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Weather orecast Current Weather Climatology Meteorology HNMS 23/11/2017
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Use and Verification of ECMWF products in Greece

Hellenic National Meteorological Service
Division of Research and Numerical Prediction
T. Andreadis, E. Avgoustoglou, G. Galanis, V. Fragouli
1. Summary of major highlights.
The products of ECMWF are widely used in HNMS both as main tools by the forecasters and as initial conditions for the local Numerical Weather Prediction (NWP) models. Here, the verification results for the output of ECMWF model are presented in contrast to the results of two local NWP models for five major stations and for the following parameters: 2 meter temperature, 10 meter wind, total precipitation, geopotential height at 500 and 1000 hPa, as well as temperature and wind speed components at 500, 850 and 1000 hPa. In addition, verification results of the models concerning the 10m wind of three typical stations in the Aegean Sea are presented. It is worthy to note that the local forecast values are obtained by an interpolation of the direct model outputs based on the five nearest grid points. The locations of the stations in study are indicated in the map bellow:
2. Objective Verification.
2.1. Direct ECMWF model outputs.
(i) In the free atmosphere.
In this paragraph, we present the Anomaly Correlation and the Root Mean Square Error (RMSE) of geopotential height at 500 and 1000 hPa, the RMSE of temperature at 500 and 850 hPa as well as the RMSE of wind components at 850 and 1000 hPa concerning the outputs of the model of ECMWF in contrast to the Analysis values. Moreover, the results obtained are compared with the analogous ones of the local weather prediction model SKIRON (for details concerning the model see 2.2).
(ii) Local weather parameters.
The 2-meter temperature forecast is verified against observations at a time period of 6 hours beginning at the 00:00 UTC analysis results of ECMWF. Basic statistical measures, such as Biases, Mean Absolute Error, Standard Deviations, Root Mean Square Errors as well as the Possibility of successful forecasts (i.e. ±2o C), are presented:
The same results are also graphically presented in paragraph 2.2 while being compared with the corresponding results of the local numerical weather prediction models that are currently used in HNMS.
2.2. ECMWF model output compared to other NWP models.
Two local weather prediction models are currently running in HNMS:
  • The hydrostatic model SKIRON which runs with a resolution of 0.1o at the area specified by the corners: (13E,44N), (31E,44N), (31E,34N), (13E,34N). SKIRON is initialized with boundary conditions and analysis from the model of ECMWF and gives forecast up to 72 hours.
  • The non-hydrostatic COSMO Local Model (LM), which covers the area from 16.125E to 28E and from 33.25N to 45.75N with resolution 0.1250. It is initialized with boundary conditions and analysis from the global model of DWD.
In the next two tables, we present the percentage for the successful prediction of the total precipitation as an event concerning three different periods: Those of 24 hour forecast, 48 hour forecast and 72 hour forecast:
On the other hand, the next five diagrams represent the evolution in time (beginning with the analysis at 00:00 UTC and proceeding with a time step of 6 hours) of the mean absolute error of 2 meter temperature’s forecast obtained by the model of ECMWF as well as by the local NWP models SKIRON and LM:
Wind roses of 10m wind of the ECMWF model, SKIRON model and observations are presented bellow. The results are those of 12:00 UTC and correspond to 24 hour forecast. The wind speed is given in meters per second. In the center of each wind rose we give the percentage of events where the wind speed was bellow 1,5 m/sec.
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