Data Sources & Methodology | Hurricane Intelligence Florida

This site exists to settle a specific kind of argument with sources instead of recall. That only works if the method is inspectable, so here is the whole thing: what counts, where each field comes from, how the datasets are joined, and what was left out on purpose.

What Counts as a Florida Impact

A storm is in this dataset if, and only if, NOAA's Continental United States Hurricane Impacts/Landfalls table records hurricane-force sustained winds in Florida for it. That table is built by NOAA's Hurricane Research Division from estimated wind fields, which matters: a hurricane's wind field extends far beyond its center, so a storm can batter Florida while its center never crosses the state (1852's "Great Mobile" made landfall in Alabama yet produced hurricane-force wind in two Florida regions), and a storm whose center crosses Florida at tropical-storm strength does not count. Center tracks alone cannot make that distinction; NOAA's wind-field analysis can, so its table is the sole authority here for the yes/no question.

Florida regions follow NOAA's own dividing lines: north/south from Cape Canaveral (28.45N) to Tarpon Springs (28.17N); west/east from 82.69W at the Georgia border to Lake Okeechobee, then south along 80.85W. Codes like SW4 mean Southwest Florida, Category 4, per the table's state-by-state Saffir-Simpson estimates. An I- prefix marks an inland impact, per the same table.

The Two-Dataset Join

Track, intensity, and lifecycle facts come from HURDAT2, NOAA's Atlantic best-track database (1851 to present). Each Florida row in the impacts table is matched to its HURDAT2 storm as follows.

The join key is the season year plus the month the storm affected Florida, never its formation month; a storm that forms in late August and reaches Florida in September joins under September, exactly as the table lists it. A storm lingering near Florida across a month boundary is eligible under every month it spent there. Named storms (1950 onward) match by name. Earlier, unnamed storms match by nearest central pressure between HURDAT2's minimum and the table's listed landfall pressure, with same-month candidates assigned one-to-one so two rows can never silently claim one storm.

When pressure cannot separate two candidates confidently, the record is flagged needs_manual_review rather than silently guessed. 33 of the current records carry that flag, every one of them pre-1950, and each is marked with a * wherever it appears on this site. One guaranteed example: June 1886 produced two different Florida hurricanes with identical 970mb listed pressures; no algorithm should pretend to tell those apart, so both are flagged.

A note on pressure figures: the impacts table lists central pressure at US landfall, while a storm's lifetime minimum in HURDAT2 can be far lower. Hurricane Wilma reached 882mb over the Caribbean but struck Florida at 950mb; both figures are real, they measure different moments. This site's tables show the HURDAT2 lifetime minimum and label it as such.

ENSO Classification

Each season's phase comes from NOAA CPC's Oceanic Nino Index: the 3-month running mean of ERSST.v5 sea-surface-temperature anomalies in the Nino 3.4 region. A hurricane season takes the phase of its ASO (August-September-October) value under CPC's official episode rule: the +/-0.5°C threshold must hold for at least five consecutive overlapping 3-month seasons to count as an El Nino or La Nina episode. A brief spike that touches the threshold outside such a run stays Neutral.

That rule produces answers that sometimes contradict casual memory, which is rather the point. The 2017 season (Irma) is often remembered as La Nina, but ASO 2017 sat at -0.34, before that winter's episode began: officially Neutral. ONI coverage begins in 1950; the 84 storms before that are shown without a phase and are excluded from phase-based counts rather than backfilled from proxy reconstructions.

Derived Fields

Approach side (Gulf vs Atlantic) is derived from the HURDAT2 track by walking backward from the Florida-relevant point to the first clearly Gulf-side or Atlantic-side position. It is a documented heuristic, useful for aggregate comparison, and it is labeled as derived rather than NOAA-published. Peak category is computed from HURDAT2 maximum sustained winds on the Saffir-Simpson scale, using the current HURDAT2 reanalysis values even where they differ from older popular figures.

Storm Genesis Type & the Current Events Base Rate

Every storm is also classified by where its very first HURDAT2 track point falls, into one of four basin types: Straits (the Florida Straits / Cuba shelf corridor -- a distinct, well-documented environment where a narrow, shallow shelf disrupts storms differently than open water), Caribbean, Gulf ("regional/homegrown" in the conversational sense -- a storm with no long ocean-crossing track to speak of), and Atlantic (everything else, including the classic Cape Verde corridor). This exists because a live storm on the Current Events page and a historical "analog" should only be compared on track shape when they're genuinely the same kind of storm to begin with -- a storm born already in the Gulf has no long approach to diverge from a typical recurve; a storm born off Africa does. Boxes are checked in a fixed priority order (Straits, then Caribbean, then Gulf, then Atlantic as the catch-all), so a point in more than one box's range resolves consistently; see etl/genesis_type.php in the codebase for the exact boundaries.

Genesis type is not always the same thing as a storm's popular "origin story." Hurricane Milton (2024) is often described as having "come out of the Yucatan," and that's true of the diffuse, undesignated disturbance that preceded it -- but Milton itself, as NHC and HURDAT2 track it, was first designated a tropical depression in the Bay of Campeche, in the Gulf proper. A precursor disturbance with no organized circulation has no track shape to compare against anything; this site classifies genesis from the point a storm actually became a tracked tropical cyclone, which is also the only point that's consistently knowable across 175 years of record-keeping.

