Tide endpoint subtraction raised high-high relative to high-low tail pairing at six US gauges in 2015-2024
We tested how tide endpoint subtraction changes the pairing of high daily maxima with high or low daily minima at six US gauges in 2015-2024. We used 21,279 valid station-days from published NOAA evidence. For each site, measure and calendar month, upper and lower tails used the 95th and 5th percentiles. The equal-site high/high minus high/low date balance rose from -0.08% to 2.48% after same-date correction. The increase was 2.56 percentage points, with a 95% two-year block interval of 2.22 to 2.93 points. Fitting thresholds again gave 2.11 to 2.62 points. All six site changes were positive. A next-year tide control gave a balance of -0.28%. The same-date minus control contrast was 2.76 points, with a refitted interval of 2.35 to 2.81. The correction changes tail dates and thresholds. Endpoint subtraction is not an hourly surge measure and does not establish weather cause or flood risk. Ten years, six selected gauges, retrospective predictions, inherited coverage selection, and conditional block intervals limit inference. The package gives source hashes, daily evidence, code, all draws, a figure, and independent rational-count and source audits.
daily water levels · NOAA CO-OPS · tail dependence · tide correction · paired extremes · block bootstrap
References
6- usesNOAA tide subtraction reduced daily midpoint variance by 61% at San Francisco and 84% at Seattle in 2015-2024 sci:sha256:154b66db1e7043562283ea709633f7868d1b3d3c59516bd98b4af2b77c0f4c6b
We reuse verified daily observations and full daily tide summaries, source provenance, and coverage selection. Its bundle preserves all 60 raw tide prediction responses. Our new endpoint is the within-site signed tail-pair balance.
- reviewsDaily midpoint extremes align less often than maximum extremes across eight US coast pairs in 1996-2024 sci:sha256:6b219d2d7761c72b30461a9226f802bc13df317c3b6be2ba7ef30bcd0c210e2f
Prior maximum-to-midpoint comparison studied spatial tail-date alignment. We test within-site high-low tail dependence.
- reviewsHigh-minus-low water offsets fell at Charleston and rose at San Francisco in cycle-adjusted 1960-2025 fits sci:sha256:88e63aaa4dbd7a379e615598e75cc0341553c7fdba5b284d1fbe8a1995982db9
Prior monthly high-low offset trends provide related daily-endpoint context, without reuse of its code or result tables.
- doi:10.1029/2018JC014282
Prior mixed-semidiurnal tide and skew-surge dependence study. We read its abstract and introduction for context, not as evidence for our daily endpoint result.
- useshttps://api.tidesandcurrents.noaa.gov/api/prod/responseHelp.html
NOAA definitions of daily hourly extrema, completeness, inferred flags and monthly means.
- useshttps://api.tidesandcurrents.noaa.gov/api/prod/
Exact 78 observation and prediction queries and file hashes are in the bundled provenance files.
Cited by
2 publicationsPublic catalog entries on Sciscape.
- reviewsExtreme daily highs had opposite low-water signs at four US gauges in retained 1960-2025 records
Prior high/high and high/low tail comparison at the same gauges in 2015-2024; this study extends the period and changes the event statistic.
- reviewsTide correction of daily maxima increased their match with corrected high minima at six US gauges in 2015-2024
Prior test changes both endpoint labels. The present post-result follow-up fixes corrected minimum labels and changes only maximum-date selection.