Re: Long Range Thread 15.0

[mikeypizano]

Rb don't forget, I got that Toro last year and the blizzard dumped 2 feet on me...

[CPcantmeasuresnow]

I think it is time to dust off my blog. May release something later today.

Your going to "dust off your blog" and "release something later"?   Totally inappropriate Frank.  

Too far?

In this environment probably, but damn funny.

[Sanchize06]

12z GFS shows snow, rain to snow for coast

[Sanchize06]

12z GFS continues the trend of west and stronger over the past few runs

[rb924119]

But rb how can we take any model seriously that can't recognize the coast line. I mean that is kinda sad. Just asking

No, you're fine!! And this actually a really good question IMO because I think the concept of the use of ensembles is confusing to a lot of people. The purpose of an ensemble, whether it be the GFS Ensemble, EURO ensemble, SREF ensemble, doesn't matter, is to simply get a sense of all of the possibilities. So when they are run, the control of each ensemble, is the exact same as the operational model that we look at every day, but just run at a lower resolution than the op/same resolution as the ensemble members (a member is one one version of the control with one initial condition changed subtlely). The purpose of the control is to see how much the forecast changes solely because of the change in resolution (sometimes atmospheric processes such as cloud formation, latent heat release from deep convection, among others, occur at scales only very finely resolved models can calculate, which can have implications on the evolution). Once we know what differences in the model output are caused solely by the change in resolution, this is where the Ensembles come in. Each ensemble member is identical to the control; resolution, inputs, formulae. Everything. However, to generate a spread of ALL POSSIBLE SOLUTIONS, and to more accurately represent the fact that we, as humans, can not completely sample the atmosphere (via balloons, drop slides, etc.) to the point that we can ensure it is being represented 100% completely accurately, one initial input (surface temperature in one, dew point in another, jet-level wind speed in a third, etc.) is changed slightly in each member. Then the ensemble is run based on those slightly altered conditions. The resolution is decreased mainly to save on computational power, as each increase in resolution would exponentially increase the amount of computations and power needed to generate the output, but it is also not needed. By running an ensemble like this, you generate a statistical distribution of outcomes; like spaghetti plots for hurricanes. Wherever you see the most spaghetti lines for a hurricane is where the model thinks that hurricane is most likely to track, even with the tweaks in conditions. However, the outliers give you the possible range (think of it like the cone of uncertainty). The tighter the cone (smaller the statistical spread/narrower the cone, the higher confidence, theoretically, you have in that forecast track). The same thing holds true when looking at those maps I posted earlier. Even though each member differs in the exact amounts for our area, regardless of the ensemble or member in an ensemble you look at, the fact that each member has some amount of snow means that the players will be on the board for a stormy stretch. The fact that so many members of both ensembles have amounts that are very high, and that the means of each ensemble (the result of each individual member averaged together) are as high as they are, means that the odds of seeing significant snow(s) in and/or around our region are heightened, and that's what we look for. We can't lay out how much willnfsll in your backyard perse', but by seeing these ensemble means and individual members putting out amounts like this for the entire area, it means that pretty much regardless of which event it happens with and to what degree, they all see SOMETHING happening. The fact that they cannot resolve a gradient along a coastline doesn't take away from the model, because the detail is not their purpose. That's what operational and control runs are for. The ensemble is there to generate a statistical probability.

On this board, we don't necessarily rely on these snowfall outputs because they can be misleading (for example, they didn't match onto either of the first two events this season until right before each event). We look at them sometimes like now to demonstrate a point, but people such as myself, sroc, Frank, Al, mugs, etc. look at a different component of the ensembles; the 500 hPa (H5/mid-level) anomalies, means, and outputs. These are much more telling about the general pattern and can give insight as to whether or not those snow maps "make sense". A great example would be the last events. The snow maps didn't have anything up until right before, but by looking at the mid-levels we could tell that the snow maps did not make sense with the pattern/evolution those same models were depicting aloft, and so forecasted based on the correction we thought was most likely to occur. That's how you want to look at and use ensembles; what type of signal are they showing? A big one, a little one, no signal at all? The maps are fun to look at, sure, but don't fret the details with them, because it's not THOSE details that matter. It's how the package looks as a whole.

Does that make sense?

[Frank_Wx]

White Christmas on today's 12z GFS!!

[Frank_Wx]

The dark blue line on the map above is freezing line at the surface. So while it may be snowing, not sure if much will still verbatim along the coast. I don't see this trending colder at the surface unfortunately given the set-up. But even if it's snowing on Christmas with a coating to maybe a couple inches that would be fantastic.

[track17]

So Frank are you saying the people at the coast will just get rain. I jena sounds like it. That is fine if it is nothing we can do stinks but at least your honest.

[amugs]

Surface will respond to teh low level cold air infiltarting rank - we've seenthis many times - rain to snow to the coast but as per climo inland about 20 miles away does best.
850's



700 cold

[jimv45]

looking pretty good for us northern folks for a white Christmas.

[rb924119]

As a follow up, track, look at the discussion we are having right now for Christmas. Many of us are thinking that at least some snow is likely. Some like myself think a moderate event for a fair chunk of the region. Notice how we are not fretting the fact that the operational runs are floundering from run to run, even now less than five days away, nor are we worried that the ensemble means do not depict these totals we are thinking. Why? Because when we look at the ensembles and their overall depictions of the the mid-levels, we are looking at the pattern, and through acquired knowledge via observation, trial and error, and info from other members and forums, we are expecting yet another correction to a snowier solution to occur, even if it's late. Case in point, that is the "trend" being referenced with the GFS of late. A more amplified solution with more precipitation and colder air. THAT is how you want to look at Ensembles. Leave the details for inside of 48-72 hours when the pattern starts to become finally better understood by the operational guidance. Once that begins to happen, then you can start focusing on things like amounts and the rain-snow line. Now some of us do like to put out early projections just as highly preliminary ideas about what we think, but those are very loose and flowing, as we understand the inherent uncertainty, and will make that clear.

