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These parameters refer to temperature anomalies at 850hPa. They are available from T+12h to T+360h at 12-hour stepintervals. For the computation of anomalies a climatology derived from ECMWF's re-forecasts is used consisting of the closest single re-forecast run (11 members, 20 years back) preceding the real-time forecast date. The same climatology replaced also replaces the outdated fixed climatology that had been used for the following (pre-existing) parameters:
- Probability of temperature anomaly less than -2 K
- Probability of temperature anomaly of at least +2 K
- Probability of temperature anomaly less than -8 K
- Probability of temperature anomaly less than -4 K
- Probability of temperature anomaly greater than +4 K
- Probability of temperature anomaly greater than +8 K.
Please note that the first two of the aforementioned parameters namely probability of temperature anomalies less than -2K and at least +2K are available for the following forecast ranges only: T+120-240h, T+120-168h, T+168-240 and T+240-360h. The other 4 parameters are available from T+12h to T+360h at 12-hour stepintervals.
An example of temperature anomaly probabilities in a case of cold snap over North America at the end of January 2019.
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