Frequently Asked Questions
- General
- IBTrACS Construction
- Why does the best track for the northern hemisphere use data from the JTWC? Ideally, should it not use data from the JMA and the IMD?
- Why did you choose a 10-min wind?
- Why does IBTrACS differ from HURDAT (or data from other agencies)?
- What are the basin boundaries?
- How are Southern Hemisphere seasons handled?
- I have 50 years of historical best track data in paper form. How can I get this included in IBTrACS?
- Data Access
- Data Values
General
Is IBTrACS a reanalysis?
No. IBTrACS is a collection of best track data from numerous agencies. The data have been objectively combined to facilitate analysis. It does not represent any reanalysis of satellite or surface data.
Why should I use IBTrACS?
The IBTrACS dataset currently combines information from twelve tropical cyclone datasets and checks the quality of storm inventories, positions, minimum central pressures, and wind speeds, passing this information onto the user. The IBTrACS dataset also provides the range in position, pressure and wind speed observations. Finally, the dataset is updated semi-annually and is provided in a variety of user-friendly formats to facilitate data analysis.
How does IBTrACS relate to HURDAT
In short, HURDAT is a reanalysis of storms in one basin while IBTrACS is a collection of global best track dataset.
As such, IBTrACS incorporates
the existing HURDAT files for the North Atlantic basin. Any and all updates
that are performed on the HURDAT data are thus automatically included and
updated in IBTrACS.
How does IBTrACS relate to HURSAT?
The Hurricane Satellite dataset ( HURSAT) is made up of satellite brightness temperatures over global tropical cyclones. HURSAT uses IBTrACS to determine storm position prior to remapping and subsetting the satellite data.
How should I cite IBTrACS?
Knapp, K. R., M. C. Kruk, D. H. Levinson, and E. J. Gibney, 2009:
Archive compiles new resource for global tropical cyclone research
Eos, Transactions, AGU., 90, 46, doi:10.1029/2009EO060002
I think I found an error in IBTrACS. What should I do?
First, if you have found an error in one or more of our storm track files, thank you! The accuracy of the dataset can only be improved through vigilant data users. Please send an email detailing the error to:
IBTrACS.Manager [at] noaa.gov
IBTrACS Construction
Why does the best track for the northern hemisphere use data
from the Joint Typhoon Warning Center? Ideally, should it not use data from the
Japan Meteorological Agency and the India Meteorological Department?
The goal of IBTrACS is to inventory each TC in all basins. To that extent, we use data from all available resource. While JMA is the RSMC for the Western Pacific, many other agnecies monitor the region (Hong Kong, China, etc.). Including everyone:
- minimizes the dependence upon the operating procedures at any one agency,
- allows more storms to be included,
- helps identify the variability between agencies, and
- identifies possible errors when differences do occur.
Variability of storm reports between agencies are maintained in IBTrACS by reporting minimum and maximum values for wind and pressure at each time. Furthermore, IBTrACS could include data from other agencies as the data become available.
Why did you choose a 10-min wind?
Maximum sustained winds are reported using various averaging periods which depends on the operating procedures of a forecast center. For example, while the HURDAT dataset uses a 1-minute wind average, a 2-minute average is employed by the Shanghai Typhoon Institute, and a 10-minute average is used by the Australian Bureau of Meteorology and many others. In order to create a dataset that was globally homogeneous, it was necessary to standardize the maximum winds to a single averaging value. Hence, the 10-minute averaging period was selected because it is the global standard as set by the World Meteorological Organization.
Why does IBTrACS differ from HURDAT (or data from other agencies)?
First, all winds are reported as 10-minute winds. Data from NOAA (HURDAT, CPHC), JTWC and the RSMC New Delhi (IMD) all provide data as 1-minute. Winds were converted to 10-min using:
V10 = 0.88 * V1
Second, IBTrACS is a compilation of data from all available agencies. So the number storms in IBTrACS will likely be larger than the number of storms from an individual agency.
Third, since IBTrACS is a compilation of data from many agencies, the IBTrACS maximum sustained winds (MSW) is an average from all available agencies and will likely be different from the reports of each agency. Calculating statistics from IBTrACS (like ACE, number of super typhoons, etc.) will result in values which are more than likely different from those of any particular agency.
What are the basin boundaries?
Basins within IBTrACS are provided for convenience. The latitude and longitudinal extents are provided in the following table. NOTE: The boundary between EP and NA was variable and determined using a polynomial which roughly follows Central America.
| Latitude (deg North) |
Longitude (deg East) |
|||
| Basin | Minimum | Maximum | Minimum | Maximum |
| North Indian | 0 | 90 | 30 | 100 |
| West Pacific | 0 | 90 | 100 | 180 |
| East Pacific | 0 | 90 | 180 | Variable |
| North Atlantic | 0 | 90 | Variable | 30 |
| South Indian | -90 | 0 | 10 | 135 |
| South Pacific | -90 | 0 | 135 | -70 |
| South Atlantic | -90 | 0 | -70 | 10 |
How are Southern Hemisphere seasons handled?
Each storm in the IBTrACS dataset was assigned a season, representative of its location and in accordance with WMO standards. Storms in the Northern Hemisphere follow the calendar year and storms in the Southern Hemisphere follow a 6-month offset year, from July to June. For example, the Southern Hemisphere 2008 season is spanned by 1 July 2007 to 30 June 2008.
I have 50 years of historical best track data in paper form.
How can I get this included in IBTrACS?
If you have historical best track data that you would like to be considered for inclusion into the IBTrACS dataset, please contact:
IBTrACS.Manager [at] noaa.gov
We may be able have the data digitized through a program at NCDC.
If you already have data in digital form, please email it as an attachment to the above address, or include a web site where the data may be downloaded.
Data access
What is the easiest way to ingest the entire dataset?
The best choice is to use the netCDF version which contains the entire data set in one netCDF file. Other formats also have an "AllStorms" file which contains all storms in one file as well. But not all other formats can store all the data generated in merging the IBTrACS dataset.
What is the best format for input into a spreadsheet or database?
The CSV format has been generated to facilitate the use of IBTrACS in spreadsheets and databases.
Data Values
Can I access best track data before it is averaged by IBTrACS?
Yes. The data as reported by each agency is provided in what is called the merged dataset. Merged data contain the original reports from the agencies combined into one netCDF file prior to any averaging or wind speed adjustment. A text representation (CDL) of one of the merged files shows that values are available from each agency.
Why all the missing standard deviation values for the
North Atlantic?
The standard deviation for inter-agency intensity variation is determined from all agencies reporting intensity (winds or pressure) at that time. In the case of the North Atlantic, the only source of wind or pressure data is the HURDAT dataset. The standard deviation does not apply since only one report is available, thus it is reported as missing
This also ocurrs in other basins when the number of agencies reporting the intensity is only one.
