The ENSO state, MJO activity, and the Pattern Change

*If you're tired of my technical rants, head to my conclusion, which explains what I believe will happen.

Further analysis of the tropical waters indicates that it is possible that a La Nina ENSO state has a possibility of occurring by late winter/early spring. I don't believe it will have much impact on the rest of the winter, but it could have serious implications on the severe weather/hurricane season this year. While there isn't a very good correlation between enhancement of severe weather and ENSO state, there is a general trend and correlation between them. In fact, the most notable tornado/severe weather outbreaks have occurred during FIRST year La Nina's (Super outbreak of 1974, Super outbreak of 2011, etc.).. Generally, because of the suppressed, split flow pattern normally characterized by El Nino's, severe weather isn't enhanced because 1.) baroclinic zones are not nearly as pronounced (during El Nino winters, the strongest baroclinic contrasts exist off the Atlantic coast, which enhance storm system development, but during the spring, especially in warmer springs, this contrast weakens greatly.), and 2.) Wind shear is not nearly as substantial, nor is instability, as warm, moist flow off of the Gulf of Mexico is inhibited with a suppressed jet stream. The thing that I have observed though is the fact that severe weather seasons that are coming out of a Neutral/Positive ENSO state will usually be enhanced (case in point 2010, especially in April and May). I should be focusing on winter weather, but I've been increasingly interested in this subject for the past week or so, and I've decided to begin working on a spring season forecast for the United States.

As for my analysis of the ENSO state, here it is: I'm trying to pinpoint an accurate timeframe from which this pattern change will occur (without using the long range GFS), and that is one of the reasons why I'm focusing on the tropical circulation. It seems as if the MJO is becoming very active once again. OLR anomaly "couplets" have been increasing in intensity over the past two weeks. They are moving very slowly to the east (which is enhancing the region of convection in a positive feedback process. The negative OLR radiation regions is causing warmer temperatures, which causes lower pressure, stronger convergence, stronger moisture flux, and stronger convective development. Thus the intensification (weakening) of the MJO can be modulated by solar activity, shifting ocean currents, as well as synoptic scale mid-latitude systems, the ITCZ and irregular heating of landmasses and ocean surfaces). Not only this, but precipitation and convection has been increasingly rapidly in the tropics. This is in fact, extremely important to the Mid-latitude general circulation over the next few weeks. When the MJO is rather weak or non-existent, then it will have little effect on mid-latitude circulation patterns. This positive feedback process, as described previously, will generate an increasingly stronger, more robust Pacific Equatorial circulation, which will most exhibit a La Nina-like circulation over the next few weeks.

Orange/red indicates stronger than normal westerly winds and blue indicates stronger than normal easterly winds.

  What does this mean for the longwave/jet stream pattern? This will generally cause a strong increase in strength of the Pacific jet stream, leading to a wetter, warmer pattern across North America (as I have stated numerous times). The increased convection across the Equator is allowing for higher 500 millibar heights, "packing" the height gradient into a smaller region, allowing for a very strong jet stream, which helps to break down the longwave pattern. The longwave pattern will dissipate into a fast-flow, progressive pattern (hence the reason why I don't think this warm-up will be on the same degree of amplitude as last March's warmth, but that's a different story). I think the progressive pattern lasts longer than is currently modulated, giving the slowing, and increasing amplitude of the MJO circulation, as well as model tendency to build in a slower more stationary longwave pattern in the long range, even though it isn't warranted. Therefore, I'll pinpoint this shifting pattern back to a colder pattern to occur right around January 20th. That's my best guess at this time.

 What does this mean for the Ohio Valley region? Expect a ridge to begin building in the far Western Atlantic/East Coast region. This will happen in response to the PNA going negative (and as I already stated before, the MJO will be modulating this shifting longwave pattern). The GFS then breaks down the flow, while keeping it more amplified than it should be, and causes a rather progressive pattern of longwave troughs/ridges. The GFS does break down the pattern rather earlier than what I'm predicting, with cold weather arriving by the 12th of December. I disagreed with what it was forecasting because I don't foresee the MJO and teleconnections aligning until that same week, upon which there will be a 7-10 day lag before the actual effects of the wave set in. So for next week, expect temperatures gradually warming above normal. As this happens, snow melt, in combination with warmer, humid air (as well as a very stable low level atmosphere) will lead to dense fog and stratus at times. Temperatures will likely approach the 40's by mid-late next week. I expect that temperatures near 50 could be attained by next weekend into the following week. By that time, a major storm system could approach the area with heavy rain, and thunderstorms possible before a cold front slides through. I don't really expect any other major warm-ups though, after the 15th. After the 15th, everything will be in a transition period. While it will not be below normal, it won't be significantly above normal either. In this case, temperatures will likely fluctuate around normal, until colder weather builds in the period between 20-27th. After the 27th, it is highly likely that a highly meriodional, blocked longwave pattern will set-up, allowing nearly ideal conditions for very cold and snowy weather across the East. More updates on this in the following days.

Using the CPC MJO composite charts, and comparing them to the actual MJO phases, it seems as if the MJO phases would support warmth, but also very wet conditions across the Midwest for the next two weeks.

The top image indicates an extremely high "confidence percentage" between most of the U.S. seeing warmth during MJO phases 4-6. MJO phases are the phases that can favor moderate intensification of cool SST anomalies across the Equatorial Pacific if other factors do as well (especially a -PDO and low solar activity). Therefore, it also looks to get rather wet in coming weeks across the Midwest. The Pacific jet will likely become active as well, even when the Southeast ridge becomes suppressed, keeping the storm systems moving into the Midwest. The bottom image indicates the GEFS mean and the GFS forecast for the MJO phases. Both forecast the MJO to remain increasingly active. The GEFS, it seems, wants to break down the MJO activity well before the GFS does, and sends it back into what is known as the "Circle of Death", which usually refers to the fact that a weak MJO usually won't favor any kind of atmospheric patterns. In this case, I tend to not go with either in the model forecasts, as just yesterday, the models were forecasting the MJO to head into phases 5-6, instead of 6-8. Hopefully, these model differences will be resolved soon so that I can more accurately pinpoint the arrival of the new pattern.

With that, here's my official long range forecast through January 27th.

Please note that when I specific above/below normal precip./temps, I am referring to the possibility, but not the actual extent of above/below precip./temps. The actual extent of the precipitation anomalies will definitely be smaller than that, but the actual extent of the temperature anomalies may be accurately depicted in my forecast images.  

As for the February forecast, that will come out either tonight or tomorrow in my preliminary late winter/early spring outlook.

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