Lowest radar echo, live analysis

What the lowest echo map shows

The echo at the lowest height the radars see at each place, from every radar in the national network joined into one analysis and cleaned of ground clutter, birds and insects. It is the nearest the radars come to what is reaching the ground; far from a radar, its lowest beam passes thousands of feet over it.

How to read it

10 to 20 dBZ

Drizzle, flurries or the faint edge of a shower.

20 to 35 dBZ

Light rain or steady snow.

35 to 45 dBZ

Moderate rain, the body of a storm.

45 to 55 dBZ

Heavy rain, a thunderstorm’s core.

Over 55 dBZ

Torrential rain, and hail likely.

What it is for

• Compare with the radar: rain the radar shows high up that is gone here may be drying before it lands.
• See the rain under a storm, not the hail and rain held aloft.
• Read a winter storm’s snow near the ground.

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=low, the times of its frames.