Interesting changes in modeling of mid-to-late week storm

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PurdueWx80
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Interesting changes in modeling of mid-to-late week storm

#1 Postby PurdueWx80 » Sun Dec 19, 2004 11:42 am

So far this morning, there has been somewhat of a consensus towards phasing and a storm heading up WEST of the mountains in the Wed-Fri time frame, w/ no storm going up east. The 12Z GFS is the most wound up and furthest west, w/ a 988 low going into the central/western Lakes by Thursday. The GEM is not far behind strengthwise, and actually gets the low caught up in the PV over Hudson Bay (with the low going down to 957 mb up there), but it is further east. They both imply some phasing of the northern and southern streams, w/ little to no energy lagging behind. Previously, there was some residual vorticity over the SW, and this was the mechanism for creating a storm east of the mountains as those height falls would translate to a low forming on the coastal trough. It's interesting how this has happened as we get closer to verification time, given that these are the first runs to show such the phasing/west solution. The 12Z Eta would also imply to me that a storm would end up west of the mountains (although there are hints of a secondary low in the deep south). Either way, (either waves will come up the front as it stalls out w/ a bigger storm along the East coast at the end, or a big storm west of the mountains) there will be a track of heavy snowfall behind the front - w/ the Eta, GFS and GEM all putting out QPF from 1-2.5". The heaviest snow totals would be in the 12-15" range most likely at some point in the OV if the phased/west solution comes true. A serious icing situation would also occur between the snow and rain shields, and severe weather would be possible in the SE as warm, moist air travels northeastwards from the Gulf. Here is a smattering of the solutions so far...it will be interesting to see the other globals (UKMET and Euro) as well as later runs.

GFS sfc at 90h -
Image

Eta sfc at 84h -
Image

GEM -
Image

The chances for late-week snow in the south would be nil with most of these solutions, aside from snow showers and flurries in the Appalachians as another polar/arctic air mass makes it's way south.
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#2 Postby aggiecutter » Sun Dec 19, 2004 12:01 pm

The GFS had this solution on a couple of its runs last week. This was the Tom Skilling snowstorm for Chicago that some were scoffing at last week. Looks like he might end up being right.

It's possible, depending on the exact track of the storm, that parts of NE Texas, Eastern Oklahoma, and parts of Western Arkansas could see a pretty decent snow event from this storm as it pulls out.

http://www.nco.ncep.noaa.gov/pmb/nwprod ... _078.shtml
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#3 Postby ohiostorm » Sun Dec 19, 2004 1:32 pm

Looks like I will get some of that if it pans out.
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#4 Postby Wnghs2007 » Sun Dec 19, 2004 1:41 pm

Well...Yall have fun with the storm that screwes are Christmas Possible Storm over. Dangit....Best chance at white christmas I will probally ever get down the drain. :cry: :cry: :cry:
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#5 Postby PurdueWx80 » Sun Dec 19, 2004 2:06 pm

Euro and UKMET models both in line with GFS, increasing the confidence in a track west of the mountains. The Euro is much weaker and slightly further east but the UKMET has an extreme look after the storm moves due N into Canada, temperature-wise w/ heights over the lakes at sub-510 levels (meaning another huge lake effect outbreak for Christmas, IF it verifies).

Image
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#6 Postby PurdueWx80 » Sun Dec 19, 2004 2:44 pm

One more thing (for now)...just checked out snow accumulations according to the 12Z eta and I just had to post it. It's from a great modeling site - http://www.wxcaster.com/models_main.htm

Image

Yeah, your eye's aren't screwing with you, it shows a widespread 12-18" storm. I imagine the exact location of the stripe will shift N and S with each run, but I hope it is slightly further south than that so we can have a white x-mas at my parent's.
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#7 Postby wx247 » Sun Dec 19, 2004 2:54 pm

How about we move the western end slightly further north and the eastern end slightly farther south. ;)
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#8 Postby PurdueWx80 » Sun Dec 19, 2004 2:58 pm

wx247 wrote:How about we move the western end slightly further north and the eastern end slightly farther south. ;)


I'll see what I can do. :lol:
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#9 Postby wx247 » Sun Dec 19, 2004 3:05 pm

Harry (King of Weather) and I were talking earlier today and he said that one of the models is forecasting a swath of greater than 2 feet in some spots. Any models still holding on to that?
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#10 Postby PurdueWx80 » Sun Dec 19, 2004 3:12 pm

wx247 wrote:Harry (King of Weather) and I were talking earlier today and he said that one of the models is forecasting a swath of greater than 2 feet in some spots. Any models still holding on to that?


I think that could be implied from the 06Z GFS for parts of southern IL, central and northern IN and perhaps far southeastern MI, but the 12Z run keeps much of the precip as rain. The GEM shows over 2" of precipitation in regions that would be near to below freezing - so that's getting in to the 2' range. Storms like that are rare so I really have a hard time believing something like that would happen - not that I wouldn't love for it to but still.
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#11 Postby Anonymous » Sun Dec 19, 2004 3:37 pm

Any Ideas on how much North Florida will get? I saw weather.com and it shows precip wed-sat with lows in the 30s here. Any accumulations would be nice :wink:
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#12 Postby PurdueWx80 » Sun Dec 19, 2004 3:53 pm

18Z eta quite a bit different, with weak low going up along spine of Appalachians - snow setup is perfect for Louisville and Cincy though - showing that 12-18" band right on top of the two cities! I'm so glad Christmas break is here - I'm going to have no life other than watching every single model run until the storm happens!

