Meteorology 302.1, Spring 2004
Class Notes for April 19, 2004

Kimiko Adachi
Randall Mena

Announcements: No new announcements

Reading Assignment : Instability Website/ Second Half of Divergence Website (Dynamic Lows) Williams: Chapters 5, 6, 7, 8Zebrowski: Chapters 5 pp. 131-135 (completes our reading of Chapter 5); Chapter 8 251-262 (completes Chapter 8); Chapter 9, pp. 263-266; 272-278 (completes our reading of Chapter 9)

Review: Dynamic Pressure Systems
Development of upper level divergence due to wind flow patterns associated with the jet stream, or storm track.

Rule of Thumb:
Divergence tends to occur on the Eastern side of upper air through.
Convergence tends to occur on the Eastern side of upper air ridges.
*Under the area of Divergence the low that forms at the surface is called a Dynamic Low, an example of this would be a Wave Cyclone.

-Troughs and Ridges travel along the Jet Stream or storm track. And Cyclones move with them due to the Divergence that occurs at the top of the Low Pressure System.

Dynamic Lows and Highs : divergence aloft can be associated with the jet stream and developed above 18000feet.

Divergence: the motion that in the neighboring air parcels at given level spreading apart.
Warm air rises up then spreading in the upper troposphere.

Trough : Area of low pressure of atmosphere and extending from the center of a low pressure. it is the opposite of ridge. 300mb Map- shows pattern in center of jet stream and assume wind speeds are the same. There is a rules: Divergence tends to occur on the A ( Eastern) side of upper air trough. Convergence tends to occur on the A side ( Eastern) side of upper ridge

Weather map/Storm Predict Center: Oklahoma - warm air comes from Gulf of Mexico, Cold air comes from Mexico continent

Hand out on Instability- Stability: is the state in which an air parcel finds itself colder than the air surrounding it at the same pressure ( elevation).The air pressure will spontaneously sink.( repose-rest) .

Instability: Air parcels can be forced to rise due to Divergence aloft, for example. But there are situations in which air parcels will spontaneously rise or sink. The general topic heading for the set of processes that govern this spontaneous motion is ìinstability.î Instability is the state in which an air parcel finds itself warmer than the air surrounding it at the same pressure (elevation). The air parcel is buoyant and it will spontaneously rise.

CAPE( convective Available potential Energy): Direct measure of instability