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Fronts and Temperature Advection

Fronts and Temperature Advection. Weather Discussion: 26 February, 2008. Outline. Definitions Types and general characteristics of ‘idealized’ fronts Today’s outlook. Source Material : Meteorology Today, An Introduction to Weather, Climate and the Environment by C. Donald Ahrens.

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Fronts and Temperature Advection

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  1. Fronts and Temperature Advection Weather Discussion: 26 February, 2008

  2. Outline • Definitions • Types and general characteristics of ‘idealized’ fronts • Today’s outlook Source Material: Meteorology Today, An Introduction to Weather, Climate and the Environment by C. Donald Ahrens

  3. What is a front? A transition zone between 2 air masses of different densities

  4. COLD WARM cold temperature advection warm temperature advection 5 10 15 And Temperature Advection? Horizontal transport of air with certain temperature characteristics

  5. cool cold warm Temperature Advection • Expect to experience T advection in the vicinity of extratropical cyclones • Can affect vertical velocity field

  6. Air Masses Extremely large body of air whose properties of temperature and humidity are fairly similar in any horizontal direction at any given altitude

  7. Air Mass Classification humidity temperature

  8. Air Mass – Source Regions • Source Region: region where air mass originates • Usually areas dominated by high pressure, generally flat, of uniform composition and light winds • Midlatitudes NOT a good source region → transition zone where air masses clash

  9. Air Mass – Source Regions cA mP mP cP mT cT

  10. A Front as a Transition Zone

  11. Stationary Front Trough of low pressure that has essentially no movement

  12. Cold Front cold, dry stable polar air is replacing warm, moist unstable subtropical air

  13. 1. Temperature 2. Humidity 3. Wind Shift 4. Pressure Tend. Cold Front Cold, dry stable polar air replacing warm, moist unstable subtropical air 5. Clouds/Precip.

  14. Not So Easy! Sanders and Doswell (1995)

  15. Cold Front • Cold, dense air wedges under warm air • Steep leading edge • Narrow band of thunderstorms • Relatively fast moving

  16. Cold Front

  17. Warm Front Advancing warm, moist subtropical air replaces the retreating cold, maritime polar air

  18. Warm Front 1. Temperature 2. Humidity 3. Wind Shift 4. Pressure Tend. 5. Clouds/Precip.

  19. Warm Front • Warm air rides up and over cold air • Gentler slope, slower moving, more stable

  20. Warm Front Weather changes less noticeable than for cold front

  21. Occluded Front • Cold front catches warm front • 2 types: • Cold Occlusion: air behind the cold front is more dense than the air ahead of the warm front • Warm Occlusion: the opposite

  22. Cold Occlusion • As front approaches, weather similar to warm front • Frontal passage similar to cold front • Most violent weather usually found near triple point

  23. Warm Occlusion • Weather similar to warm front • Due to the mild winter air over the North Atlantic, common over Europe

  24. Occluded Front

  25. Satellite Identification Precipitation in a narrow band for cold front, much wider band associated with warm and occluded front

  26. Cyclone Lifecycle

  27. Today’s Weather Chart

  28. Forecast θe & Wind at 850 mb Rain

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