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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

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

slide2

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.
slide3

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
slide4

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

slide5

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.
slide6

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
slide7

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
slide8

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
slide9

14 April 2012 – Severe Weather and Tornado Outbreak

L

L

  • GFS 120-h Forecast valid 20120415/0000
  • 850-mb Winds
slide10

14 April 2012 – Severe Weather and Tornado Outbreak

L

L

  • GFS 120-h Forecast valid 20120415/0000
  • 300-mb Isotachs
slide11

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
slide12

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
slide13

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
slide14

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
slide15

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
slide16

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)
slide17

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)
slide18

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
slide19

SPC Guidance – Valid on 29 June 2012

  • Day 6 Outlook
  • Day 5 Outlook
  • SPC 24-h Storm Reports ending 20120630/1200
  • Day 4 Outlook
slide20

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
slide21

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
slide22

29-30 June 2012 – Great Lakes/Ohio Valley Derecho

L

L

  • GFS 108-h Forecast valid 20120629/1200
  • 850-mb Winds
slide23

29-30 June 2012 – Great Lakes/Ohio Valley Derecho

L

L

  • GFS 108-h Forecast valid 20120629/1200
  • 500-mb Winds
slide24

29-30 June 2012 – Great Lakes/Ohio Valley Derecho

L

L

  • GFS 108-h Forecast valid 20120629/1200
  • 300-mb Isotachs
slide25

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
slide26

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
slide27

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
slide28

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
slide29

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
slide30

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
slide31

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
slide32

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)
slide33

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)
slide34

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
slide35

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
slide36

Analog Guidance 20120625/0000 F096 and F144

  • F096 – The Day Before
  • F144 – The Day After
slide37

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.
slide38

Questions

Questions or comments?

chad.gravelle@noaa.gov