Developments of Low-
and High-Pressure Centers
•Dynamic Effects: Combined curvature and jetstreak effects produce upper-level convergence on the west side of the trough to the north of the jetsreak, which
add air
mass into the vertical air column and tend to produce a surface high-pressure center. The same combined effects produce a upper-level divergence on the east side of the trough and favors the formation of a low-level low-pressure center.
•Frictional Effect: Surface friction will cause convergence
into the surface low-pressure center after it is produced by upper-level dynamic effects,
which adds air mass into the low center to “fill” and weaken the low center (increase the
pressure)
•Low Pressure: The evolution of a low center depends on the relative
strengths of the upper-level development and low-level friction damping.
•High Pressure: The development of a high center is controlled more by
the convergence of surface
cooling than by the upper-level dynamic effects. Surface friction again tends
to destroy the
surface high center.
•Thermodynamic Effect: heating è surface low pressure; cooling è surface high pressure.