Temperature

BCRMSE

    • For both the 00 and 12 UTC initializations, a diurnal trend is noted in the distributions of BC-RMSE values, which generally range between 2 – 3 °C for the CONUS and CONUS-East domains, where the highest error occurs during the late afternoon hours.
    • For forecasts valid between 15 and 21 UTC (daytime), regardless of initialization hour, the CONUS-East and CONUS-West domains have similar BC-RMSE values; however, at the other valid times, the West domain has consistently higher BC-RMSE values.
    • As the lead times increases out to 24 hours, the growth in error values is relatively small.

Bias

    • In general, a statistically significant (SS) warm bias is noted for several lead times during the overnight hours for all three domains, regardless of initialization hour. During the day, the CONUS-West domain has a consistent SS cold bias; however, a similar result is noted for forecasts valid at 15 UTC only for the CONUS and CONUS-East domains.

Relative Humidity

BCRMSE

    • An overall smaller diurnal trend is noted, as compared to the distribution of surface temperature BC-RMSE.
    • For both initialization hours, all domains show steady increase in error during the daytime hours, with overall errors ranging between 12-18%.
    • With the exception of the CONUS-East domain initialized at 12 UTC, the 24-hour lead time was SS higher error than the 3-hour lead time, indicating an overall increase in BC-RMSE as the forecast lead time increases.

Bias

    • For the 00 UTC initializations, the CONUS domain has a dry bias at the 12-hour forecast lead time, while both the CONUS and CONUS-East domains have a moist bias at the 15- and 18-hour forecast lead times.
    • For the CONUS-West domain, there is a SS dry bias between the 6- and 12-hour forecast lead times (overnight hours) for the 00 UTC initializations, while both the 00 and 12 UTC initializations reveal a SS moist bias for forecasts valid during the afternoon hours.

Wind

BCRMSE

    • The distribution of the surface vector wind BC-RMSE values range between 3 – 5 m/s for all three domains.
    •For all three domains, the overall vector wind errors tend to be SS higher for the longest lead times for the 00 UTC initializations, conversely this trend is not noted for the 12 UTC initializations, leading to the possibility it is related to the diurnal cycle rather than lead time (indicating the highest errors occur during the late afternoon hours).

Bias

    • All domains, for both initializations, exhibit a high wind speed bias for all lead times.  In addition, the CONUS-East domain has a SS higher bias as compared to the CONUS-West domain.

3-hour Precipitation Accumulation

ETS

    • For both initializations, all three domains, and all forecast lead times examined, the ETS decreases with increasing threshold.
    •For all thresholds and valid times, the CONUS-East domain has a higher median ETS value than the CONUS-West domain.

Bias

    •For the 12- and 24-hour lead times from both the 00 and 12 UTC initializations, the CONUS domain has a SS high bias (over-forecast) for all thresholds up to 0.15", while the CONUS-West domain exhibits the same behavior for thresholds up to 0.25".  Beyond that threshold, the confidence intervals (CIs) for both domains generally encompass one.
    • A similar result as seen for the CONUS domain is noted for the 12 UTC initialization at the 12-hour lead time and the 00 UTC initialization at the 24-hour lead time (both valid at 00 UTC) for the CONUS-East domain; conversely for the 12 UTC initialization at the 24-hour lead time and the 00 UTC initialization at the 12-hour lead time (both valid at 12 UTC) all the CIs encompass one for all thresholds.
    • As the thresholds increase, the CIs for the CONUS-West domain become substantially larger than for the CONUS-East domain.

24-hour Precipitation Accumulation

ETS

    • For all three domains, there is a steady decrease in ETS from the lowest threshold (0.01") to highest threshold (2.00").

Bias

    • With only a few exceptions, the CONUS and CONUS-East domains have a SS high bias for all thresholds, whereas the CIs for the CONUS-West domain more frequently encompass one, except for the 0.1", 0.25" and 0.5" thresholds where there is also a SS high bias.

Temperature

BCRMSE

    • For all domains, a minimum in the BC-RMSE value occurs near 400 hPa with maximum values at and above 200 hPa. Errors are less than 2.5 degree C for all domains at any level and forecast lead time.
    • Particularly for lower levels at the 24-hour lead time, the CONUS-East domain has SS lower BC-RMSE values compared to the CONUS-West domain.
    • As expected, an increase in BC-RMSE is noted with increasing forecast lead time.

Bias

    • At all forecast times, and for all domains a SS warm bias is observed above 250 hPa, except at 150 hPa, which exhibits a SS cold bias. A SS cold bias is noted at and below400 hPa for the CONUS-West domain, but only for the 700 and 500 hPa levels for the CONUS-East domain.

Relative Humidity

BCRMSE

    • For all three domains, from the initial time to the 12- and 24-hour lead times, the BC-RMSE increases, with median forecast errors of over 20% at the 24-hour lead time.

Bias

    • The CONUS domain has a consistent SS moist bias at 500 hPa for all forecast lead times, while the CIs often encompass one for other levels and lead times.
    • For all lead times and levels, the CONUS-West domain has a SS moist bias at 700 and 500 hPa and a SS moist bias at 850 hPa at the 24-hour forecast time.
    • The CONUS-East domain has a SS dry bias for all lead times at 850 hPa; however, except for the 24-hour lead time, a SS moist bias is seen at 500 hPa.

Wind

BCRMSE

    • For all domains, as lead time increases, BC-RMSE values increase less in the lower-levels as compared to the mid- and upper-levels. The maximum values for the 12- and 24-hour lead times are typically at 300 or 250 hPa and are always less than 10 m/s.

Bias

    • At the 24-hour lead time, all domains have a strong wind bias at 850 hPa. This is the only level that displays a high bias.
    • For the CONUS domain, a SS low wind speed bias is noted at 500, 250, 200, and 100 hPa for both the 12- and 24-hour lead times, while a SS high bias is noted at 850 hPa.
    • SS wind speed for the CONUS-West domain depends on the forecast lead time and level, however, if a SS bias is noted, it is generally a low bias.
    • Forecasts at 850 hPa for the CONUS-East domain have a SS high bias, while a SS low bias is noted at 250 hPa. The CIs for all other levels typically encompass zero.