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Using Historical Analogs as Medium-Range Guidance for Severe Weather Episodes

Using Historical Analogs as Medium-Range Guidance for Severe Weather Episodes. Chad M. Gravelle * and Charles E. Graves Saint Louis University - Department of Earth and Atmospheric Sciences * Current affiliation: CIMSS-University of Wisconsin / NWS Operations Proving Ground Jeffrey P. Craven

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Using Historical Analogs as Medium-Range Guidance for Severe Weather Episodes

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  1. Using Historical Analogs as Medium-Range Guidance for Severe Weather Episodes Chad M. Gravelle* and Charles E. Graves Saint Louis University - Department of Earth and Atmospheric Sciences * Current affiliation: CIMSS-University of Wisconsin / NWS Operations Proving Ground Jeffrey P. Craven NOAA/NWS Weather Forecast Office - Milwaukee/Sullivan, WI Alan E. Gerard NOAA/NWS Weather Forecast Office - Jackson, MS John P. Gagan NOAA/NWS Weather Forecast Office - Springfield, MO 2012 National Weather Association Annual Meeting – Madison, WI 8 October 2012

  2. CIPS Analog Guidance History • Began in 2008 after science meetings between SGF/LSX and SLU. • Started with cold-season guidance and expanded to the warm season in 2011. • Completely driven by a grassroots movement, no outside funding has ever been awarded. • Since November 2009, the CIPS analog guidance has been mentioned in over 250 AFDs by 38 WFOs across the CONUS.

  3. What are Historical Analogs? • Early Analog Definition: If the current state of the atmosphere resembles a previous state then the two are termed analogs, and for a period of time the current state may evolve in a similar fashion as the past state (Lorenz 1969). • Modern Analog Definition: Analogs are found using the perfect prognostic (“perfect prog”) approach. NWP forecast fields are used as a pattern-recognition tool in contrast to using analysis maps as a forecast tool (Root et al. 2007). • GFS 30-h Forecast • Analog – 19830212/0000

  4. CIPS Analog Guidance – “How Do We Do This?” • Search the 31-yr North American Regional Reanalysis (NARR) dataset against the model forecast (NAM/GFS212-40km) for potential analogs. • 3 months (±45 days from current day) • 6 h temporal resolution • 11,160 potential analogs (31 years, 90 days, 4 per day) • Remove duplicate times by choosing the “best” analog over a 24-h period. 1984011512, 1984011518, 1984011600, 1984011606 • Refine and rank (using the analog time and ±6h from analog time) the resulting analogs (prefect analog score is 21). • Create “impact-based” guidance products. • Fields: Field weights are in parenthesis. • 300HGHT • 300SPED • 500HGHT • 500SPED • 850HGHT(3) 850SPED (2) • PMSL (2) • 850TMPC • 850MIXR (3) • 2mTMP (2) • 2mDWP (2) • AVGRELH • PWTR 6 CONUS Domains

  5. CIPS Analog Guidance – Guidance Based on Most Similar Analogs • Impact Guidance • Precipitation and COOP Snow Mean and Exceedance Probabilities • Severe Thunderstorm Probabilities • Surface Temperature, Heat Index, and Wind Chill Exceedance Probabilities • Surface Wind Gusts Exceedance Probabilities • Surface Flight Rules Exceedance Probabilities (coming soon) • Severe thunderstorm probabilities are developed from the mean of the individual analog Practically Perfect Forecasts (PPFs). • Developed by SPC forecasters (Brooks et al. 1998), the approach of the PPF method is that it tries to “mimic” what a near-perfect forecast would look like.

  6. Historical Analogs – Why in the Medium Range of the Forecast? • Forecasters use deterministic and ensemble medium-range (days 4-7) NWP output to help formulate: • Growing need for NWS partners to know the potential that a high-impact weather event may occur 4-8 days in advance. • Identifying significant events is challenging. • Historical analogs can be used as a “decision assistance tool”. • SPC Day 4-8 Outlook • NWS Hazardous Weather Outlook • CPC U.S. Hazards Outlook

  7. SPC Guidance – Valid on 14 April 2012 • Day 6 Outlook • Day 5 Outlook • SPC 24-h Storm Reports ending 20120415/1200 • Day 4 Outlook • Day 2 Outlook

  8. 14 April 2012 – Severe Weather and Tornado Outbreak L L • GFS 120-h Forecast valid 20120415/0000 • PMSL, 2-m TMPF, and 2-m DWPF

  9. 14 April 2012 – Severe Weather and Tornado Outbreak L L • GFS 120-h Forecast valid 20120415/0000 • 850-mb Winds

  10. 14 April 2012 – Severe Weather and Tornado Outbreak L L • GFS 120-h Forecast valid 20120415/0000 • 300-mb Isotachs

  11. 14 April 2012 – Severe Weather and Tornado Outbreak L L • GFS 120-h Forecast Synoptic-Scale Features valid 20120415/0000 • 24-h SPC Severe reports ending 20120415/1200

  12. 14 April 2012 – Severe Weather and Tornado Outbreak L L • GFS 120-h Forecast Synoptic-Scale Features valid 20120415/0000 • 24-h SPC Severe reports ending 20120415/1200

  13. 14 April 2012 – Severe Weather and Tornado Outbreak L • Mean of Top 15 Analogs Based on GFS 120-h Forecast valid 20120415/0000 • PMSL, 2-m TMPF, and 2-m DWPF

