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Cooperative Institute for Meteorological Satellite Studies / University of Wisconsin-Madison
CIMSS Tropical Cyclone Team
Atmospheric Motion Vectors (AMV) - Product Description

Mid-Level Atmospheric Shear
Background: Using the gridded atmospheric motion vector output u and v AMV components are averaged over a mid troposphere layer (400, 500, and 600 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 lower and mid layers. The contours show the vector magnitude shear (absolute value, kts). 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 20 kts (10 m/s) are considered low enough for tropical cyclogenesis.
For more AMV information, please visit the International Winds Working Group (IWWG) page.
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