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Weekend Storm Discussion Part II, 2/18-2/19


stormtracker

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The difference I see, is up in New England. Heights are flatter and more west to even west-northwest flow helping to flatten the height field.

Yeah synoptically slightly different, but also early on w.r.t. convective initiation and the diabatic low along the front. It does influence the early cyclone low development by even a few hours...and in this feedback scenario that 3 hr difference makes a difference on advective processes/shortwave ridge building, etc. I think the latter may be another reason why it looks flatter.

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I've referenced it, so have others, but remember that the move north with the precip in jan 2010 didn't even show until 24 hours out. In fact at 36 hours all models abandoned us. This may end up better than we think.

im not sure if someone mentioned it but this was the top analog storm for last night's 0z gfs.

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Yeah synoptically slightly different, but also early on w.r.t. convective initiation and the diabatic low along the front. It does influence the early cyclone low development by even a few hours...and in this feedback scenario that 3 hr difference makes a difference on advective processes/shortwave ridge building, etc. I think the latter may be another reason why it looks flatter.

I'm pretty big on latent heat having some effects on the height field, but I think models have a good handle right now. Pretty good guidance agreement, and it's not like convection will force the low 100 miles north. I think where people will nit pick, are the 30-40 mile changes that can happen as a result from things like diabatic heating.latent heat release..all of which will have an effect on downstream ridging. But I think we are converging on a general solution.give or take 30-50 miles on either side of these current solutions.

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I'm pretty big on latent heat having some effects on the height field, but I think models have a good handle right now. Pretty good guidance agreement, and it's not like convection will force the low 100 miles north. I think where people will nit pick, are the 30-40 mile changes that can happen as a result from things like diabatic heating.latent heat release..all of which will have an effect on downstream ridging. But I think we are converging on a general solution.give or take 30-50 miles.

In the big scheme of things, I fully agree that they do have a generally good handle on this setup now. Unfortunately the big city lies along the northern edge, so those tiny differences will make huge differences in the final solution given the mild positive feedback here. I personally do believe convective processes and latent processes along the front are the key player here in terms of this GFS solution (also the ECMWF). I am not saying I buy any solution verbatim, but that is likely why you are seeing vastly different solution from the amped NAM to the flatter globals.

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Split the difference of all the different QPFs and DC gets maybe 0.3-0.4 snow and it's still far and away the best event of the year.

If the QPF is in the .3 range, that strikes me as a low snow total unless it's a lot of mixing or insanely low ratios. Otherwise a lot angst over something that's not much more than an extra heavy dusting.

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Thanks, I had not heard that. If the models were to follow that pattern, we could expect to see the models tank on us this evening and rebound tomorrow

Remember though, that the analog is not saying what the models will predict in a specific order - it's just saying the pattern is similar. That doesn't mean model forecasts on certain runs will follow that pattern from the storm.

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I'm glad the GGEM is back north this run. It was bugging the heck out of me that a typically amped up model was so surpressed. Shouldn't be a surprise that the GFS is a touch sparcer/south with the precip as it usually follows the Euro's lead within the next run or two.

500MB vort interaction still looks screwy this morning.. and still plenty of time for things to work themselves out.

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Remember though, that the analog is not saying what the models will predict in a specific order - it's just saying the pattern is similar. That doesn't mean model forecasts on certain runs will follow that pattern from the storm.

Oh yeah, I know that. No two situations are the same, and, even if they were, they may not play out the same. I just keep remembering mets here saying that often those blocking vortices (?) were modeled too strong/south. In the event two years ago, that's exactly what ended up being the case. As game time approached, that vortex kept getting weaker and more north. I'm hoping for the same result.

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Looking at the h5 flow and where the confluence is, this does have room to adjust north. I have also seen this depiction of the heavy precip banding moving into WV then just dying out northeast of there time and again and usually it is wrong. The globals have major issues with the point of transfer when a low is inland over the southeast and too many times they make mistakes during the process or redevelopment along the NC coast. This more then anything else seems to lead to this "north trend" in the last 36 hours we usually see as they resolve this problem. I have much less confidence of a northward trend in a Nina then in other years but I would lean towards a northward adjustment with this storm in the final 36 hours.

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Oh yeah, I know that. No two situations are the same, and, even if they were, they may not play out the same. I just keep remembering mets here saying that often those blocking vortices (?) were modeled too strong/south. In the event two years ago, that's exactly what ended up being the case. As game time approached, that vortex kept getting weaker and more north. I'm hoping for the same result.

that storm was much colder both during the storm and in the leadup.. not to mention it was almost a month earlier. so there are critical differences.

this was the gfs a day out

gfs_ten_030m_1-29-10.gif

Forecast map for midday Saturday from the Global Forecast System model shows high pressure to the north of D.C. with the storm centered to the south. Credit: NCEP.

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that storm was much colder both during the storm and in the leadup.. not to mention it was almost a month earlier. so there are critical differences.

this was the gfs a day out

gfs_ten_030m_1-29-10.gif

Forecast map for midday Saturday from the Global Forecast System model shows high pressure to the north of D.C. with the storm centered to the south. Credit: NCEP.

Yeah, I mentioned earlier this morning that it was much colder for that one. The real "item" I was focusing on was the blocking in the northeast. If you had 500 maps from 0z Jan 29 and then compared them to the maps at 0z on Jan 30, iirc, you'd see quite a difference in them, again, iirc. That's what I'd think is at least on the table here. Weaken that or speed it up, and I'd think the precip might gain some latitude.

Also, do you have the time stamp for that map? I'll bet it came sometime late day Jan 29, because the 0z maps from the night before gave us virtually no precip, and my morning forecast on that Friday was for a 20% chance of flurries on Saturday that turned into 7 inches of snow.

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that storm was much colder both during the storm and in the leadup.. not to mention it was almost a month earlier. so there are critical differences.

this was the gfs a day out

gfs_ten_030m_1-29-10.gif

Forecast map for midday Saturday from the Global Forecast System model shows high pressure to the north of D.C. with the storm centered to the south. Credit: NCEP.

It's storms like that, where the north tick runs in the back of my mind.

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