[bobjohnsonforthehall]

The 12z really seems to have moved that low off the coast. It seems to be about 100 miles west and 50 miles south of where it was on the 6z. What is causing that?

[track17]

Oh I get what your saying Rb and it makes a lot of sense. Franks's last map though makes me think the coast areas will just see Iran he kinda hinted at that but I do feel confident with what you are saying for after. Thank you for your had work

[rb924119]

Oh I get what your saying Rb and it makes a lot of sense. Franks's last map though makes me think the coast areas will just see Iran he kinda hinted at that but I do feel confident with what you are saying for after. Thank you for your had work

No, no. He said that verbatim it would be snowing all the way to the coast, but having it readily accumulate at the coast might be a little bit of an issue give the project surface temperatures on that model. That's all.

[rb924119]

The 12z really seems to have moved that low off the coast. It seems to be about 100 miles west and 50 miles south of where it was on the 6z. What is causing that?

It's all about how it's handling the mid-level energy. This run was bit sharper with the trough, more consolidated and stronger with the energy, and as a result allowed it to dig a little further south than the previous run. By doing that, as it continues to tilt negative, the precipitation field expands further west and the low tracks further west because the atmospheric forcing has shifted further west.

[track17]

Oh ok I did not understand it

[bobjohnsonforthehall]

The 12z really seems to have moved that low off the coast. It seems to be about 100 miles west and 50 miles south of where it was on the 6z. What is causing that?

It's all about how it's handling the mid-level energy. This run was bit sharper with the trough, more consolidated and stronger with the energy, and as a result allowed it to dig a little further south than the previous run. By doing that, as it continues to tilt negative, the precipitation field expands further west and the low tracks further west because the atmospheric forcing has shifted further west.

So when the trough tilts more negative it acts kind of like a magnet for a low off the coast? Drawing it closer and increasing the breadth of the precip associated with it?

[rb924119]

The 12z really seems to have moved that low off the coast. It seems to be about 100 miles west and 50 miles south of where it was on the 6z. What is causing that?

It's all about how it's handling the mid-level energy. This run was bit sharper with the trough, more consolidated and stronger with the energy, and as a result allowed it to dig a little further south than the previous run. By doing that, as it continues to tilt negative, the precipitation field expands further west and the low tracks further west because the atmospheric forcing has shifted further west.

So when the trough tilts more negative it acts kind of like a magnet for a low off the coast? Drawing it closer and increasing the breadth of the precip associated with it?

As Lucy from Peanuts would say, "THAT'S ITTTTTT!!!!!!!!!!" Haha yup, in a nutshell. Now there are other factors to consider, and if I had my dang Accuweather subscription I could do a really nice video showing how all the forcing mechanisms interact, but I don't have it this year :/ maybe I can pull one from my archives and post it as an example at some point if you want. Speaking of, I still have to Skins' video. I completely forgot about that!

[rb924119]

I'm almost beginning to question why we may not see this thing trend further negative and even attempt closing off at the mid-levels closer to our region.......the idea is beginning to intrigue me.

[bobjohnsonforthehall]

The 12z really seems to have moved that low off the coast. It seems to be about 100 miles west and 50 miles south of where it was on the 6z. What is causing that?

It's all about how it's handling the mid-level energy. This run was bit sharper with the trough, more consolidated and stronger with the energy, and as a result allowed it to dig a little further south than the previous run. By doing that, as it continues to tilt negative, the precipitation field expands further west and the low tracks further west because the atmospheric forcing has shifted further west.

So when the trough tilts more negative it acts kind of like a magnet for a low off the coast? Drawing it closer and increasing the breadth of the precip associated with it?

As Lucy from Peanuts would say, "THAT'S ITTTTTT!!!!!!!!!!" Haha yup, in a nutshell. Now there are other factors to consider, and if I had my dang Accuweather subscription I could do a really nice video showing how all the forcing mechanisms interact, but I don't have it this year :/ maybe I can pull one from my archives and post it as an example at some point if you want. Speaking of, I still have to Skins' video. I completely forgot about that!

And my eighth grade science teacher said I had no future in the sciences.

TAKE THAT MRS. SUTER!!!

[sroc4]

I'm almost beginning to question why we may not see this thing trend further negative and even attempt closing off at the mid-levels closer to our region.......the idea is beginning to intrigue me.

EXACTLY!!!!! No one believes me. The energy just has to dig a little more into the Tenn Valley. It is so freaking close.

[Sanchize06]

GFS and CMC still like the idea of a big storm for next Friday

[rb924119]

@ Bob - ahahahahahahahahahahahahaha wooooooooooooo!!!!!

@scott - I've never dismissed it entirely, I just wasn't personally considering it to be likely enough to bring up with any gusto. However, it is a VERY delicate balance in this particular situation because it could go one of two ways; it could either close off or shear out. There's no middle ground with the type of situation we would need.

[RJB8525]

GFS and CMC still like the idea of a big storm for next Friday

OHHHHHHH CANADA OUR HOME AND NATIVE LAND

[Sanchize06]

12z GEFS west of 6z

[track17]

Rb though I thought it would be better if this thing goes east because west means warmer correct or am I wrong

[amugs]

GEFS ENS BOOMMMM!!!

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