Tracking and Extrapolating Precipitation Episodes in the National Convective Weather Forecast

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

Warm Season Precipitation Episodes

Rainfall Streaks

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?

Rainfall Streak Detection

TITAN Software

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

Extrapolated Precipitation Zone

6 hours later…

6 hours later…

Extrapolation issues

Mergers and splits

Back building & sudden southward propagation

Dissipation Issues

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

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

Final Thoughts

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

Regime dependency?Some periods work better than others