tracking and extrapolating precipitation episodes in the national convective weather forecast d....

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Tracking and Extrapolating Precipitation Episodes in the National Convective Weather Forecast D. Ahijevych, S. Trier, C. Mueller, D. Megenhardt

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Page 1: Tracking and Extrapolating Precipitation Episodes in the National Convective Weather Forecast D. Ahijevych, S. Trier, C. Mueller, D. Megenhardt

Tracking and Extrapolating Precipitation Episodes in the National Convective Weather Forecast

D. Ahijevych, S. Trier, C. Mueller,D. Megenhardt

Page 2: Tracking and Extrapolating Precipitation Episodes in the National Convective Weather Forecast D. Ahijevych, S. Trier, C. Mueller, D. Megenhardt

Warm Season Precipitation Episodes

Page 3: Tracking and Extrapolating Precipitation Episodes in the National Convective Weather Forecast D. Ahijevych, S. Trier, C. Mueller, D. Megenhardt

Rainfall Streaks

Page 4: Tracking and Extrapolating Precipitation Episodes in the National Convective Weather Forecast D. Ahijevych, S. Trier, C. Mueller, D. Megenhardt

Potential Predictability

Coherent regeneration of convective rainfallAnchored to diurnal cycle and topographyFrequent when forecast skill is lowestCan we identify and track long-lived episodes in real time?

Page 5: Tracking and Extrapolating Precipitation Episodes in the National Convective Weather Forecast D. Ahijevych, S. Trier, C. Mueller, D. Megenhardt

Rainfall Streak Detection

Page 6: Tracking and Extrapolating Precipitation Episodes in the National Convective Weather Forecast D. Ahijevych, S. Trier, C. Mueller, D. Megenhardt
Page 7: Tracking and Extrapolating Precipitation Episodes in the National Convective Weather Forecast D. Ahijevych, S. Trier, C. Mueller, D. Megenhardt
Page 8: Tracking and Extrapolating Precipitation Episodes in the National Convective Weather Forecast D. Ahijevych, S. Trier, C. Mueller, D. Megenhardt

TITAN Software

Finds coherent precipitation zones in smoothed radar reflectivity (>10dBZ)Extrapolates based on last 6 hours of propagation

Page 9: Tracking and Extrapolating Precipitation Episodes in the National Convective Weather Forecast D. Ahijevych, S. Trier, C. Mueller, D. Megenhardt

Extrapolated Precipitation Zone

Page 10: Tracking and Extrapolating Precipitation Episodes in the National Convective Weather Forecast D. Ahijevych, S. Trier, C. Mueller, D. Megenhardt

6 hours later…

Page 11: Tracking and Extrapolating Precipitation Episodes in the National Convective Weather Forecast D. Ahijevych, S. Trier, C. Mueller, D. Megenhardt

6 hours later…

Page 12: Tracking and Extrapolating Precipitation Episodes in the National Convective Weather Forecast D. Ahijevych, S. Trier, C. Mueller, D. Megenhardt

Extrapolation issues

Mergers and splits

Back building & sudden southward propagation

Page 13: Tracking and Extrapolating Precipitation Episodes in the National Convective Weather Forecast D. Ahijevych, S. Trier, C. Mueller, D. Megenhardt

Dissipation Issues

False alarm rateUse new episode climatology based on TITAN track historyFilter by time-of-day and longitude with current rain streak climatology

Page 14: Tracking and Extrapolating Precipitation Episodes in the National Convective Weather Forecast D. Ahijevych, S. Trier, C. Mueller, D. Megenhardt

Probability of Rain Streak Continuance (red=high blue=low)

Page 15: Tracking and Extrapolating Precipitation Episodes in the National Convective Weather Forecast D. Ahijevych, S. Trier, C. Mueller, D. Megenhardt

Final Thoughts

Implementing in NCWFBest lead time to use (3-9h?)Blending with numerical model

Regime dependency?Some periods work better than others