Detection-Era Reliability

Genesis-point reliability is not constant across the historical record, and this site does not pretend otherwise. Per NHC's own HURDAT2 format documentation: a storm's formation (tropical depression) stage was not consistently recorded in best track before 1882; aircraft reconnaissance began in 1944, improving detection near reconnaissance range but not basin-wide; and "routine satellite imagery for the Atlantic basin" -- NHC's own words -- began in 1968. Before that year, a storm's first recorded position is disproportionately likely to be wherever a ship or coastal observer first happened to notice it, near land or a shipping lane, rather than where it actually formed. This is not a small effect: of the storms in this dataset whose genesis point falls in the Straits corridor specifically -- a heavily-trafficked shipping lane -- roughly seven in ten predate 1968.

Because of this, genesis type is shown for every storm regardless of era -- nothing is hidden -- but it is only used for live-storm comparisons on the Current Events page when the historical candidate's own genesis falls in 1968 or later. A live storm's own genesis point is always current, high-confidence NHC data; comparing it against a pre-1968 storm's detection artifact would not be a fair fight. Storm-to-storm comparisons in the Analog Finder's Compare mode are not restricted this way, since both sides of that comparison are already historical.

The "Went On To Become" Percentage

The Current Events page shows a live tropical storm or hurricane's historical base rate: of all Atlantic storms that formed the same way (same genesis type) in the same calendar month since 1968, what share went on to produce hurricane-force wind in Florida. This is computed from the full, unfiltered HURDAT2 basin -- 2004 Atlantic storms total, 976 of them in the modern (1968+) era used for this calculation -- not just the storms that hit Florida. It is bucketed by genesis type and month only, deliberately not ENSO phase: adding ENSO as a third bucket dimension was tested and found to sharply thin real sample sizes without meaningfully changing the numbers. When fewer than eight historical storms share a live storm's exact genesis type and month, no percentage is shown at all -- an honest "not enough data" rather than a precise-looking number built on two or three storms. That minimum-sample threshold, like the pressure-gap threshold above, is a considered starting point rather than a formal statistical derivation, and is open to revision.

Storm Tags

Each storm carries machine-derived tags computed from its HURDAT2 track. Rapid Intensification: maximum sustained wind rose at least 30 knots within any 24-hour span of the storm's life, the standard NHC threshold, scoped to the whole lifetime (a Gulf intensification counts even if the storm weakened before landfall). Cross-Peninsula Track: the storm center traversed the Florida peninsula, judged by an interior track point plus presence on both the west and east flanks; track segments are interpolated between six-hourly fixes so a coast exit between recorded positions still registers, while Keys-only, Panhandle-only, and offshore-looping tracks correctly do not qualify. Major Hurricane: lifetime Category 3 or higher; note a storm can be a lifetime major yet strike Florida below Cat 3, and the per-region impact categories remain the Florida truth. Tags are stamped with the enrichment version that produced them and are re-derived, never hand-edited, whenever that logic changes.

Storm Surge

Surge data is landfall-zone scoped: one curated peak figure for the zone where the storm came ashore, not a full-coastline analysis. Values come from NHC Tropical Cyclone Reports (or the earlier Preliminary Reports) and are recorded with the datum the source used; datums vary by era, from storm tide above sea level in older reports to inundation above ground level in modern ones, so cross-era comparisons carry that caveat. Coverage is deliberately null-tolerant: only storms whose figures have been verified against an NHC source carry a value, and everything else, including all pre-TCR-era storms, shows no curated record. Reliable surge observation drops off sharply before the modern gauge and survey network existed, which skews surge comparisons toward modern storms. That skew is disclosed here rather than papered over: it is a property of the historical record, not a flaw this tool can fix.

Deliberately Excluded

Rainfall is excluded outright, not deferred. Hurricane rainfall varies too sharply over short distances (15 inches to 2 inches within a mile is documented) to honestly represent as one number per storm; a single figure would misrepresent the storm rather than describe it.

Casualty figures are excluded outright. Direct-versus- indirect death attribution is genuinely contested even within official records, and this site does not present contested numbers as settled fact.

Sources

HURDAT2 (Atlantic best track): NOAA National Hurricane Center. Tracks, winds, pressures, landfall records, 1851 to present.
Continental US Hurricane Impacts/Landfalls: NOAA AOML Hurricane Research Division. The authoritative per-state, per-region hurricane-force impact record, 1851 to present.
Oceanic Nino Index: NOAA Climate Prediction Center. Season phase classification, 1950 to present.

Current Dataset Vintage

generated 2026-07-21T02:12:49Z
enrichment logic v1.3.0
HURDAT2: 1851-2025 complete (2025 post-season data, via GitHub mirror of NOAA HURDAT2; production re-pulls from NOAA)
impacts table: 1851-2025, March 2026 revision (fetched from aoml.noaa.gov 2026-07-20)
ONI: DJF 1950 - AMJ 2026 (fetched from cpc.ncep.noaa.gov 2026-07-20)

Raw source files are archived exactly as fetched, in dated snapshots that are never overwritten, so every dataset build can be reproduced and audited against the originals.

Download the full dataset as CSV and check the numbers yourself; the export includes join methods, confidence levels, and review flags for every storm.