The Tropical Cyclone Information Processing System (TIPS)
of the Hong Kong Observatory
S W Li and P W Ng
Hong Kong Observatory
Hong Kong, China
Abstract
A decision-support tool named Tropical Cyclone Information Processing System (TIPS)
was developed by the Hong Kong Observatory, Hong Kong, China to facilitate decision
making in forecasting and warning operations during tropical cyclone (TC) situations.
TIPS serves four main functions: (i) integrate all TC related information and data,
including satellite/radar fixes and imageries, forecast tracks from warning centres and
those derived from NWP models for display; (ii) assimilate track data for computation of
an ensemble track for operational forecasting; (iii) compute key parameters for
evaluating local impact to facilitate warning decisions; and (iv) generate and dispatch
forecast and warning products to the local public and other weather centres. The system
has been in operation since 2001 and forecasters at the Hong Kong Observatory find
TIPS to be user-friendly and indispensable in TC forecast and warning operations. This
paper describes the design and features of TIPS.
1.
Introduction
On average, six to seven tropical cyclones affect Hong Kong (HK) each year. The
Hong Kong Observatory (HKO) is responsible for operating the Tropical Cyclone
Warning Service in HK.
The volume of meteorological information available to forecasters, such as
meteorological observations and numerical products, are ever on the increase especially
during TC situations. A tool to consolidate and assimilate large volumes of data is
essential for forecasters. In 2001, HKO developed a prototype Tropical Cyclone
Information Processing System (TIPS) to automate the plotting of satellite/radar fixes,
observed and predicted TC positions and tracks, as well as to calculate ensemble forecast
tracks, etc. With experience gained while operating the prototype, TIPS was overhauled
and enhanced in 2003. The new TIPS has improved architecture and functions and was
put into operation in 2004.
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2.
Tropical Cyclone Information Processing System (TIPS)
TIPS is designed to automate the ingestion and processing of TC data, present the
products in a consolidated display and generate bulletins for public dissemination.
Automation would enable forecasters to concentrate on the formulation of forecast and
warning strategies and reduce the chance of human error.
A modular design has been adopted in TIPS, adding flexibility to system
development as modules can be modified individually without affecting other modules.
Currently, TIPS has five modules, each comprising a number of sub-modules with
specific functions. Figure 1 is a schematic showing the five TIPS modules, each of
which will be discussed in details in subsequent sections.
Figure 1: Schematic diagram showing the major modules in TIPS.
2.1
TC Operation Module
This module includes a number of sub-modules to facilitate forecasters in
(a) assimilating TC data in different formats and from various sources; (b) producing the
forecast track; (c) generating and disseminating forecast and warning bulletins based on
the forecast track.
2.1.1 TC Centre Location Sub-module
Satellite and radar imageries are useful in locating the centre of a TC, especially
over open oceans where surface observations are sparse. This sub-module allows
forecasters to overlay satellite and radar imageries onto other data, such as TC positions.
Animation of these imageries is possible to facilitate easy tracking. Figure 2 shows an
overlay of satellite and radar imageries on the base map. TIPS also retrieves the analysis
data from other National Meteorological and Hydrological Services (NMHSs), such as
satellite/radar fixes and TC positions, and plot them on the same base map for references
(Figure 3). A “zoom-in” function offers more detailed features on a magnified map.
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Figure 2 -- Satellite and radar pictures
Figure 3 -- satellite and radar fixes together
on base map.
with the tracks in the zoom-in mode.
2.1.2 Forecast TC Information Sub-module
Apart from observation data, subjective forecast positions from other NMHSs and
NWP models are routinely received. This sub-module automatically extracts these data
from the HKO Unified Meteorological Database and displays them on the base map.
Forecasters can toggle on or off individual tracks for easy reference. Figure 4 is a
sample display of forecast tracks for Typhoon Chanchu from NMHSs and NWP models.
Figure 4 -- Sample display showing forecast TC tracks from NMHSs
and NWP models for Typhoon Chanchu.
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2.1.3 Forecast and Warning Products Sub-module
After the operational TC track has been finalised (using the Computation Module
described in Section 2.2), this sub-module will generate forecast and warning products
based on the forecast positions and intensities for subsequent dispatch to the public
through multiple channels, such as the HKO website, TV, radio, telephone, fax,
newspaper, etc… A click on the “Export-Server” button at bottom of the display shown
in Figure 5 will initiate the processes of product generation and dissemination. An
automatically generated TC track chart for the HKO website is shown in Figure 6.
Figure 5 – A single mouse click to send TC data to
Figure 6 -- TC Track in the HKO Website
generate forecast and warning products.
generated using data from the TIPS.
2.1.4 Past Tracks Sub-module
Past TC track data can be retrieved easily from the HKO Unified Meteorological
Database via TIPS and displayed alongside the current data (e.g. other TC tracks) for post
analysis as well as for presentation purpose. Figure 7 is an illustration of this function.
Figure 7 -- Loading and displaying past TC track data
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2.2
Computation Module
This module calculates forecast TC positions, forecast rainfall and probability of
evening thunderstorms associated with the TC, as well as other key parameters to
facilitate decision making.
2.2.1 Forecast TC Track Sub-module
Forecasters can use the “Forecast TC Track” sub-module to generate the forecast
TC track via one or a combination of the following methods: (a) automatic calculation of
an ensemble track with data from NWP models and meteorological centres (Lee and
Wong, 2002). Forecasters can select specific models to be included, and assign
appropriate weighting factors to generate the ensemble track and use it as the forecast
track; (b) extrapolation from the existing HKO TC track in its “Warning for Shipping”
bulletins; (c) copying of a selected NWP TC track; (d) extrapolation from past data; and
(e) creation of a track by manual input. A user-friendly tool is available to facilitate
editing of the forecast track by either dragging the “track” on the base map or via manual
input in a table format. Figure 8 shows how the “track” may be modified using this
“drag” tool.
Figure 8 -- Modifying a forecast track using the “drag” tool.
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2.2.2 Rainfall and Evening Thunderstorm Sub-module
TCs can bring heavy rain to Hong Kong. Typhoon Sam brought a total of 616.5
millimetres during its passage from 21 to 26 August 1999 (HKO 2000). Also, when a
TC passes to the east or southeast of Hong Kong, the associated northerlies in its outer
circulation may bring heat thunderstorms that have developed further inland during the
afternoon (Peterson and Leong 1978). These thunderstorms usually affect Hong Kong
in the evening after a day of hot weather, thus the name “evening thunderstorms”.
Once the forecast TC track is finalized, the “Rainfall and Evening Thunderstorm”
sub-module calculates the amount of rainfall and the probability of evening
thunderstorms (Peterson and Leong 1978) due to a TC using the Analogue Method
(Kwong 1974) and past statistics respectively. Examples are shown in Figures 9 and 10.
Figure 9 -- Textual output for the analogue TC
Figure 10 -- Textual output for the probability of
rainfall prediction.
evening thunderstorms.
2.2.3 Local Wind Parameters Sub-module
To facilitate decision making and formulation of forecast and warning strategies,
critical information such as the TC’s closest approach to HK, duration of associated
strong and gale winds, time and location of landfall etc. are required. The “Local Wind
Parameters” sub-module enables forecasters to estimate these parameters.
The closest approach distance and time of landfall are computed directly using the
forecast TC track. For onset and cessation of strong and gale force winds, the timing
can be estimated based on the strong and gale wind radii of the TC and NWP model
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outputs or from statistical data.
Wind strength forecasts at various locations in Hong
Kong are performed using a set of wind strength probability contours derived from
statistical data. Figure 11 depicts the probability contours selected during the passage of
Typhoon Chanchu in 2006.
Cessation time
Onset time
Figure 11 -- Track of Typhoon Chanchu with probability contours of gale and strong winds (red for gales
and black for strong winds) and onset and cessation times of strong winds.
2.2.4 Storm-Surge-Interface Sub-module
Some areas in HK are relatively low-lying and prone to sea flooding due to storm
surge brought about by TCs. The HKO runs a separate Storm Surge Model to predict
storm surge heights. The “Storm-Surge-Interface” sub-module injects TC data to the
Storm Surge Model, initiates computation and retrieves the output for display on TIPS.
2.3
e-Tools Module
An e-tools module provides an electronic version of common handy tools to
facilitate forecasters in assimilating and analyzing TC data and information. The
following are some of these handy tools:



