Hail and wind: the two numbers

The notice that set both numbers

Both national severe criteria come from one service change notice, and it is worth seeing in the original because it does two things at once: it changes the hail number and states explicitly that the wind number is not changing.

EFFECTIVE TUESDAY...JANUARY 5 2010 AT 0001 COORDINATED UNIVERSAL
TIME...ALL NWS WEATHER FORECAST OFFICES...WILL OPERATIONALLY CHANGE
THE MINIMUM HAIL SIZE CRITERION...FROM 3/4 INCH /PENNY/ DIAMETER OR
LARGER HAIL TO 1 INCH /QUARTER/ DIAMETER OR LARGER HAIL. NO CHANGE IS
BEING MADE TO THE...WIND CRITERION OF WIND GUSTS EQUAL TO OR IN
EXCESS OF 50 KNOTS /58 MPH/.

Severe is national. Reportable is local.

Those two criteria decide what is severe, everywhere in the country, and they do not move. They do not decide what is worth reporting, which is a different question with a different answer in every forecast area. Each office publishes its own list of what it wants to hear about, and the lists genuinely differ.

Hail is the easy case, because most offices ask for it the same way. This is the wording used by the Mobile and Pensacola office, which is typical:

Hail: Specify the size, location, and time of occurrence.

There is no minimum size in that sentence, and there usually is not. Report all hail, whatever size it is, and let the office decide what crosses a threshold. Pea-sized hail in a place with no radar coverage is a useful data point; it is just not a severe report.

Wind, where the offices diverge

Wind is where a "please report at least" figure would be useful and where the country is least consistent. Some offices publish a number below the severe criterion so that they hear about sub-severe gusts. Others publish none at all and ask for damage instead.

Describing hail so the number survives

1. Give a diameter if you measured one. A number in inches beats every reference object there is.
2. Otherwise give a fixed reference object. Coins are ideal: everybody has one and they do not vary. Quarter, half dollar, golf ball, hen egg, tennis ball, baseball.
3. Never use an object whose size varies. Marbles, pebbles, mothballs, balloons. NWS guidance names marbles specifically, and module 5 lesson 2 shows the awkward fact that an NWS reference table still carries a legacy marble row anyway.
4. Say measured or estimated. This becomes a tag in the record and it is the difference between a data point and an impression.
5. Report the largest stone, and say it is the largest. "Mostly pea size with a few quarters" is a better report than either half of it alone.

The full NWS size chart is reproduced verbatim in module 5 lesson 2, along with the measurement procedure and the reason a photograph beside a coin turns your estimate into somebody else's measurement. It is not reprinted here.

Describing wind when you have no anemometerAn instrument that measures wind speed. The standard exposure is ten metres above open ground, which almost no backyard or vehicle-mounted unit achieves.

Most wind reports are damage reports, because most spotters do not have a calibrated instrument and the ones who do are often measuring in a sheltered back garden. So describe the damage, concretely, and let the survey assign a speed.

• Trees. Limbs down, and roughly what diameter. Trees snapped. Trees uprooted. These are three different things and they mean three different wind speeds.
• Power. Lines down. Poles snapped or leaning. A pole broken off is a much stronger statement than a line down.
• Structures. Roof material lifted, shingles, decking, a wall, an outbuilding. Say what moved and roughly how far.
• Objects. Anything heavy that was moved, and how far. The May 2025 survey recorded a barbecue smoker thrown twenty to thirty yards; that sentence does real work.