Topic 1.5: Operational guidance and skill in forecasting structure change

1. Topic 1.5: Operational guidance and skill in forecasting structure change Presented by John Knaff CIRA/CSU Working Group: C. Guard, J. Kossin, T. Marchok, B. Sampson, T. Smith, N. Surgi

2. Presentation Outline • Review Typical Measures of TC structure • Operational TC Structure Guidance • Intensity verification • Long-term operational • Long-term guidance • Wind Radii Verification • 2005 Atlantic • Summary and Recommendations SIXTH INTERNATIONAL WORKSHOP ON TROPICAL CYCLONES

3. Measures of TC Structure • Intensity • Minimum Sea Level Pressure (MSLP) • Maximum Surface Winds (MSW)* • Wind Structure • Radii of significant winds/wind speed thresholds (e.g., Radii of 34-, 50-, 64-kt winds) * • Pressure Distribution • Outer closed or outer closed & circular isobar * Are used for the verification presented here SIXTH INTERNATIONAL WORKSHOP ON TROPICAL CYCLONES

4. Few Methods 24-h Dvorak extrapolation – subjective/statistical Purely statistical models based on historical best tracks (CLIPER, climatology, analogs) Statistical-dynamical models that use NWP forecasts of environmental conditions to make statistical forecasts Numerical Weather Prediction (NWP) methods that make deterministic forecasts. Consensus Methods, combination of skillful forecast methods Weaknesses Short-term, subjective Do not use current synoptic information, conservative best used for verification Conservative - cannot predict rapid intensity changes, timing at long leads, over intensify weak systems, poorly handle high latitude decay Spin-up issues, over intensify some systems, poor physical initialization, parameterized physics Only as good as the independent guidance Current TC Intensity Guidance Methods SIXTH INTERNATIONAL WORKSHOP ON TROPICAL CYCLONES

5. Fewer methods Climatology (tabular, equation form as a function of intensity) Vary among forecast centers Simple Statistical (CLIPER models) Basin dependent Numerical Weather Prediction. Weaknesses Only as good as the climatology, not documented Based on past operational estimates (are they good?) Scatterometry, aircraft? Effected by resolution, and vortex initialization Current Operational TC Wind Structure Guidance SIXTH INTERNATIONAL WORKSHOP ON TROPICAL CYCLONES

6. Operational Intensity Verification Caveats: • Datasets come from the RSMC, Miami (NOAA/TPC) and USA/Joint Typhoon Warning Center. • 1-minute sustained 10-m wind • Post season re-analyzed intensities making use of all available intensity estimates (i.e., Dvorak, AMSU, Quickscat, Aircraft (flight-level, MSLP) etc.) • Measurements for Verification • All intensities • Mean Absolute Errors (MAE) • Percent Reduction in Variance (PRV) SIXTH INTERNATIONAL WORKSHOP ON TROPICAL CYCLONES

7. Long-Term Operational Intensity Verification (MAE) All intensities Forecasts from RSMC, Miami (NOAA/TPC) SIXTH INTERNATIONAL WORKSHOP ON TROPICAL CYCLONES

8. Long-Term Operational Intensity Verification (MAE) All intensities Forecasts from USA/JTWC SIXTH INTERNATIONAL WORKSHOP ON TROPICAL CYCLONES

9. Intensity Verification other RSMCs Tropical Storm Intensity 2004-2005 RSMC, La Reunion 2000-2004 RSMC, Tokyo m/s & (kt) Taken from annual reports SIXTH INTERNATIONAL WORKSHOP ON TROPICAL CYCLONES

10. Trends in MAE kt per decade Significance is marginal (70%) using annual number of degrees of freedom SIXTH INTERNATIONAL WORKSHOP ON TROPICAL CYCLONES

11. Long-Term Operational Intensity Verification (PRV) Variance of the forecast errors Variance climatological errors • Where o is the observed intensity and p is the predicted intensity and the overbar represents a mean value. • Can be negative if the numerator (forecast error variance) is larger than the denominator (climatological variance) • This methodology penalizes forecasts methodologies for having non-random errors (e.g., bias) SIXTH INTERNATIONAL WORKSHOP ON TROPICAL CYCLONES

