We continue to watch substantial changes in the high latitudes and the modeling (on a daily basis) is being forced to correct towards more of a blocky look by Thanksgiving week. My suspicion is this has to do with Phase 2 of the MJO.
This morning, note the changes highlighted from now (image 1) to the 2 positives beginning to combine (image 2) to eventually form more of a high latitude ridge, or block (image 3).
Lack of any sort of blocking observed presently. As such, the chilly air masses that do impact the region are very transient.
Changes begin taking place next week as 2 separate areas of high pressure form over AK and Baffin Bay/ Greenland.
That then forms a more “mature” high latitude block by Thanksgiving.
By the time we get to Thanksgiving, note how there’s a totally different look and a pattern has ‘suddenly’ developed that can drive cold air (in more of a sustained manner) south into the Lower 48- particularly eastern portion of the country.
This doesn’t just happen overnight, but what we should begin to see on the modeling is more substantial cold shots for the last 10 days of November, including the threat of some sort of wintry “fun and games” from the Plains, stretching out to the Great Lakes and interior Northeast around Thanksgiving, itself. (Too soon to call for the OHV).
My suspicion is this is all thanks to the MJO. Note how the European continues to slow things in Phase 2 (a cold phase this time of year for our portion of the country).
The question then becomes “can we take things back into Phase(s) 7, 8, and 1 in December (all traditionally cold phases).
Or do we roll right into Phases 3, 4, 5, and 6 (all big time warm phases). That’s what our December forecast hinges on and we’ll keep a very close eye on things. Stay tuned.
The latest JMA Weeklies are in and are beginning to “hint” at where I think the ‘mean’ winter pattern is going. While we’re not ready to lock in to that pattern yet, chances of more meaningful rainfall will be on the increase over the next few weeks across the Ohio Valley, including central Indiana. Before we look at the specific 500mb, rainfall, and temperature patterns, let’s take a look at the pattern drivers into the first few days of November:
The PNA (Pacific North America pattern) is forecast negative to begin the period before transitioning positive around the 25th.
Simply put, the Pacific North American pattern measures the upper air pattern between the Aleutian Islands (in Alaska) to the West coast of the US mainland. When the PNA is negative, this typically drives a western trough and eastern ridge. Conversely, when the PNA is positive, we see the opposite occur (eastern trough and western ridge).
Simply looking at the PNA (keep in mind we also have to take into account other elements), with it being forecast strongly negative through the next week, it gives pause for the chill being able to lock in for any length of time.
The EPO (East Pacific Oscillation) is forecast negative throughout the period. As mentioned yesterday, the EPO measures the upper air pattern between the east Pacific Ocean and Alaska. During negative phases, a trough is favored (and associated cooler than normal pattern) across the East. Positive phases drive the trough into the West and lead to a milder ridge across our portion of the country.
We also need to keep a close eye on the MJO (Madden-Julian Oscillation). We’ve posted many times on this in the past (you can search the archives if bored ;-)). Note the potential impacts of the MJO movement over the next couple of weeks below. Keep in mind, Phase(s) 5, 6, and 7 in late October are much different come winter.
Not to get ahead of ourselves here, but the early thinking is that we’ll spend a lot of time in Phases 5, 6, and 7 this winter. Note how those phases blow torch come the December through February time period.
Given all of what we’ve described from a pattern driver perspective above, we believe the next 2-3 weeks will run cooler than normal as a whole, but that’s not to say there won’t be periods of transitional warmth thrown in the mix (remember, we have the negative PNA to deal with in the short-medium range period). We’ll need to keep a close eye on the potential of a bigger jab of unseasonably cold air to close the month and open the first couple of days of November.
Let’s take a look at the new JMA Weeklies:
Week 1– top to bottom: upper air pattern, temperature anomalies, and rainfall
Week 2
Weeks 3-4
A couple of take-aways: Given the pattern drivers (teleconnections) above, I’d be surprised if the model doesn’t trend colder in the Weeks 2-3 time period moving forward. Secondly, notice how the wet anomalies are beginning to show up around the Ohio Valley. While not yet to where I think this pattern is going to go from a precipitation perspective, we’re beginning to transition to more active/ wetter times during this period.
The latest GFS ensemble sees a similar pattern over the next couple of weeks.