  14. 14 April 2012 – Severe Weather and Tornado Outbreak L • Mean of Top 15 Analogs Based on GFS 120-h Forecast valid 20120415/0000 • 850-mb Winds

  15. 14 April 2012 – Severe Weather and Tornado Outbreak L • Mean of Top 15 Analogs Based on GFS 120-h Forecast valid 20120415/0000 • 300-mb Isotachs

  16. 14 April 2012 – Severe Weather and Tornado Outbreak L • Mean of Top 15 Analog Features Based on GFS 120-h Forecast valid 20120415/0000 • Probability of Severe Weather Within 40km Grid Point (8 most severe analogs)

  17. 14 April 2012 – Severe Weather and Tornado Outbreak • Synoptic-Scale Features Based on GFS 120-h Forecast • 24-h SPC Severe Reports ending 20120415/1200 L • Mean of Top 15 Analog Features Based on GFS 120-h Forecast valid 20120415/0000 • Probability of Severe Weather Within 40km Grid Point (8 most severe analogs)

  18. Analog Guidance (F144-F072) – 14 April 2012 • Based on 6-day Forecast • Based on 5-day Forecast • Based on 4-day Forecast • Based on 3-day Forecast

  19. SPC Guidance – Valid on 29 June 2012 • Day 6 Outlook • Day 5 Outlook • SPC 24-h Storm Reports ending 20120630/1200 • Day 4 Outlook

  20. 29-30 June 2012 – Great Lakes/Ohio Valley Derecho L L • GFS 108-h Forecast valid 20120629/1200 • PMSL, 2-m TMPF, and 2-m DWPF

  21. 29-30 June 2012 – Great Lakes/Ohio Valley Derecho L L • GFS 108-h Forecast valid 20120629/1200 • PMSL, 2-m TMPF, and 2-m DWPF

  22. 29-30 June 2012 – Great Lakes/Ohio Valley Derecho L L • GFS 108-h Forecast valid 20120629/1200 • 850-mb Winds

  23. 29-30 June 2012 – Great Lakes/Ohio Valley Derecho L L • GFS 108-h Forecast valid 20120629/1200 • 500-mb Winds

  24. 29-30 June 2012 – Great Lakes/Ohio Valley Derecho L L • GFS 108-h Forecast valid 20120629/1200 • 300-mb Isotachs

  25. 29-30 June 2012 – Great Lakes/Ohio Valley Derecho L L • GFS 108-h Forecast Synoptic-Scale Features valid 20120629/1200 • GFS 48-h QPF ending 20120701/0000V144

  26. 29-30 June 2012 – Great Lakes/Ohio Valley Derecho L L • GFS 108-h Forecast Synoptic-Scale Features valid 20120629/1200 • 24-h SPC Severe Reports ending 20120630/1200

  27. 29-30 June 2012 – Great Lakes/Ohio Valley Derecho L L • GFS 108-h Forecast Synoptic-Scale Features valid 20120629/1200 • 24-h SPC Severe Reports ending 20120630/1200

  28. 29-30 June 2012 – Great Lakes/Ohio Valley Derecho L L • Mean of Top 15 Analogs Based on GFS 108-h Forecast valid 20120629/1200 • PMSL, 2-m TMPF, and 2-m DWPF

  29. 29-30 June 2012 – Great Lakes/Ohio Valley Derecho L L • Mean of Top 15 Analogs Based on GFS 108-h Forecast valid 20120629/1200 • 850-mb Winds

  30. 29-30 June 2012 – Great Lakes/Ohio Valley Derecho L L • Mean of Top 15 Analogs Based on GFS 108-h Forecast valid 20120629/1200 • 500-mb Winds

  31. 29-30 June 2012 – Great Lakes/Ohio Valley Derecho L L • Mean of Top 15 Analogs Based on GFS 108-h Forecast valid 20120629/1200 • 300-mb Isotachs

  32. 29-30 June 2012 – Great Lakes/Ohio Valley Derecho L L • Mean of Top 15 Analog Features Based on GFS 108-h Forecast valid 20120629/1200 • Probability of Severe Weather Within 40km Grid Point (8 most severe analogs)

  33. 29-30 June 2012 – Great Lakes/Ohio Valley Derecho L • Surface Features Based on GFS 108-h Forecast • 24-h SPC Severe Reports ending 20120630/1200 L • Mean of Top 15 Analog Features Based on GFS 108-h Forecast valid 20120629/1200 • Probability of Severe Weather Within 40km Grid Point (8 most severe analogs)

  34. Analog Guidance (F144-F072) – 29 June 2012 • Based on 6-day Forecast • Based on 5-day Forecast • Based on 4-day Forecast • Based on 3-day Forecast

  35. Analog Guidance Individual Events (F144-F072) – 29 June 2012 • 22 July 1998 • 09 August 2000 • 20 July 1998 • 08 July 1991 • 08 July 2000 • 05 July 1980

  36. Analog Guidance 20120625/0000 F096 and F144 • F096 – The Day Before • F144 – The Day After

  37. Conclusions and Takeaways • Analog guidance has qualitative skill to provide situational awareness in the medium range of the forecast. • Meteorological patterns are not created equal…some are more “predictable” and easier to identify than others. • In the medium range, the analog guidance should be used with deterministic and ensemble model output to assist in identifying patterns that are historically associated with a weather impact. • A “perfect” analog does not exist. • Only a few, good quality analogs may exist for anomalous and record breaking events.

  38. Questions Questions or comments? chad.gravelle@noaa.gov

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