12. Long-Term Operational Intensity Verification (PRV) All intensities Forecasts from RSMC, Miami (NOAA/TPC) in EP and ATL All intensities Forecasts from USA/JTWC in WP and SH SIXTH INTERNATIONAL WORKSHOP ON TROPICAL CYCLONES

13. Long-Term Operational Intensity Verification (PRV) SIXTH INTERNATIONAL WORKSHOP ON TROPICAL CYCLONES

14. Trends in PRV Percent per decade Significant (95%) in the Atlantic, marginally significant (70%) in the other basins when based on annual number of degrees of freedom SIXTH INTERNATIONAL WORKSHOP ON TROPICAL CYCLONES

15. Intensity Guidance Methods Atlantic and East Pacific SHIFOR (1988-present) Statistical Hurricane Intensity FORecast, which uses simple climatology and persistence parameters SHIPS (1991-present, ATLC) Statistical Hurricane Intensity Prediction Scheme, (1996-present, EPAC) which uses climatology, persistence and real- time atmospheric and oceanic parameters GFDL (1995-present) Operational version of the Geophysical Fluid Dynamics Laboratory hurricane model GFDN (2001-present) GFDL model initialized from Navy global model fields SHIFOR5 (2001-present) Updated version of SHIFOR with 5 day forecasts West Pacific CLIM (1985-present) Climatological analog model STIFOR (1991-present) Statistical Typhoon FORecast Model, similar to SHIFOR GFDN (1995-present) GFDL model initialized from Navy global model fields AFW (2000-present) MM5 mesoscale model adapted to typhoon forecasts JTYM (2001-present) Japanese Meteorological Agency limited area typhoon model ST5D (2002-present) Updated STIFOR model and extended to 5 days STIPS (2003-present) Statistical Typhoon Intensity Prediction Scheme, similar to SHIPS ST10 (2005-present) Ensemble version of STIPS Southern Hemisphere CLIM(2000- present) Climatological analog. GFDN (2000- present) GFDL model initialized from Navy global model fields TC-LAPS (2001-present) BOM limited area prediction system ST5D (2004 –present) 5-day Climatology and persistence STIPS(2005 – present) STIPS SH (experimental run at NRLM) ST10 (2005 – present) STIPS SH ensemble (experimental, run at NRLM)

16. Comparison with Best 48-hr Intensity Guidance SIXTH INTERNATIONAL WORKSHOP ON TROPICAL CYCLONES

17. Comparison with Best 48-hr Intensity Guidance SIXTH INTERNATIONAL WORKSHOP ON TROPICAL CYCLONES

18. Best Guidance (Atlantic, E. Pacific and W. Pacific) Atlantic East Pacific West Pacific 1991 SHIPS SHIFOR CLIM 1992 SHIFOR SHIFOR CLIM 1993 SHIFOR SHIFOR CLIM 1994 SHIFOR SHIFOR CLIM 1995 SHIFOR SHIFOR CLIM 1996 SHIPS SHIFOR GFDN 1997 GFDL SHIPS STIFOR 1998 SHIPS SHIPS STIFOR 1999 SHIPS SHIPS STIFOR 2000 SHIPS SHIFOR STIFOR 2001 SHIPS SHIPS ST5D 2002 SHIPS GFDL ST5D 2003 SHIPS SHIFOR STIPS 2004 SHIPS GFDL STIPS 2005 SHIPS SHIPS ST10 2006-preliminary GFDL SHIPS/ICON ST10 SIXTH INTERNATIONAL WORKSHOP ON TROPICAL CYCLONES

19. Summary: Intensity Forecasting • There is evidence that forecasts, in general, are improving very slowly • Operational forecast improvements are being driven by improvements in guidance methods • Statistical-dynamical and regional/specialized NWP guidance are most skillful • Global models do not have skill and have larger errors than climatology and persistence based forecasts • Consensus methods created from skillful guidance have been demonstrated to produce better forecasts than single methods SIXTH INTERNATIONAL WORKSHOP ON TROPICAL CYCLONES

20. Wind Radii verification Caveats: • Post-season reanalyzed estimates of R34 used for verification • These make use of the best available data (variable) • QuickScat, AMSU, SSMI • Flight-level winds • SFMR • Ships/buoys • One year, Atlantic only Methods: • MAE in n. mi • Hit & False alarm rates. SIXTH INTERNATIONAL WORKSHOP ON TROPICAL CYCLONES

