QPF? So it s a Land-falling Atmospheric River, Can That Help the Forecaster Make a Better. David W. Reynolds

Transcription

1 So it s a Land-falling Atmospheric River, Can That Help the Forecaster Make a Better QPF? David W. Reynolds Cooperative Institute for Research in Environmental Sciences Boulder, CO Brian Kawzenuk Center for Western Weather and Water Extremes August 8, 216 International Workshop on Atmospheric Rivers

2 Outline Review historical CNRFC (California Nevada River Forecast Center) derived 24-hr Mean Areal Precipitation (MAP) and IVT correlations for Lake Mendocino Watershed Is IVT a good proxy for 24-hr rainfall? Review CNRFC and GEFS forecast to observed MAPs Are model and model derived QPFs better related to observed rainfall than IVT? Review a land-falling AR case from 216 Looked at some 1 cases but will only show early March 216 Summary and Recommendations

3 Russian River Watershed IVT calculated here 4N 125W Potter Valley Dam 37.5N 125W Hopland Healdsburg Guerneville BBY

4 Landfalling AR depicted by IWV and IVT Z 6 March 216

5 AR Strength (water vapor transport; kg/m/s) AR summary for Pt Reyes, CA area, including Russian River Normal-duration AR landfall (12-24 hours) What is a more reliable predictor of AR impacts? IVT strength or QPF derived from models? AR Plume Diagram by J. Cordeira/Plymouth St.Univ Days from 1 AM PT Thursday 3 March 216 Summary by F.M. Ralph 8 AM PT Fri 4 March 216 Moderate strength AR Minimal strength AR Not an AR 6-9 inches of rain in favored mountain locations over 3 days (4 AM Fri 4 AM Mon) Precipitation forecast from NOAA/NWS California/Nevada River Forecast Center

6 * ** IVT QPF Methodology Utilize Rutz NCEP/NCAR* AR catalog from and NASA MERRA data** from Use 1-2 mb IVT show max 6-hr IVT 12z-12z as this showed best results Correlate to 24-hr Mean Areal Precipitation (MAP) available from Recalculate using upslope wind direction, precipitation threshold of >=.1 /day and for matching sample years using Rutz catalog. Lavers et al. (216) showed IVT more predictable than rainfall but is IVT well correlated with subsequent rainfall? Correlate 16-yrs of CNRFC 24-hr forecast MAPs issued daily at 12z to observed MAPs Compare member GEFS (V9.1 ) Ensemble Mean MAPs utilized by CNRFC for probabilistic inflows to Lake Mendocino Rutz and Alcott, 214 did a similar study using 2 yr GEFS data and CPC QPE for CONUS

7 Case-study Approach Focus on Lake Mendocino Watershed Use MAP Utilize 12z model runs to coordinate with CNRFC 5-Day 6-hr QPFs Utilize NWS GFE software Calculate MAPs for each model available Using GFS4 analysis compute layer average vapor transport for each case at 4N 125W at 6-hr intervals 55-7, 7-85, 85-1, 2-1 MB

8 QPF verification using NWS GFE Software Lake Mendocino Watershed Derive the Mean Areal Precipitation (MAP)for each model available Compare to MAP provided by CNRFC Compare to IVT at landfall

9 Max 6-hr IVT NCEP/NCAR from 12z-12z at 4n 125W and 12-12z 24-hr QPE Lake Mendocino R2 =.24 Max 6-hr IVT 12z-12z hr sum

10 Max 6-hr IVT 12z-12z Max 6-hr IVT MERRA 12z-12z at 4n 125W and 12-12z 24-hr QPE Lake Mendocino R 2 = hr sum

11 Fcst Day 1 24 hr (in) CNRFC Day 1 24 hr QPF Correlation to Observed Lake Mendocino Watershed (2-216) Day 1 Fcst vs Obs y = 1.36x R² = Obs 24 hr (in) Fcst vs Obs Linear (Fcst vs Obs)

