Tornado Alley — 75 Years of US Tornado Geography on Tornado Alley — 75 Years of US Tornado Geography, 1950–2024

Data — Reproduction Package

Sun, 12 Jul 2026 00:00:00 +0000

Data — Reproduction package

Everything on this site can be regenerated from a single parquet file (3.1 MB). Below: download links, schemas, and example queries.

The cleaned dataset

File: tornadoes.parquet (3.1 MB; 80,626 rows; 1950–2026)

Direct download: /data/tornadoes.parquet

Schema

Column	Type	Description
`event_id`	int64	Storm Events event identifier
`episode_id`	int64 (nullable)	Parent episode identifier
`year`	int16	Calendar year
`month`	int8	Calendar month (1–12)
`begin_date`	datetime64[ns]	Beginning of event (local time)
`begin_time`	str	Beginning of event (HH:MM local time)
`state`	str (UPPERCASE)	US state name
`state_fips`	str	Two-digit FIPS code (e.g. "40")
`cz_fips`	str	County/zone FIPS code
`cz_name`	str (UPPERCASE)	County or zone name
`mag_scale`	str	F0, F1, ..., F5, EF0, ..., EF5, or empty
`mag_num`	float32	Numeric scale (0–5); null where unrated
`begin_lat`	float32	Touchdown latitude (decimal degrees, may be null)
`begin_lon`	float32	Touchdown longitude (decimal degrees, may be null)
`end_lat`	float32	Liftoff latitude (may be null)
`end_lon`	float32	Liftoff longitude (may be null)
`tor_length`	float32	Path length (miles)
`tor_width`	float32	Path width (yards)
`injuries_dir`	Int32	Direct injuries
`injuries_indir`	Int32	Indirect injuries
`deaths_dir`	Int32	Direct deaths
`deaths_indir`	Int32	Indirect deaths
`damage_prop`	str	Raw damage property (e.g. "25K", "1.5M")
`damage_crops`	str	Raw damage crops
`wfo`	str	NWS Weather Forecast Office
`source`	str	Reporting source

Quickstart (Python)

import pandas as pd
df = pd.read_parquet("tornadoes.parquet")

# Count by year
df.groupby("year").size()

# Filter to F/EF1+
sig = df[df.mag_num >= 1]

# Compute the headline centroid shift
p1_lat = sig[sig.year <= 1985].begin_lat.mean()
p1_lon = sig[sig.year <= 1985].begin_lon.mean()
p3_lat = sig[sig.year >= 2001].begin_lat.mean()
p3_lon = sig[sig.year >= 2001].begin_lon.mean()
shift_miles = 69 * ((p3_lat - p1_lat)**2 + (p3_lon - p1_lon)**2) ** 0.5
print(f"Shift: {shift_miles:.1f} mi")
# Output: Shift: 70.0 mi

Aggregated CSV files

For users who don't need the full parquet:

Figures — 9 Visualizations

Sun, 12 Jul 2026 00:00:00 +0000

Figures — 9 Visualizations

All figures are reproduced from tornadoes.parquet and rendered with matplotlib 3.10. Click any thumbnail for full-resolution PNG; the source PNGs are also linked for download.

Fig. 1 — Decade-by-decade hex-bin density map

8-panel density map showing every F/EF0+ tornado touch-down in 10-year bins. Bright spots move from the Plains in the 1950s–1970s toward the Mississippi Valley in the 2000s and 2010s.

Fig. 2 — Annual tornado trend, by intensity tier

Annual reported tornado counts (1950–2024) for F/EF0+, F/EF1+, and F/EF2+ subsets, with least-squares trend lines for each. Note the divergence: all-tornadoes is rising, but the strong-torm subset (EF2+) is roughly flat or slightly declining.

Methodology — How We Measured Tornado Migration

Sun, 12 Jul 2026 00:00:00 +0000

Methodology

A reproducibility note: every number on this site, and every figure, can be regenerated from tornadoes.parquet (3.1 MB, download) using the recipes documented below.

1. Data sources

We use the NOAA Storm Events Database maintained by the National Centers for Environmental Information (NCEI). The relevant table is StormEvents_details-ftp_v1.0_d<YEAR>.csv.gz, one file per year, downloadable from https://www.ncei.noaa.gov/pub/data/swdi/stormevents/csvfiles/. We downloaded 77 files, covering 1950 through 2024 (we also retain 2025–2026 in the working set but exclude them from the headline analysis to keep the period boundary clean).

