnticycloneCyclone Motion of air causes a zone of… DivergenceConvergence Stability of atmosphere StableUnstable Typical weather Clear sky Dry Stormy Compare/Contrast Chart High and Low Pressure
Fronts are shown by lines with symbols that show the type of front and the direction of movement
Fronts- Warm front: an area where a warm air mass is replacing a cooler air mass
What to Expect Before the front passes: cool or cold temperatures, a falling barometer, an increase and thickening in clouds, light-to- moderate precipitation, winds from the south-southeast, rise in dewpoint
After the front has passed: Warmer and more humid weather conditions, clearing clouds, a brief rise in pressure, winds from the south-southwest, high dewpoint
NOTE: “A high dewpoint” means that the temperature and dewpoint are close together. (ex. 32F temp, 30 F dewpoint) “A low dewpoint” means that the temperature and dewpoint are far apart (ex. 55F temp, 30F dewpoint) There is ALWAYS a dewpoint!
Cold Front Cold front: an area where a cold air mass is replacing a warmer air mass
What to Expect Before the Front: winds from the south-southwest, warm temperatures, a falling barometer (dropping pressure), an increase in clouds, a short period of precipitation and a high dew point
After the Front: winds from the west-northwest, a drop in temps, a rise in pressure, showers followed by clearing skies, and a falling dewpoint
Occluded Fronts Occluded Front: occur when warm air is pushed above Earth’s surface by cooler air that is closing in from both sides
A developing cyclone usually has a warm front and a faster moving cold front that wraps around the storm. An occluded front forms when cold air behind the cold front catches up to the warm front, which is stuck behind the cool air already in place What to expect: A change in temp., dewpoint or wind direction is possible
Movement of Weather Revisited Most of the tracks (paths) follow a southwest to northeast pattern because of the United States’ location in the prevailing southwest wind belt Video: Tying it Together!: Jet Streams, Pressure Systems and FrontsTying it Together!: Jet Streams, Pressure Systems and Fronts
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