12 Coefficient of Determination R2 R 2 Values for CNRFC-GEFS Mean and IVT to 24 hr MAP Lake Mendocino.9 CNRFC vs GEFS Mean 24 hr QPF.8.7 CNRFC GEFS v member mean Range of 6-Hr Max IVT Rutz, Merra or match GEFS or CNRFC years Also SW flow only or >.1 day R 2 values fall in a very narrow range For various correlations listed Forecast Lead Time (Hours) CNRFC 24 hr QPF R2 GEFS Mean 24 hr QPF R2

13 NCEP/NCAR 3-Day Time-Average 6-hr IVT vs 3-day MAP Lake Mendocino 4N and 37.5N Regression of 3-Day Time Avg IVT 37.5N by 3 Day Rainfall (R²=.364) Day IVT 37.5N 3day Time Avg IVT kg/m/s Regression of 3day Time Avg Ivt 4N by 3-Day Rainfall (R²=.297) Day Precip 1 12 Active Model Conf. interval (Mean 95%) Conf. interval (Obs. 95%) Day precip 1 12 Active Model Conf. interval (Mean 95%) Conf. interval (Obs. 95%) 14

14 3-Day Fcst (inches) 3 Day CNRFC Total QPF vs Observations Day CNRFC Forecast Lake Mendocino y =.9483x R² = Observed 3 day (inches)

15 Mean Error (inches) 2/15/2 1/2/22 3/15/23 2/18/24 2/27/24 12/9/24 12/29/24 3/2/25 12/21/25 12/31/25 2/28/26 3/2/26 2/11/27 1/6/28 1/27/28 2/3/28 2/17/211 3/21/211 3/26/211 1/22/212 11/3/212 12/3/212 12/24/212 2/1/214 12/5/214 12/12/214 2/8/215 12/23/215 1/7/216 1/18/216 3/7/216 3/14/216 Trends in 3-Day Forecast Mean Error (Bias) 2 CNRFC Mean Error 3-Day Obs >= 3" Year Mean Error Obs >= 3" Linear (Mean Error Obs >= 3") y =.426x

16 IVT Plume Diagrams GEFS 138 hrs > 25 kg/m/s 42 hrs > 5 kg/m/s Z 6 March Z 11 March GFS control forecast (black line), the ensemble-mean (green line), and the maximum (red line) and minimum (blue line) ensemble value at each forecast time. White shading represents +/- 1 standard deviation forecast from the ensemble mean

17 Rainfall (inches) 5-7 Mar 216 Layer IVT and CNRFC 6-hr Fcst and Obs MAPs Mar Layer IVT (4n 125W) and Lake Mendocino Watershed 6-hr Precip IVT per layer kg m -1 s hr in Z day 5-7 Mar Z 6 March 6-Hr Precip COY Res Day 1 Fcst Day 2 Fcst Day 3 Fcst Day 4 Fcst Day 5 Fcst

18 24-hr rainfall (inches) Mar 5-6, 216 MAP QPF Verification 3.5 MAP QPF valid 12z-12z 5-6 Mar 216 Lake Mendocino Watershed CNRFC GFS4 WestWrf NAM12 HiResNmm OBS Forecast Lead Time

19 IVT per layer kg m-1s-1 Rainfall (inches) 9-11 Mar 216 Layer IVT and CNRFC 6-hr Fcst and Obs MAPs Mar Layer IVT (4n 125W) and Lake Mendocino Watershed 6-hr Precip hr in Z day 9-11 Mar 11 March 6-Hr Precip COY Res Day 1 Fcst Day 2 Fcst Day 3 Fcst Day 4 Fcst Day 5 Fcst

20 24-hr rainfall (inches) Mar 1-11, 216 MAP QPF Verification 3 MAP QPF valid z-z 1-11 Mar 216 Lake Mendocino Watershed CNRFC GFS4 WestWrf NAM12 HIRESNMM OBS Forecast Lead Time

