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Hamza Kabelwa Contributions from Richard H. Grumm

Numerical Weather Prediction and EPS Products: Severe Weather and Quantitative Precipitation Forecasts. Hamza Kabelwa Contributions from Richard H. Grumm. Motivation and overview. A good forecasts is of little meaning If it does not allow for a good decision

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Hamza Kabelwa Contributions from Richard H. Grumm

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  1. Numerical Weather Prediction and EPS Products: Severe Weather and Quantitative Precipitation Forecasts Hamza Kabelwa Contributions from Richard H. Grumm

  2. Motivation and overview A good forecasts is of little meaning If it does not allow for a good decision NWP and Ensembles aid in assigning confidence to a forecast Forecasting severe weather is key role Including convection, flooding and flash flooding How to effectively accomplish this Flooding requires good QPF Tools to predict high impact weather and assign confidence is our focus

  3. The intial elements of a good Forecast

  4. Severe Weather Ingredients associated with severe weather Critical and favorable large scale pattern Critical parameters • Instability (CAPE, helicity, stability indices) • Precipitable watermoisture is critical • Lift • Terrain, density currents, and larger scale features • Models • Omega show ascent • QPF may show or imply convection

  5. Quantitative Precipitation Forecasting (QPF) High confidence a low uncertainty Need good QPF Best QPF is likely a probabilistic QPF • Based on key thresholds which relate to flood potential Best potential for QPF in high probability areas Convection will limit predictability at times. Best QPF during floods require known Patterns and Probabilities Can refine high end amounts with higher resolution models

  6. Precipitation Probabilities10 mm in 24 hours

  7. Why the focus?Instability, convergence, model ascent

  8. Mesoscale model QPF

  9. Ensemble Spaghetti 50 mm

  10. Salient points Use known meteorological reasoning Know the favorable patterns Instability where expect region of convection Gain confidence in pattern, instability, and forcing Tie in ensemble data High probability outcomes and gain confidence Better region and better confidence of event This case locally heavy rainfall • But in this case not record rainfall. • Anomalies can help with the pattern and with high end events

  11. Raw GEFS PoPs and spaghetti

  12. What Ensemble AddPatterns and probabilities Confidence in the pattern • To include high values of PW; other parameters we forecast with • Implies knowledge of patterns of high impact weather • Standardized anomalies add value too. Probabilities • Outcomes we can assign a number too. • Highlight areas of concern and interest Forecasters • Need to tie in confidence with the pattern and probabilities from the EPS

  13. Severe weather forecast summary Know the pattern(s) associated with severe weather Determine if the pattern is present Determine instability and shear High probability Of instability such has high CAPE/TTI/KI Of precipitation in the region Of the pattern you expect with severe weather

  14. Satellite evolution of the example

  15. Rainfall estimateshttp://www.cpc.ncep.noaa.gov/products/fews/global/CMORPH/cmorph_dly_africa_east.png

  16. QPF forecastingWe reversed and improved the severe weather version Use EFS to determine a high probability Of instability associated with convective rainfall? Of heavy rainfall in the region based ensembles? Of a pattern conducive for heavy rainfall? • Assumes you know the patterns Check the pattern and parameters In single models and high resolution models You are already confident of the large scale Check instability and shear In high resolution models compare to EFS

  17. End-to-end forecast-QPF Flood Example Area of high probability for high QPF Area or region you will likely predict Temper or adjust with high resolution model Think of high end amounts as a probability Impacts (A good forecast is useless if it cannot aid in making a good decision!) You need to know the antecedent conditions • Is the ground saturated or dry? • Are flows in rivers already high? • Antecedent conditions can be as important as the forecast. Ensure good forecast aids in good decisions

  18. Revised Forecast Concept

  19. Review A good forecasts is of little meaning If it does not allow for a good decision NWP and Ensembles aid in assigning confidence to a forecast Forecasting severe weather is key role Including convection, flooding and flash flooding How to effectively accomplish this Tools to predict high impact weather and assign confidence is our focus

  20. Test Drive Site for Products • Try main entry point • Examine text products bulletin • Examine use of maps and data+- • http://www.cpc.ncep.noaa.gov/products/african_desk/cpc_intl/ • http://www.cpc.ncep.noaa.gov/products/african_desk/cpc_intl/africa/africa.shtml

  21. Links • International Jump off point: • http://www.cpc.ncep.noaa.gov/products/african_desk/cpc_intl/ • Main Forecast entry point • http://www.cpc.ncep.noaa.gov/products/african_desk/cpc_intl/africa/africa.shtml • East Africa tools: • http://www.cpc.ncep.noaa.gov/products/african_desk/cpc_intl/eafrica/eafrica.shtml

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