21. Wind Radii Guidance/Forecasts • OFCL – Official RSMC, Miami forecast • AVNI – NOAA Global Forecast System • GFTI – NOAA/GFDL model forecasts • MRCL – Multiple linear regression CLIPER Model, 3-days • DRCL – Statistical-Parametric CLIPER model, 5-days SIXTH INTERNATIONAL WORKSHOP ON TROPICAL CYCLONES

22. Wind Radii Verification (R-34 kt) 1596 1456 1316 1156 872 SIXTH INTERNATIONAL WORKSHOP ON TROPICAL CYCLONES

23. Wind Structure Verification Probability of Detection Radii of 34-kt winds MAE vs. False Alarm Trade off Probability of False Detection Radii of 34-kt winds SIXTH INTERNATIONAL WORKSHOP ON TROPICAL CYCLONES

24. Influence of Intensity Forecast Errors on Wind Radii 1832 1700 1544 1400 1104 860 668 Forecasts using Forecast intensities Forecasts using Best Track Intensities SIXTH INTERNATIONAL WORKSHOP ON TROPICAL CYCLONES

25. Influence of Intensity Forecast Errors on Wind Radii Hit Rate Increase False Alarm Decrease SIXTH INTERNATIONAL WORKSHOP ON TROPICAL CYCLONES

26. Summary: Wind Radii Forecasting • There are very few models • poor understanding of processes • poor developmental datasets • There are no skillful models • No higher level statistical models • NWP does not initialize the vortex properly, have sufficient resolution (global) • More accurate intensity forecasts will improve wind radii forecasts • There is a trade off between false alarm rates and MAE in current forecasts schemes (i.e. symmetric forecasts produce smaller MAE statistics) SIXTH INTERNATIONAL WORKSHOP ON TROPICAL CYCLONES

27. Summary TC Structure Forecasting Overall Forecasting of TC structure change is rather poor. • The forecasting process is still subjective • Best intensity forecasts are used as a baseline that is modified by the forecaster • Skillful wind radii guidance is unavailable • Intensity forecasts are improving very slowly and are being driven by improved guidance • Wind radii forecasting is in its infancy and is hindered by • Poor developmental datasets • Poor physical understanding • Has not been an operational priority • Only recently have such forecasts been verified. SIXTH INTERNATIONAL WORKSHOP ON TROPICAL CYCLONES

28. Future/Current Research and Development • Making better use of existing technology and datasets. Examples include : • Diagnostic studies to understand tropical cyclone wind field growth • Development of models to predict structure change using environmental and storm conditions • Model output statistics to predict wind radii • Indices to predict rapid intensification, annular hurricanes, secondary eyewall formation, etc. • Forecast techniques to improve short-term intensity forecasts that leverage existing and longstanding satellite technologies • Probabilistic models that account for track, intensity and wind radii error distributions • … Items for discussion SIXTH INTERNATIONAL WORKSHOP ON TROPICAL CYCLONES

29. Future/Current Research and Development • Development of new technology. • Next Generation Hurricane Forecast Model, the Hurricane – Weather Research and Forecasting (H-WRF) Model is being tested/developed • Physical initialization using a 3D-var framework that can make use of Dopplar radar information (WR-88D, airborne) and new instrument packages on the G-IV, and satellite data. • Coupling with waves via the Wavewatch III wave model • Parameterizations developed using the recent results of the CBLAST experiment • New instrumentation on operational aircraft • like the SFMR. • Others etc. Discussion? SIXTH INTERNATIONAL WORKSHOP ON TROPICAL CYCLONES

30. Recommendations • Continued development of consensus methods to improve intensity forecasts. • Use of model output statistics, particularly in wind radii prediction. • Greater effort toward high resolution NWP that has physical initialization and advanced data assimilation capabilities • Effort to make the newest technology/instrumentation and resulting observations available to real-time operational centers and tropical cyclone researchers. Additional recommendation based on knowledge gained during the process of writing the topic summary • There is a need for more operational scatterometry and similar active remote sensing instrumentation to detect tropical cyclone wind fields. None is currently planned. SIXTH INTERNATIONAL WORKSHOP ON TROPICAL CYCLONES