Temperature

BCRMSE

    • A diurnal trend is seen for each seasonal aggregation, but becomes somewhat averaged out for the annual aggregation. The distribution of BCRMSE values range from 2.2 - 4.0 C among all temporal aggregations. An increase in the median value of BCRMSE with forecast lead time is also noted.
    • For the summer and spring aggregations, the largest errors occur for forecasts valid at 21 UTC and the smallest errors are seen for forecasts valid at 15 UTC. The fall and winter aggregations exhibit the largest error for forecasts valid around 9 or 12 UTC and the smallest at either 21 or 00 UTC. These differences lead to a weaker diurnal signal in the annual aggregation, however, it trends more towards the summer and spring aggregations in terms of when the maximum and minimum errors occur.

Bias

    • A consistent statistically significant (SS) warm bias is noted by forecast lead time, from both the 00 and 12 UTC initializations, and all temporal aggregations, with only a few exceptions for the summer and spring aggregations. A diurnal trend is also noted, where the largest warm bias occurs with forecasts valid around 12 - 15 UTC and the smallest around 21 UTC.

Relative Humidity

BCRMSE

    • A diurnal trend is noted in the distribution of both the summer and spring aggregations, however this trend is much weaker for the winter and fall aggregations. A general increase of BCRMSE values with forecast lead time is noted, regardless of temporal aggregation, and the values range from about 12 - 20 %.
    • For the spring, summer and annual temporal aggregations, the largest errors occur for forecasts valid around 00 UTC, while the smallest errors occur for forecasts valid around 12 UTC.

Bias

    • Typically, forecasts valid between 03 and 15 UTC have a SS low bias while all other CIs encompass zero, for all temporal aggregations except winter, which, overall, has very few SS biases.

Wind

BCRMSE

    • The distribution of BCRMSE values range from 2.5 - 4.5 m/s. The largest errors are noted for forecasts valid at 21 UTC, while the smallest errors are typically seen for forecasts valid around 09 - 12 UTC, both of which are generally displayed for all temporal aggregations.

Bias

    • A SS high bias is noted at all forecast lead times for both 00 and 12 UTC initializations for the annual aggregation and for a majority of lead times within the seasonal aggregations. The values range from 0.2 - 1.4 m/s.
    • The largest bias values are typically seen for forecasts valid around 09 - 12 UTC and the smallest at 21 UTC, for the spring, summer and annual aggregations.

3-hour Precipitation Accumulation

ETS

    • ETS values decrease with increasing threshold for both 00 and 12 UTC initializations, all forecast lead times and all temporal aggregations. The CIs are generally larger during the fall and winter aggregations when compared to the spring and summer aggregations.

Bias

    • In general, all of the temporal aggregations have a SS high bias at the lowest thresholds, which transitions towards a SS low bias at the highest thresholds for the summer and annual aggregations, especially at longer forecast lead times. The mid-range thresholds for all aggregations and highest thresholds for the fall, winter and spring aggregations typically encompass one, and thus are not significantly different from an unbiased forecast.

24-hour Precipitation Accumulation

ETS

    • Similar to that seen for the 3-hour accumulations, ETS values decrease with increasing threshold for both initializations and all forecast lead times. The winter aggregation tends to have SS higher ETS values for the mid-range thresholds compared to the summer aggregation due to a more gradual decrease with increasing threshold.

Bias

    • The thresholds which exhibit SS biases depend on forecast lead time and temporal aggregation and must be examined individually for more detail.

Temperature

BCRMSE

    • As forecast lead time increases, BCRMSE values also increase, where errors at the 60 hour lead time are SS higher than those seen at the 12 hour lead time. The BCRMSE values range from 0.8 - 3.5 C, depending on the temporal aggregation and lead time examined.
    • The smallest errors are seen between 300 - 500 hPa, while the largest errors are observed between 200 - 100 hPa for a majority of forecast lead times and temporal aggregations.

Bias

    • Regardless of the temporal aggregation and, in particular, for the short lead times, a general SS cold bias is noted for the 700 hPa level and a SS high bias noted at and above 400 hPa, with the exception of 150 hPa. As the lead time increases, there are fewer SS biases, especially for the winter aggregation.

Relative Humidity

BCRMSE

    • For all forecast lead times, BCRMSE values increase from 850 to 500 hPa and the values range from 8.5 - 30%, depending on forecast lead time and temporal aggregation.

Bias

    • If a SS bias is noted, which depends on the level, forecast lead time and temporal aggregation examined, it is consistently a moist bias.

Wind

BCRMSE

    • Regardless of the temporal aggregation, the largest BCRMSE values occur between the 300 - 200 hPa levels for all forecast lead times, while the smallest errors generally occur at the top- (100 hPa) and bottom- (850 hPa) most levels. The values range from 3.0 - 16 m/s.

Bias

    • In general, for the annual aggregation, between 700 and 200 hPa a SS low bias is seen for many forecast lead times. At 100 hPa, a trend towards a SS high bias is seen. The CIs for all other levels typically encompass zero. When examining the seasonal aggregations, SS biases depend on the level and forecast lead time.