Points on wind speed shear

Courtesy: CIMSS Tropical Cyclone Team
Atmospheric Motion Vectors (AMV) -

 

Atmospheric Shear   Background: Using the gridded atmospheric motion vector output u and v AMV components are averaged over an upper layer (150, 200, 250, 300, and 350 hPa) and a lower layer (700, 775, 850, and 925 hPa). The difference in these averaged components is used to compute the speed shear between the upper and lower layers. The contours show the vector magnitude shear (absolute value). The streamlines indicate the direction of the shear. In the case when a tropical cyclone (TC) is present, the analyses are modified in the storm region by a procedure which removes the storm circulation within a prescribed radii. This allows a more representative depiction of the environmental shear acting on the storm. Uses: The presence/lack of atmospheric wind shear is vital to hindering/supporting TC development. A low shear environment is favorable for tropical cyclone development, while a high shear environment will deter a immature TC region from (further) developing or destroy an already mature TC. Shear values below 10 m/s (20 kts) are considered low enough for tropical cyclogenesis.