Monday, January 12, 2015

Long Range Outlook: Dynamic Pattern Unfolding into February

This is the Long Range Outlook, covering the period from mid-January (present day) to around the middle of February.

Tropical Tidbits
The above image shows 500mb geopotential height anomalies across the West Pacific, projected from the GFS ensembles and valid on January 13th. Notice the strong ridge forcing itself north to the west of Japan, likely bringing substantial warmth along with it. If we apply the Typhoon Rule to this situation, which states weather phenomenon occurring in Japan is reciprocated 6-10 days later in the United States, we should expect a period of warm weather commencing around January 15th to 17th, evidenced by a gradual warming trend unfolding in short range forecasts here at home. The Typhoon Rule supports such warmth lasting for about 3-5 days, before a storm system ushers in another wave of cool air. From here, we go to our impending cold blast.

Paul Roundy
A look at the hovmoller diagram above will help us diagnose the atmosphere. We see our current Madden-Julian Oscillation (MJO) wave moving eastward to the 180 degree longitude mark by around the 18th of January. From here, typical MJO phase space diagrams (not shown) show the index moving into territory too weak to identify the phase, but that's just because another MJO wave is forming out by the 50E longitude line, around January 21st. This positioning around the 50E line puts us in a Phase 1 MJO event, as seen below.

This chart shows typical alignment of outgoing longwave radiation (OLR) values by MJO phase in the west-central Equatorial Pacific. Notice that we see negative OLR anomalies (blue colors) in the hovmoller diagram around January 21st near that 50E longitude line, which matches up with Phase 1 (top-left panel) in this graphic immediately above. This, along with some Typhoon Rule support, should enable a sharp Arctic blast to round out January, possibly to begin February. I do have concern that this wintry return may be weaker than what is currently advertised, as stormy weather over Japan only lasts about 24 hours, if that. This should be a cold event lasting anywhere from 2-5 days for the USA.

As we move ahead into February, things get a little dicey.

We saw a notable stratospheric warming event strike to kick off the New Year, with temperatures at the 30hPa level only now settling back down to normal levels, as the graphic above displays. Let me please clarify: This was not a Sudden Stratospheric Warming (SSW) event. In order to deem an event a true SSW, wind direction in the stratosphere must either significantly slow or even reverse, in addition to intense warming of temperatures. We saw the latter, to some degree, while the former wasn't as prevalent as we needed. For this reason, it's referred to as just a notable warming event.

The concept right now is that this warming event will lead to more wintry weather about 2-4 weeks down the road from when the warming occurred, which brings us to that late January-early February period. With unfavorable indications from Japan, though, I worry that the cold (while intense) may not stick around for long. In order for that to happen, we may need another warming event, ideally a true SSW. However, even that prospect is quickly fading, as we see a strengthening of the upper polar vortex in coming days and weeks.

Let's dive into February a bit deeper.

Kyle MacRitchie
The above image once again shows forecasted outgoing longwave radiation (OLR) anomalies, but now forecasted well out into the spring. Due to such low confidence, we're only going to look at the long range OLR forecast as an indicator of what may come, not necessarily as something that's "set in stone". Notice how we see our ongoing MJO wave fading near the 21st of January with the dissipation of negative OLR anomalies, as well as our second wave forming well off to the west. As the Paul Roundy hovmoller showed, this second wave slowly shifts east as we move into February, but then note what this forecast predicts in the middle and late stages of February. We see the MJO stalling out around the 160E longitude mark. Going back to our MJO OLR composite image earlier in this post, we see this correlating to Phase 6, also known as the warm weather phase. Here's a graphic displaying a Phase 6 MJO event in February, to give you an idea of what we could see if this forecast verified.

We see a strong ridge unfolding across the East US into the Ohio Valley and Great Lakes during this February Phase 6 MJO event, with stormy weather impacting the Pacific Northwest. Ridging is shunted south and east across the Northeast Pacific, into the Southwest US. This should be particularly concerning for winter weather fans in the East, because this set-up does have additional support. Model guidance is expecting the atmosphere as a whole to dive into a La Nina-esque pattern, which is shown like the image below.

During a typical La Nina pattern, we tend to see strong high pressure across the Gulf of Alaska, before the jet stream buckles south and delivers cold weather into the North Plains and Northwest. Ridging then is provoked in the East US (the reason why cold weather fans in the East see La Nina's in their nightmares). This, of course, is not a perfect correlation, but you can make key connections between the typical La Nina environment, as well as the projected Phase 6 MJO event in February. This would not bode well for a cold and stormy end to winter for most east of the Rockies, unfortunately.

On a side note, many have asked why I am using the MJO in my forecasts, since we are currently in the pro-warmth Phase 6, but cold weather is prevailing. I continue to use the MJO because it usually provides a good idea as to where we are going in the future. The MJO's effects were being overruled by a very strong ridge along the West Coast; remember that the MJO is not the sole player in this atmosphere, and that's being exhibited well. We are currently seeing warmth return to the US as that ridge breaks down in accordance with the warm MJO phase.

