Temperature

BCRMSE

    • For both the 00 and 12 UTC initializations, a diurnal trend is displayed in the distribution of BCRMSE values, which generally range between 2.3 - 3.9 °C, depending on the temporal aggregation.
    • The smallest errors generally occur for forecasts valid at 06 and 09 UTC for all temporal aggregations, with exception to forecasts valid at 03 UTC for 00 initializations during the winter aggregation. The largest errors occur for forecasts valid at 15 UTC during the fall and winter aggregations and forecasts valid at 21 and 00 UTC for the annual, spring, and summer aggregations.

Bias

    • For the spring and summer aggregations, a SS cold bias is observed at all forecast lead times for both 00 and 12 UTC intializations. The annual and fall aggregations generally display a SS cold bias at forecast lead times valid between 15 and 00 UTC, with confidence intervals (CIs) encompassing zero at a majority of the other lead times, indicating unbiased forecasts. SS bias results are noted for the winter aggregation; however, the sign and magnitude of the bias depends strongly on the initialization and lead time.
    • The amplitude of the bias does not generally increase with forecast lead time, for any temporal aggregation.

Dew Point Temperature

BCRMSE

    • All temporal aggregations reveal an increase in BCRMSE values with lead time. A diurnal trend is noted in all but the fall aggregation.
    • For both the 00 and 12 UTC initializations, BCRMSE values generally range from 2.2 - 4.2 °C. For the winter aggregation, the largest errors are associated with forecasts valid at 12 UTC, while for all other temporal aggregations the largest error is seen often seen at times valid at 21 UTC. The smallest errors are noted for forecasts valid between 06 and 09 UTC for the annual and spring aggregations, between 00 and 03 UTC for the fall and winter aggregations, and 15 UTC for the summer aggregation.

Bias

    • Generally, there is a SS high bias for forecasts valid between 18 and 00 UTC for the annual, spring, and summer aggregations; a SS high bias is also noted at forecasts valid 21 UTC only for the fall aggregation. The winter aggregation has a SS high bias for all forecasts, regardless of initialization time. A SS low bias is noted for most forecasts between 06 and 12 UTC for the summer aggregation and valid between 12 and 15 UTC for the fall aggregation.

Wind

BCRMSE

    • For both initializations, the BCRMSE values range from approximately 1.8 - 2.6 m s^-1, with a diurnal trend noted for all temporal aggregations except winter and increasing error with lead time.
    • For all temporal aggregations, the largest BCRMSE values are seen at forecast lead times valid at 00 UTC, regardless of initialization time, while the smallest errors are generally around the 09 - 12 UTC valid times.

Bias

    • A SS high wind speed bias is noted for nearly all forecast lead times, regardless of initialization hour or temporal aggregation.
    • For both the 00 and 12 UTC initializations, a very large diurnal cycle is noted with SS larger high bias during the overnight hours compared to the daytime hours.

3-hour Precipitation Accumulation

GSS

    • Regardless of initialization time or forecast lead time examined, the highest GSS values are seen at the lowest precipitation threshold and steadily decrease to near-zero for higher thresholds. The number of observed events (base rate) by threshold has a similar trend. The largest CIs are typically noted for the winter aggregation, which also has the lowest base rate.

Frequency Bias

    • For both the 00 and 12 UTC initializations, a SS high bias is generally noted for all thresholds below 0.25", regardless of forecast lead time or temporal aggregation. Winter has a SS high bias at the majority of thresholds for both initializations and forecast lead times. For the summer aggregation, above the 0.25" threshold, a transition towards a SS low bias is noted for the highest thresholds. For the other temporal aggregations, the higher thresholds generally encompass one.

24-hour Precipitation Accumulation

GSS

    • A general decrease in GSS with increasing threshold and lead time, similar to that seen for 3-hour precipitation accumulations, is noted for all temporal aggregations except winter. Again, a similar trend is noted in the base rate, with very few observed events of 3" accumulations in 24 hours.
    • For the winter aggregation, the median GSS value for the 24- and 36-hour lead times remains higher for higher threshold values; however, the CIs associated with those values are very large, indicating a low confidence.

Frequency Bias

    • Most temporal aggregations exhibit a fairly consistent high bias for all but the highest thresholds, which have CIs that encompass one; however, the fall and winter aggregations occasionally have CIs that encompass one for several other thresholds at the different initialization hours and lead times.
    • In general, as the threshold increases, the width of the CIs increase, indicating more spread and less confidence in the median bias value, likely related to the decreasing base rate.

Temperature

BCRMSE

    • Regardless of forecast lead time or temporal aggregation, a minimum in the BCRMSE values occurs between 300 and 500 hPa and increases to a maximum at both the near-surface and upper levels.
    • A SS increase in BCRMSE values between the 12-hour and 48-hour forecast lead times is noted for all levels for the annual aggregation. For the seasonal aggregations similar behavior is noted, with exception to the 100 hPa level. For all aggregations and lead times, errors are less than 2.4 °C.

Bias

    • For all temporal aggregations, a SS cold bias is seen for all lead times at the 850 and 700 hPa levels transitioning to a SS warm bias at all levels above 500 hPa with the exception of the 400 hPa level during the summer aggregation and the 150 hPa level for several seasonal aggregations, where the CIs frequently encompass zero or a warm bias is seen. The largest magnitude bias is generally at the 850 or 100 hPa levels.

Dew Point Temperature

BCRMSE

    • As the pressure level decreases from 850 to 500 hPa and the forecast lead time increases from 12 hours to 48 hours, median BCRMSE values increase for all temporal aggregations except winter, where the median value decreases from the 700 to 500 hPa level.
    • Compared to the other seasonal aggregations, the summer aggregation has a SS lower BCRMSE at 850 and 700 hPa.

Bias

    • A SS high bias is noted for all forecast levels and lead times for all temporal aggregations except summer, which has a SS low bias at 700 hPa for the 24-, 36-, and 48-hour lead times and an unbiased forecast at 850 hPa for the 12- and 48-hour lead times.
    • Similar to the results for BCRMSE with pressure level and lead time, the highest bias values are generally seen at the 500 hPa level for the 48-hour forecast lead time.

Wind

BCRMSE

    • A general increase from the minimum BCRMSE values at the lowest levels, typically at the 850 or 700 hPa, to a maximum at the 300 or 200 hPa level for all forecast lead times and temporal aggregations, is noted.
    • Overall, the errors generally range between 2.5 and 6.0 m s^-1 depending on lead time and temporal aggregation, with a SS increase in BCRMSE values between the 12- and 48-hour lead times seen for several levels and all temporal aggregations.

Bias

    • In general, the forecast at 850 hPa is unbiased, regardless of the temporal aggregation and lead time, which transitions with height to a fairly consistent low wind speed bias in the mid-levels, peaking in magnitude around 200 hPa. Above 200 hPa, bias values for most lead times and all temporal aggregations become less negative, with a number of unbiased forecasts.