1. Eric Jones Senior Hydrologist Lower Mississippi River Forecast Center
Verification of Ensemble Streamflow Predictions from the Lower Mississippi River Forecast Center
Eric Jones
Senior Hydrologist
Lower Mississippi River Forecast Center

2. LMRFC ESP Verification
Little was known to explain to users how well ESP forecasts performed.
Many questions – no answers
Need was there to show users benefits of ESP forecasts.

3. ESP Verification Verification only done on maximum stage forecasts.
Four basins used for verification – SALV2, TAZT1, NWPT1, CARM6.
Comparison of Conditional vs Historical simulations.

4. LMRFC ESP Background Two forecasted simulations made
Historical simulation based off of calibrated model only.
Conditional simulation based off of current soil moisture states and streamflow conditions.
LMRFC started issuing ESP forecasts in 2002 for West NC, East TN, Central MS. Due to data sparseness, verification stats only from
Forecasts are issued each Monday afternoon.
Forecasts extend 90 days.

5. LMRFC ESP Background
CPC forecasts were taken account on the Carthage MS (CARM6) forecast only (only used for a few forecasts).
No comparison without CPC forecasts.
The rest of the basin forecasts were driven by historical precipitation from and current hydrologic model and river states.
The 4 points used in verification basins have fairly well model calibrations.

6. ESP Verification Results
Ranked Probability Skill Score showed slightly better to markedly better results over climatology.
Saltville VA (SALV2) … %
Tazewell TN (TAZT1) … +2.36%
Newport TN (NWPT1) … %
Carthage MS (CARM6) … +10.5%

7. ESP Results vs RPSS skewed to the right
+2.36%
+31.03%
+10.5%
+7.87%
Talagrand Diagrams

8. ESP Results
Reliability Diagrams

9. Precipitation vs Normal 2004-2006
% of normal
SALV %
TAZT %
-NWPT %
-CARM %
Extreme events
SALV2 averaged 2.3 top 99 events/year
TAZT1 averaged 2.3 top 99 events/year
NWPT1 averaged 1.3 top 99 events/year
Point precip – not basin averaged
Normal was 1.8 top 99 events/year

10. ESP Results vs. % of normal/extreme events
+0.26%
2.3/1.8
-12.01
1.3/1.8
-4.52%
+8.79%
2.3/1.8
Talagrand Diagrams

11. Caveats and Future Work
Heavy precipitation falling in less than model time step (6 hrs) could skew the results to the heavier side.
Work has just begun. Many more years needed for proper verification.
Verification of rest of LMRFC area. ESP not completed until 2013.
Verification is needed on mean/max/average flow and daily volume.
LMRFC instituting using CPC forecast for all ESP basins.
Verification of CPC vs non-CPC forecasts vs climatology

12. Acknowledgements David Welch – SR Hydrologist LMRFC
Jason Caldwell – HAS Forecaster - LMRFC

13. QUESTIONS ???