Per the Climatic Data Center, the MJO (Madden-Julian Oscillation) is characterized by an eastward progression of large regions of both enhanced and suppressed tropical rainfall, observed mainly over the Indian Ocean and Pacific Ocean. The anomalous rainfall is usually first evident over the western Indian Ocean, and remains evident as it propagates over the very warm ocean waters of the western and central tropical Pacific. This pattern of tropical rainfall then generally becomes nondescript as it moves over the cooler ocean waters of the eastern Pacific (except over the region of warmer water off the west coast of Central America) but occasionally reappears at low amplitude over the tropical Atlantic and higher amplitude over the Indian Ocean. The wet phase of enhanced convection and precipitation is followed by a dry phase where thunderstorm activity is suppressed. Each cycle lasts approximately 30–60 days. Because of this pattern, the MJO is also known as the 30–60 day oscillation, 30–60 day wave, or intraseasonal oscillation.
We lean on the current and forecast phases of the MJO frequently in building our medium and long range forecasts. At times the MJO can take more control of the pattern than others. A great example of that can be seen playing out in front of us over the next couple weeks.
Note the current GEFS forecast plot. Though the MJO is expected to move into Phases 4 and 5, the amplitude isn’t nearly as great as when it was moving through Phases 8, 1, and 2 over the past few weeks. This means we have to also start paying attention to other global teleconnections to gain more insight as to what will take place with the weather pattern in the short to medium term.
At other times, especially this time of year and into the winter, the MJO can be so amplified, it’ll take over as the primary driver of the pattern.
Note the way the European monthly re-amplifies things as we head into the 2nd half of September. This is what’s tipping us off to the warmth that likely looms as we traverse the last couple weeks of the month.
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As another year comes to a close and the winter pattern begins to “mature,” we thought we’d do a little rambling…
This evening’s rambles have to do with the variety of “drivers” that at times like to take control of our weather pattern. You hear us use terms like the MJO, EPO, AO, PNA, and NAO (amongst others) often, but at times, these various pattern drivers can have more impact than others, and at varied times of the year.
Traditionally, if the MJO (Madden Julian Oscillation) is highly amplified, that’s going to serve as the basis of our medium or longer range forecasts. However, if the MJO is in the null phase, other teleconnections can take control of the wheel. Sea-surface temperature configuration can give hints to the way these elements may behave during the season(s) ahead, but we caution each respective season takes on a flavor unique to it’s own. That’s what makes this business so fun, challenging, and, at times, frustrating. 🙂
It’s also important to understand when the ingredients noted above have the greatest impact on our immediate weather. We love to lean more heavily towards the NAO and AO mid-to-late winter into the spring, for instance. Case in point, a negative EPO and positive PNA can quickly trump a positive AO/ NAO this time of year, and vice-versa.
In the event you didn’t have a chance to see it Sunday, we released our January Outlook. We have a very stormy month outlined that includes cold “overwhelming” things as the month progresses. A lot of this has to do with the fact we think we see a “shake-up” with the MJO out of the warm phases and into the traditional cold phases of 8,1, and 2 taking shape during the 2nd half of the month. Additionally, we continue to believe the favorable north Pacific sea surface temperature configuration (for a cold Great Lakes and OHV) will begin to force the negative EPO/ positive PNA.
The NEW European Weeklies show the transitional time of things through the 1st half of the month, but note the building more persistent NW NA ridge during the 2nd half of the month and corresponding reflection of an eastern trough. Should the MJO be heading into Phase 8 around this time frame (and we think it will), this trough will likely correct stronger in future updates for late month.
The model sees the stormy time of things through the month and into February. (Important to note that even “warm” months this time of year can also feature above normal snow. Just see this December- nearly an inch above normal for the month). As things stand now, we see multiple opportunities for snow as January gets underway, including Saturday PM, and again Tuesday night into Wednesday.
Make it a great evening! We’ll be back early in the morning with a fresh video update.
A fascinating case study lies in front of us as we go through the next couple of weeks. This evening’s video update dives deeper.
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I want to give a couple examples of significant conflicting signals- both short and long-term. The end result is a situation where long range, climate, and seasonal models are likely to have a very tough time not only in the medium to long range (2-4 week period), but thinking seasonally, as well (winter and next spring).
