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One of the software algorithms within the
WSR-88D calculates wind direction and speed at various atmospheric
levels. The resulting product is called the Velocity Azimuth
Display (VAD) Wind Profile (VWP), shown at left. The x-axis is
time in UTC (e.g., 1401 UTC is 1001 am EDT); the y-axis is thousands
of ft altitude (e.g., 5 is 5000 ft). Vertical wind shear is crucial
to potential thunderstorm organization and severity. The greater
the shear, the greater the potential for organized severe weather,
assuming storm development. In this figure, radar calculated winds increase substantially
in speed (speed shear) and "veer" from east and southeast in
low-levels to southwest
(directional shear) at mid and upper levels. This deep-layered
strong shear is conducive to severe storms, including supercells
and squall lines/bow echoes. Knowledge of environmental wind
shear assists forecasters in the warning decision process. |
