WMO Workshop on Public Weather Services –

Effective Warning Systems

David Hui

Macao, 18 April 2013

Group exercise

Create a check list for effective warning system

Users’ response

Real time dataWarning strategy

& operations

Internal training

Public education & outreach

BusinessContingency Plan

warnings

Dissemination

Identifyextreme / hazardousweather

Knowclimatology

Understandimpacts &

users’ requirements

Set upwarning criteria

Considerations when formulating operational warning strategy

• Tools– Essential vs supporting

• Value– belated warnings are of little use– early warning with intrinsic flexibility of the system

• Partners– Understand & work together

• Pace and Timing– various level to trigger matching actions – time when criteria reached– time that are important for users’ decision making

TC warning system in Hong Kong

• Standby Signal No. 1

• Strong Wind Signal No. 3

• No. 8 Gale or Storm Signal

• Increasing Gale or Storm Signal No. 9

• Hurricane Signal No. 10

• Average no. of TC affecting Hong Kong: 6.4 / year• Warning Purpose: High wind and related impact• No. of days with warning effective in 2006:20

Experience during passage of Vicente

NO. 10NO. 8

Hurricane force

Gale force

Valued added messages

Signal

Issuing Cancelling

Time Extract of Messageshh m

mdd/mon/yyyy

hh mm

dd/mon/yyyy

1 15:40 21/Jul/2012 05:20 23/Jul/2012

04:45LOCAL WINDS ARE EXPECTED TO STRENGTHEN.  THE OBSERVATORY WILL ISSUE THE STRONG WIND SIGNAL, NO.3 SHORTLY.

3 05:20 23/Jul/2012 17:40 23/Jul/2012

06:45 THE CHANCE FOR ISSUING THE GALE OR STORM SIGNAL, NO. 8 DURING THE DAY IS NOT HIGH.

11:49IF VICENTE FURTHER INTENSIFIES OR SPEEDS UP TOWARDS THE COAST OF GUANGDONG, THE OBSERVATORY WILL CONSIDER THE NEED OF ISSUING THE GALE OR STORM SIGNAL NO. 8 AROUND SUNSET.

13:55LOCAL WINDS ARE EXPECTED TO STRENGTHEN FURTHER. THE OBSERVATORY WILL CONSIDER ISSUING THE GALE OR STORM SIGNAL NO. 8 BETWEEN 5 P.M. AND 8 P.M.

8 NE 17:40 23/Jul/2012 23:20 23/Jul/2012

Hour of the Day that Respondents Most Likely to Access Weather Information

Hour of the Day that Respondents Most Likely to Access Weather Information

1%

35%

1%

54%

39%

20%

0%3%

0%

10%

20%

30%

40%

50%

60%

01:01 -05:00

05:01 -08:00

08:01 -10:00

10:01 -14:00

14:01 -17:00

17:01 -21:00

21:01 -01:00

Noparticular

time

Warnings must evolve to survive

Enhanced Warning System

Changing Needsof society Warning

System

Evolution of warnings in Hong Kong

Warning Process

Monitoring & Review ProcessDesign Process

Considering Needs of Society & Stakeholders

Decision-making/Response Process

Education & Reaching-out

Process

Development of an Effective Warning System + Operational Strategy

Warning Process

Monitoring & Review ProcessDesign Process

Considering Needs of Society & Stakeholders

Decision-making/Response Process

Education & Reaching-out

Process

Development of an Effective Warning System + Operational Strategy

Monitoring & Review Process

• Forecast Verification objective score• Public Opinion Survey perception, users’

needs/expectations• Focus group testing new services/products• Liaison group tailor-make products for special

users• Talks, public lectures collecting opinion in

casual way• News reports immediate public perception

• Weather forecast in qualitative terms

Mainly cloudy. A few rain patches and squally thunderstorms at first. The temperature will range between 24 and 28 degrees. Moderate east to northeasterly winds, occasionally fresh over offshore waters.

• Marking schemes for the six weather elements: wind speed, state of sky, precipitation, visibility, maximum temperature and minimum temperature

• A score was given for each element

• An aggregate score with weighting characteristics of seasons

HKO Objective Verification Scheme

Marking schemeState of sky

Category Sunshine duration(in %)

Mean cloud amount (in oktas)

Overcast 0 7.6-8

Cloudy 0-5 6.1-7.5

Mainly cloudy 5.1-10 6.1-7.5

Mainly fine 10.1-50 0-6

Fine/sunny/clear >50.1 0-6

State of sky

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25

Mar

ks

Sunshine duration (%)

Marking scheme of sunshine duration for the category of cloudycloudy

• Different weightings (in %) assigned to different weather elements at different time of the year according to climatology and the relative

importance of the elements in the eye of the public Wind State of sky Precipitation Visibility Max temperature Min temperature

January 15 15 20 0 20 30

February 10 10 20 10 20 30

March 5 5 30 30 15 15

April 5 5 40 30 10 10

May 10 10 60 0 10 10

June 20 10 60 0 5 5

July 20 15 60 0 3 2

August 20 15 60 0 3 2

September 20 20 50 0 5 5

October 20 20 30 0 15 15

November 20 20 20 0 15 25

December 15 20 20 0 15 30

HKO Objective Verification Scheme

• The score was in general on the rising trend in line with scientific advancement in weather observations, remote sensing technology, NWP and weather forecasting skills

Trend of verification scoresMonthly mean score of Local Weather Forecast

75

80

85

90

95

10019

89

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

Year

Sco

re

Monthly Mean Score

12-Month Running Average