What not to report from a screen
- View
Radar is for knowing where to be and what is coming. It is not a source of observations, and a report sourced from it is not a spotter report.
In this lesson you will
- Use radar for situational awareness and positioning.
- Explain why radar complements rather than replaces observation.
- State what must never be reported from radar alone.
- Identify the common amateur misinterpretations.
What radar is genuinely good for, to you
Everything in this module has a use, and the uses are mostly about where you are and what is about to arrive, which is module 8 material with better inputs.
- Knowing what is coming and roughly when, so you are in a sensible place beforehand rather than reacting.
- Choosing standoff distance, with lesson 3's latency arithmetic applied so your margin accounts for the picture being old.
- Watching your escape routes, because a second line of storms arriving behind you is visible on radar long before it is visible to you.
- Knowing which part of the storm you are looking at, so what you describe in a report is anchored to structure rather than to a direction.
- Knowing when to stop, which is the module 8 lesson 8 decision and is much better informed with radar than without.
The line
Report what you observed. Never report what you saw on radar. A spotter report is a statement that a human being witnessed something at a place and a time. A radar interpretation is not that and cannot become that by being confident. Radar-only reports are flagged on this platform, and the reason is not pedantry: the entire value of the network is that it supplies the one thing radar cannot.
The field guide puts the same point from the other end: "Radar is an excellent tool, but it is just that: one tool among many that NWS uses." The office already has the radar. It has it at full resolution, sooner than you do, with training you do not have. What it does not have is your eyes.
| You saw on radar | You may report |
|---|---|
| A hook echo | Nothing. Go and look. Report the cloud features you can actually see |
| A velocity couplet | Nothing. It is rotation aloft |
| A debris signature | Nothing, though it is a very good reason to look hard and to be somewhere safe |
| 60 dBZ overhead | Nothing. But go outside and measure the hail, which you may then report |
| A bow echo approaching | Nothing yet. Afterwards, report the wind damage you can see |
The pattern is the same in every row. Radar tells you where to point your attention. The observation is still something you have to make.
Four amateur misinterpretations
- Calling a tornado from a hook. The hook is precipitation wrapping around rotation, thousands of feet up, and most hooks produce no tornado. Lesson 5.
- Reading gate-to-gate shear at long range. At 100 km the sample volume is kilometers wide and a tight circulation is averaged away, so a convincing couplet there is either large or is not what you think. Lessons 2 and 6.
- Treating purple as severity. On many color scales purple is range-folded data, meaning no data. It is the absence of a measurement being read as an extreme one. Lesson 6.
- Trusting a composite as a surface observation. It is a column maximum with the height thrown away. Lesson 4.
Reporting scud as a tornado. The field guide has the worked example: "Not a tornado! Scud cloud formed on outflow... there was no rotation seen... nor was any indicated by radar." Module 4 is the lesson on telling them apart. It appears here because the radar was the corroborating evidence that it was not a tornado, which is exactly the role radar should play in a spotter's thinking: a check on your interpretation, not a substitute for your observation.
Apps
This course recommends no product and endorses none. What it can tell you is what to require of whichever one you use.
- A visible timestamp on every frame. Lesson 3. An app that hides the age of its data is unusable for positioning.
- Base products, not only composites. If you cannot get base reflectivity and base velocity, you cannot do most of this module.
- Storm-relative velocity, and ideally control over the assumed storm motion.
- The dual-pol fields, without which lesson 7 is theory.
- Honest handling of missing data, so range folding looks like absence rather than like a value.
Warning polygons
One last practical item. A warning polygon is a forecast of where the hazard will be during the valid period, not a drawing of where it is now. It has a start and an end time, and being just outside one is not a statement that you are safe. Module 1 lesson 5 covers the anatomy of the product and module 7 lesson 5 covers how your report can change one while it is running.
Check yourself
Your app shows a textbook hook echo with a tight velocity couplet two miles west of you. You can see nothing but rain and low cloud. What do you report?
- Nothing yet. Get somewhere safe and report only what you can actually observe
- A tornado two miles west, citing the hook and couplet as the source
- A rain-wrapped tornado, since the rain explains why you cannot see it
- A funnel cloud, as the conservative version of what the radar shows
Hint
Every wrong answer here has the same defect, and it is not about tornado identification.
Answer
Nothing yet. Get somewhere safe and report only what you can actually observe
All three wrong answers report a radar interpretation as an observation, which is the one thing this module forbids. The office already has that radar data, in better form and sooner. Your value is the thing it does not have, and in this situation the honest answer is that you cannot see anything, which is itself worth saying if asked.