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Local Radar- Help Page

Precipitation Mode | Wind Mode | Icon Glossary | Radar Help

How Radar Works

Doppler Radar sends out a beam of energy at a slightly inclined angle. When this beam encounters a partical- whether it be rain, snow, bugs or a wind farm, the energy is scattered. Some of this energy makes its way back to the radar site, where the data is analyzed. A computer converts the energy signal into a useful image that can show precipitation intensity and movement.

Precipitation Mode Basics

Light preciptiation is shown in blue, while extremely heavy precipitation is shown in pink.
The precipitation mode of the radar shows precipitation intesity using a color scale. The brighter the color, the heavier the precipitation. Blue colors correspond to light precipitation. Greens and Yellows correspond to moderate precipitation. Red is heavy precipitation. Pink and white colors indicate extreme precipitation and, possibly, hail.

Snow does not show up as well on radar, so the color scale needs to be interpreted differently. Under the standard color scheme, blue is light or moderate snow, green is heavy snow, and yellow is extremely heavy snow.

Radar "Bugs"

Radar is capable of detecting non-precipitation objects, including dust, bugs, bats and birds. These are called "false echoes", as there is no preciptitation where the radar is indicating. False echoes are most common between sunset and sunrise close to the radar and show up as light blue colors, often in a circular pattern.

Storm Structure

A strong bow echo associated with widespread damaging winds.
The shape of a thunderstorm on radar can give a clue to what threats it may carry. A line of storms that seems to bulge forward is called a bow echo. Bow echoes are caused by strong winds pushing the thunderstorms forward faster than the rest of the line of storms. The strongest winds are often found at the apex of the bow. At times, the ends of the bow can rotate and spawn tornadoes. This is especially true of the north end of the bow. Bow echos can be large, spanning many counties, or more localized events. Lines of storms may have numerous individual bow echos embedded within it.

This classic hook-shaped storm produced a tornado just north of Deposit, NY on May 24, 2004.
A hook echo is present when the storm takes on a hook-like appearance on its rear side. Often, hook echos will be accompanied by a Storm Rotation Icon. Storms with hook echoes are likely rotating and are often capable of producing all types of severe weather. While not all hook echoes produce tornadoes, if a tornado were to form in such a storm, it would form in the hook itself. Hail and damaging winds are possibe on the back side of the hook. This structure is caused by a strong updraft within a rotating storm. As air rushes spiriling into the storm, it pushes precipitation out of the way, causing the precipitation void where the hook is. This type of thunderstorm is also called a supercell.

Wind Mode Basics

Green colors are winds blowing towards the radar while red blows away. The Binghamton radar is in the center of this image. The green/red pattern clearly shows southeast winds over the area, as indicated by the white arrows.
The wind mode of the radar shows wind intensity relative to the radar site using a color scale. The brighter the color, the stronger the wind. Green colors represent winds blowing towards the radar, while red colors represent wind blowing away from the radar.

For Central New York, the radar site is located about 10 miles northwest of Binghamton. Therefore, green colors over the eastern Finger Lakes represent north, northwest or west winds. Red colors will represent south, southeast or east winds. Winds from the northeast and southwest may not show up well for the eastern Finger Lakes.

This radar tends to be more difficult to read, with streaks of red and green intermingled. Unless looking at a specific storm, it is a good idea to just look at the general color patterns, not a specific area.

The green colors on this radar image are winds blowing from the west, while the red are blowing from the east. Placing a pinwheel where the colors meet reveals counter-clockwise rotation. The National Weather Service later confirmed that a tornado was on the ground at this time just to the east of Elmira, NY on July 26, 2012.

Finding Rotation

One of the most useful aspect of the wind mode of radar is identifying rotation in thunderstorms. The closer a thunderstorm is to the radar site, the better the chance of detecting rotation if it is present.

To find rotation in a thunderstorm, look for a couplet of bright green directly adjacent to bright red. This indicates that winds in the thunderstorm are going both away from and towards the radar in a localized area.

Drawing an imaginary arrow towards the radar in the green area and away from the radar in the red area and imagining a pinwheel in between can help give a mental picture of how the storm is rotating. Areas of strong rotation may be enough to prompt tornado warnings and are often accompanied by a Storm Rotation Icon.

If you have any questions regarding radar, feel free to contact me!

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