EPS 46-Day Teleconnection Pattern Evaluation For Winter 2024-25 (Based on the Bi-weekly updates on Monday and Thursdays)
Arctic Oscillation:
0Z Nov 25 forecast showed the first hints of a strong negative signal for late Dec but the timing was a week early. 0Z November 28 delayed the signal by a week, which was realized (Jan 3-10). 0Z Dec 02 lost the strongly negative signal in early January, but then it returned.
Strong signal for a sustainable positive AO was observed in the 0Z Dec 12 forecast and was maintained.
North Atlantic Oscillation:
Initial forecasts on 00Z Nov 25 did a good job with observed trends. The dip to negative was a week too late in the data for early January. The early Jan negative signal then went away. The negative early Jan signal returned in the 0Z Dec 19 forecast.
The sustainable positive signal now expected to happen Jan 22 was well-modeled in the 0Z Dec 9 run. It became much clearer in the 0Z Dec 19 forecast.
East Pacific Oscillation: (Most consistent and well-captured signal)
Trends have been consistent and matched observed trends. Even the 0Z Nov 25 forecast showed a moderate signal for a negative EPO in early to mid January.
West Pacific Oscillation: (Second best well-captured signal)
The initial forecast captured the observed trends well. It showed the positive spike around Christmas and the upside risk for a turn back to negative in early January. The 0Z Nov 28 run showed a stronger signal for a negative trend in early January. The 0Z Dec 02 run showed the robust Christmas spike that came to fruition. The 0Z Dec 5 0Z Dec 16 trends reverted to a positive WPO through early January. The 0Z Dec 19 forecast showed the strongest signal for an early January negative WPO.
Pacific North American Pattern: (This signal had the worst prediction)
The 0Z Nov 25 forecast showed correct observed trends through Dec 16 and then lost the positive signal from there on out through Jan 15. We started to see a flip back to a positive pattern with the 0Z Dec 02 run, but it was too transient. The 0Z Dec 26 run showed the most sustainability of the positive PNA (through Jan 21).
The negative PNA trend being forecast after Jan 23 has been forecast since 0Z Dec 09 because Jan 23 was the end of the forecast.
Key Forecast Cycle Updates in Identifying The Observed Trends:
0Z Nov 25: EPO: This cycle run showed a moderate signal for a negative phase to develop in early to mid-January.
0Z Dec 2: WPO: This cycle run showed a robust spike around Christmas, which came to fruition. PNA: A flip back to a positive phase following failed attempts occurred with this cycle run but it was too transient in the data compared to what actually came to fruition.
0Z Dec 9: EPO: The negative trend for early January was captured with this cycle run. PNA: The negative trend observed after January 23 was captured well by this cycle run.
0Z Dec 19: NAO: Negative signal observed in early January showed up in this cycle run. The sustainable positive signal expected to occur on January 22 became much clearer and defined in this cycle run. WPO: This model run showed the strongest signal for a negative phase to develop in early January.
