eduggs

I was taking another look at the GFS and CMC 500mb charts for Thursday night into Friday. Yes it's a massive cutter with rain to interior Quebec. But if that strengthening and tilting ULL somehow manages to dive 200 miles further SE, the upper level divergence would start interacting with the coastline and we might start talking about a discrete secondary SLP. Any kind of moisture wrapped back into that arctic air would do wonders for the holiday spirit. Most likely any wraparound snow will remain far to the north and west. But the GFS has been gradually shifting the ULL SE the past few runs. Grasping at straws...

The raw model output is/was not showing snow locally. 3rd party vendors process the raw data to generate clown maps. Some do a very crude job at it, but it's not the fault of the GFS in this case - it's tropicaltidbits etc.

I like cold weather for its capacity to facilitate snowstorms. Since this cold likely won't be associated with snow locally, it's the worst kind of cold.

I was wondering the same last night. Hopefully someone with access to the individuals answered it. By now most of those wacky members have probably been weeded out of the suite.

Misleading graphic. There's little, if any actual snow for our area there. I think the rapid movement and extreme temp gradient of the front is playing tricks on the ptype algorithm.

The aftermath of next week's massive vortex looks miserable. Windy and bitterly cold with the continental height field entirely dominated for days.

March snow melts fast. It drips off trees, melting the snow beneath. It becomes dirty snow and mud. December snow lasts. It can form a snowpack. It's festive.

Explain what a meteorologist interprets with respect to model output? What is the reference point for that interpretation? And what does that have to do with wishing the word "pattern" went out of use? You might say, for example, that a model outcome doesn't fit a "pattern." But how is a future model outcome separate from a future modeled "pattern." They are both unknown and both depicted by modeling.

Humans cannot accurately predict future weather outcomes without models. We are entirely dependent on them. Meteorologists are biased by gut instinct, wish-casting, and false pattern recognition. It's why long-term forecasting has such a low success rate. Most meteorologists are not scientists. The constant mistake that is made is assuming that a modeled future "pattern" will come to exist. And then lots of effort is spent analyzing likely weather outcomes based on that assumed pattern. This is illogical and highly problematic for forecasting. "Patterns" aren't specific enough or stable enough to be useful in most mid-latitude regions. And we can't accurately see particular combinations of features, e.g., "patterns", coming very far out. Meteorologists should stop trying to be experts in things they don't understand.

All of that is very non scientific. The use of the word "pattern" should be banned from the lexicon.

The ULL/PV over Hudson Bay with soaring 500mb heights to Northern Quebec and a strong shortwave diving south through the Pac NW just looks so ugly. I guess we can hope that the weak preceding coastal precipitation scrapes us before the cutter, but it feels like a depressing consolation.

Disagree. 1) Our ability to recognize a future "pattern" is completely dependent on models. 2) "Patterns" only exist in a broad sense. They are not intrinsic nor defined to a fine scale. They are just descriptive and statistical human inventions. Our feeble brains try to simplify things into "patterns" for better understanding. But in truth, the weather, characterized by height fields, temperature, pressure, and all the other parameters is unique. Relying on general pattern recognition to very generally predict synoptic scale weather probabilities might be plausible. But anticipating specific weather in a local region based on "patterns" is fruitless.

So by now it seems likely that we'll be dealing with a cutter next week. But we can't forget the obvious lesson of uncertainty, which cuts both ways. The final outcome is still highly sensitive to the height field in key regions. Especially with an amplifying and anomalous trof, guidance could come storming back towards an east coast low. Chances have dwindled as we've used up lead time, but useful uncertainty remains.

That's how I see it.

Specific local impacts - 1-2 days. General signal for storm vs dry - 7-10 days. But obviously with increasing uncertainty as you move out in time. Other regions may have other characteristic lead times for reliable forecasts.

I think of it more like tugging on a buckled string. The impacts are continuous and simultaneous in all directions.

Well stated. As far as I know, CPC keeps things very general with broad brushed AN and BN for temp and precipitation. They avoid talking about specific patterns.

I don't agree. The climate indices are a snapshot representation of the atmosphere, not a driver of its state. The driver is global temperature gradients.

Snow melts so fast in March. And outside the hills, we're always battling marginal temps. You need intense snowfall rates in March. For me, Dec - Feb are the snow months.

If December ends up above normal temperature-wise, I'm hoping some of the long-term weeklies huggers and "pattern" obsessers start to appreciate the inherent uncertainty in long-term weather forecasting.

-4 SD AO is just a statistic; a number. It's a very crude way of characterizing the state of the pressure field/atmospheric circulation at a continental scale. Weather is a local phenomenon.

If we're in a "pattern" - which I argue we are not - then it's a terrible pattern for coastal plain snow.

ULL/PV near Hudson Bay at day 5 is not going to work. We need that in the Canadian Maritimes. Ensembles have been shifting the low heights further NW with time. Cutter City.

All the degreed or professional meteorologists who study 10+ day anomaly charts and climate indices have contributed nothing to local weather prediction so far this winter. We've experienced average to below average snowfall, mostly above average precipitation, and average temperatures with slightly more extreme highs than lows but no big extremes either way. Maybe this is a fruitful endeavor if you're forecasting drought in the western US and even if you're an energy trader... but if you're a medium range forecaster along the highly baroclinic east coast, I see very little utility studying the charts at day 10 and beyond. Maybe in the future, model skill will improve to the point of usefulness. But right now it only serves to create false expectations.

Climate indices aren't causally connected to weather. They are only loosely correlated to weather outcomes, particularly at the local level. So even if we could forecast their state 7 days in advance, we wouldn't know for sure if we were getting a coastal storm or cutter. But of course we can't forecast the state of climate indices that well 7 days out, especially the finer details like magnitude and orientation. So we are left using climate indices in hindsight to identify correlations instead of using them in advance for prediction. Everybody wants it to be so simple... That we move from one stable, definable weather regime to the next, and that we can see the discrete change coming. But instead of existing as a pattern, weather is characterized by a continuously changing set of features.