21 Based on Correlations QPF better Predictor of Impacts than IVT CNRFC 6 Day QPF from 1 Mar 216 Lake Mendocino

22 GEFS Model Probability of >= 6 March 1-March 12, 216

23 Plume Diagrams from GEFS

24 Conclusions and Recommendations IVT (2-1mb) not as good an indicator of potential rainfall impacts of land-falling ARs as is model or manual QPFs Supports Rutz-Alcott 214 study for CONUS IVT may be more predictable (Lavers) but IVT not well correlated to subsequent rainfall for this study area over long term Utilize model QPFs (3 day totals) to define strength of land-falling ARs? R-Cats to define AR strength as defined by Ralph and Dettinger, 212-BAMS Forecaster situational awareness better served by focusing on model QPF- especially looking at day totals given timing and exact locations can be off utilizing hr model QPFs

25 International AR Workshop Thank You

26 EXTRAS

27 IVT per layer kg m-1s-1 Rainfall (inches) Feb 5-1, 215 Layer IVT and CNRFC 6-hr Fcst and Obs MAPs Feb 5-1, 215 Layer IVT and Lake Mendocino Watershed 6-hr Precip hr in Z day 5-1 Feb LMAC1 Precip Day 1 Fcst Day 2 Fcst Day 3 Fcst Day 4 Fcst Day 5 Fcst

28 24-hr rainfall (inches) Feb 6-7, hr MAP QPF Verification 6 MAP QPF valid 12z-12z 6-7 Feb 215 Lake Mendocino Watershed CNRFC GFS4 WestWrf NAM12 HIRESNMM OBS Forecast Lead Time

29 IVT per layer kg m-1s-1 Rainfall (inches) Dec 1-12, 214 IVT vs CNRFC MAP 6-hr QPE 25* and 5** kg m -1 s -1 IVT annotated with respect to 2-1 mb IVT Dec 1-12, 214 Layer IVT and Lake Mendocino Watershed 6-hr Precip hr in Z day 1-12 Dec LMAC1 Precip Day 1 Fcst Day 2 Fcst Day 3 Fcst Day 4 Fcst Day 5 Fcst * After Rutz et al, 214 Mon. Wea. Rev. **Cordeira -

30 24-hr rainfall (inches) Comparison of MAPs CNRFC and NWP Lake Mendocino Watershed 24 hr Amounts 7 MAP QPF valid z-z Dec 214 Lake Mendocino Watershed CNRFC GFS4 WestWrf NAM12 HIRESNMM OBS Forecast Lead Time

31 Rainfall (inches) Dec 19-22, 215 Layer IVT and 6-hr Fcst and Obs CNRFC MAPs Dec 19-22, 215 Layer IVT and Lake Mendocino Watershed 6-hr Precip IVT per layer kg m -1 s hr in Z day Dec LAMC1 6-hr Precip Day 1 Fcst Day 3 Fcst Day 4 Fcst Day 5 Fcst

32 24-hr rainfall (inches) Dec 215 MAP QPF Verification MAP QPF valid 12z-12z Dec 215 Lake Mendocino Watershed CNRFC GFS4 WestWrf NAM12 HIRESNMM OBS Forecast Lead Time

33 1-Oct 6-Oct 11-Oct 16-Oct 21-Oct 26-Oct 31-Oct 5-Nov 1-Nov 15-Nov 2-Nov 25-Nov 3-Nov 5-Dec 1-Dec 15-Dec 2-Dec 25-Dec 3-Dec 4-Jan 9-Jan 14-Jan 19-Jan 24-Jan 29-Jan 3-Feb 8-Feb 13-Feb 18-Feb 23-Feb 28-Feb 4-Mar 9-Mar 14-Mar 19-Mar 24-Mar 29-Mar 3-Apr 8-Apr 13-Apr 18-Apr 23-Apr 28-Apr 3-May 8-May 13-May 18-May 23-May 28-May 6 5 Storage (acre-feet) 4 3 Lake Mendocino Watershed Rainfall (inches) 2 1 Lake Mendocino Operations Lake Mendocino Guide Curve Date COY MAP MAP 2 Baseline Deviation STO 1 STO 2

34 Forecasts Flows and Stage at Hopland Day 5 Forecast

35 Forecasts Flows and Stage at Hopland Day 4 Forecast

36 Forecasts Flows and Stage at Hopland Day 2 Forecast

37 Forecasts Flows and Stage at Hopland Day 1 Forecast