claims

Was This Address in the Swath?

Why the central question in a storm claim resists a quick answer, and what belongs in an answer a second reader can check.

The shape of the disagreement

Almost every contested storm claim narrows to one sentence. One side says the neighborhood was hit. The other side says this parcel was not. Everything else in the file sits downstream of that disagreement.

The argument is usually not about honesty. A contractor who opened six roofs on one street saw bruising on all six. An adjuster who pulled the record for one address found nothing near it. Both can be describing something real, because hail does not fall evenly across a city and because the record of hail is not the same object as the hail.

So "was this address in the swath" is the right question. It is also harder to answer than it sounds, and most of the shortcuts people reach for cannot carry the weight.

A warning polygon is not a damage footprint

The most common shortcut is the warning. Someone pulls up the severe thunderstorm or tornado warning that was active that afternoon and treats the shape on the screen as the area that got hit.

Warnings were not built for that. The NWS Birmingham awareness handout records that the National Weather Service upgraded warning capabilities on October 1, 2007. Before then the agency issued county-based warnings, which covered an entire county regardless of which portion of the county the storm was in. Under storm-based warnings, "warning polygons only cover the portion of the county actually threatened by the storm."

The worked example on that page is the one to remember. Tornado warnings were in effect for Hale, Bibb, Perry, Tuscaloosa, Jefferson and Shelby counties, while the cities of Tuscaloosa, Birmingham and Calera were not inside the polygons and were therefore not under a tornado warning. Six counties warned. Three named cities inside them not warned.

The same handout notes that NOAA Weather Radio All Hazards continues to alert the entire county, while several vendors alert only if you are inside the storm-based warning. Two neighbors with different alerting setups received genuinely different information about one storm.

A warning is a forecaster's statement about expected threat, issued before the event, over an area chosen to cover a moving storm. A claim needs a statement about observed or estimated conditions at one location. Those are different products, and one does not substitute for the other.

ZIP codes and city names are the wrong resolution

The second shortcut is administrative geography. A ZIP code is a mail routing construct. A city boundary is a political one. Neither was drawn around a storm, and both are far coarser than the thing in dispute.

The Birmingham example settles that without further argument. Three cities sat inside six warned counties and outside every polygon. If a city name can be inside and outside at the same time, a city name cannot answer the question. A ZIP code is no better: a storm that clips one side of a subdivision respects neither line.

What a real answer is made of

A defensible answer has three parts, and all three belong in the file.

The first is a geometry. If you are going to say an address fell inside something, the something needs a definition precise enough that another person can test it. GeoJSON, RFC 7946 is the usual format, and it is specific about the details that get fumbled. A position is an array whose first two elements are longitude then latitude, in that order. The default coordinate reference system is the WGS 84 datum in decimal degrees. A linear ring has to be a closed LineString carrying at least four positions, with the first and last positions identical.

Those read like implementation trivia. They are also the two quietest ways a swath file goes wrong: coordinates reversed, so the polygon lands where it has no business being, or a ring that never closes, so the shape is not a polygon at all.

The second part is a point. The address has to become a coordinate pair before it can be tested against a shape. The US Census Geocoder offers interactive and REST access, with one-line address, parsed address, batch and coordinate options, and it states that it "only geocodes addresses that are within the United States, Puerto Rico, and the U.S. Island Areas." It also asks the caller to choose a benchmark and a vintage, which is another way of saying the coordinate depends on which reference data produced it.

The third part is provenance: which source the geometry came from, and when you pulled it.

Say which source, and say when you pulled it

Provenance is not bookkeeping.

NCEI's Severe Weather Data Inventory serves NEXRAD Level-III hail signatures in a filtered version and an all-signature version. The page is direct about its limits. It adds no quality control beyond archival processing. Missing data does not mean no severe weather occurred. Much of the automatically derived data is radar-based and represents probable rather than confirmed conditions.

The same page notes that NCEI is migrating data to the cloud, which may result in temporary data access delays, and that order fulfillment is intermittently degraded. The same query against the same archive can therefore behave differently on two different days, and nothing in the file will say which day you were on unless you wrote it down.

The answer is binary and the storm was not

A point-in-polygon test returns one bit. Inside, or outside. The physical event graded off continuously across the ground. That mismatch is not a defect anyone can engineer away, but it does tell you where the answer deserves the least confidence: at the edge of the polygon.

The research on radar estimates makes the point from the other direction. MESH, the maximum estimated size of hail, estimates hail size from the radar reflectivity properties of a storm above the environmental 0 degree C level, and is produced by the Multi-Radar Multi-Sensor system. Wendt and Jirak, in Weather and Forecasting, April 2021, covering 2012 to 2019 over the contiguous United States, found MESH estimates of severe hail hours per year higher at all locations in the contiguous United States than estimates built from reports. In plains areas where population density is relatively high, severe hail hours estimated from MESH can be 2 to 4 times greater than those estimated from Storm Data, and where population density is low the differences can be higher. They also found relative minima in that difference across much of the Intermountain West, the West Coast, the Appalachians and the Northeast, partly from missing radar coverage caused by beam blockage or widely spaced radars.

A radar-derived footprint is therefore an estimate with known regional behavior, not a confirmation. Labeling it radar-estimated is accurate, not evasive.

Why Florida raises the stakes on getting this right

In Florida the identity of the event is a statutory fact rather than a field on a form. Florida Statutes section 627.70132 provides that for claims resulting from hurricanes, tornadoes, windstorms, severe rain, or other weather-related events, the date of loss is the date the hurricane made landfall or the other weather-related event "is verified by the National Oceanic and Atmospheric Administration." The same section bars a claim or reopened claim unless notice was given to the insurer in accordance with the terms of the policy within 1 year after the date of loss, and bars a supplemental claim unless noticed within 18 months after the date of loss.

That is Florida law describing Florida policies, not a rule about any other state, and policy language can be stricter than a statutory floor. Read your own policy, check your own state's law, and do not take a deadline from an article.

What the provision shows is structural. Where a statute attaches consequences to a verified event, "which event" becomes as load-bearing as "which parcel." A file saying the roof was hit by hail last spring is not an answer. A file that names a date and names the source of that date is the start of one.

Write the answer so it survives a second reader

Four lines, every time. Source: which dataset or product the geometry came from, named rather than described. Geometry: the shape itself, with coordinate order and ring closure stated or verifiable from the file. Point: the geocoded coordinate, and which geocoder produced it. Date pulled: the day you ran the query.

A second reader who disagrees can then disagree with something specific, which is the point. An answer nobody can check is worth no more than the argument it was meant to end.

Storm Stream is an API over these same public feeds: it builds swath geometry, serves it as GeoJSON, and answers which of a list of caller-supplied points fell inside it.