evaluation of selected winter ’04/’05 performance results
DESCRIPTION
Evaluation of Selected Winter ’04/’05 Performance Results. Seth Linden and Jamie Wolff NCAR/RAL. Weather Forecast Verification. Consensus (RWFS) forecast is compared to individual model components Air-temperature, dewpoint, wind-speed and cloud-cover forecasts - PowerPoint PPT PresentationTRANSCRIPT
Seth Linden and Jamie Wolff
NCAR/RAL
Evaluation of Selected Winter ’04/’05 Performance Results
Weather Forecast Verification
• Consensus (RWFS) forecast is compared to individual model components
• Air-temperature, dewpoint, wind-speed and cloud-cover forecasts– 18 UTC runs for the entire
season (1 November 2004 to 15 April 2005)
• Error (RMSE) calculated for:– Colorado Plains: 176 sites– Mountains: 119 sites
Blizzard of March 2003
Air temperature RMSE
Colorado Plains
RWFS
Colorado Mountains
Dewpoint RMSE
Colorado Plains
Forward Error Correction
Colorado Mountains
Due to 3-hour MOS data
Wind Speed RMSE
Colorado Plains
Colorado Mountains
Colorado PlainsCloud Cover
RMSE
Colorado Mountains
•The ensemble approach utilized by the RWFS does improve the predictions on average for all verifiable parameters
•No single model performs better for all parameters
•A blend of weather models will provide better results
Summary/Recommendations
Forecast Model Weights Used by the RWFS
• System automatically weights forecasts based on skill
• Distribution of weight values per lead time for air-temperature, dewpoint, and wind-speed– 18 UTC run on 3 May 2005
• Weights looked at for two sites:– Denver International Airport– I-70 at Genesse
Which models have the most skill?
Air Temperature Model Weights
Denver Int. Airport
ETA
GFSMOSMOSI-70 at Genesee
RUC
Dewpoint Model Weights
Denver Int. Airport
I-70 at Genesee
Denver Int. Airport Wind SpeedModel Weights
MM5I-70 at Genesee
WRF
Insolation Weights
0
100
200
300
400
500
600
700
800
12 0 12 0 12 0 12 0 12 0 12 0 12 0 12 0 12 0 12 0 12 0
Time (UTC)
W/m
2MSH_obEtaGFSMM5WRFeta_12gfs_12mm5_16wrf_16
1/29 1/30 1/31 2/1 2/3 2/4 2/5 2/62/2 2/7 2/8
•No one model consistently outperforms the others•MM5 and WRF forecast hourly instantaneous values, ETA forecasts 3-hour instantaneous values and GFS forecasts 3-hour averages
Clear Conditions
For MDSS static weights were applied:- 50/50 split between MM5 and WRF for the
0-23 hour forecast- All Eta for the 24-48 hour forecast
QPF Weights
Model GFS EtaMM5 2hr
MM5 3hr
MM5 4hr
Total MM5
WRF 2 hr
WRF 3hr
WRF 4hr
Total WRF RUC
MAV- MOS Total %
TOTAL MM5+WRF Contribution
QPF Weights (%) 9 11 15 12 10 37 17 14 12 43 0 0 100.00 80
•Due to a lack of quality precipitation observations static weights were applied•Weights fixed based on expert opinion•MM5 and WRF were given 80% of the total weight
•Weight distribution reflects that the corrected (dynamic MOS) NWS models (ETA, GFS, and RUC) had the most overall skill
•No one model dominates for all parameters•The limitation of the NWS models is their 3-hr temporal resolution
•WRF and MM5 were given the highest static weights for Insolation and QPF
Summary/Recommendations
Road Temp Observation Variance
• Tr variance across E-470 corridor– Shading by permanent structures or passing
clouds– Make/model/installation/age of temperature
sensors
E-470 Road/Bridge SitesColorado Blvd Platte Valley
(road and bridge)
6th Ave Pkwy
Plaza ASmokey Hill Rd
(road and bridge)
SCT BKN OVC
LOCAL TIME (19 = noon, 07 = midnight)
27 Nov 2004 28 Nov 2004
OVC CLRBKN SCT
LOCAL TIME (19 = noon, 07 = midnight)
29 Nov 2004 30 Nov 2004
Summary/Recommendations
• Large variations in observed road and bridge temperatures– Over relatively small area
(10s of miles)
• Makes prediction and verification of pavement temperatures very challenging– Difficult to establish ground
truth
Road/Bridge Forecast Verification
• Road and bridge temperature forecasts– Using recommended
treatments from MDSS
• Error (MAE) and bias calculated for:– For each lead time (0-48hrs)
18 UTC runs
– E-470: 6 roads/2 bridge (1 Nov 2004 – 15 Apr 2005)
– Mountains: 5 roads (1 Feb 2004 – 15 Apr 2005)
East bound lane of I-70 at the summit of Vail Pass
Consistent low bias
Lead Time (0 = 18 UTC = noon, 18 = 12 UTC = 6am)
Peak insolation
Morning hours
E-470 road sites
Perfect forecast
Lead Time (0 = 18 UTC ~ noon, 18 = 12 UTC ~ 6am)
Shadowing?
