|SKEW-T: A LOOK AT 0-3 KM SHEAR
METEOROLOGIST JEFF HABY
1. What is 0-3 KM SHEAR?
0-3 KM SHEAR is
speed shear between the surface and 3 km above the surface.
2. How is 0-3 KM SHEAR determined?
The formula is the change in wind speed (m/s) divided by the change in distance (m). This number is then multiplied by
1000 to simplify the number. The units come out to s^-1. These units result from m/s divided by m.
Example: The surface wind speed is 7 m/s while the wind speed 3 km up is 25 m/s. This gives a change in
wind speed of 25 - 7 = 18 m/s. The change in distance is 3 km = 3,000 m
18/3,000 = 0.006 s^-1 * 1000 = 6 units of shear
3. Operational significance of 0-3 KM SHEAR:
|0 to 3 ||Weak||4 to 5 ||Moderate
||6 to 8 ||Large
UPDRAFT: Speed shear
tilts a storms updraft-- thus increasing its longevity.
HELICITY: Strong speed shear is one factor than leads to high Helicity values.