LIKE HERDING ONE-EYED CATS

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SHOW ME SOME WARMTH

If you are ready for some warmer weather, raise your hand. That's what I figured, pretty unanimous on the yes ledger. And there certainly is plenty of reason to be ready; we've been living in the temperature tank the last 3 weeks, with daily departures running 9 to 11 degrees below normal per day. At least we've had company with the whole eastern half of the nation shivering under northwest flow.

That's all about to change as a significant atmospheric realignment takes place that brings us above normal readings the next 8-14 days starting Sunday. That's the one part of the forecast that is on solid ground. The National Blend of Models shows this for highs out to February 17th.

That translates to national temperature departures that look like this over the next 10 days.

LIKE HERDING ONE-EYED CATS

I can say with high confidence we are in the ballpark with those temperatures and a continuation of dry weather through at least the end of next week. After that, we go off the rails as the pattern continues to evolve into one that has the potential to be highly energetic and stormier the 20th and beyond.

The issue that is rearing its head, is the uncertain phasing of a western trough and how it impacts approaching energy capable of creating wetter weather. The operational models are diverging daily on what happens mid-month and are, what I would say, rather conflicted. Right now it's like herding one eyeed cats in a parade. When you get this much uncertainty and you need something to lean on, that's when you call in the ensembles.

Using the cat metaphor, I'll try to explain why, in the graphic below, with cats representing energy that is emerging into the pattern. On the right they are running around causing mischief and chaos. The ensemble rounds up all the cats (energy) and herds them into a pen. Once contained, the EURO ensemble runs them through a computer and comes up with 51 alternative solutions as to how they will behave. In general, there is reasonable agreement or clustering as to where they go. However, there are always the loners who don't conform, and they are labeled outliers. The ensemble then creates a mean solution of all the 51 outcomes. The mean is the most likely solution of that particular model run.

The operational EURO (or GFS) is a single solution that can be significantly different from the ensemble mean (comprised of the 51 solution average), especially if it represents one of those outliers. With every model, the further out you go, the less chance it has of verifying. However, the physics behind the EURO are so good that it maintains a one-day accuracy advantage over its competitors. Its 51-member ensemble system provides the most reliable probability forecasts for extreme weather events.

Just like a cat, energy is often reluctant to conform and does what it wants, when it wants to. It is the key to the puzzle; identifying it and ingesting it properly into a model is essential for a great forecast. Unfortunately, we can never get data from every square inch of the atmosphere. To combat that, we use grids that, by way of linear algebra and Newton's second law, compute how a temperature at a certain point influences surrounding points at future times. It's the foundation of numerical weather models, which, thanks to today's powerful computers, spits out the data I show here regularly. The higher the model resolution, the more likely it is to portray the atmosphere.

Where our weather has the potential to get quite interesting is in the extended range. That's based on many of the teleconnections I utilize to identify long-range trends. Taking those into consideration along with the ensembles takes some of the doubt out of the raw model output. So, today we are running with the ensembles of the "big dog" known as the EURO to get a glimpse of what's ahead.

To get to the time frame of interest, mid-February and beyond, I'm dialing up the EURO weeklies, which are run out to 46 days. That takes a ton of computing power, and so the resolution is not nearly as high as shorter-range models, so keep in mind the chances of error are higher due to that and the distance they are trying to predict.

The first thing we focus on is the storm track at 500 mb. We know that the PNA (Pacific North America Oscillation) is projected to go negative from mid-February into March, favoring below-normal temperatures at that time. However, before that happens, the positive phase rules the next 10 days with relatively mild readings. The evolving West Coast trough, now in the formative stages, begins to look like this in week 2 (February 13th through the 20th). That's not a cold look, but it shows an impressive West Coast trough that is beginning to inject moisture into the Midwest.

In week 3, the trough is broadly cutting across the country, implying multiple systems are quite possible. Also, the red blob approaching Alaska signifies the WPO (Western Pacific Oscillation) transitioning from a positive phase to one that's negative. That means colder air should start to push, and that's a combination ripe for snow to the north of any system that cuts along the southern fringe of the jet in the period February 20th-27th.

Week 4 and even week 5 look similar at 500 mb, so the next month or so has a lot of potential to be active. To that point, this is the EURO ensemble precipitation depiction from February 7th through March 27th. It's very wet further south over the Ohio Valley. Even so, the northwest fringe of the heavier precipitation shield extends back into eastern Iowa. This is encouraging because the teleconnections support what the model ensemble depicts; that's not always the case. Since the ensemble is made up of 51 members, keep in mind that some solutions were likely higher or lower well into eastern Iowa. Below is the average of the cats with the high-end bullseye located over Tennessee; confidence appears high that a wetter period is on the way.

The next thing to surmise is that with the WPO going negative, there should be enough cold air in place for snow to fall somewhere in the central Midwest in the 2-3 week period and beyond. The ensemble mean shows this for amounts. I am not focused on the totals and stress that amounts indicated were over a 46-day period ending in March. Even if they were correct, the snow would be spread out over time.

My takeaway is that the projected storm track is laid out in such a fashion that it would reside from southern Missouri to the Ohio Valley, promising snow from that area north. It also implies that there has to be enough cold air around for such healthy snow amounts. Flat out, no model is going to hit this precisely, and the true value is in the trends I mentioned, nothing related to specifics. It's called guidance for a reason.

Temperatures will likely average above normal the next 2 weeks before getting colder towards the 20th and beyond. The ensemble shows this for departures from February 20th to March 24th.

If by chance the snow shown materializes in the 2-3 week period, I would not be surprised if temperatures end up colder. The EURO has a hard time seeing cold at that distance, a known bias.

So, packing all this information away, this is what I come away with from mid-February to mid-March:

• The next 2 weeks look mild, near to above normal

• Precipitation remains minimal for another 7 days, gradually increasing after that.

• Weeks 3-5 have the potential to be active with above-normal precipitation.

• Temperatures from late month into mid-March appear to fall below normal

• There is a strong signal for near- to above-normal snowfall the 2nd half of February into March

Well, time to round up my cats before they read this and focus on something besides weather maps. Thanks for checking out the site, and have a splendid weekend. Roll weather...TS

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