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Central PA Fall Thread II


JamieOber

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0z CMC went the way of the GFS with the weekend storm. Early looks at the Euro continue to hang a decent low along the coast, albeit weaker and perhaps a hair southeast of 12z. Altoona and UNV's precip printouts have a few tenths shaved off of 12z (bout 0.8 and 1"). MDT has 1.5". Still pretty cold as well.

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Well, well - some consistancy in the Euro runs 12z - 0z. Wet sloppy snow for trick or treat becomes increasingly possible.

WiiNii Central is monitoring a very robust and snowy situation for late this upcoming weekend. After a storm moves through towards the end of this week things get very interesting.

The departing storm continues on to set up as what is called a quazi 50/50 (latitude/longitude) low. Behind that, in Eastern Canada, High Pressure builds in and they conspire to draw very cool, dare I say, cold air out of Canada. While that is happening, the heights over Montana rise and set up a sliding board through the nation's mid-section. An area of energy out of Canada uses that sliding board to ride towards the bottom of a moderately deep trough at the 500mb level. Said energy rounds the base of the slightly negative trough and spawns an area of low pressure that rides north towards the southern benchmark of the DelMarVa by Sunday. Areas from the App front range and north and west seem to be in the ball game for accumulation.

Colder air, energy, moisture from down south and from the Atlantic = snow on the pumpkins.

WiiNii Central must caution that such a happening is not etched in stone. But all the models are in fair agreement. Arguing against an accumulating snow is climatology. But if this year is known for anything, it's that it features very odd weather events.

post-2399-0-29471400-1319534489.gif

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The key difference between the Euro and the GFS early on is how they handle the vortmax and baroclinicity down in the deep south around days 2-4. The GFS has weaker temperature gradients located a little further south, away from a slightly weaker 500mb vortmax that just dies since there is no feedback from the surface. The Euro has a stronger baroclinic band in central Texas that feed the 500mb vortmax lobe moving eastward, with the pair getting much further east. This is key for us, since the high accumulations the Euro paints (5"+?) comes almost entirely from wraparound moisture that was once part of that very same baroclinic band. By hour 84, the GFS doesn't even have any moisture remaining from the band, whereas the Euro most certainly does.

This baroclinicity and slight additional vorticity also helps to deepen the coastal low more rapidly and swing it further north/west, which is quite important as well.

Though I normally trust the Euro over the GFS, the Euro has virtually no support from any other models at this time... so it's hard to go with the snowy solution, unfortunately. Hopefully all the other models will finally give in at the last minute and we'll have ourselves a snow event... if that were the case, I'd expect the NAM to be last, since it's 1) a terrible model and 2) showing the least Euro-like solution currently.

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How are the Northern areas as far as your trees still having leaves? In South central we haven't even reached our peak yet. A heavy wet snow could do some damage.

Crazy to think its October and we have some potential already..

Here we're probably a bit past peak. Heavy leaf drop the last couple days. There will still be plenty of leaves on the trees, but no repeat of Oct '09 (not that we'd get that much snow anyway!).

Interesting that the NWS has become decidedly more optimistic regarding snowfall in C PA. Decent accum to the north (which isn't all that farfetched) but also rain changing to snow on Thurs and also a chance Fri night/Sat morning. While from the looks of it the GFS at least doesn't entirely shut us out from snow, it definitely seems like they leaned toward the Euro for this.

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Here we're probably a bit past peak. Heavy leaf drop the last couple days. There will still be plenty of leaves on the trees, but no repeat of Oct '09 (not that we'd get that much snow anyway!).

Interesting that the NWS has become decidedly more optimistic regarding snowfall in C PA. Decent accum to the north (which isn't all that farfetched) but also rain changing to snow on Thurs and also a chance Fri night/Sat morning. While from the looks of it the GFS at least doesn't entirely shut us out from snow, it definitely seems like they leaned toward the Euro for this.

A decent bit of ensemble members from the SREF and GEFS have a nice changeover Thursday afternoon. Going to be interesting to see if we can pull it off.

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Unbelievable.

Anybody get text data from the Euro?

What's the 2m temp of Ft Indiantown Gap/ Muir Army Field when the deformation banding comes through? Hrs 96-102.

Thanks in advance.

It's odd that both the Euro and the GFS are so insistent on their respective solutions. Normally when there's so much disagreement between the two models, there's also a lot of shifting-around of details from model run to model run as well (just due to the increased uncertainty in the forecast). But in this case, both models have been nearly identical run-to-run, and yet are so far apart between the two of them.

Definitely glad to see the Euro still on board, but it's still quite worrisome that it's the ONLY model on board.

EDIT: That being said, one out of 11 GFS ensemble members (P006) does have a solution like the Euro's. First one in a while, too. Probably not worth much, but at least something similar can even be found among the GFS ensembles.

