Amplitudes of 1-15 hPa/MB and Wavelengths of 50-500 KM (Uccellini
and Koch, 1987) Periods of 1-4 HR
Most likely energy source mechanisms are latent heat release in deep
convection and shear instability in which waves can extract energy from
the Jet Stream when vertical wind shear is sufficiently strong to reduce
the Richardson number below 0.25. Alternatively wave energy loss
can be prevented by an efficient wave duct, which appears to be the most
prevalent of the three mechanisms described.
Strongest upward motions with Gravity Waves occur just following
the surface pressure trough and lead to maximum precipitation rates just
ahead of the ridge.
Gravity waves typically form within or near the back edge of a precipitation
Recent studies indicate that Gravity Waves may occur as frequently
as 34% of the time in the Central US during the Winter months.
Current poor understanding of gravity waves and acknowledged skepticism
of their existence stems from the fact that it is both difficult and tedious
to conduct a study of even a single event. In addition forecasters have
often been mislead by the existence of large scale gravity waves in 2 noteworthy
This is changing due to an increase in the spatial and temporal
resolution of meteorological data
Rapid pressure falls associated with a strong gravity wave mislead forecasters
into believing that secondary cyclogenesis was taking place along a coastal
front (Bosart and Seimon, 1988).
Schneider (1990) presented a case which occurred in Illinois in December
1987 in which the minimum pressure associated with one of the wave troughs
was lower than that of the synoptic scale cyclone through which it passed.
The isallobaric fall region associated with the wave was noted by forecasters,
who lacking knowledge of the wave, mistakenly attempted to correct the
model forecasts of the track.
Barnes et al 1996 has shown that the 29 KM Meso-Eta produces coherent
gravity waves with wavelengths under 300 KM and that these waves can dominate
the QG field.
5 MIN sampling by ASOS - The availability of high temporal resolution
data from ASOS is an important factor in the determination of whether
an operational detection of gravity waves is feasible.
ASOS data is expected to meet that need. ASOS allows for the automated
bandpass filtering of digital pressure time series data.
6 MIN Wind Profiles
WSR-88D VWP/VAD winds