Diagnosing High-impact Weather
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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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Diagnosing High-impact Weather

NAEFS Teleconference: 14th September 2006

Helen Watkin


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


Parameter-based probability plots

Analysis 00Z 09/07/06


Postage stamps / Mean and spread / Spaghetti


Heatwave probability plot


Persistent dry/wet plots


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


Cyclone database snapshot

Barotropic low

Standard diminutive wave

Standard frontal wave

Weak frontal wave

Weak diminutive wave


Cyclone database 24-up


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


Cyclone database case study


Cyclone database feature-specific plumes

Analysis 00Z 12/01/05

Pressure

1km Relative Vorticity

Max 1km wind in 300km radius


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


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


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


Tropical cyclone tracking


Florence


Objective-Grosswetterlagen


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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