Visually Enhanced Composite Charts for Severe Weather Forecasting and Real-time Diagnosis

1. Visually Enhanced Composite Charts for Severe Weather Forecasting and Real-time Diagnosis Josh Korotky NWS Pittsburgh PA NROW Annual Meeting 2002

2. Agenda • Composite Chart Approach and Diagnostic Templates • A Case study • LES 4 Panels • Cyclogenesis 4 Panels • GFS

3. The real atmosphere has great difficulty simulating the model atmosphere……many good forecasts will continue to be ruined by atmospheric error! The Forecaster’s Paradox

4. Motivation • Due to the growing volume of available data… • …and the time intensive process of generating / disseminating forecast and warning products… • …it is critical that forecasters extract relevant information quickly before and during severe weather forecast and warning operations • Diagnostic and forecast methods that use visualization to highlight essential physical processes … • Promote a better (and quicker) understanding of the real-time potential • Allow forecasters to better anticipate the most probable range of convective evolutions for a given environment

5. Composite Chart Approach • Effective composite charts: • Highlight important information….not all information • Reveal the physical processes that promote severe storm development, convective organization, and storm mode • Lead to quick recognition of the convective potential • Composite chart contents include: • Measures of instability and vertical wind shear • 3D moisture content, distribution, and availability • Synoptic and mesoscale forcing mechanisms • Charts are enhanced visually by managing colors, images, and contours

6. Evaluating the Convective Potential

7. Composite Chart Model Diagnostic Templates

8. Low – level Features

10. Upper – level Features

12. RUC Analysis

13. A Case Study • Highlights a severe convective wind event that effected parts of Ohio, Pennsylvania, West Virginia, New York, and Maryland on 9 March 2002 • Composite charts of model forecast fields (Eta) are supplemented with composite charts of hourly RUC surface analysis • Eta for evaluating large scale convective potential • Hourly RUC provides a critical link to the model forecasts

14. 850mb Wind (kt) and Normalized Vcomp Wind Anomaly 08/12 UTC Eta: 33hr Forecast Valid 3/9/02 - 21 UTC 4 – 4.5 SD

15. 850mb Wind and Normalized Vcomp Wind Anomaly 27hr Forecast Valid 3/9/02 - 21 UTC > 4.5 SD

16. Upper and Low-level Features • 33, 21, 9 hr forecasts valid at 21 UTC 9 March

17. Upper-level Features - 08/12 UTC Eta 33hr Forecast Valid 3/9/02 - 21 UTC

18. Low-level Features - 08/12 UTC Eta 33hr Forecast Valid 3/9/02 - 21 UTC

19. Upper-level Features – 09/00 UTC Eta 21hr Forecast Valid 3/9/02 - 21 UTC

20. Low-level Features – 09/00 UTC Eta 21hr Forecast Valid 3/9/02 - 21 UTC

21. Upper-level Features – 09/12 UTC Eta 9hr Forecast Valid 3/9/02 - 21 UTC

22. Low-level Features – 09/12 UTC Eta 9hr Forecast Valid 3/9/02 - 21 UTC

23. Summary of the Large Scale Potential Successive runs of the Eta indicate: • Deep layer of strong flow • 65 – 70 kts at 850mb over Ohio Valley • Significant vertical wind shear associated with vigorous low-level jet • SRH 400 – 500 m2s2 • 0-3km normalized shear > .014 s-1 • Moderate moisture • Warm sector surface dew points 55 – 57oF • Narrow layer of deep moisture • Potential for cloud breaks ahead of front • Destabilizing potential

24. Summary of the Large Scale Potential • Considerable low-level forcing • Strong moisture flux convergence • Strong frontogenesis along a vigorous frontal system • Significant pressure rise/fall couplet indicates deepening/dynamic system • 10mb/3hr pressure rises behind front • 8mb/3hr pressure falls ahead of front • But….only marginal instability • CAPE forecast to remain less than 500 jkg-1 • Best Lifted Index (BLI) expected to reduce no further than -2

25. A Range of Expectations • Expectations • Strong linear forcing will promote a narrow low-topped squall line • Isolated/scattered wind damage the primary threat … unless the real-time environment destabilizes more than indicated • The real time challenge • Do observations / RUC / LAPS analysis indicate greater instability? • Greater instability would indicate more widespread severe potential

26. Real Time RUC Surface Analysis3/9/02/ 18 UTC – 3/9/02/ 21 UTC Linking the model forecast to real-time events…

27. 18 UTC RUC Analysis

28. 19 UTC RUC Analysis

29. 20 UTC RUC Analysis

30. RUC / Observational Summary at 20 UTC • The moisture, forcing, vertical wind shear, pressure pattern, and pressure tendency substantiate initial expectations… • The environment has destabilized more than expected !! • Observations • Winds gusting mid 30s kts ahead of front • Radar indicated a developing low-topped narrow squall line • Reports from CLE and ILN indicated wind gusts > 80 mph and wind damage associated with convective line • New Expectations • With indications of greater instability and real-time reports… • Damage is going to be widespread rather than scattered/isolated • Damage will be from winds…low probability of tornadoes

31. 23 UTC Radar and Satellite

32. Conclusions • A narrow, low-topped squall line produced significant wind damage throughout the NWS PBZ CWA • Forecast (Eta) and diagnostic (RUC) methods that combine science and visualization… • Allowed forecasters to better anticipate the most probable range of convective evolutions before the event • Promoted a better (and quicker) understanding of the changing convective potential during the event • Contributed to more effective warning decisions.

33. LES 4 Panels

34. Low – level Features

35. Low-level Features – Valid 00 UTC

36. Low-level Features – Valid 00 UTC

37. Low-level Features – Valid 12 UTC

38. Low-level Features – Valid 12 UTC

39. Cyclogenesis 4 Panels

40. Upper-level Features – Valid 21 UTC 16 Oct 2002

41. Low-level Features – Valid 21 UTC 16 Oct 2002

42. GFS