Cyclone Exchange

The Sixth WMO International Workshop on Tropical Cyclones recommended that all tropical cyclone-related Numerical Weather Prediction (NWP) products, including full set of ensemble forecasts, be made available to all operational and research users in real-time. Meanwhile, the THORPEX GIFS-TIGGE Working Group is developing plans for the Global Interactive Forecast System (GIFS) for the real time dissemination of ensemble data and products in support of high impact weather prediction, including prediction of tropical cyclones.

A pilot project has been established by the TIGGE Working Group to test the real-time exchange of ensemble TC track forecasts; the format for TC data exchange will be Cyclone XML (CXML). Exchange of real-time TC forecasts was done in the THORPEX Pacific-Asian Regional Campaign (T-PARC) (August 2008-March 2009), designed to study the life-cycle of tropical and extra-tropical cyclones over the northern Pacific.

CXML is being used in the North Western Pacific Tropical Cyclone (TC) Ensemble Forecast project which provides near real time ensemble forecasts of TCs based on the TIGGE dataset. Ongoing exchange of TC tracks in real time is expected to lead to improved tropical cyclone prediction, benefiting society in general.

Data: The table below lists FTP sites from which it is possible to download real-time ensemble tropical cyclone track forecasts. A more sophisticated web interface will be developed in due course.

More information about ensemble system and/or track forecasts
http://www.weatheroffice.gc.ca/ensemble/index_e.html

More information about ensemble system and/or track forecasts
 http://www.jma.go.jp/en/typh/

More information about ensemble system and/or track forecasts
 http://tigge.ecmwf.int/models.html

More information about ensemble system and/or track forecasts

These data are also available at the Research Data Archives at NCAR at http://rda.ucar.edu/datasets/ds330.3/  under ‘Data Access’ and ‘Internet Download’.

To make collection and combination of track forecasts easier,  the WMO standard file naming convention has been followed. The standard naming convention for ensemble TC track forecast files is similar to the existing TIGGE file name convention, and has the form:

z_tigge_c_cccc_yyyyMMddhhmmss_nnn_mmmm_vvvv_pppp_bbb.xml[.compression]

(to be confirmed)
where

• tigge
  is a product identifier (use of the ‘tigge’ identifier is optional; other product identifiers are permitted)
• cccc
  is the originating center code (see table above)
• yyyyMMddhhmmss
  gives the year, month, day, hour, minute, and second
  corresponding to the initial time of the forecast
• nnn
  indicates the name of the model or production system (e.g., ‘GFS’)
• mmmm
  is the model type (‘glob’ or ‘lam’)
• vvvv
  is the version (‘test’ or ‘prod’).
• pppp
  indicates the product (‘etctr’ for ensemble TC tracks, ‘tctr’ for deterministic
  TC track forecasts, ‘tcan’ for TC analyses).
• bbb
  is the basin (‘atl’, ‘nep’, ‘nwp’, ‘nio’, ‘swi’, ‘sei’, ‘swp’, or ‘glo’ for global).
• The compression may be .Z, .gz, .zip, or .bz2.

CXML format

To facilitate easy exchange of information, particularly in a research environment, an XML-based format called Cyclone XML (CXML) has been developed to represent analyzed and forecast data for tropical and extra-tropical cyclones. CXML is descriptive and human-legible, making it easy for all human users and most automated applications to read. CXML is defined so it can carry data from observations and analyses, manual and NWP forecasts, multiple cyclones and multiple forecasts (ensembles). In its current version, it can include all information conveyed in other existing formats, while its flexibility and extensibility makes it simple to add new kinds of data as needed. CXML is not envisioned as a replacement for the WMO standard BUFR and CREX formats or other formats used in operational centers, but as a simple alternative.

Click here to learn more about CXML, including how to read CXML files. Click here to see what a sample ensemble TC track forecast written in CXML format looks like (courtesy of Piers Buchanan, Met Office).

Tracking algorithms

The producing centers use different tracking algorithms to identify and track cyclones in NWP output. They typically use information on central pressure, cyclonic vorticity, low level winds, etc., with the details varying among algorithms. In some cases, the TIGGE data providers use different algorithms to identify and track extra-tropical cyclones.

This section links to specific information on the tracking algorithms. Producers and users are encouraged to share their codes.

Tropical cyclones
CMC and NCEP –

How the NCEP tropical cyclone tracker works (Tim Marchok, 2002 AMS Conference on Hurricanes and Tropical Meteorology)
CMA –
ECMWF – Tropical cyclone forecasting at ECMWF: new products and validation(Gerald van der Grijn, 2002 ECMWF Tech. Mem. 386)
JMA –
KMA –
UKMO –

Extra-tropical cyclones
CMC and NCEP – The NCEP extra-tropical tracker is similar to the tropical cyclone tracker, but extra-tropical cyclones are identified using mean sea level pressure while more parameters are used for TCs.
Tracking uses a combination of wind vectors and linear extrapolation. (Marchok, 2002)
CMA –
ECMWF and UKMO – First θ_w at 1 km is used to identify fronts, then vorticity is used to identify and characterise developing cyclones along the fronts. Barotropic lows are identified from vorticity alone. Tracking uses a combination of steering level wind, extrapolation and lifecycle information (Hewson and Titley, 2010)
JMA –
KMA – Cyclones are identified using mean sea level pressure. Tracking uses combination of extrapolation (motion and p tendency) and climatological cyclone movement (Murray and Simmonds, 1991a, 1991b)

Sample ensemble TC products

The Korean Meteorological Administration and the Met Office have been investigating methods for combining ensemble TC forecasts from multiple models. A small number of sample products can be viewed here.

Links

North Western Pacific Tropical Cyclone (TC) Ensemble Forecast – Near real time TIGGE ensemble TC forecasts for the Northwest Pacific
Experimental Tropical Cyclone Tracks from Ensemble Models – NOAA ESRL demo site using Google Earth
Mio Matsueda’s TIGGE Museum – semi-operational forecast products for non-commercial use
T-PARC – THORPEX Pacific-Asian Regional Campaign
GIFS/TIGGE – Global Interactive Forecast System / THORPEX Interactive Grand Global Ensemble
ECMWF TIGGE data portal
NCAR TIGGE data portal (closing end of 2014)
CXML – Cyclone XML
IWTC-VI – Sixth WMO International Workshop on Tropical Cyclones (2006)
IWTC-VII – Seventh WMO International Workshop on Tropical Cyclones (2010)
IWTC-VIII – Eighth WMO International Workshop on Tropical Cyclones (2014)
IBTrACS – International Best Track Archive for Climate Stewardship

Last modified: 27 January 2015.
Please send feedback and comments to Beth Ebert (e.ebert@bom.gov.au)

Suggestions for improving this web page should be sent to Beth Ebert (e.ebert@bom.gov.au).
Image credits: North Pacific extratropical cyclone, 10 Jan 2008, Joe Sienkiewicz, NOAA;
Hurricane Katrina, 29 Aug 2005, NOAA; Tropical cyclone Ingrid, 8 Mar 2005, NASA; Victorian storm, 3 Feb 2005, Bureau of Meteorology