evening
morning
E-470 bridge sites
Lead Time (0 = 18 UTC = noon, 18 = 12 UTC = 6am)
evening
morning
CDOT mountain road sites
Summary/Recommendations
• Larger Tr differences during times of high solar insolation likely due to several factors:– Errors in measuring pavement skin temp– Mountain shading during low sun angle– Limitations in insolation prediction in models– Limitations in pavement heat balance model
• Simplified assumptions about pavement characteristics
• Tb analysis compromised by:– Sensors shadowed by bridge rail– Bias results suggest tuning may be beneficial
• Overall Issue:– Actual/Recommended treatments not the same
Case Study Analysis• 183 day demonstration
– 16 winter weather days• 10 light snow• 5 moderate snow• 1 heavy snow
November 27-29, 2004
• First significant snow storm of the season– 5-8” in the Denver area
• Large variations in parameter predictions– Forecast vs. observations
• Denver International Airport• Ta, Td, Wspd, Cloud Cover and Precipitation
• 12 UTC 28th examined – Captured the start time of event
-12
-10
-8
-6
-4
-2
0
2
4
6
12 13 14 15 16 17 18 19 20 21 22 23 0 1 2 3 4 5 6 7 8 9 10 11
Time (UTC)
Air
T (
C)
OB
RWFS
Eta
GFS
MM5_2
MM5_3
MM5_4
RUC
WRF_2
WRF_3
WRF_4
SN
LOCAL TIME (19 = noon, 06 = midnight)
28 Nov 2005
8C/14F diff2C/4F diff
Air Temperature
Snow
-12
-10
-8
-6
-4
-2
0
12 13 14 15 16 17 18 19 20 21 22 23 0 1 2 3 4 5 6 7 8 9 10 11
Time (UTC)
Td
(C
)
OB
RWFS
Eta
GFS
MM5_2
MM5_3
MM5_4
RUC
WRF_2
WRF_3
WRF_4
SN
LOCAL TIME (19 = noon, 06 = midnight)
28 Nov 2005
6C/11F diff
Dewpoint Temperature
Snow
0
1
2
3
4
5
6
7
8
9
10
12 13 14 15 16 17 18 19 20 21 22 23 0 1 2 3 4 5 6 7 8 9 10 11
Time (UTC)
WS
d (
m/s
)
OB
RWFS
Eta
GFS
MM5_2
MM5_3
MM5_4
RUC
WRF_2
WRF_3
WRF_4
SN
LOCAL TIME (19 = noon, 06 = midnight)
28 Nov 2005
Snow
Wind Speed
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
12 13 14 15 16 17 18 19 20 21 22 23 0 1 2 3 4 5 6 7 8 9 10 11
Time (UTC)
CC
OB
RWFS
Eta
GFS
MM5_2
MM5_3
MM5_4
RUC
WRF_2
WRF_3
WRF_4
OVC
BKN
SCT
FEW
CLR
SN
FEC
LOCAL TIME (19 = noon, 06 = midnight)
28 Nov 2005
Cloud Cover
Snow
0
0.05
0.1
0.15
0.2
0.25
0.3
12 13 14 15 16 17 18 19 20 21 22 23 0 1 2 3 4 5 6 7 8 9 10 11
Time (UTC)
QP
E (
in)
OB
RWFS
Eta
GFS
MM5_2
MM5_3
MM5_4
RUC
WRF_2
WRF_3
WRF_4
SN
LOCAL TIME (19 = noon, 06 = midnight)
28 Nov 2005
Quantitative Precipitation Forecast
Snow
March 13, 2005
• Moderate Snow Event – 4-6” along the E-470 corridor
• Warm air temps before start of snow– Dropped from 11C (52F) to -2C (29F) in 5 hours
• Large variations in parameter predictions– Forecast vs. observations
• Denver International Airport• Ta, Wspd, Cloud Cover and Precipitation
• 00 UTC 13 March 2005 run examined– Captured both start and end times
-8
-6
-4
-2
0
2
4
6
8
10
12
14
16
18
20
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Time (UTC)
Air
T (
C)
OB
RWFS
Eta
GFS
MM5_2
MM5_3
MM5_4
RUC
WRF_2
WRF_3
WRF_4
SN
LOCAL TIME (18 = noon, 07 = midnight)
13 March 2005
Air Temperature
Snow
0
1
2
3
4
5
6
7
8
9
10
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Time (UTC)
WS
d (
m/s
)
OB
RWFS
Eta
GFS
MM5_2
MM5_3
MM5_4
RUC
WRF_2
WRF_3
WRF_4
SN
LOCAL TIME (18 = noon, 07 = midnight)
13 March 2005
Wind Speed
Snow
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Time (UTC)
CC
OB
RWFS
Eta
GFS
MM5_2
MM5_3
MM5_4
RUC
WRF_2
WRF_3
WRF_4
OVC
BKN
SCT
FEW
CLR
SN
LOCAL TIME (18 = noon, 07 = midnight)
13 March 2005
SCT - OVC
Cloud Cover
Snow
actual forecast
Start timeactual forecast
End timeLOCAL TIME (18 = noon, 07 = midnight)
13 March 2005
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Time (UTC)
QP
F (
in)
OB
RWFS
Eta
GFS
MM5_2
MM5_3
MM5_4
RUC
WRF_2
WRF_3
WRF_4
Quantitative Precipitation Forecast
Summary/Recommendations
• Large discrepancies between weather models in predicting state weather parameters– All too dry for Td and cloud cover– Low wind speed bias during windy conditions– Overall, no ONE model outperforms => Ensemble
approach key
• Supports probabilistic forecast presentation– Atmosphere is unpredictable– Best approach to present uncertainty to end users?
Thank You!
Questions?