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.