Every storm in Hurricane Calendar comes from official records, and every figure in the app names the agency that recorded it. This page lists each source, what the app uses it for and how it is credited. The archive currently holds 13,314 storms from 1842 to 2026, built in September 2026 from NOAA’s IBTrACS version 4r01 merged with the National Hurricane Center’s HURDAT2 databases.
The International Best Track Archive for Climate Stewardship (IBTrACS), version 4r01, from NOAA’s National Centers for Environmental Information, gathers the official best-track records of the world’s tropical cyclone forecast centers into one global archive. Hurricane Calendar uses it for every ocean basin: positions, intensities, the responsible agency and the storm’s names.
Real-time (provisional) records are labeled, and storms that may still have been active when the archive was downloaded are held back until their records settle.
The National Hurricane Center’s HURDAT2 databases cover the Atlantic from 1851 and the Northeast and North Central Pacific from 1949, including decades of reanalysis. Where both archives cover a storm, the app uses HURDAT2’s positions, intensities and recorded landfalls. The September 2026 archive uses the editions released on 12 and 14 September 2026, which run through the 2025 season.
Wind speeds appear exactly as each agency recorded them, labeled with the agency and averaging period: 1-minute sustained winds for the U.S. centers, 3-minute for the India Meteorological Department and 10-minute for most other agencies. Values are never converted from one agency’s scale to another’s. The Saffir-Simpson category is used only where the National Hurricane Center or the Central Pacific Hurricane Center is responsible, and a missing value is shown as missing, never as zero.
Daily true-color images come from NASA’s Global Imagery Browse Services (GIBS), part of NASA’s Earth Science Data and Information System: MODIS on the Terra satellite from 24 February 2000, MODIS on Aqua from 3 July 2002, and VIIRS on Suomi NPP from 24 November 2015. The app shows them for the actual days a storm was active. Storms before 2000 are drawn over NASA’s Blue Marble relief, labeled as such. No image is ever generated or AI-made.
Daily sea-surface temperature comes from NOAA’s Optimum Interpolation Sea Surface Temperature (OISST) version 2.1, produced by NCEI and served by NOAA CoastWatch. It begins on 1 September 1981; for earlier storms the app shows no temperature layer rather than a modern stand-in.
Ocean depth is drawn in six bands from NOAA NCEI’s global DEM mosaic, built on the ETOPO 2022 global relief model. It is a background layer and doesn’t change with the storm date.
Map tiles come from OpenFreeMap in the OpenMapTiles schema, with shaded relief from Natural Earth. Map data © OpenStreetMap contributors, available under the Open Database License.
The naming lists, the order they rotate in and the retired names come from the World Meteorological Organization’s regional tropical cyclone committees, which maintain the official lists for each ocean. Hurricane Calendar carries the lists for eight regions.
Damage figures are shown in the currency and price year the source reported. For U.S.-dollar figures with a stated price year from 1913 on, the app can add a comparison in today’s prices using the U.S. Bureau of Labor Statistics’ Consumer Price Index for All Urban Consumers (CPI-U, series CUUR0000SA0). It is labeled as an inflation comparison, not a new estimate of the damage.
Story pages for landmark storms are researched from official reports — the National Hurricane Center’s Tropical Cyclone Reports, national meteorological services, disaster agencies and the WMO’s Weather and Climate Extremes Archive — and every claim links to its source. Damage figures appear only after an editor has checked them against the source.
Tropical cyclone records are most complete in the satellite era, from the 1960s on. Earlier storms far from ships and coasts could go unrecorded, and early intensities were often estimated from sparse observations. Hurricane Calendar shows these gaps as gaps and labels provisional records, so the archive never looks more certain than it is.
Found something that doesn’t match the official record? Use “Report a suspected error” on the storm’s page in the app, or email support@meetamsai.com. Every correction is checked against the official source before the next data update.
Last updated September 26, 2026.