Reflectivity
Radar
Latest
Rain, snow and hail across the country now, from every radar in the national network, a new picture every five minutes.
1070 dBZ
Live/Radar
Live radar
Over Guerneville, California, where the map opens. The whole country
Radar across the United States, live: the echo and the storms’ tops every five minutes, the rain falling now, and the rain of the last hour to three days in motion. Below them, the storm analysis: hail and its track, rotation and its track, what is falling, the gauged hour and the radars’ view; the forecast maps: seven days of temperature, wind, rain, snow, sky and thunder; and the sea maps: the waves, the swell and their period off every coast. Each picture opens on its own page, its own map.
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.
Live radar
Seven pictures of the same storms: where rain and snow are now, how tall the storms stand, how hard it falls, and how much has come down.
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
Falling now
Rain rate
Latest
How hard rain and snow are falling at this moment, in inches of water an hour, a new picture every two minutes.
.014 in an hour
Rain total, 1 hour
Last hour
Latest
All the rain of the last hour, in inches: the quickest way to see where the downpours are falling now.
.0112 in
Rain total, 24 hours
Last day
Latest
The rain of the last 24 hours, in inches: where the heaviest totals of the day fell, and which ground is soaked.
.0112 in
Rain total, 48 hours
2 days
Latest
The rain of the last 48 hours, in inches: a slow storm, or two in a row, added up across the country.
.0112 in
Rain total, 72 hours
3 days
Latest
The rain of the last three days, in inches: a long storm whole, and the totals that lead to river flooding.
.0112 in
Storm analysis
Every radar in the country joined into one analysis and measured: the echo nearest the ground, the largest hail and its track, how high a storm’s hail core reaches, the turning of the wind near the ground and its track, what is falling, the last hour’s rain checked by the gauges, and how well the radars see each place. The lower 48, every ten minutes.
Echo near the ground
Lowest echo
Latest
The echo at the lowest height the radars see, every ten minutes: the nearest the radars come to the rain and snow reaching the ground.
1070 dBZ
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.
.255 in
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.
.255 in
Heavy echo above freezing
Hail core
Latest
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.
035,000 ft
Turning wind near the ground
Rotation
Latest
How sharply the wind turns near the ground in each storm, in mph across a mile: where storms are rotating now.
-150150 mph a mile
Turning wind, last hour
Rotation track
Latest
The sharpest turning of the wind near the ground in the last hour, in mph across a mile: the path each rotating storm took.
10150 mph a mile
What is falling
Rain or snow
Latest
What is falling at each place: rain, cold rain, snow, showers and storms, or rain with hail, every ten minutes.
RainHail
Rain, checked by gauges
Gauged hour
Latest
The rain of each hour, in inches, checked against the rain gauges: the truest measure of an hour’s rain, posted about an hour after it ends.
.0112 in
How well the radars see
Radar view
Latest
How well the radars see each place, in percent: where the radar picture can be trusted, and where rain and snow can fall unseen.
0100%
Forecast maps
The forecast for the lower 48, Alaska, Hawaii and Puerto Rico (the snow maps for the lower 48 and Alaska), to seven days ahead, each playing forward from now on the same map as the radar.
Forecast, hour by hour
Temperature
For
The temperature ahead across the lower 48, Alaska, Hawaii and Puerto Rico, hour by hour, for seven days: warm and cold air on the move.
-20110 F
Forecast, each day
Highs
For
The highest temperature of each day for the next seven days: where heat builds and where cold air holds.
-20110 F
Forecast, each night
Lows
For
The lowest temperature of each night for the next seven days: frost, freeze, and warm nights that bring no relief.
-20110 F
Forecast, hour by hour
Wind
For
The wind ahead, in miles an hour, with lines that flow the way it blows: calm, breezy, or strong enough to harm.
075 mph
Forecast, hour by hour
Gusts
For
The strongest gusts ahead, in miles an hour: the brief bursts that bring down limbs and power lines.
075 mph
Forecast, each 12 hours
Chance of rain
For
The chance of rain or snow in each 12 hours, day and night, for seven days: when to expect it, and how surely.
0100%
Forecast amount
Rain, 6 hours
For
How much rain will fall in each 6 hours, in inches, snow as its water: the bands of rain crossing storm by storm.
.0112 in
Forecast total
Rain total
For
All the rain forecast from now to each frame, in inches: the week’s rain adding up, and where it builds highest.
.0112 in
Forecast amount
Snow, 6 hours
For
How much snow will fall in each 6 hours, in inches on the ground: where a storm turns to snow, and how heavy.
.136 in
Forecast total
Snow total
For
All the snow forecast from now to each frame, in inches: a storm’s whole snowfall, and the week’s.
.136 in
Forecast, hour by hour
Sky cover
For
How much of the sky cloud will cover, hour by hour: clear sky is the map itself, the brighter the thicker the cloud.
0100%
Forecast, each 12 hours
Thunder
For
The chance of a thunderstorm in each 12 hours for seven days: where storms are likely, before any radar sees them.
080%
Sea maps
The waves off the coasts of the lower 48, Alaska, Hawaii and Puerto Rico, to seven days ahead: how high they run, the swell among them, and the seconds between, with lines that run the way they travel.
Forecast, every 3 hours
Waves
For
The height of the waves ahead off every coast, in feet, every 3 hours for seven days, with lines that run the way the waves travel.
030 ft
Forecast, every 3 hours
Swell
For
The height of the main swell ahead, in feet: the long, even waves raised by storms far away, and the way they travel toward the coast.
030 ft
Forecast, every 3 hours
Wave period
For
The seconds between the main waves ahead: short and choppy near a wind, long and powerful when a swell has crossed an ocean.
222 s
How the pictures are made
Every radar in the national network, more than 150 of them, sweeps the sky every few minutes, tilting up through a set of angles. The sweeps are joined into one picture of the country on a grid about a third of a mile across, each place taking the lowest beam that sees it clearly. Each picture is checked against the national analysis before it is drawn, and echo it does not confirm (birds, insects, ground clutter, the beam bent back to the ground) is left out. From the same sweeps, the rain falling now and the rain that has fallen are worked out. Storm Station draws each picture in its own colours, in the browser, at every zoom, so the map stays sharp as it is enlarged.
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.
The forecast maps are drawn from the national blend of the forecast models: the models joined into one forecast and corrected against what each place has measured, on a grid 1.6 miles across, the forecast the country’s forecasters start from. Each of its main runs, four a day, is read whole, laid onto the same grid of latitude and longitude as the radar at 2.8 miles a cell, and played forward from now.
The sea maps are drawn from the weather service’s wave model: the waves the wind raises over every ocean, worked out from the wind forecast, on fine grids along the coasts of the United States (a point about every 11 miles) and a coarser one over the open ocean (about every 17 miles). Each of its runs, four a day, is read whole, laid onto the same grid of latitude and longitude as the radar at 2.8 miles a cell, the finest grid first where they meet, and played forward from the hour it starts.
Each of the weather service’s radars on its own, its pictures at four tilts from its lowest up, and the storms it tracks: every radar.
The same pictures, as tiles: /radar/now.json gives the times of the latest frames, /radar/now.json?show=p24h those of a total, and /radar/now.json?show=ft those of the forecast.