Lecture 11:

Occluded fronts and weather symbols

Read Chapter 8: 220-229

Occluded Front: If a cold front catches up to and overtakes a cold front, the frontal boundary between the two air masses.

Cold occlusion

warm occlusion

Idealized life cycle of a mid-latitude cyclone(Polar Front Theory)

Upper-level Waves

Short Waves and Long Waves

The formation of convergence (CON) and divergence (DIV) of air with a constant wind speed (indicated by flags) in the upper troposphere. Circles represent air parcels that are moving parallel to the contour lines on a constant pressure chart. Below the area of convergence the air is sinking, and we find the surface high (H). Below the area of divergence the air is rising, and we find the surface low (L).

As westerly winds blow over a mountain range, the airflow is deflected in such a way that a trough forms on the downwind (leeward) side of the mountain. Troughs and developing storms that form in this manner are called lee-side lows.

(a)Typical paths of winter mid-latitude cyclones. The lows are named after the region where they form.

(b) Typical paths of winter anticyclones.

Surface station symbols