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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