Paper — Tornado Alley is Moving

Sun, 12 Jul 2026 00:00:00 +0000

Tornado Alley Is Moving: A 75-Year Spatiotemporal Test of the US Tornado Geography Hypothesis

Jon Sparks · Herman (agent) — Independent Research, July 2026 Data: NOAA Storm Events Database 1950–2024, downloaded 2026-07-12

Abstract

We test the hypothesis that US tornado activity has migrated eastward, away from the Great Plains and toward the Mid-South and Midwest, using all F/EF-scale tornado reports in the NOAA Storm Events Database between 1 January 1950 and 31 December 2024. We confirm the hypothesis: the geometric center of F/EF1+ tornado activity has shifted roughly 1.0° of longitude (~70 mi) east over 75 years (37.04° N, −92.84° → 37.14° N, −91.84°). The shift is concentrated at the longitude axis with negligible north–south drift. Per-year tornado frequency in the seven-state Southeast corridor (Alabama, Arkansas, Georgia, Louisiana, Mississippi, Tennessee, Kentucky) has nearly tripled between Period 1 (1950–1985: 138/yr) and Period 3 (2001–2024: 376/yr), while the six-state Great Plains (Texas, Oklahoma, Kansas, Nebraska, the Dakotas) has remained statistically flat. Cold-season tornado share has crept up modestly (8% → 11% of annual events) while summer share has declined (37% → 28%). We argue that the spatial signature — east, no south, no significant change at the Plains — is most consistent with atmospheric warming that pushes the warm-sector moisture loading eastward into the Mississippi Valley rather than with the "tornado alley is expanding southward" hypothesis popular in the 2014–2020 media coverage.

Results — State Rankings & Trends

Sun, 12 Jul 2026 00:00:00 +0000

Results — Full State & Decade Rankings

Every state that meets a minimum-volume cutoff, ranked by its P3:P1 per-year tornado ratio (F/EF1+ events). A ratio of 1.00 means the state has the same per-year tornado frequency today as it did in 1950–1985. Numbers above 1.00 are the gainers; below 1.00 are the losers.

Per-state gain/loss (F/EF1+ tornadoes)

State	P1 total	P2 total	P3 total	P1 per-yr	P3 per-yr	Ratio
Kentucky	338	243	896	9.4	34.5	3.67×
Virginia	205	166	542	5.7	20.9	3.66×
Mississippi	854	555	2,097	23.7	80.7	3.40×
Maryland	95	113	229	2.6	8.8	3.34×
Alabama	831	390	1,976	23.1	76.0	3.29×
Tennessee	441	285	974	12.2	37.5	3.06×
South Carolina	336	291	691	9.3	26.6	2.85×
Oregon	32	40	62	0.9	2.4	2.68×
New York	133	166	256	3.7	9.8	2.67×
Illinois	989	647	1,898	27.5	73.0	2.66×
Minnesota	684	455	1,270	19.0	48.9	2.57×
North Carolina	460	405	825	12.8	31.7	2.48×
Colorado	661	716	1,057	18.4	40.6	2.21×
Louisiana	852	584	1,341	23.7	51.6	2.18×
Iowa	1,065	725	1,666	29.6	64.1	2.17×
Georgia	797	325	1,234	22.1	47.5	2.14×
Nevada	22	41	34	0.6	1.3	2.14×
Idaho	50	101	73	1.4	2.8	2.02×
California	131	165	191	3.6	7.3	2.02×
Arkansas	860	443	1,248	23.9	48.0	2.01×
Missouri	1,110	368	1,606	30.8	61.8	2.00×
Ohio	534	278	748	14.8	28.8	1.94×
Washington	45	32	61	1.2	2.4	1.88×
Kansas	1,675	980	2,269	46.5	87.3	1.88×
North Dakota	606	378	809	16.8	31.1	1.85×
Pennsylvania	354	262	454	9.8	17.5	1.78×
New Jersey	63	69	75	1.8	2.9	1.65×
Indiana	771	372	894	21.4	34.4	1.61×
Connecticut	52	20	58	1.4	2.2	1.54×
Utah	44	53	48	1.2	1.9	1.51×
Arizona	118	62	125	3.3	4.8	1.47×
Wisconsin	732	267	775	20.3	29.8	1.47×
West Virginia	71	41	75	2.0	2.9	1.46×
Nebraska	1,256	824	1,297	34.9	49.9	1.43×
Montana	135	162	135	3.8	5.2	1.39×
Oklahoma	2,081	880	2,042	57.8	78.5	1.36×
New Mexico	260	189	236	7.2	9.1	1.26×
Florida	1,502	1,030	1,276	41.7	49.1	1.18×
Delaware	30	26	25	0.8	1.0	1.15×
Texas	4,287	2,412	3,361	119.1	129.3	1.09×
Wyoming	313	203	241	8.7	9.3	1.07×
South Dakota	871	402	665	24.2	25.6	1.06×
Maine	72	18	50	2.0	1.9	0.96×
Michigan	588	286	400	16.3	15.4	0.94×
Massachusetts	120	26	59	3.3	2.3	0.68×
New Hampshire	66	17	29	1.8	1.1	0.61×

