Storm Track
Where is it going, and when does it get here
Draw the leading edge of a storm and the app tells you where it is heading, when it arrives, and which towns are in the way. It reads the motion off the radar for you.
Using it
Six taps, start to finish
- 1
Open Storm Track
From the map menu. The map stays live behind it.
- 2
Pick Cell or Line
Cell for a single storm. Line for a squall line or any leading edge. This can only be changed before you start drawing.
- 3
Tap the storm
Cell takes one tap. For a line, tap your way along the leading edge, following its shape as closely as you like.
- 4
Finish the line
Tap the last point a second time, or double tap anywhere. On Windows, double click.
- 5
Read it
The projection appears straight away. No confirmation step and no dialog, because the motion has already been worked out.
- 6
Adjust if you disagree
Drag the round handle at the end of the arrow to change the direction or how far ahead you are looking. Drag any point on the edge to move it.
One finger draws, two fingers move the map. There is no mode to switch. Pinch and pan with two fingers at any time, even part way through drawing a line. On Windows, right click and drag still pans as normal.
The readout
What the numbers mean
- 23.7 mi
- How far ahead you are projecting. This is set by where you put the arrow, not by the speed.
- ESE 115°
- The direction the storm is travelling.
- 24 mph
- How fast it is moving.
- You +33m
- Shown only when the storm reaches your own position. It sits at the top of the list and does not hide behind anything.
- 1h
- How long the storm takes to cross the whole projection.
On the map
- The shaded band is where the storm will pass.
- The amber lines across it are time marks. They thin out or fill in as you zoom, so they never pile up on top of each other.
- Amber dots are places in the path, each labelled with its arrival time. In a built up area the app shows the notable ones rather than every suburb, so the map stays readable. The full list is always in the panel.
- The dashed line at the far end is the limit of what you asked for, not a limit of the storm.
Countdown or clock. Times show as a countdown by default. Switch to clock times in Options if you are reading a track out on the air, which is what most people end up doing. A countdown is only true at the moment you read it.
Where the numbers come from
The app does not guess quietly
Speed and direction are both read from the storms the radar is already tracking. Tap the chevron on the readout to see exactly what was used.
Auto
KILN, 4 cells
The motion came from four tracked storm cells near the line you drew, averaged together. A whole squall line is not held hostage to one cell, and a cell heading somewhere unrelated is thrown out rather than dragged into the average.
Manual
Dragged, or set by hand
If the radar has nothing useful nearby, the app says so instead of inventing a number. Same if two groups of storms disagree. You then aim it yourself with the arrow.
Timing
from 10:28 AM frame
Every arrival time counts from the radar image you drew on, not from the clock on your phone. Radar is always a few minutes behind live, and ignoring that would make every town arrive early.
Warning
motion 9m older
The tracking data the radar publishes can lag the picture you are looking at. When it does, the app tells you by how much, so you know how much weight to give the projection.
Options
Everything else, one tap away
- Storm speed
- Override the speed if you think the radar has it wrong. The direction stays credited to the radar, because you have not changed it.
- Cell size
- How wide a single storm is. The projection sweeps that width forward as a corridor.
- Spread
- Off by default. Turn it on and the projection stays rigid for the first half hour, then widens to say the storm could end up further left or right than the straight line suggests.
- Arrival times
- Countdown or clock.
- Share this track
- Produces a written summary you can read out or paste into a net log. Direction, speed, your own arrival, then the towns with times.
- Clear this track
- Removes it. Deliberately kept away from Done, which just puts the tool away and leaves the track on the map.
Worth knowing
What it does not do
It projects a straight line
Real storms turn, speed up, decay and build. The further out you look, the less the projection is worth. Half an hour is confident, ninety minutes is a conversation starter.
It does not know what you know
A projection is arithmetic on a radar image. It has no view of terrain, boundaries, or the storm you can see out of the window, and it does not replace looking at the sky.
It is not a warning
Official watches and warnings come from the National Weather Service and appear on the map separately. This is a tool for thinking with, not an alert.
Place names and locations come from the GeoNames gazetteer, used under CC BY 4.0. Storm motion comes from the NEXRAD Level III storm tracking product for the radar site you have selected.
Storm Track is one tool of many
It sits on top of on-device NEXRAD Level 2 radar, the full Level III product set, satellite, models, and push alerts that fire even when the app is closed.