Improvement of the JMA typhoon track forecast
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Transcript of Improvement of the JMA typhoon track forecast
Improvement of the JMA typhoon
track forecast
Kenji KISHIMOTO Kenji KISHIMOTO National Typhoon Center National Typhoon Center Forecast Division Forecast Division JMA JMA
1. Objective of track forecast1. Objective of track forecast
2. JMA display form for track forecast2. JMA display form for track forecast
3. Future challenge3. Future challenge
1. Objective of track forecast1. Objective of track forecast
2. JMA display form for track forecast2. JMA display form for track forecast
3. Future challenge3. Future challenge
Disaster-prevention activities are carried out Disaster-prevention activities are carried out
based on based on typhoon track forecasts.typhoon track forecasts.
Various disasters caused by typhoonsVarious disasters caused by typhoons
flood
storm surgelandslide
strong wind
high wave
A forecasted track shown as A forecasted track shown as area that covers forecast area that covers forecast
uncertainty (Probability Circle: uncertainty (Probability Circle: PC)PC)
I should prepare for the
typhoon.
Provider (Met. Service)
wants to show a PCas big as possible when forecast is difficult.
User (government, etc.)
wants to see a PC as small as possible in view of saving costs of disaster preparation activities.
Participation of 1,614 local governments all over Japan
high fair relative low low no answer
Satisfaction levelSatisfaction level
Only 30% were highly satisfied.
65% demands more accuracy
(smaller PC).
1 day
2 day
3 day
4 day
5 day
Forecast from 1 to 5 October
Analysis
Survey of user satisfaction of 5-day track forecastSurvey of user satisfaction of 5-day track forecast- MELOR (0918) in October 2009 -- MELOR (0918) in October 2009 -
Improvements of typhoon track forecastImprovements of typhoon track forecast
technical technical
componentcomponent
presentation presentation
componentcomponent
Typhoon track forecastTyphoon track forecast
1. Objective of track forecast1. Objective of track forecast
2. JMA display form for track forecast2. JMA display form for track forecast
3. Future challenge3. Future challenge
4 times/day (00, 06, 12, 18 UTC)
3-day track &
intensity forecast
5-day track
forecast
If it is expected to hold TS intensity or higher in the next 3 days, then
Day 3
Day 4
Day 5
Over-30kt-wind
area (analysis)
Over-50kt-wind area(analysis)
issued in 50
minutes
issued in 90
minutes
Storm warning area:
70 % PC + forecasted area of 0ver-50kt-wind
70% probability circle (PC):
the range into which the center of a TC is expected to move with 70% probability at each validation time.
Present display form of JMA track forecastPresent display form of JMA track forecast
70% PC
Track of track forecast errors Track of track forecast errors (annual & 5-year (annual & 5-year mean)mean)
km
year
3 day
2 day
1 day
19531953 19821982 19861986 19971997 20042004 88 PresentPresent(Start of TV service)
sectorial form
circular form
Only directional accuracy
directional accuracy +
speed accuracy
60% PC
PC + over-50kt-wind area
60% PC to 70% PC in 1997 PC reduction by 10%in 2004 by 15%in 2008
circular form + strong wind area
misunderstanding of PC center as TC
centerand
PC as strong wind area
no display ofTC movement
speed accuracy
Needs to be improved
Display form
History of display formHistory of display form
1. Objective of track forecast1. Objective of track forecast
2. JMA display form for track forecast2. JMA display form for track forecast
3. Future challenge3. Future challenge
1) Typhoon EPS operated experimentally since 2007 operated since 2008
Information on the
distribution of forecast
uncertainty
Motivation of the introduction of new display Motivation of the introduction of new display formform
2) 5-day track forecast operated
experimentally since 2007 operated since 2009
950km
Provisional forecast verification Provisional forecast verification (Jul. 2007 - Oct. 2009) (Jul. 2007 - Oct. 2009)
5-day
4-day
error
CFT
error
AFT error
3-day
vertical axis:
along FT
(AFT)
horizontal axis:
cross FT (CFT)
analysis track
forecast track (FT)
step.1 error relative to forecast track step.1 error relative to forecast track
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4-day 5-day
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4-day 5-day 4-day 5-day
FT direction
10 deg.
130 deg.
step.1 error relative to forecast track step.1 error relative to forecast track
AF
T e
rror
(km
)
CFT error (km)
AF
T e
rror
(km
)
CFT error (km)
AF
T e
rror
(km
)
CFT error (km)
AF
T e
rror
(km
)
CFT error (km)
AF
T e
rror
(km
)
CFT error (km)
AF
T e
rror
(km
)
CFT error (km)
332 cases
224 cases 108 cases
228 cases
84 cases
144 cases
step2. comparison of performance step2. comparison of performance between “circle” and “ellipse” with the same between “circle” and “ellipse” with the same
sizesize
Hitting ratio (%)
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AF
T e
rror
(km
)
CFT error (km)
510km
729km (510/0.7km)
357km (510x0.7km)
729km (510/0.7km)
357km (510x0.7km)
70%72%
56%
4-day, FT direction: 10-130 deg.
108 cases
Idea of makig “probability ellipse”Idea of makig “probability ellipse”
Step 2. making a basic circle based on ensemble spreadStep 2. making a basic circle based on ensemble spread
Step 3. deforming a basic circle within a fixed range Step 3. deforming a basic circle within a fixed range
to make an ellipse to make an ellipse
using the distribution of Typhoon EPS members using the distribution of Typhoon EPS members
Step 1. deciding centers of a circle Step 1. deciding centers of a circle
4-day, FT direction: 10-130 deg.
SummarySummary
• JMA has changed display form for typhoon JMA has changed display form for typhoon track forecast with the improvements.track forecast with the improvements.
• Typhoon EPS, operated since 2008, Typhoon EPS, operated since 2008, provides the information on the distribution provides the information on the distribution of forecast uncertainty. of forecast uncertainty.
• JMA is considering the introduction of a JMA is considering the introduction of a new display form to track forecast in the next new display form to track forecast in the next few years. few years.
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4-day 5-day 4-day 5-day
circle radius: 440km circle radius: 510km circle radius: 650km circle radius: 550km
hitting ratio (%)
hitting ratio (%)
hitting ratio (%)
hitting ratio (%)
step2. comparison of performance step2. comparison of performance between “circle” and “ellipse” with the between “circle” and “ellipse” with the
same sizesame size
224 cases 108 cases 84 cases
144 cases
• We judge a forecast confidence level (A/B/C) by using the confidence information Typhoon EPS ensemble spread.
What do we use for deciding a circle radius?
AA BB CC
480km480km 700km700km 950km950km
• 70% PC radius is decided by using the conversion table from confidence level into the radius.
as of 2009
TEPS
Group A
Group B
Group C
70% of cases of this Group are included within this position error (950km)
• The circle radius in each group is estimated based on the forecast verification result.
How do we make the conversion table?
as of 2009
AA BB CC
480km480km 700km700km 950km950km
5-day circle radius