Ruler – to measure distance and bearing of two points
Pens – to add annotations on the base map
Calculator – to calculate distance and bearing
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2.4

Notepad – to jot down short note for future reference

Lookup tables – to convert wind speed and distance to different units, etc.
Online Help Module
User-friendliness is one of the major features built into the TIPS. The familiar
Windows “look” user interface reduces the training time for system operation.
Furthermore, an Online Help menu (Figure 12) common to other Windows applications is
incorporated. Users can display the manual whenever he/she is uncertain of any TIPS
functions and features. Indexing is also available for quick search of interest topics.
Figure 12 -- Online help manual in TIPS
2.5
Security Module
Data integrity is crucial to forecast and warning operations. Inadvertent deletion
or modification of TC data will have huge impact on the operation of the TC warning
system which might result in damage of properties and even loss of lives. Strong data
security is maintained by this module for gaining access to TIPS. Unauthorised users
are only allowed to view the data and editing is prohibited. Authentication is carried out
at the user and the machine level, i.e. users are allowed to log onto TIPS with correct
passwords from designated PCs only.
3.
Future Work
TIPS is an indispensable decision support tool for HKO forecasters in TC operations.
The system enhances the efficiency of forecast and warning operations by integrating
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data and information which may be scattered around the forecasting office, in different
workstations and various forms, into a single integrated display. The system also has a
box of tools to aid forecasters in formulating their TC forecast and making decisions in
the forecast and warning operations. Selected TIPS displays, with observed and
predicted TC tracks, are routinely output to a special Internet website. Other users can
log into this special website using password provided to view the displays.
The system will continue to evolve with modifications and enhancements in
response to changes in the HK Tropical Cyclone Warning System and feedbacks from
forecasters. More TC forecasting tools, such as analogue TC tracks, will be added to the
system in future. Analysis and forecast data from more NMHSs and NWP models will
be included when available. A web-based user interface to facilitate remote log-in is
being considered to enable users to access basic TIPS functions, such as panning and
zooming, selecting and deselecting tracks for display, using e-tools to generating various
decision support parameters, etc…
References
HKO 2000, Tropical Cyclones in 1999, Hong Kong Observatory (HKO), the Government
of Hong Kong Special Administrative Region, Hong Kong.
Kwong, W.P., 1974: Tropical Cyclone Rainfall in Hong Kong, Technical Note No. 38,
Hong Kong Observatory, the Government of Hong Kong Special Administrative Region,
Hong Kong.
Lee T.C. and M.S. Wong 2002, The use of Multi-model Ensemble Techniques for
Tropical Cyclone Track Forecast at the Hong Kong Observatory, WMO Commission for
Basic Systems Technical Conference on Data Processing and Forecasting Systems 2002.
Peterson, P. and H.C. Leong, 1978: Evening Thunderstorms in Hong Kong Associated
with Tropical Cyclones, Technical Note (Local) No. 33, Hong Kong Observatory, the
Government of Hong Kong Special Administrative Region, Hong Kong.
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