Even when the MJO seemed to be failing, it still managed to reflect itself well in the atmosphere. Shown below is a side-by-side comparison of the last few days of January 500mb geopotential height anomalies (left), as well as typical 500mb height anomalies during a January Phase 6 MJO event, in an ENSO atmosphere reflective of this one. The comparison isn't perfect, by any means, but it's there.

ESRL and Meteonetwork

To summarize:

- Warmer than normal weather is expected around a January 15-23rd period.
- A storm system may impact the country around January 21-25.
- Cooler than normal weather is expected in the final days of January, possibly into February.
- There is increasing potential for a warming trend in the middle of February back to above-normal temperatures.



BearCub said...

I am wondering why most forecasters (perhaps the NWS saw it with their blast furnace maps-and everybody laughed )saw all of this un-winter like weather before. Andrew, you hinted at it a day after putting out a city-by-city Winter forecast that was favorable for cold and snow. You hinted at the warm possibility afterwards as well. I did not want to hear it and looked for Winter where there was no Winter, only wishes: Joe Bastardi has run for the hills and and can't be found these days. Accuweather has egg on their faces, writes about every snowfall, and temperature under 32 as signs of an ice age happening now. I am now in the process of planning what to plant for the vast flower gardens I have each year. I will think about Winter next November.

Frank-0 said...

Andrew: Everything that happened in October, is now happening. The Lezak
theory is alive and well. It really looks like.....A-Stick-A-Fork in it...Sucks for us winter lovers here in the east.....

Anonymous said...

Blast furnace? Where do you live? So far January is 4-5 degrees below normal in NJ, PA, NY. It sure does not feel like any blast furnace in the east

Anonymous said...

I say the forecasting for this winter made back in the fall have not been that good.

Especially the climate models namely the cfsv2. Way off

Cameron Fry said...

This post makes me really sad. Looking like our fourth consecutive BAD winter here in Nashville. At some point, the streak of bad luck as to end.

Anonymous said...

I could not disagree more with all of this warm sentiment. You've got to be kidding me. January has been very cold in the east. There will be a brief warmup (with temps only slightly above average), and then back to the icebox to round out the month. It will wind up being a very cold month overall in the east.

I have to say, Andrew, you don't hold yourself accountable for your repeated busts. All you've been saying for a while now is warm warm warm for the east as far as January has been concerned, and you've been flat out wrong thus far. Yet, you make no mention of the fact that you've been wrong and that it has been cold, and you continue to push this warm idea into February now, and are basically indicating that winter is over.

I think you need to stop focusing on specific teleconnections, that have proved to be useless, and look at the bigger picture.

The MJO, as it was for much of last winter, has been a non factor. We've experienced significant cold, all while the MJO has been in the traditionally warm phases, yet you keep using the MJO to support your ideas of warm.

You also place great emphasis on the NAO, which is not a big factor until the latter part of winter and into Spring.

Say what you want about Joe Bastardi, but I happen to think he's right on the money with regard to how this winter is going to shake out, but more importantly with regard to this rant, he fully acknowledges when he is wrong and attempts to correct and learn from the mistakes he has made.

I want to make it clear that I greatly respect what you do, Andrew. And I appreciate your enthusiasm for the weather, but you're repeatedly making the same mistakes, not acknowledging them, and thus its no surprise that you're not correcting them.

I think you are very talented and good at what you do, which is why it pains me to see you not improving your craft by acknowledging and learning from your mistakes.

Andrew said...

Anonymous at 12:30: Let me address your points separately:

- The Central US into the Rockies have been "very cold". The East has been cool, so long as we're on the subject. Please refer to the ESRL daily composites for a chart.

- January has been cool, as was expected. I have not said early January will be warm; please see my post from December 29:

- The "big picture" would be looking at ENSO, which is tied to the MJO. The only way to get a bigger picture from there is to go into the stratosphere, which supports the calls I'm making.

- The MJO has been a factor, please read this very post for additional information.

- The NAO maintains an influence throughout winter; to say it is only active in late winter into spring is inaccurate.

- Joe Bastardi already suffered a substantial failure with regards to his December forecast, please see this post for more information:

On a side note, if you're saying I called for a warm East back on December 26th, you'd be right- until my post on the 29th took precedence.

Anonymous said...

Let me put my two cents of worth in here.

ENSO is heading toward La Nada which means very cold weather for the U.S.A when the AO index is negative. The question is how will the AO index fair going forward? Will it stay at least neutral?
The second component is the structure of the Pacific Ocean temp. pattern aside from ENSO which in the past when it has looked like it does now has favored a cold weather pattern for the U.S.A.

I have no idea how a La Nina pattern seems to be the pattern Andrew is basing his forecast on.

This Jan is looking like it will be colder then the cold Jan last winter and Feb. looks quite cold going forward.