1 / 20

REGIONAL-SCALE ENSEMBLE FORECASTS OF THE 7 FEBRUARY 2007 LAKE EFFECT SNOW EVENT

REGIONAL-SCALE ENSEMBLE FORECASTS OF THE 7 FEBRUARY 2007 LAKE EFFECT SNOW EVENT. Justin Arnott and Michael Evans NOAA/NWS Binghamton, NY Richard Grumm NOAA/NWS State College, PA George Young Penn State University, University Park, PA NROW IX, 7-8 November 2007. Motivation.

neo
Download Presentation

REGIONAL-SCALE ENSEMBLE FORECASTS OF THE 7 FEBRUARY 2007 LAKE EFFECT SNOW EVENT

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. REGIONAL-SCALE ENSEMBLE FORECASTS OF THE 7 FEBRUARY 2007 LAKE EFFECT SNOW EVENT Justin Arnott and Michael Evans NOAA/NWS Binghamton, NY Richard Grumm NOAA/NWS State College, PA George Young Penn State University, University Park, PA NROW IX, 7-8 November 2007

  2. Motivation Past LES Forecasting LES a Pattern Recognition Problem • GFS unable to resolve bands • Rely on tools such as BUFKIT

  3. Motivation, continued Present/Future LES Forecasting • 12 km NAM grossly resolves lake-parallel bands • Each NWS office can run a local version of this model • Individual runs often have problems with band location/orientation • Can multiple simulations of the NAM (an ensemble) provide added value? • This question has prompted the development of the Northeast Regional Ensemble

  4. What is the Northeast Regional Ensemble? • 12 km Workstation WRF • 24-36 hr run length • 2007-2008: 7-8 Members • 2 CTP members • 1 Operational • Goal: Improve operational forecasts of lake effect snowfall

  5. Case Day: 07FEB2007 • Part of a ~10-day prolific lake effect snow event east of Lake Ontario • Band moved significantly throughout the day • Excellent test for the ensemble

  6. The Ensemble – 07FEB2007

  7. 07FEB2007 – Synoptic Setup

  8. 07FEB2007 – Synoptic Setup TLAKE: +4C

  9. 07FEB2007 – Synoptic Setup

  10. Radar Loop

  11. Operational NAM Performance

  12. Operational NAM Performance • Captures basic band evolution • Slow with initial southward band movement • Problems with inland extent of the band • Frequently too far inland • Can the ensemble add value to this simulation?

  13. Ensemble Performance

  14. Ensemble Performance • All members able to simulate a band • Like NAM, ensemble successfully captures basic band evolution • Probability plots indicate operational NAM an outlier with inland extent • Ensemble provides added value

  15. Individual Member Performance • Quantitatively assess each ensemble member • Method: MODE pattern matching software (Davis et al. 2006) • Identify precipitation “objects” in forecast/observations • Match objects based on different attributes • Distance apart, similarity in area/orientation, overlap • Precipitation Obs: NCEP Stage IV Analysis

  16. Individual Member Performance • Example:

  17. Individual Member Performance • The Statistics: Primary Band Identification • POD/FAR/CSI * 3 hourly time steps

  18. Individual Member Performance • The Statistics: Basic Position/Intensity * 3 hourly time steps

  19. Conclusions • Case study suggests ensemble approach to LES may be valuable • Hone in on high-probability impact areas • Highlight outlier (low-probability) outcomes • Initial Quantitative Analysis shows diversity in “best member” for different variables • Ensemble mean likely to have increased skill over individual members

  20. Contact Info/Acknowledgements • Have Questions? • justin.arnott@noaa.gov Acknowledgements: • Ensemble Participants • For agreeing on a common domain/sharing data • Ron Murphy, ITO BGM • For gathering 7 February 2007 case data • MODE Software designers • http://www.dtcenter.org/met/users/

More Related