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


stormtracker

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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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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.

no.. not sure on time but says midday so probably midday. ;) i think i have some other maps at home saved but that came from cwg. the gyre to the north and confluence with it zipped out with great speed that time. it could happen here too but so far there's not a super signal for that. still time tho.

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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.

Too bad I'm going to wisp for the weekend, but yea no one should be complaining if the storm delivers enough snow to cover grass blades fully... which >.2'' of precip can easily do.

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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.

How did that one end up? Did it shift north?

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Great points raised.. I think this will come down to just monitoring the models, because this storm looks be really big with lots of moisture.. Definitely will monitoring satellite and radar imagery tomorrow. But back to the Euro, to me its precip shield should be larger. I do think the track will be near the Virginia Capes. Just some thoughts there.

We'll see what happens.

That is what happens when DMC takes over along the front. I wouldn't go jumping off bridges across the north yet though. DMC can wreak havoc on any one deterministic model run.

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Thanks. Could I trouble you to explain a bit more? Are you saying that deep moist convection at the nothern front causes a sharper cut off due to, I guess, 'burn out' issues?

I kind of discussed it to you in post 720 ;)http://www.americanw...ost__p__1381549

But in short, how moist convection develops across the warm sector in positive tilt waves can have large influences in how energy is distributed during cyclone development. Large MCS's that develop along the warm front can displace large amounts of energy away from the cyclone center/upper shortwave/anomaly which can inhibit northward moisture transport as well as change advective processes which also play a role in cyclone development. Negative tilt troughs/waves are not affected nearly as much in a negative manner like this, and in fact, usually are enhanced by the presence of deep, moist convection since it has a tendency to "feed" directly into the upper cyclone which results in rapid intensification/bombing.

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