Saturday, February 2, 2013

MJO Hinting at Active Beginning, End of February

Preword: The Long Range Lookout issued a few days ago is void. This is a replacement post.

The first part and last part of February should be the final pushes for winter, while the middle of February appears to be lost.

The last 40 days has brought the Madden-Julian Oscillation to Phase 8, the phase most commonly associated with winter snow and cold. We have indeed been seeing pushes for cold and snow into the States, most recently with a snowfall event that hit areas across the Midwest, helping their snow drought. Medium range forecasts indicate a continuation of these snowfall threats, with an additional several inches possible across portions of the Midwest and especially the lakeside areas of the Great Lakes.

Long range forecasts portray a Rex Block setting up across the West Coast, with high pressure squeezing into the Pacific Northwest and low pressure residing in the Southwest. The European forecast for this event is on the left, and the American's forecast on the right. The European model predicts high pressure developing across the East US in response to this Rex Block. I do not feel that is the likely scenario; Rex Blocks are more known for producing a more zonally-oriented flow east of the block. I prefer to side with the American model on this one. Low pressure persisting in the Bering Sea is indicative of a positive WPO pattern, something that does favor the European model over the American with warmer temperatures spread across the nation in a positive WPO regime. However, the Rex Block should affect the synoptic US more than the positive WPO, although periodic ridges and warm-ups are definitely within the spectrum of reality. That persistant low pressure anomaly in the Southwest will provide a base for storm threats across the nation, but with my predicted lack of high latitude blocking across Greenland, these storms should take more of an inland path, rather than one going up the East Coast. The long range is more supportive of a solid blocking pattern, but I would rather stick to the more inland tracks for now. These inland tracks may not support snowstorms as a byproduct of the Rex Block (and its zonal flow) is a warmer air mass overall.

Looking ahead into the very long range, into late February, we see that the second image in the first column is predicting strong negative OLR anomalies in the last week or two of February. Negative OLR anomalies are most commonly associated with enhanced convection, and this leads to the predicted Phase 1-2 stages of the Madden-Julian Oscillation. Do not think that this Phase 1-2 regime will continue through mid-February- this would be a sudden rebound event from less favorable conditions in the MJO.

A constructed analog forecast of the OLR anomalies in late February enhances the forecast of the early MJO phases in the late month. One can see the deep blues across the Indian Ocean east into extreme western Pacific waters. These deep blues once again exhibit negative OLR anomalies, and they would be placed in a location suitable for borderline Phase 1- Phase 3. These three phases do support low pressure along the East Coast, but also high pressure in the Rockies that could spill over into the Central US. 

A third long range OLR and 850mb wind forecast from the Roundy MJO page (the above 3 images are from that same page) once again confirms suspicions of deep tropical convection in late February in the bottom-most image. The arrows depicting 850mb wind motions reveal strong westerly winds centered over the Indian Ocean, something that does support tropical convection formation and sustainability. Some models that project the Madden-Julian Oscillation have been hinting at a circling pattern occurring within Phases 8-1 in coming days. While this could indeed happen as exhibited by the analog forecasts and the image just above, I'm not that open to speculating on it, as it is multiple models versus the European suite, something I don't have the confidence to inspect and choose my favored solution.

On a related note, the MJO in Phases 1 and 2 does not favor blocking in the higher latitudes of Greenland, for those of you wondering why I support more inland tracks.

A strong Kelvin wave is currently moving east across the Equatorial Pacific. This Kelvin Wave will result in enhanced warm water anomalies across the ENSO area, which can lend itself to cooler weather in the nation as February progresses. This event will be analyzed more in coming days.

I'm hard pressed to rule out the end of February as a stormy time period, but I'm also hesitant on cold weather for those same dates. It is very apparent we will see chances for snow (likely accumulating in a few cases) as the month drags on, but as the sun begins to strengthen as winter begins to end, it's very possible some systems may just not be able to hold onto the cold air long enough to allow snow to fall. This concern will be addressed in coming days.


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