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Diagnosing High-impact Weather

Diagnosing High-impact Weather NAEFS Teleconference: 14 th September 2006 Helen Watkin THORPEX and High-Impact weather THORPEX aim: “to accelerate improvements in the accuracy of 1 to 14-day high-impact weather forecasts for the benefit of society, the economy and the environment”

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Diagnosing High-impact Weather

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  1. Diagnosing High-impact Weather NAEFS Teleconference: 14th September 2006 Helen Watkin

  2. THORPEX and High-Impact weather • THORPEX aim: “to accelerate improvements in the accuracy of 1 to 14-day high-impactweather forecasts for the benefit of society, the economy and the environment” Develop diagnostic tools to identify high-impact weather using ensemble data Parameter-based & Feature-based Develop appropriate forecast products to predict the risk of high-impact events Use diagnostics to analyse ability of TIGGE and component models to predict high-impact weather events

  3. Parameter-based probability plots Analysis 00Z 09/07/06

  4. Postage stamps / Mean and spread / Spaghetti

  5. Heatwave probability plot

  6. Persistent dry/wet plots

  7. High-Impact weather and features • Almost all high-impact weather is feature-related e.g. extra-tropical cyclones leading to strong winds/heavy rain in the UK • Numerical models often do not explicitly represent the severe weather parameters, especially in lower resolution ensembles • They can however represent the features causing the high-impact weather • For high-impact weather prediction, focus on post-processing ensemble data through automated identification and tracking of synoptic features • Analysis of feature tracks and attributes allows evaluation of the potential for high-impact weather Extra-tropical cyclones: Tim Hewson’s Cyclone Database Tropical cyclones: Julian Heming’s storm identification and tracking program

  8. Cyclone database snapshot Barotropic low Standard diminutive wave Standard frontal wave Weak frontal wave Weak diminutive wave

  9. Cyclone database 24-up

  10. In order to produce “feature-specific” diagnostics, need to track each feature in each member and cross-reference or “match” each feature across the ensemble Tracking and matching schemes developed to select the optimum match based on distance and feature attributes Cyclone database: Tracking and Matching

  11. Cyclone database case study

  12. Cyclone database feature-specific plumes Analysis 00Z 12/01/05 Pressure 1km Relative Vorticity Max 1km wind in 300km radius

  13. Storm tracks: Centred on T+72 (3 days)

  14. Storm tracks: Centred on T+120 (5 days)

  15. Storm tracks: Centred on T+216 (9 days)

  16. Tropical cyclone tracking

  17. Florence

  18. Objective-Grosswetterlagen

  19. Summary and future plans • Developing diagnostic tools to identify high-impact weather • Parameter-based products e.g. Probability plots, persistent dry/wet • Feature-based tools e.g. Cyclone Database for extra-tropical cyclones Tropical Cyclone tracking • Forecast circulation types e.g. Objective-Grosswetterlagen method Future Plans • Parameter and feature-based diagnostics will be used in combination to evaluate the performance in case studies of high-impact weather of i) new Met Office 15-day ensemble ii) TIGGE multi-model ensemble • Continue the development of parameter and feature-based diagnostics, and prototype products for forecasters

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