The companion finding — that the storm season at La Saladita is arriving earlier, more often, and more intensely — raised an obvious follow-up: are the tracks themselves shifting geometry? If storms are recurving further north over time, that would mechanistically explain why more of them reach the 1,500 km swing zone. Four metrics, 77 years, 1,262 storms.
Short answer: two metrics show significant long-record trends, but both are driven by the 1950s-to-1970s period when geostationary satellites were added and the catalog began capturing short-lived equatorial storms that were previously missed. Restrict the analysis to the satellite era (1978–2025) and all four trends become statistically inconclusive. The honest reading is: no confirmed geometric northward shift — though a weak northward lean in the satellite era (northernmost latitude: +0.24°/decade) sits at p=0.11, short of confidence but worth watching.
The tracks have not demonstrably shifted north in the satellite era. The long-record signals reflect surveillance improvement, not changed geometry.
Genesis latitude trended strongly southward across the full 77 years (p<0.001) — but that reflects the 1950s-to-1970s expansion of storm detection to shorter-lived equatorial systems. Post-1978, the same metric shows a weak, insignificant northward lean. The phenology shift (earlier, more frequent arrivals) is real; the track geometry change is not yet confirmed.
Two apparent trends — both driven by the pre-satellite period.
OLS regression of annual means; all four tested simultaneously (Bonferroni threshold: p<0.0125).
Restricting to the geostationary satellite era — when catalog quality is consistent — removes all significant trends. Genesis latitude: +0.14°/decade, p=0.17. Recurvature latitude: −0.08°/decade, p=0.77. Northernmost latitude: +0.24°/decade, p=0.11 — the weakest northward signal in the data, not yet significant but directionally consistent with a poleward expansion hypothesis.
The satellite-era northernmost-latitude trend is the one metric that would most directly explain more storms reaching the Saladita swing zone. At p=0.11 with n=48 years, it is suggestive but inconclusive. Another decade of data would likely settle it.
A large shift in the 1960s–70s, stable since.
The 1950s mean genesis was ~16°N. By the 1970s it was ~12.9°N — a 3° drop that coincides exactly with the expansion of geostationary satellite coverage, which detected shorter-lived, more equatorial storms that aircraft and ship reports missed. Since 1980, the mean has been nearly flat at 13–14°N.
Where storms turn poleward — no clear recent trend.
About 26% of EPAC storms show detectable recurvature by the algorithm (westward→eastward zonal motion with concurrent poleward motion). Among those, mean recurvature latitude was ~21°N in the 1950s and has drifted to ~17–18°N — again driven by the pre-satellite period. Since 1980 there is no clear direction.
Surveillance bias dominates the long record. The HURDAT2 catalog before 1966 is significantly incomplete — no geostationary satellites, sparse ship and aircraft reports. The 1950s mean genesis latitude of ~16°N is not a reflection of where storms formed; it is a reflection of which storms were detected. The big apparent southward shift in the 1960s–70s is catalog improvement, not climate change.
Recurvature is ambiguous. About 74% of EPAC storms track steadily westward and dissipate over cooler water or land — they never recurve. The recurvature subsample (26% of storms) is not a random draw from the full population; it skews toward storms that survive long enough to encounter mid-latitude steering flows. Trends in that subsample may reflect changing storm duration, not track curvature per se.
Annual averages mask within-year variability. A single long-tracked recurving storm can shift the annual mean recurvature latitude by several degrees. High interannual variance means confidence intervals are wide.
Four simultaneous tests. Bonferroni threshold is p<0.0125. The genesis-latitude result (p<0.001) clears it but is a surveillance artifact. The recurvature result (p=0.013) is right at threshold and pre-satellite driven. Nothing clears threshold in the satellite era.
This does not contradict the phenology shift finding. The storm season at La Saladita is starting earlier, more storms enter the swing zone, and they are more intense — all strongly confirmed. Track geometry (where storms form and how they curve) is a separate question with a less clear answer so far.
The phenology trend is real. The geometry trend is not yet confirmed. A decade more of satellite data at the current +0.24°/decade northernmost-latitude rate would likely decide it.Synthesis · June 2026
Sources and method
NHC HURDAT2 NEPAC 1949–2025 (1,262 EP+CP storms). Per-storm metrics derived from 6-hourly best-track fixes: genesis = first recorded fix; max latitude = northernmost fix over full track; mean heading = circular mean of bearings between consecutive fixes; recurvature = first inflection where 2-step net zonal displacement flips westward→eastward with concurrent poleward motion (2-fix smoothing window). Annual values = mean across all storms forming that year. Linear trends by OLS; p-values via normal approximation (~77 df). Script: scripts/analyze_hurricane_tracks.py → functions/api/_findings_hurricane_tracks.js.
Satellite era defined as 1978–present (GOES-1 operational late 1975; full geostationary EPAC coverage effectively established 1977–1978). Pre-1966 caveat per NHC HURDAT2 documentation.