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Christmas Grinch Storm Potential


Chicago Storm

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It'll be interesting to see how much the lake plays in.  I have a rooting interest in this as I will be in Lake county IN during this event.  Have been looking at lake temps and they seem to be in the mid-upper 30s for the most part.  Have to go to the eastern side of the lake to encounter readings above 40F.  It's a marginal setup thermally but those lake temps are not really anything to write home about.

 

Yeah something to watch. On this run though the winds starting backing around to the NW after 18z and start to advect slightly cooler air into northeast IL. 

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5-day 500mb height correlation puts it in second place, behind the Euro.

cor_day5_HGT_P500_G2NHX.png

Which, obviously, doesn't always tell the whole story. IIRC it's always been up near the top on that particular metric... But get down to the surface and it probably somewhere between the GFS and GEM
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meteocentre website has this cool cyclone tracking feature for various models.  I was looking at it for the GGEM.  The red line coming out of the Gulf is the 00z run.  I wonder if we'll get this kind of track as it's not that easy to get a NNE tracking Gulf low way up into Canada like that.  There's some spread in where it goes though amongst the models.

 

post-14-0-00108000-1419229485_thumb.gif

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Regardless of where this one goes, I don't see it having any significant accumulation with it. Sure, 850s are marginally below freezing, but there's a warm layer above freezing from the surface up to about 900mb.

Poor surface temps coupled with rainfall and temps in the 40s the days leading up to the event do not spell meaningful accumulation.

Just my two cents (or 100 rubles).

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Regardless of where this one goes, I don't see it having any significant accumulation with it. Sure, 850s are marginally below freezing, but there's a warm layer above freezing from the surface up to about 900mb.

Poor surface temps coupled with rainfall and temps in the 40s the days leading up to the event do not spell meaningful accumulation.

Just my two cents (or 100 rubles).

 

Never want to ignore those factors, but if it snows hard enough it will stick with no problem.  We've seen it time and time again.  Assuming the models don't back off on having a healthy band of precip, whoever gets in the meat of that band won't have trouble getting it to accumulate imo.

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Never want to ignore those factors, but if it snows hard enough it will stick with no problem.  We've seen it time and time again.  Assuming the models don't back off on having a healthy band of precip, whoever gets in the meat of that band won't have trouble getting it to accumulate imo.

Yeah we hear it every year, it isn't going to snow because it was warm before the event or it rained before it. Every time that is brought up it is proven to be incorrect. Also that being said I don't think the temperatures are that marginal at 850mb either.

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I'm buying the eastern track (if that's what we're calling it) for now, but I'm still scratching my head over ensemble guidance's insistence on a westward shift.

 

For example, here's the spread of the CMC ensembles, superimposed with the model itself. Note how the ensembles are stronger with the storm (not necessarily a surprise, since it is the CMC) and also a tick west of the model.

PN_PN_PN_072_0000.gif

 

Add to that 0z GFS ensemble guidance seemingly divided into two groups; one favoring the GFS OP track, the other trying to go through Lake Michigan (the latter arguably the favored group, in terms of number of members):

track.aeperts.2014122200.east_coast.sing

The continued weakening of the trough and slower progression should favor a more eastern track. But then why are the ensembles in disagreement, merely a matter of hours away?

Perhaps I'm not seeing something others are, but that's my 1AM head-scratcher.

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Yeah we hear it every year, it isn't going to snow because it was warm before the event or it rained before it. Every time that is brought up it is proven to be incorrect. Also that being said I don't think the temperatures are that marginal at 850mb either.

Well, I don't think it's particularly fair to say that every time it is brought up it has proven to be incorrect...especially for us folks in the cities. And also, don't get me wrong-- I didn't refute it being able to snow, I refuted the chance of significant accumulation given warm surface temps and rain the day before.

It is true though from 12z to 00z, the GFS has backed off a tad on the low level warming in the shallow layers of the atmosphere. Soundings indicate 850 temps around -3, warming as you get closer to the surface at hour 72. 12z had these temps more around -1.5 to -2. I guess it depends on your definition of marginal, but regardless I'd like to see cooler temps in the column before committing to those maps as representative of accumulating snowfall.

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Well, I don't think it's particularly fair to say that every time it is brought up it has proven to be incorrect...especially for us folks in the cities. And also, don't get me wrong-- I didn't refute it being able to snow, I refuted the chance of significant accumulation given warm surface temps and rain the day before.

It is true though from 12z to 00z, the GFS has backed off a tad on the low level warming in the shallow layers of the atmosphere. Soundings indicate 850 temps around -3, warming as you get closer to the surface at hour 72. 12z had these temps more around -1.5 to -2. I guess it depends on your definition of marginal, but regardless I'd like to see cooler temps in the column before committing to those maps as representative of accumulating snowfall.

-3c is fine at 850mb especially in December. This isn't a October/November or March/April setup. Early or late season marginal temps are fine this time of year.

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