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Preliminary reports and the official record: how the Wire's storm desk counts
Every issue of The Roofing Wire reports what the Storm Prediction Center logged that week. They are real, they are fast, and they are provisional. This page explains where the weekly figures come from, how they differ from the official federal record, and what a roofing contractor should and should not read into them.
The weekly numbers are SPC preliminary reports
The Wire's Notable Weather and The Numbers departments count reports from the Storm Prediction Center. Issue 014, for example, counted 151 hail, 1,858 wind and 19 tornado reports over seven convective days, and says plainly that these are preliminary spotter reports, not damage counts.
SPC describes how its lists are built on its frequently asked questions page:
- Source. Listings on the SPC Storm Reports page are collected automatically from thunderstorm-related local storm reports sent by National Weather Service offices.
- Gaps. If no local storm report was issued, or it arrived more than 10 days after the event, it does not appear. SPC says its list is preliminary and likely does not contain every severe report for any event.
- Confirmation. Storm surveys may be needed to confirm a tornado, set its EF rating, or decide whether damage came from a tornado or straight-line wind.
- The day. Each daily page covers reports received from 1200 UTC to 1159 UTC the next day, the span forecasters call a convective day.
- Duplicates. Since March 8, 2011, SPC has published unfiltered reports, removing only identical duplicates. Its older filtered method treated hail and wind reports in the same county within 10 miles and 15 minutes as one, keeping the largest.
Each line on those lists is a single report. Issue 014's biggest stone shows what that means: the 3.25-inch report from Phillips County, Montana, on SPC's September 6 hail list came from the mPING reporting app, and the list notes its time was estimated from radar.
The official record is NOAA's Storm Events Database
SPC's FAQ points to NOAA's Storm Events Database as the source of official, final data for severe weather reports, and warns that it takes a few months to compile. The database is NOAA's publicly accessible source for Storm Data, the Weather Service's official record of significant weather.
The database's FAQ fills in the details:
- Timing. Weather Service offices have 60 days to submit their data files. NOAA's National Centers for Environmental Information receives a copy about 75 days after the end of a month and updates the database within 75 to 90 days; January's data is usually available around April 15.
- Sources. Reports come from emergency managers, law enforcement, SKYWARN spotters, Weather Service damage surveys, newspaper clipping services, the insurance industry and the public, among others.
- Accuracy. Some of that information may be unverified by the Weather Service, so users are told to be cautious.
- Damage figures. Property and crop damage estimates are made with the information available when the event is reported and should be treated as broad estimates, not adjusted for inflation.
- Geography. Tornadoes, thunderstorm winds, hail and flash floods are recorded by county. A tornado that crosses a county or state line becomes a separate segment in each.
Side by side
| SPC storm reports | NOAA Storm Events Database | |
|---|---|---|
| How fast | Same day, updated as reports arrive | Roughly 75 to 90 days after the month ends |
| What a row is | One local storm report | One event per county, grouped into episodes |
| Checked? | Preliminary; may be incomplete | Official Storm Data, though some source reports may be unverified |
| Best use | This week's activity and where it happened | Multi-year counts and history for a county or state |
Reading the numbers as a contractor
- A report is a point, not a footprint. It marks where someone saw or measured something at one time. The storm that produced it may have hit a wider area, or a narrower one.
- Wind counts mix gusts and damage. SPC's derecho case maps, for example, plot wind damage and gusts of 50 knots or more with the same symbol.
- Counts are not claims. Issue 014 states that its storm figures are not a report of damage to any particular building. Neither is a Storm Events entry.
- Long-run counts need the database. For a market comparison, use the official record. NOAA's Storm Events Database records 6,054 hail events of 1 inch or larger across Kansas counties from 2016 through 2025, along with 7,454 thunderstorm wind events.
Where to watch in real time
The Wire's Monday Storm Watch email lists the active National Weather Service watches, warnings and advisories for the states you choose, as issued. Between emails, the National Roofing Directory's Storm Center shows active NWS alerts by state. Subscribe to The Roofing Wire to get Storm Watch for your territory.
Frequently asked questions
Why don't the Wire's weekly counts match NOAA's database?
Because they measure different things at different times. The weekly numbers are preliminary SPC reports, while the Storm Events Database holds Weather Service Storm Data that is compiled and published months later, counted by county.
When will this week's storms show up in the official record?
NOAA says the database is updated within about 75 to 90 days after the end of each month, so a September storm would typically appear in December.
Is a hail report proof that roofs were damaged?
No. A report records hail seen or measured at a point. The Wire states that its storm figures are not a report of damage to any particular building, and only an inspection can establish roof damage.
Sources
- frequently asked questions page — spc.noaa.gov
- SPC Storm Reports page — spc.noaa.gov
- September 6 hail list — spc.noaa.gov
- Storm Events Database — ncei.noaa.gov
- database's FAQ — ncei.noaa.gov
- the same symbol — spc.noaa.gov