Introduction
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). This exchange of real-time TC forecasts will further
the immediate goals of the THORPEX Pacific-Asian
Regional Campaign (T-PARC)
(August 2008-March 2009), designed to study the lifecycle of tropical and
extratropical cyclones over the northern Pacific. 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.
These data are also available at the Research Data Archives at NCAR at
http://dss.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.
This section links to specific information on the tracking algorithms.
Producers and users are encouraged to share their codes.
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 -
Met Office forecast tracks verification method
(based on article in Dec 1994 NWP Gazette)
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
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
CXML
- Cyclone XML
IWTC-VI - Sixth WMO
International Workshop on Tropical Cyclones
Last modified: 25 March 2009.
Please send feedback and comments to Beth Ebert (e.ebert@bom.gov.au), cc to Zoltan
Toth (zoltan.toth@noaa.gov).
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
