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Forecasting Tropical cyclones

Forecasting Tropical cyclones. Regional Training Workshop on Severe Weather Forecasting and Warning Services (Macao, China, 9 April 2013). Contents. Outline of TC forecasting process TC Analysis TC Forecasting Verification of TC forecast and models. Outline of TC forecasting process.

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Forecasting Tropical cyclones

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  1. Forecasting Tropical cyclones Regional Training Workshop on Severe Weather Forecasting and Warning Services (Macao, China, 9 April 2013)

  2. Contents Outline of TC forecasting process TC Analysis TC Forecasting Verification of TC forecast and models

  3. Outline of TC forecasting process Operational process Observations SYNOP,SHIP Radar Satellite, etc. Analysis Forecasting Forecast Models Forecast products Reanalysis Verification Best track

  4. Outline of TC forecasting process Operational TC analysis and Forecasting • 1. TC Analysis • satellite observations (Dvorak Method) • surface observations • radar observations (only position) • 2. TC Forecasting • NWP models • Persistence (for very short-term forecast)

  5. Contents Outline of TC forecasting process TC Analysis TC Forecasting Verification of TC forecast and models

  6. TC Analysis • Analysis of current position and intensity • satellite observations • surface observations • radar observations (position only) • TC analysis is important for TC forecasting. • With a wrong TC analysis of current position and intensity, TC forecast will be wrong even if the NWP model performance is excellent.

  7. TC Analysis IR & VIS image provided every 30 min. by MTSAT MTSAT microwave image(35GHz & 85GHz) available when satellites hit a cyclone TRMM DMSP Series GCOM-W1 From JAXA webpage From NASA webpage From JAXA webpage

  8. TC Analysis Observations such as SYNOP/SHIP/BUOY

  9. TC Analysis Naha Radar image

  10. TC Analysis Satellite image (Dvorak method) cloud pattern intensity

  11. TC Analysis 0 Estimate of pressure profile of a tropical cyclone Exponential ordinate = Takahashi’s diagram Normal ordinate

  12. TC Analysis Estimate of pressure profile of a tropical cyclone (0) This method is available if you can determine TC Center accurately. (1) Measure the distance from TC Centerto SYNOP data A on the weather map. (2) Plot the pointAwhich show the observed pressure(PA)and distance from the TC center (rA) on the pressure profile chart. (3) Same processes (1) & (2), plot B, C… (4) Draw a linear regression line on the pressure profile chart, then extrapolate the line to the TC center for estimating PCN. B PB A PA C PC PCN rC rA rB

  13. TC Analysis Estimate of 30-kt/50-kt wind area

  14. Contents Outline of TC forecasting process TC Analysis TC Forecasting Verification of TC forecast and models

  15. TC Forecasting • Forecasting track and intensity • Based on NWP models • Deterministic model (GSM) • Ensemble system (TEPS) • Consensus method (average of various models) • Multi ensemble system • Persistence • Note: • valid only for short-term forecast • small scale oscillations leads to wrong interpretations.

  16. JMA NWP models medium rangeforecast short range forecast one-week forecast tropical cyclone forecast

  17. TC forecasting based on NWP models 3-day forecast NWP Model outputs 5-day track forecast

  18. TC forecasting (track) Track forecast Center position forecast Radius of probability circle

  19. TC forecasting (track) 1. Center position forecast • main: GSM and TEPS • reference: One-Week EPS, ECMWF, ECMWF EPS

  20. TC forecasting (track) 2. Radius of probability circle (PC) • PC shows uncertainty of track forecast. • radius of PC is based on verification of recent track forecast. • PC decision method is different between 72-hour forecast and 120-hour forecast.

  21. TC forecasting (track) 2. Radius of probability circle (1) 24, 48 and 72-hour forecast PC radius depends on forecasted TC movement based on the verification of TC track forecast in 2004 to 2007. NW other Unit: nm

  22. TC forecasting (track) 2. Radius of probability circle (2) 96 and 120-hour forecast PC radius depends on ensemble spread of TEPS based on verification of track forecasts in 2007-2008. Tracks of TEPS membersPink track: ensemble mean track Black track: GSM track Ensemble spread 6-hourly accumulated ensemble spread (km) (2007-2008)

  23. TC forecasting (track) 2. Radius of probability circle (2) 96 and 120-hour forecast Unit: nautical mile Our verification result says that the radius of 70% probability circle enlarges in proportion to ensemble spread.

  24. TC forecasting (Intensity) Intensity forecast Central pressure (CP) Maximum sustained wind (MSW) Peak gust Storm warning area

  25. Operational TC forecast 1. Central Pressure(CP) • Model output and the guidance Central Pressure Initial intensity adjustment GSM prediction G M G A M M A M M A M M G G G G G Analysis G A GSM guidance Time present forecast time termination of adjustment (FT=36)

  26. Operational TC forecast 1. Central Pressure (CP) • Statistical development curve

  27. Operational TC forecast CP MSW 2. & 3. Forecast of MSW & peak gust Statistical method • MSW conversion from CP • Peak gust MSW x 1.4

  28. Operational TC forecast Storm Warning Area 50-kt wind radius CP Large Central Pressure (hPa) PC radius Standard Small 50kt-wind radius 50kt wind radius (NM) 4. Forecast of Storm warning area Statistical method • 50-kt wind radius (converted from CP) + PC radius

  29. Operational TC forecast 4. Forecast of Storm warning area Developing stage Mature stage

  30. Contents Outline of TC forecasting process TC Analysis TC Forecasting Verification of TC forecast and models

  31. Verification of TC forecast and models Position errors of track forecasts in 2011

  32. Verification of TC forecast and models Position errors of GSM in 2011

  33. Verification of TC forecast and models Position errors of GSM in 2011 FT=48 FT=72 direction of movement

  34. Verification of TC forecast and models Intensity errors of GSM in 2011 Developing stage Weakening stage develop more slowly than analysis development persists in many cases

  35. Verification of TC forecast and models Position errors of TEPS in 2011

  36. Verification of TC forecast and models example of model outputs: Nock-ten (1108) 26 Jul, 12UTC Initial

  37. Verification of TC forecast and models example of track forecast: Nock-ten (1108) 26 Jul, 18UTC Initial

  38. Verification of TC forecast and models example of model outputs: Nanmadol (1111) 24 Aug, 12UTC Initial

  39. Verification of TC forecast and models example of track forecast : Nanmadol (1111) 24 Aug, 18UTC Initial

  40. End

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