Good day to all and a very HAPPY NEW YEAR!
It’s amazing what a great night of sleep will do to help get over the flu!
I’ve been meaning to write this for a bit, but have been under the weather for the last 5 or so days. I’d like to cover our current scenario, discuss why we’re missing the snow, and what has to happen to help things out. It's a long read - but hopefully a good one.
First I want to start with a cold hard fact. We are in ENSO neutral conditions overall with a current ONI value that indicates potential El Nino conditions. We are NOT in a weak El Nino yet. I’ve seen a lot of people state that and I thought we would be there by now, but we are not.
The definition of El Nino is a bit confusing. On one hand the CPC considers El Nino “conditions” to occur when the Nino 3.4 index is +0.5 for 3 straight months, however, they also say that in order to get into a full fledged El Nino episode we need to have five over-lapping Oceanic Nino Index (ONI) periods register +0.5 or better. (an ONI period is a 3 month indices – e.g., SOD was +0.5)
So the question is whether or not we have some El Nino conditions impacting the current patterns, or if they aren’t since it really isn’t a full-fledged El Nino episode yet. Always nice when it’s so straight forward!!
The first question to ask is what does El Nino “conditions” mean? Well, here ya go. There are three components to having an El Nino “condition”. (sounds like a bad rash!)
“In a nutshell, the typical El Niño atmospheric response includes reduced rainfall over Indonesia, more rainfall over the central Pacific, and some weakening of the low-level easterly winds and upper-level westerly winds (the Walker circulation) along the equator. “ (source: December's ENSO Update: Close, but no cigar. Author: Emily Becker)
Highly recommended reading: http://www.climate.gov/news-features/blogs/enso/decembers-enso-update-close-no-cigar
Based on the sited article above – we’re not quite there yet because #3 isn’t a complete yes. However, that doesn’t’ mean we can’t see some impact in different parts of the globe.
I’ve looked at the weekly indices for the Nino 3.4 region. Even if the current negative anomalies continue, it looks like the ONI values will hover around the +0.5 mark. It could go below, it could go above, we’ll have to wait and see. Even the monthly outlook has been trending down on the chances of El Nino compared to a few months ago.
So for now we have an El Nino not quite there, but looks to be setting in, and maybe some impact being seen in current weather patterns, with a recent negative anomaly in the 3.4 region – will that continue?
You could look for analogs of other El Nino winters, but I’m not usually a big fan of doing that unless you combine it with all the other signals (and SSTs) and then look for more true analog comparisons. I’m not saying it’s wrong to look at analogs, it’s ok to give a general sense of potential outcome, but given our weather is so different than even 10 years ago with more volatile storms, plus other conditions of that analog year could have been very different, etc.. So I take it with a grain of salt, and don’t base any of my outlooks off analogs for that reason. Consider what we saw last winter. Who wasn’t surprised by that outcome given the setup and looking at analogs for that year?
If you're going to do an analog, then do your homework, and do it right. Connect other factors to form a more true analog. Indices, SSTs, seasonal precip outcome, monthly temps, snow cover, ICE extent, etc.. Find analgos that connect all those things together that look similar to what we're seeing. It's too easy to merely reference a high level analog and state an outlook. Use them as a starting point to indicate potential outcomes, but dig in further.
The bottom line to me is that our current scenario is not as much a pure factor of ENSO as it is other things.
If we roll with that, then the truth lies somewhere else. What else is more of a cause of this weird pattern where the east is being blocked from getting the winter weather and more importantly, the snowstorms?
This is where I believe we have to look at the other contributing factors to patterns. There are so many it really is hard to connect all the dots, and they always interact differently with just minor changes, but that’s the challenge. But we at LWB don’t back away from challenges.
Here’s my take on things.
There has been a lot of discussion on the QBO, and yes, it is a contributing factor. So let’s say that is one part of the equation. But I think we’d be foolish to think that’s all it is about. Below are a few other major players to cover.
EPO – negative. Wow. We like negative, but it’s not making the impact like we saw last year, at least not yet. So it’s a good thing, but maybe a bit different than last year (maybe more west based), but still a good thing. If it stays negative and some things change, then we’re in business.
AO – combine this with the SSW and I think we have another case of signals trying to come to the table, but are struggling to get there. Th outlook is not supoprtive for the AO - yet.
PNA – I liken this signal more to the influence of some other things around it, so while it looks non-supportive, I don’t think it is the contributing factor, I think it’s being held back by other things.
MJO – a difficult and hard to connect factor. From what I’ve read it has been disorganized recently but showing signs of reorganization. (Does that help El Nino set in more?) The outlook has it heading toward phase 5. The question I ask is whether this is a factor in influencing our weather pattern, or more of an indicator of understanding potential weather patterns given its current state. Maybe a little of both.
NAO – positive, results in fast moving storms as far as current impact. But there’s more to it than that. Based on some research I’ve done a negative NAO leads to SST warming in the Atlantic, and a positive NAO leads to SST cooling. We had a fairly negative NAO this past year. See chart below. More to come on this later.
SSTs – ah yes. Let’s spend a little time here as I think this is having the most impact on what’s going on right now.
Below is the current SST map.
More importantly is the SST anomalies below.
Let’s start on the left side, the Pacific. These warm Pac waters (particularly northern and along the US west coast) combined with a strong SJET are just pummeling the storms into the west coast. Good stuff, but it’s not working out for us in the east. Yet. So keep it up Pacific! We’ll need you in the end.
Next let’s look at our own pond on the right side, the Atlantic. Warm, warm, warm. The western and northern Atlantic are warm, too warm. Go back to a negative NAO causing Atlantic SSTs to warm. Well, they did, and they are.
Having a warm Atlantic is not a bad thing, but it really depends on how warm, and where it’s warm. The western Atlantic is too warm, I’d like it to cool down a bit, but maybe stay a nudge warm. The northern Atlantic is just too warm and needs to cool down.
This current Atlantic SST scenario is supporting the main ingredient to our lousy winter so far. A ridge in the east. The SE ridge is part of it, but it really is a ridge along the entire east. This is causing a west-based winter so far. It also is a factor as to why we have a postive NAO/AO. This setup is also forcing the SJET up into the Ohio valley which warms up the upper atmosphere, and eventually warms up the lower levels. I believe this is also contributing to the spilt flow as well. As a result this provides the main path of systems to be, unfortunately, cutters. Below is a picture of the current scenario.
I'm not saying this is the only scenario we've seen. But I think it's been the dominant one over the last few weeks.
But there is some good news. The Atlantic is starting to cool (see below for the current weekly SST change). How much does it need to cool to relax the ridge and allow winter to shift east? I have no freakin idea. I just want to see it keep cooling over the next couple of weeks, which I believe it will do. That will result in the ridge relaxing in the east and allow for the other signals to become more of a factor. Troughs will come east, SJET will more shift towards east coast, cold air will be allowed to come in and stay, etc..
This doesn’t mean it will snow big, or snow at all, but it does mean we stand much better chance that we see snow events in the east. The larger impact of ENSO needs to be watched, particularly the “conditions” we need to monitor.
Hold tight folks. In the end it may end up nil, but by my calcs we have at least 10 weeks to go and things are already in motion to support change. I, like all of you, wish it would change overnight, but it is what it is and we have to roll with it.
I always think of events in terms of players, placement and timing. We've had players, but the placement and timing has sucked. If these changes stay on course, then we'll be in better shape across all three.
My outlook was 28-35" for the Phily area. I don't change my winter outlooks. They're either wrong or right. No harm in being wrong. And for now, even if I did consider changing it, I wouldn't.