Short-term
To start, let’s look at the EPO. While strongly positive at present, both the EPS and GEFS pictured below take the EPO, or East Pacific Oscillation, negative in the coming couple of weeks.
A negative EPO pattern favors a trough across the eastern portion of the country, especially here in our neck of the woods, with western ridging.
All well and good, right? WRONG. The MJO, or Madden Julian Oscillation, is forecast to stall out into early October in Phase 1.
This time of year, Phase 1 argues strongly for eastern ridging and well above normal warmth while the western portion of the country can experience early wintry conditions.
Talk about contradiction! That’s what makes weather so fun and fascinating. Expect to be humbled often and to always learn! At various times of the year, select teleconnections can mean a lot more than other times of the year. For example, during the summer and fall, we lean heavily on the EPO, PNA, and MJO (if amplified). During the winter and spring, it’s important to take into account what the AO and NAO have to say. It’s important to know when to “pick and choose” when to use particular teleconnections… Furthermore, the various MJO phases (1-8) mean drastically different things at different times of the year. While lovers of chilly fall conditions have grown to hate an amplified Phase 1, they have to love it come winter (shown below). Just look at that difference!
Before jumping ahead to another example of “contradicting signals,” we’re confident the amplified MJO Phase 1 will carry the day through the short to medium range period. Note the strong agreement between the EPS and GEFS below with respect to temperature anomalies in the 6-10 day period.
With that said, there will be challenges within (the big difference as early as this weekend between the GFS and European operational data). A lot of that has to do with the “fight” between the EPO and MJO to take control.
As all of this unfolds across the East, the west will begin to cash in on early winter. Well below average cold and snowy conditions will begin to make headlines over the weekend into next week across not only the Rockies, but some of the low ground, as well. Should the MJO swing into Phase 2 (and I think it will towards mid-Oct), then watch out. We’ll be looking at a rather significant shift towards a much colder feel- and it’ll sting even more so with the late season heat over the better part of the next couple of weeks.
Flipping the page to winter (remember, our prelim. winter outlook will be posted later this week) and the contradiction continues. Upon looking at the current SST configuration, one could easily argue we’re talking about a La Nina winter unfolding ahead.
Meanwhile, the current SOI would suggest we’re in a moderate El Nino.
If you think this can’t wreck havoc even on the short-term forecast pattern, think again…
To close, while the conflicting data can create headaches at times, it’s more fascinating than ever trying to sift through the data and build our forecast(s). It’d be wise to expect more wild swings ahead- leave it to us to try and minimize the impacts of those swings in your day-to-day personal and professional lives. Accordingly, it’s also ultra-important to factor in additional items, such as solar and PDO into the equation for the upcoming winter.
Speaking of, without giving too much away, if I’m a winter weather fan (and I am), I wouldn’t worry in the least about the current warmth… 😉
The short-term period will continue to be dominated by unseasonably warm and dry weather. While we’ll notice a drier air mass (lower humidity) in place the next couple of days, temperatures will remain much warmer than where we should be in mid to late September.
As we close out the month and head into early October, there’s opportunity for a cooler change and we can look to the MJO and EPO for these clues.
Let’s start with the EPO. The GEFS has been leading the way on the negative transition late September for some time now. The EPS is now trending more strongly negative as of the past couple of days. This argues for a cooler than normal period of weather as we put a bow on September and open October.
(The strongly positive EPO will promote more well above normal warmth in the short to medium term period).
The MJO is becoming more amplified and the result is that we can add another “tool to the belt” moving forward in determining the overall direction of the longer range pattern.
Phase 8 argues for widespread warmth, but as we transition from Phase 1 into Phase 2 (easy to see that’s where the MJO wants to head), cooler air swings into the East/ South.
That transition may also result in needed moisture. Note the wetter period that develops during the movement from Phase 1-2.
Speaking of moisture, Sunday appears to offer up the best chance of widespread, organized rain/ storms we’ve seen month-to-date. Models are keying in on the potential of 0.50″ to 1″ (fingers crossed) as a cold front moves into the region.
The CFSv2 is following the plan outlined above- transitioning towards a wetter and eventually cooler pattern Weeks 2-3.
Discussing the reasons behind the frigid open to March and the mid-month changes that await…
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