This page displays several versions of a combined IVT, AR, and AR Scale figure for the NCEP GFS forecast initialized at 00 UTC each day. Figures in the first two rows include:

• Vertically Integrated Water Vapor Transport (IVT) shaded with magnitude in units of kg m^-1 s^-1.
• Atmospheric Rivers (ARs) identified by the Tracking Atmospheric Rivers Globally as Elongated Targets (tARget) version 4 AR detection algorithm by Guan and Waliser outlined in black.
• AR Scale values (first row) shown as colored dots on the map at every fourth lat/lon grid point. The Modified AR Scale (second row) is an experimental version of the AR Scale that treats values from the original AR Scale the same while adding in lower IVT events that would be identified using the Enhanced AR Scale.

The remaining 5 rows provide additional information about whether each IVT object meets the tARget criteria, explaining why a given object is identified as an AR or otherwise rejected. IVT objects that meet all 3 criteria listed below are identified as an AR (outlined in black), while those that fail one or more criteria are rejected (outlined in red). There are 5 IVT percentile iterations, meaning that an object may be rejected at a lower percentile and then the smaller core region at a higher percentile may meet the AR requirements. Objects crossing the equator or with an area smaller than 200,000 km² are also filtered out (not shown). Objects with a centroid located within the map bounds are included in the table below the figure. The description of the tARget criteria is somewhat simplified here: for more details refer to Guan and Waliser 2024.

• Standard deviation of IVT directions within the object does not exceed 67.5° (IVT arrows are shown where IVT is at least 100 kg m^-1 s^-1 at every eighth lat/lon grid point)
• Sum of axis segments where the poleward IVT component exceeds 25% of the total IVT is longer than 1000 km (axis segments meeting the requirement are shaded blue; segments failing the requirement are shaded white)
• Length exceeds 2000 km and the length-to-width ratio is greater than 2 (object axis, or length, is shaded as described above; object transect, or width, is shaded gray)

The figures on this page are experimental and subject to change, they are provided “as is” and are intended for research purposes only (disclaimer).