A new historical database of tropical cyclone (TC) parameters has been constructed from satellite and aircraft observations. Called the Tropical Cyclone Observations-Based Structure Database (TC-OBS), this database uses objective state estimation algorithms to refine existing historical estimates of the following key parameters: track, intensity, and size (radial extent of winds of a given threshold). Additionally, TC-OBS provides estimates of the radius of maximum winds (RMW), a quantity that has not previously been included as a "best-tracked" quantity in existing historical databases. TC-OBS also provides time-dependent uncertainty bounds on the estimates of these four main quantities. Compared with existing historical databases such as the Hurricane Database (HURDAT2, also known as the "Best Track Dataset"), TC-OBS provides track, intensity, and radius information at higher spatial and temporal precision. Whereas HURDAT2 rounds track points to the nearest tenth of a degree, intensity to the nearest 5-kt increment, and wind radii to 5-nm or even 10-nm increments, TC-OBS does not round any of its estimates to artificial thresholds. While HURDAT generally provides parameters every six hours, TC-OBS provides estimates of all parameters for each hour as well as any of the off-synoptic time points included in HURDAT2. Like HURDAT2, TC-OBS provides estimates of the 34- , 50-, and 64-kt wind radii (size), but TC-OBS also adds estimates for the radial extent of Category 2, 3, 4, and 5 wind speed thresholds (83-kt, 96-kt, 113-kt, and 135-kt). Whenever data coverages are sufficient, TC-OBS also includes estimates of the azimuthal mean wind speed. Finally, TC-OBS is set up to include alternative metrics beyond the traditional metrics for intensity and size. One such metric is related to the spatial and temporal coherence of the location of wind maxima. The database was originally built for wind risk applications, but a wide range of scientific and commercial uses can be envisioned.
TC-OBS currently includes data for all TCs that occurred in the North Atlantic basin from 1999 to 2013. Somewhat more than half of all Atlantic TCs were sampled by aircraft frequently enough to provide useful input data for TC-OBS. Additionally, since aircraft reconnaissance generally commences when TCs move west of 55 deg in the basin, TC-OBS does not provide observational refinement for TCs in the eastern half of the basin. For the most part however, there is good aircraft coverage during nearly all periods in which TCs were threatening land, so TC-OBS provides observational refinements for nearly all the impactful landfalls in the basin. The current version of TC-OBS (v0.42) provides observational refinements for 253 of the 416 TCs that occurred during 1999 to 2013.