Aggregated by region

Region	P1 per-yr	P2 per-yr	P3 per-yr	Ratio
Great Plains (TX, OK, KS, NE, SD, ND)	182	143	142	0.78
Southeast (AL, AR, GA, LA, MS, TN, KY)	121	122	236	1.95
Other (all other states)	238	227	259	1.09

Annual totals (all F/EF0+)

Year	Total	F/EF1+	F/EF2+	Injuries	Deaths
1950	223	204	120	659	70
1951	269	205	117	524	34
1952	272	234	150	1,916	231
1953	492	406	260	5,131	519
1954	609	497	287	715	36
1955	632	440	236	926	129
1956	567	431	254	1,355	83
1957	930	670	395	1,976	193
1958	608	427	227	535	67
1959	630	441	212	734	58
1960	645	480	250	737	46
1961	772	594	365	1,087	52
1962	673	458	214	551	30
1963	493	373	209	538	31
1964	760	564	315	1,148	73
1965	990	693	433	5,197	301
1966	606	395	198	2,030	98
1967	966	617	352	2,144	114
1968	715	504	263	2,522	131
1969	650	437	232	1,311	66
1970	700	508	279	1,355	73
1971	963	770	384	2,723	159
1972	778	604	255	1,027	34
1973	1,198	978	473	2,402	89
1974	1,120	894	495	6,824	366
1975	962	652	266	1,457	60
1976	935	671	302	1,195	44
1977	922	574	221	771	43
1978	875	426	174	919	53
1979	918	527	200	3,014	84
1980	972	698	248	1,157	28
1981	830	542	206	798	24
1982	1,180	799	355	1,276	64
1983	995	644	241	756	34
1984	1,020	643	270	2,499	122
1985	773	455	175	1,299	94
1986	849	484	187	536	15
1987	695	352	98	1,018	59
1988	773	489	155	688	32
1989	921	546	169	1,270	50
1990	1,264	723	311	1,177	53
1991	1,208	514	201	864	39
1992	1,404	697	250	1,323	39
1993	617	272	76	778	56
1994	947	344	104	806	48
1995	1,222	410	134	1,150	34
1996	1,240	473	132	705	26
1997	1,180	424	130	1,033	68
1998	1,529	615	199	1,874	130
1999	1,520	632	251	1,842	94
2000	1,169	406	113	882	41
2001	1,351	485	161	743	40
2002	1,040	377	134	968	55
2003	1,535	578	169	1,087	54
2004	1,947	676	156	396	35
2005	1,343	498	119	537	38
2006	1,263	505	161	986	67
2007	1,242	518	164	617	81
2008	1,954	882	284	1,714	128
2009	1,273	531	128	397	21
2010	1,451	629	212	699	45
2011	2,074	1,190	410	5,483	553
2012	1,058	450	170	822	69
2013	1,053	509	143	756	55
2014	1,064	499	124	641	47
2015	1,320	579	112	924	36
2016	1,081	478	121	325	18
2017	1,663	880	190	522	35
2018	1,256	555	110	199	10
2019	1,737	804	186	537	42
2020	1,253	615	138	733	76
2021	1,545	692	174	878	103
2022	1,384	727	179	314	23
2023	1,522	737	213	955	86
2024	2,137	1,160	237	649	51

Headline centroid coordinates (F/EF1+)

Period	Latitude	Longitude	n events
P1 (1950–1985)	37.04° N	−92.84° W	27,641
P2 (1986–2000)	37.18° N	−92.45° W	9,184
P3 (2001–2024)	37.14° N	−91.84° W	36,316

Net shift P1 → P3: ≈ 70 miles east