1. An Examination of the Diurnal Cycle in the NCEP GFS (and Eta) Model Precipitation Forecasts (during NAME) John Janowiak, Valery Dagostaro*, Vern Kousky, Bob Joyce Climate Prediction Center/NCEP/NWS, Camp Springs, MD Meteorological Development Laboratory/NWS, Silver Spring, MD 30 th Climate Diagnostics and Prediction Workshop, Penn State University, October 26, 2005

2. MODEL FORECASTS Every 3 hours after 1 st 12 hours from 00Z runs (12h, 15h, …, 36h) 1 o 1 o x lat/lon grid Study Period: July 12 – August 15, 2004 (during NAME field campaign)

3. VALIDATION DATA A new member of the “MORPH” family: “RMORPH” (Research-quality) Land: CPC daily gauge analysis (Higgins & Shi) disaggregated by CMORPH satellite estimates Ocean: CMORPH only Interpolated to match space-time resolution of model forecasts

4. VALIDATION DATA A new member of the “MORPH” family: “RMORPH” (Research-quality) Land: CPC daily gauge analysis (Higgins & Shi) dissaggregated by CMORPH satellite estimates Ocean: CMORPH only Interpolated to match space-time resolution of model forecasts

5. RMORPH & Gauge Comparison

6. mm/day Precipitation Difference from Validation Data

7. Eta - RMORPH GFS - RMORPH Percentage Difference Difference in Frequency (%) by Intensity

8. Distribution of Heavy Rainfall Events

9. (Land only)

10. Mean 3-hour Precipitation

11. HARMONIC ANALYSIS Applied to period mean diurnal cycle

12. HARMONIC ANALYSIS Applied to period mean diurnal cycle

14. % of Daily Mean Precipitation @ 35 o N

16. CONCLUSIONS 1.Peak daily rainfall 3-6 hrs too early in Eta (SE US) and GFS (eastern U.S.) 2.Better phase agreement over NAME “Tier-1” 3.Models propagate rainfall well (central US -> east ) 4.Light rain rate OVERforecast in the models & heavy events UNDERforecast