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

AMV Product Display Information
AMV Level/Height Information: AMVs are grouped into specified layers within each product for display purposes. Layers are given in pressure units of either millibars or hectopascals (which are equivalent).
mb km feet
150 13.7 45000
250 10.5 34000
350 8.0 26500
500 5.5 18000
600 4.3 14000
700 3.0 10000
850 1.5 5000
950 0.5 1500
The AMVs are assigned a level (mb) height. However, for display on the CIMSS Tropical Cyclone Page, the winds are grouped into the layers shown below to allow for easy identification of atmospheric feature heights (e.g. hurricane outflow, jet streams, and upper level circulation centers). Information on wind derivation and specific uses can be found at the links below.
Mid-Upper Level Water Vapor and Infrared Winds
Low-Mid Level Infrared Winds
Low Level Visible/Shortwave Infrared Winds

AMV Speed/Direction Information : Wind vectors are labeled using "wind barbs". Direction is given by the orientation of the post, with speed given by the barbs/flags at the end of the post. The head of the post is the location at which the wind was determined. Speeds are indicated using three symbols : a "flag" (triangle) indicating units of 50, a "full-barb" (long line) indicating units of 10, and a "half-barb" (shorter line) indicating units of 5.
1 knot (nautical mile/hour) is approximately 1.15 miles/hour or 0.51 meters/second.
5 knot wind from the
northwest. One half-barb.
10 knot wind from the
southwest. One barb.
30 knot wind from the
northeast. Three barbs.
35 knot wind from the
southeast. Three barbs and one half-barb.
50 knot wind from the
northwest. One flag.
75 knot wind from the
south-southwest. One flag, two barbs, and one half-barb.
110 knot wind from the
southwest. Two flags and one barb.

Analysis and Products: AMV are extracted automatically every 3 hours from GOES, METEOSAT, and MTSAT data producing near real-time wind fields and the related atmospheric analysis products over all basins - NE/SE/NW Pacific, North Atlantic, East Atlantic and Africa, Indian and W/E Australia. Link to real-time products here.
The wind vectors can be used qualitatively by TC forecasters help visualize the wind field around TCs, as well as quantitatively within numerical weather prediction (NWP) models. Atmospheric analysis products, such as deep layer wind shear, mid layer wind shear, wind shear tendency, vorticity, divergence, and convergence can be also be derived from these wind fields.

For more AMV information, please visit the International Winds Working Group (IWWG) page.