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It's odd that both the Euro and the GFS are so insistent on their respective solutions. Normally when there's so much disagreement between the two models, there's also a lot of shifting-around of details from model run to model run as well (just due to the increased uncertainty in the forecast). But in this case, both models have been nearly identical run-to-run, and yet are so far apart between the two of them.

Definitely glad to see the Euro still on board, but it's still quite worrisome that it's the ONLY model on board.

Even more disturbing is that the Ukie has gone flatter in the past three runs.

Its gone from being all wound up this time yesterday, to nearly as flat as the GFS.

I'm only 500 some feet in elevation...with lil blue mountain behind me breaking 1k.

To see high temps, during the heart of the day in the mid 30's....wow. Euro is going to break my heart when it yanks it in a run or two. hotdog.gif

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Holy crap.

Thanks.

I think Hurricane Rina is part of the main reason why models all showing different scenarios for the weekend. GFS is only one bringing it north into Florida and I think that is having an influence on how far south any shortwave is able to dig (a certain JB is thrilled that 12z GFS is showing his forecast even though it's the only model doing so). The Euro still wants nothing to do with Rina. IF Euro wins out and this does come up east coast I still think it will be tough for lower elevations in southeast PA to see much more than a couple flakes being this early in the season. Timing will be key as well since solar radiation during daylight hours will still be a factor for a couple more weeks compared to nighttime when temps will be a little colder. Another factor to watch will be how low the dew point temperatures drop after the front on Thursday. If they do not fall any lower than the mid 30s it will be hard to get temps cold enough around here for snow once again IF what Euro shows plays out. I also think it will be interesting to see how the new upgraded NAM handles potential winter weather this week as we get closer to the weekend.

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I think Hurricane Rina is part of the main reason why models all showing different scenarios for the weekend. GFS is only one bringing it north into Florida and I think that is having an influence on how far south any shortwave is able to dig (a certain JB is thrilled that 12z GFS is showing his forecast even though it's the only model doing so). The Euro still wants nothing to do with Rina. IF Euro wins out and this does come up east coast I still think it will be tough for lower elevations in southeast PA to see much more than a couple flakes being this early in the season. Timing will be key as well since solar radiation during daylight hours will still be a factor for a couple more weeks compared to nighttime when temps will be a little colder. Another factor to watch will be how low the dew point temperatures drop after the front on Thursday. If they do not fall any lower than the mid 30s it will be hard to get temps cold enough around here for snow once again IF what Euro shows plays out. I also think it will be interesting to see how the new upgraded NAM handles potential winter weather this week as we get closer to the weekend.

Do you get Skew T's too? How warm are the mid levels? How high up is the freezing mark? With 500 feet sitting at 34F it can't be much more that 700 maybe 800 feet up.

So seems obtainable to me....if the crazy uncle somehow wins out.

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Do you get Skew T's too? How warm are the mid levels? How high up is the freezing mark? With 500 feet sitting at 34F it can't be much more that 700 maybe 800 feet up.

So seems obtainable to me....if the crazy uncle somehow wins out.

That is the one thing I do not have for Euro is Skew T's... there is an option for that on wunderground but nothing comes up for me here so if anyone has links please share. If this scenario were to happen I agree it seems obtainable if everything falls in place... though there are a lot of factors that have to come together for it to happen... such as GFS has temps near 50 in same time frame Euro has them in mid 30s. Let's just hope it doesnt toy with us until Friday then lose it east!!

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That is the one thing I do not have for Euro is Skew T's... there is an option for that on wunderground but nothing comes up for me here so if anyone has links please share. If this scenario were to happen I agree it seems obtainable if everything falls in place... though there are a lot of factors that have to come together for it to happen... such as GFS has temps near 50 in same time frame Euro has them in mid 30s. Let's just hope it doesnt toy with us until Friday then lose it east!!

lTM7y.jpg skew t chart for harrisburg according to wunderground

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That is the one thing I do not have for Euro is Skew T's... there is an option for that on wunderground but nothing comes up for me here so if anyone has links please share. If this scenario were to happen I agree it seems obtainable if everything falls in place... though there are a lot of factors that have to come together for it to happen... such as GFS has temps near 50 in same time frame Euro has them in mid 30s. Let's just hope it doesnt toy with us until Friday then lose it east!!

Yeah it does the same thing for me.

lTM7y.jpg skew t chart for harrisburg according to wunderground

Is that the Euro? If so how did you prevent it from showing the broken image tag?

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This is 18Z run.

18z Nogaps? Is there such a thing?

EDIT: I had to accept a security thingy for it to load... still not good enough, but an improvement for sure.

1-2 hits and a few close. Getting there, baby steps.

It definitely trended in the right direction, but not nearly as much as I was hoping for. :arrowhead:

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