Week 9-10: Winds and Weather
- What main factors determine why the wind blows? (Hint, during what seasons/locations are winds strongest?)
- Where does the Geostrophic Wind balance work? Under what circumstances would it fail?
- Upper-level support for a cyclone requires horizontal divergence. Why is this?
- Why is a ridge at 500mb generally associated with warm air?
- Pressure Gradient Force
- Coriolis Force
- Geostrophic Wind and Gradient Wind
- Rossby wave
- Mesoscale and Synoptic-scale
- Blocking patterns
- Jet stream and jet streak
- Chapter 8 and pages 290-296 of Ch 9 of Moran
- Geostrophic Wind relationships (pages 1-8)
Here is a recipe to help you determine the geostrophic and surface wind directions:
- The first thing that you should focus on is the geostrophic wind direction. Remember that the geostrophic wind always follows the isobars, with lower pressure on the left. If you're finding the wind direction for an upper-level wind (not at the surface), this is all you need to do. Remember that wind direction is always given as the direction that it is blowing from.
- Next, if you are finding a surface wind direction, you need to take the geostrophic wind (which you just determined) and turn it inward towards lower pressure. This is called the crossing angle -- it's the angle that the wind crosses the isobars. Remember that the crossing angle is typically around 30 degrees, but can range from as little as 10 degrees (over water) to more than 45 degrees (over mountainous terrain). Finally, don't forget to express the wind direction as the direction that it is blowing from.