Largest hail now
Hail size
Latest
The largest hail each storm is holding now, in inches across, every ten minutes: which storms carry hail, and how large.
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Storm analysis / Heavy echo above freezing
Hail core height, live radar analysis
Over Pennsboro, West Virginia, where the map opens. The whole country
How far above the freezing level each storm holds its heaviest echo, in thousands of feet: the taller the core, the larger the hail it can grow. How to read it.
The rings are the storms the radars detect, the larger ring a severe one; each line runs to where its storm will be in an hour if it keeps its present speed and heading. Rotation and hail are what the radars detect and the analysis measures, not warnings: the official watches and warnings in force are drawn on the map in their own colours and set out in full under Alerts.
What the hail core map shows
How far above the freezing level each storm holds its heaviest echo, 50 dBZ, in thousands of feet. Hail grows where a storm’s updraft carries rain high into air below freezing: the higher that core reaches, the larger the hail the storm can make.
How to read it
- Under 5,000 ft
- A low core; small hail at most.
- 5,000 to 10,000 ft
- Hail likely; some of it severe.
- 10,000 to 20,000 ft
- Large hail likely.
- Over 20,000 ft
- A towering core; giant hail possible.
What it is for
- See which storms are strengthening before the hail reaches the ground.
- Tell a heavy rain storm from a hail storm when both look alike on the radar.
- Read with hail size: a core that climbs means the hail is growing.
How it is made
The storm analysis joins every radar in the national network every two minutes into one picture of the country on a grid about two thirds of a mile across, cleaned of ground clutter, birds and insects, and measures from it what no single radar shows: the largest hail, the turning of the wind, how high a storm’s heavy echo reaches above the freezing level, and what is falling, read with the temperature of the air. Storm Station keeps it every ten minutes for a day, the gauged rain and the radars’ view each hour, and draws it at every zoom from the analysis’s own grid.
A frame every 10 minutes, played as a loop of 1 to 24 hours. As data: /radar/now.json?show=h50, the times of its frames.
In the Field Book
- Cumulonimbus architectureFB-SKY-041
- SupercellFB-EVT-007
- Lapse rates and stabilityFB-ENG-005
Over a state
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With it
Severe AlertsWeather by stateForecast accuracyInstrument atlas
Beside it
Echo tops
Storm tops
Latest
How tall each storm stands, in feet: the higher the top, the stronger the storm and the more likely hail and wind.
560,000 ft
Largest hail, last hour
Hail track
Latest
The largest hail of the last hour at each place, in inches across: the path each hail storm has cut.
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