How Long Does The Evolving Cold U.S. Pattern Last?

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Discussion: An extremely cold pattern evolves next week across Canada extending into the U.S. Arctic air is involved and enhanced by snow cover. Snow cover is near to below normal ahead of the cold outbreak(s). However, the European ensemble (model) indicates a massive amount of snow is possible in the Northeast Corridor the next 2 weeks implying the arctic air developing in Canada will be most likely to migrate into the Northeast across the fresh snow cover.

Pictured: The 15-day departure from normal temperature anomaly forecast across Canada and the U.S. according to the ECM ensemble as depicted by Storm Vista WX Models indicates developing/expanding cold.

Pictured: The 15-day snowfall forecast by the ECM ensemble across Canada and the U.S. as depicted by Storm Vista WX models identifies major expansion in the East.

Models agree on the widespread cold through the first week of January and the snow cover forecasts certainly support the cold projections. Interestingly, the ECMWF “weeklies” forecast model indicates that in 3 weeks the cold is gone and replaced by anomalous warmth. Will this happen?

Pictured: The European model cold week 2 ahead forecast and much warmer week 3 ahead forecast as depicted by Storm Vista WX models.

There are 2 ways to cause the implied profound pattern change forecast by the European model: Stratospheric cooling and/or strengthening and shifting Madden Julian oscillation.

To determine whether the stratosphere is cooling (or not) we take a look at both the ECM and GFS ensembles at 360 hours for temperature anomalies at 10 MB. The recent trend is toward a warming stratosphere into northern North America while the cooling stratosphere is very intense and centered over Russia. Remember…the warming and expanding stratosphere implies the troposphere (where weather occurs) contacts and cools forcing arctic air generation. The trend of the stratosphere forecast is to sustain the U.S. cold and not reverse the pattern as implied by the European model.

Pictured: The European and America ensemble hour 360 10 MB temperature anomaly forecasts to determine whether the stratosphere is warming (or not). A warming stratosphere over northern North America suggests regenerating arctic air at the surface in Canada.

The Madden Julian oscillation forecasts extend to 2 weeks. The European model indicates strengthening in phase 2 similar to the American model in 11-14 days. The European model stalls the MJO in phase 2 while the American model suggests phase 3 may follow (after 14 days). Phase 2 represents anomalous tropical convection in the Indian Ocean. The convection affects the northern hemisphere weather patterns to the north favoring a downstream colder than normal regime across the U.S. (according to NOAA climatology). If the MJO shifts east across the Indian Ocean (phase 3) there emerges a warming sign for the U.S. Of course, any Pacific warming would be resisted initially by an immense U.S. snow cover.

Pictured: The European and America operational models forecast of the Madden Julian oscillation indicating an intensifying phase_2 (Indian Ocean) in 11-14 days.

Pictured: NOAA temperature anomaly climatology for January given MJO phase 2 and phase 3.

Conclusion: Based on the trend toward a return to stratospheric warming across northern North America as the middle third of January approaches coupled with uncertainty as to whether the Madden Julian oscillation can shift east far enough from the Indian Ocean toward the Pacific Ocean to inspire a milder Pacific influence on the U.S. climate the preferred forecast for week 3 ahead is sustained cold and not a warm pattern change as indicated by the European model. Once MJO shifts across the Pacific a warmer pattern in the U.S. south of snow cover emerges later in January.