National Weather Service San Diego WRF - Leveraging Operational WRF Runs
University of Arizona 1.8km WRF Verification
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Transcript of University of Arizona 1.8km WRF Verification
Fly - Fight - Win
25th Operational Weather Squadron
University of Arizona1.8km WRF Verification
2Lt Erik NeemannWeather Operations Officer
30 Apr 08
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Purpose
To analyze data from University of Arizona 1.8km WRF model for use in 25 OWS Forecast Process Provide feedback for use in model improvements Study included forecasts for winds, temperatures, and
stability (surface-based CAPE) Additional purpose of deriving tool to approximate wind
gust speed from model sustained winds
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Methodology
Compared actual observations to 1.8km WRF forecasts GFS and NAM output from 12z model runs
Three 25 OWS AZ forecast locations used: Davis-Monthan AFB (KDMA) Ft. Huachuca (KFHU) Luke AFB (KLUF)
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Winds
Model wind forecasts compared to 18z and 00z observations only
Data was thrown out if observed gusts or sustained winds were at less than 15 knots
If gusts were reported, gusts were used; if no gusts were reported, sustained winds were used)
Results are from 13 Dec 07 to 30 Apr 08 KDMA: 38 obs KFHU: 58 obs KLUF: 26 obs
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Winds
Speed error determined by average difference in observed and forecast speed
Ratio of observed speed to forecast speed used to determine “gust coefficient”
Direction error determined by absolute value of difference between observed and forecast wind direction
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Wind Speed (knots)
GFS Gust Coef NAM Gust Coef
KDMA 2.154 1.878 2.016KFHU 2.116 2.250 2.183KLUF 3.978 4.138 4.058
2.749 2.755
Avg GFS Error Avg NAM Error
KDMA -8.632 -7.997 -8.315KFHU -10.852 -10.638 -10.745KLUF -12.038 -12.462 -12.250
-10.507 -10.366
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Wind Speed Trends
Davis-Monthan had the best at model forecasts of wind speed, while Luke had the worst
Average for all locations was an underestimation of about 10.5 knots
Both DM and Ft. Huachuca observed/forecast ratios around 2:1 while Luke was closer to 4:1
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Wind Direction (degrees)
GFS Error NAM ErrorKDMA 30.263 24.386 27.325KFHU 21.132 22.632 21.882KLUF 36.154 34.231 35.193
29.183 27.083
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Wind Direction Trends
Forecasts most accurate for Ft. Huachuca, and worst at Luke AFB
Overall, the models did fairly well for all three locations with error generally less than 35 degrees
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Temperature
Compared model forecasts for Max/Min temperature to observed daily Max and Min
Number of cases limited to when both GFS and NAM model runs were available from 13 Dec 07 to 30 Apr 08 (78 days)
Absolute value or error used to examine accuracy
Average error used to determine potential model bias
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Min Temperature (Celsius)
GFS Bias NAM BiasKDMA -0.423 -1.346 -0.885KFHU -0.649 -1.558 -1.104KLUF 1.909 1.325 1.617
0.279 -0.526
GFS Abs Err NAM Abs ErrKDMA 1.628 2.115 1.872KFHU 1.792 2.519 2.156KLUF 2.636 2.390 2.513
2.019 2.341
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Min Temperature Trends
Min temperatures did the best and DM, and the worst a Luke
GFS more accurate at DM and FHU; both models about the same at Luke
Cold biases at DM and FHU; strong warm bias at Luke
Absolute error for all locations was about 1.5° C
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Max Temperature (Celsius)
GFS Bias NAM BiasKDMA 0.423 0.282 0.353KFHU -1.519 -1.896 -1.708KLUF 0.922 0.286 0.604
-0.058 -0.443
GFS Abs Err NAM Abs ErrKDMA 1.346 1.410 1.378KFHU 1.987 2.182 2.085KLUF 1.208 1.143 1.176
1.514 1.578
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Max Temperature Trends
Max temperature did the best at Luke and DM, while performing poorly at Ft. Huachuca
Both models had similar accuracy
Warm biases DM and Luke, strong cold bias at FHU
Absolute error for all locations was 1.5° C
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Stability
Stability results inconclusive due to scarcity of positive CAPE at any location during time period
More robust dataset expected during summer months
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Conclusion
NAM model forecast wind direction well for all locations
Wind speed gusts may be applicable for DM and Ft Huachuca with a corrective adjustment, but performed poorly at Luke
Max temps most reliable at DM and Luke using NAM model