Inside the Storm: Decoding Radar’s Secrets – From Bow Echo to Debris Ball
Radar meteorology is one of the most important tools for monitoring and predicting severe weather events. By analyzing radar data, meteorologists can identify specific features that indicate the presence of dangerous storms, such as supercell thunderstorms and tornadoes. In this article, we will discuss some of the most common radar features to look for when assessing severe weather threats.
- Hook Echo:
A hook echo is a distinctive radar signature that often indicates the presence of a supercell thunderstorm capable of producing tornadoes. This feature appears as a hook-shaped appendage extending from the main storm cell on the radar display. The hook shape is formed by the rotation of the storm’s updraft, which can cause rain and hail to wrap around the updraft, creating a hook-like appearance.
When a hook echo is detected, it is essential to monitor the storm closely, as it has a higher likelihood of producing a tornado. The tightness and persistence of the hook echo can provide clues about the storm’s intensity and potential for tornadogenesis. A tight, well-defined hook echo that persists for an extended period is more likely to be associated with a strong, long-lived tornado.
- Bow Echo:
A bow echo is a radar signature that indicates the presence of a strong, linear wind storm known as a derecho. This feature appears as a bow-shaped line of storms on the radar display, with the apex of the bow pointing in the direction of the storm’s movement. Bow echoes are often associated with widespread damaging winds, which can exceed 100 mph in extreme cases.
The formation of a bow echo is related to the development of a strong rear-inflow jet behind the main line of storms. This jet of fast-moving air descends to the surface and spreads out, causing the line of storms to bow outward. As the rear-inflow jet continues to strengthen, it can lead to the formation of embedded circulations within the line, known as mesovortices, which can produce brief, spin-up tornadoes.
- Debris Ball:
A debris ball, also known as a tornado debris signature (TDS), is a radar feature that indicates the presence of lofted debris associated with a tornado. This signature appears as a localized area of high reflectivity (bright colors) on the radar display, often coinciding with the location of a hook echo or other tornado-related features.
The debris ball is caused by the tornado lofting large amounts of debris, such as trees, building materials, and other objects, high into the air. When the radar beam intersects this debris, it produces a strong return signal, which appears as a bright, concentrated area on the radar display. The presence of a debris ball is a strong indication that a tornado is causing damage on the ground.
- Three-Body Scatter Spike (TBSS):
A three-body scatter spike is a radar signature that can indicate the presence of a large hail core within a thunderstorm. This feature appears as a narrow, linear spike of high reflectivity extending radially outward from the storm on the radar display. The TBSS is caused by the radar beam reflecting off a layer of large hailstones and then reflecting again off the ground before returning to the radar.
The presence of a TBSS suggests that the storm contains a significant amount of large hail, which can cause extensive damage to property and pose a serious risk to public safety. When a TBSS is detected, it is important to issue warnings for large hail and to advise people to seek shelter immediately.
- Bounded Weak Echo Region (BWER):
A bounded weak echo region is a radar feature that indicates the presence of a strong, persistent updraft within a thunderstorm. This feature appears as a localized area of low reflectivity (dark colors) surrounded by higher reflectivity values on the radar display. The BWER is caused by the strong updraft lifting precipitation particles high into the storm, creating a region of relatively low radar returns.
The presence of a BWER suggests that the storm has a powerful updraft, which can support the formation of large hail and tornadoes. When a BWER is detected, it is important to monitor the storm closely for the development of other severe weather signatures, such as hook echoes or debris balls.
- Inflow Notch:
An inflow notch is a radar signature that indicates the presence of strong, localized inflow into a thunderstorm. This feature appears as a small, localized area of low reflectivity (dark colors) along the leading edge of the storm on the radar display. The inflow notch is caused by the rapid inflow of warm, moist air into the storm, which can fuel the development of strong updrafts and severe weather.
The presence of an inflow notch suggests that the storm is actively ingesting warm, moist air, which can lead to rapid intensification and the formation of severe weather hazards, such as large hail, damaging winds, and tornadoes. When an inflow notch is detected, it is important to monitor the storm closely for the development of other severe weather signatures.
- Rear Inflow Notch (RIN):
A rear inflow notch is a radar feature that indicates the presence of strong, localized inflow into the back side of a thunderstorm. This feature appears as a small, localized area of low reflectivity (dark colors) along the rear flank of the storm on the radar display. The RIN is caused by the rapid inflow of cooler, drier air into the storm, which can help to strengthen the storm’s updraft and increase the potential for severe weather.
The presence of a RIN suggests that the storm is actively ingesting cooler, drier air on its back side, which can lead to the formation of a strong rear-flank downdraft (RFD). The RFD can help to tighten the storm’s rotation and increase the risk of tornadogenesis. When a RIN is detected, it is important to monitor the storm closely for the development of hook echoes, debris balls, and other tornado-related signatures.
- Hail Spike:
A hail spike is a radar signature that indicates the presence of a strong updraft capable of producing large hail. This feature appears as a narrow, vertical spike of high reflectivity extending upward from the storm on the radar display. The hail spike is caused by the strong updraft lofting large hailstones high into the storm, where they can grow even larger before falling back to the ground.
The presence of a hail spike suggests that the storm has a powerful updraft that can support the formation of large, damaging hail. When a hail spike is detected, it is important to issue warnings for large hail and to advise people to seek shelter immediately.
