Improvement of the JMA typhoon track forecast

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Improvement of the JMA typhoon track forecast Kenji KISHIMOTO Kenji KISHIMOTO National Typhoon National Typhoon Center Forecast Division Center Forecast Division JMA JMA

description

Improvement of the JMA typhoon track forecast. Kenji KISHIMOTO National Typhoon Center Forecast Division JMA. 1. Objective of track forecast. 2. JMA display form for track forecast. 3. Future challenge. - PowerPoint PPT Presentation

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

NEPARTAK (0919)NEPARTAK (0919)

New display formNew display form

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 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

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CFT error (km)

AF

T e

rror

(km

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CFT error (km)

AF

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rror

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CFT error (km)

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rror

(km

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CFT error (km)

AF

T e

rror

(km

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CFT error (km)

AF

T e

rror

(km

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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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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.

Thank you Thank you

very much very much

for your attention!for your attention!

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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