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Jan 11-12 Model/Forecasting Discussion


Ji

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If we can get 4-6 inches out of this, we'll be just about exactly where we should be at this point in January for the season, going by averages. Maybe even ahead. Easy to forget that after last year.

It's got nothing to do with "normal", and everything to do with the fact that almost everyone South and North of us has cashed in and we have gotten shafted.

I can toooootally accept an average or below average winter - low-snow winters happen around here more often than not. But when storms keeping bending around us and skipping over us and NC and NJ/NY/NE keep getting buried, it hurts.

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If we can get 4-6 inches out of this, we'll be just about exactly where we should be at this point in January for the season, going by averages. Maybe even ahead. Easy to forget that after last year.

This is true overall. However, I don't think it's so much everyone comparing to last year. While 4-6" would equal or exceed our January average in DC, keep in mind that the variance around that mean is pretty large. Which perhaps renders the average somewhat...errr..."mean"ingless? (Pun slightly intended there!) Well, not meaningless of course, but the point is the average includes a lot of meager monthly amounts and the occasional big one over the years. So when it does snow here, it tends to come in bigger storms.

But yes, 4-6" right now would seem like a veritable miracle.

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It's got nothing to do with "normal", and everything to do with the fact that almost everyone South and North of us has cashed in and we have gotten shafted.

I can toooootally accept an average or below average winter - low-snow winters happen around here more often than not. But when storms keeping bending around us and skipping over us and NC and NJ/NY/NE keep getting buried, it hurts.

I seem to recall a lot of tearing of hair and gnashing of teeth because the mid-Atlantic got pounded by almost every storm last year. Cries of "unfair" because New England got shafted as the systems hit the mid-Atlantic and slid east. All I could do is roll my eyes and think, "well, every other winter you guys get hammered, and NYC recently had 3 straight 40"+ seasons or something, so whatever." But yes, even New England and NYC cashed in later in the season, with the end of Feb. storm, that bypassed us. This year, yes, it's aggravating to see everywhere south of us get lots of snow, and not too far north of us get even more, while we're in the relative desert even though it's been favorable and cold so far. Philly is really in a good position, they got in on the big winter last year...and now they scored pretty well Dec. 26, and look to score again with the current system.

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not really, looking at the sim radar and h7 vv's compared to 6z its not going to look nearly as good next frame. Snow is just about over at DCA at 24 hours. I really doubt the next frame looks anything like it did at 6z.

agree

sim/rad much weaker returns this run at 12Z vs. 18Z at 6z

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was not honestly all that surprised to see the changes to the NAM this morning. 2 things helping us out.... the backside vorticity with the actual ULL over SD is coming in stronger than even the 6z nam forecast. this is helping to dig the trough and more importantly speed it up so that piece of energy can rotate through and phase in.

post-3403-0-48534100-1294753856.png

the second thing to watch is this feature. by 18Z today the models seem to agree on separating a piece of the northern shortwave to take it up thru PA...if this does NOT happen... look out... we will get the kind of storm the NAM is showing for NYC... the less of a degree this happens the better we will do. right about now, I think the 6z NAM which shows slight separation is almost the best we can help for. I really dont think there will be no separation but very minimal.

the reason this vorticity impulse causes a problem is because it delays a full phase early on, so you get the storm trying to bomb but the dynamics to support it aren't really there til it gets to the NJ coast... thats when the energy transfer occurs likely due to the more favorable gult stream environment (in other words where the longwave trough begins to "feel" the gulf stream). This stupid packet of vorticity is also what drags the 850/700/500 lows to our north.... if you took it out of the equation and entirely, there would be no energy transfer, a single 700/850/500 low would stay consolidated and bowl east right across Washington DC. Note there's no way to save the Shenendoah Valley from a dry slot in this case... by nature as the coastal develops and the CCB starts, someone is going to get fringed. Things are just already too late for them. If the timing works perfefctly, DC might have a chance but moreso up toward baltimore and NE

The reason the GFS is not coming around to this is because these are tiny mesoscale features far beyond its grid resolution. its even difficult to see on the NAM but peeking at last nights ARW WRF gave me an idea where to look.

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was not honestly all that surprised to see the changes to the NAM this morning. 2 things helping us out.... the backside vorticity with the actual ULL over SD is coming in stronger than even the 6z nam forecast. this is helping to dig the trough and more importantly speed it up so that piece of energy can rotate through and phase in.

post-3403-0-48534100-1294753856.png

the second thing to watch is this feature. by 18Z today the models seem to agree on separating a piece of the northern shortwave to take it up thru PA...if this does NOT happen... look out... we will get the kind of storm the NAM is showing for NYC... the less of a degree this happens the better we will do. right about now, I think the 6z NAM which shows slight separation is almost the best we can help for. I really dont think there will be no separation but very minimal.

the reason this vorticity impulse causes a problem is because it delays a full phase early on, so you get the storm trying to bomb but the dynamics to support it aren't really there til it gets to the NJ coast... thats when the energy transfer occurs likely due to the more favorable gult stream environment (in other words where the longwave trough begins to "feel" the gulf stream). This stupid packet of vorticity is also what drags the 850/700/500 lows to our north.... if you took it out of the equation and entirely, there would be no energy transfer, a single 700/850/500 low would stay consolidated and bowl east right across Washington DC. Note there's no way to save the Shenendoah Valley from a dry slot in this case... by nature as the coastal develops and the CCB starts, someone is going to get fringed. Things are just already too late for them. If the timing works perfefctly, DC might have a chance but moreso up toward baltimore and NE

The reason the GFS is not coming around to this is because these are tiny mesoscale features far beyond its grid resolution. its even difficult to see on the NAM but peeking at last nights ARW WRF gave me an idea where to look.

what are you talking about, the NAM just took away the storm here...now is 1-3 like the GFS.

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