Jekyhe32210 wrote:Any Ideas on how much North Florida will get? I saw weather.com and it shows precip wed-sat with lows in the 30s here. Any accumulations would be nice :wink:


14.53"!!

J/K...Under none of the circumstances currently being portrayed do I see JAX getting snow - it'll definitely be cold next weekend, but after all precip is out of the area. Lows will be in the teens or low 20's in outlying areas of the city and a hard freeze should make it down to the orange groves...I think.
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#13 Postby IndianaWxOnline » Sun Dec 19, 2004 4:16 pm

Yeah the northern Indiana forecast office had that the gfs had as much as 18 inches of snow falling. I personally am going with a forecast close to that of the ETA, and will have out a prelim map tonight, but the problem with the ETA like always, is it has a way to tight precip. cutoff, and I would say the heaviest snowfall will extend from southern and eastern missouri, northern kentucky, central and southern illinois, indiana and into western and northern Ohio. I am still looking at the models some, but an area of significant freezing rain might be possible as well. Also K index approach 30, so thundersnow? Quite possible!
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#14 Postby PurdueWx80 » Sun Dec 19, 2004 4:39 pm

IndianaWxOnline wrote:Yeah the northern Indiana forecast office had that the gfs had as much as 18 inches of snow falling. I personally am going with a forecast close to that of the ETA, and will have out a prelim map tonight, but the problem with the ETA like always, is it has a way to tight precip. cutoff, and I would say the heaviest snowfall will extend from southern and eastern missouri, northern kentucky, central and southern illinois, indiana and into western and northern Ohio. I am still looking at the models some, but an area of significant freezing rain might be possible as well. Also K index approach 30, so thundersnow? Quite possible!


I am getting a strange feeling about this storm, given such high forecast amounts of QPF. Back in 1994 (Jan 17th), there was a famous snowstorm in Louisville that was well-studied because of mesoscale banding that lead to heavy thundersnow and 2-4" snow rates. This was the biggest snowfall I had ever seen (we had about 16" at my house, many places in Louisville had 18-24"). The forecast went from 5-8" to 1 inch of ice and back to 6-10". Of course when I woke up it was totally different than forecast. Under the snow was a layer of ice about a quarter of an inch thick, so I can't imagine what it would've been like without the ice. Anyway, we also had record cold temps after that as a deep vortex built in behind the storm - down to about -25F in my parent's backyard.

I went back and checked out the maps - and bang, there are many similarities - at least from looking at NCEP reanalyses and upper air data...I can't find archived surface data yet but I'll keep looking. In any event, there was a major outbreak of cold air a few days before the storm came in, followed by rapidly rising heights ahead of a shortwave digging into the NW US and Plains states. I'll have to keep checking out the maps, but they are remarkably similar to the setup in January '94 at first approach.
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#15 Postby PurdueWx80 » Sun Dec 19, 2004 5:02 pm

Interesting read about the case study and mechanisms for convective enhancement - it's technical but fascinating.

http://www.crh.noaa.gov/lmk/soo/research/paps_11794.htm
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#16 Postby aggiecutter » Sun Dec 19, 2004 5:26 pm

The NWS forcast just issued for Texarkana has a 60% chance of rain turning to snow around noon on wednesday.

http://www.srh.noaa.gov/ifps/MapClick.p ... 3&map.y=89
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#17 Postby IndianaWxOnline » Sun Dec 19, 2004 6:50 pm

Here is my discussion from my website, and remember, my discussion is geared towards the non-weather folk

A significant weather system is in the offing and will have a tremendous impact on this week’s weather, but first….

A wind chill advisory is in affect tonight for parts of the area. There is no question about it, tonight will be cold, and in fact will be the coldest night of the season since January. Low temperatures tonight will drop to 3 degrees, and with winds still breezy, windchills will fall to fifteen below zero. Most schools will not be in school on Monday, but any that are, I just remind you that with windchills that cold, skin that is exposed for over a duration of several minutes to those temperatures and windchills will result in frostbite.

NOW….. Moving on to Wednesday. It is going to be interesting, as our forecast models are all offering significant but slightly different solutions.

The main thing first though, is that someone in Indiana or Ohio is going to get a lot of snow. This storm system does mean business.

As the system develops, it will begin to track Northeast into Arkansas and Kentucky. The big difference in our forecast models at that point, is does the storm go into Western, Central or Eastern Ohio? At this point, I am going to base my forecast on a Central to Northeastern Ohio track.

Here’s what I believe will happen. On Tuesday Night, some light snow will break out across the area, but nothing too significant. The heavy precipitation will get underway on Wednesday. Temperatures across South Central Indiana are still up in the air somewhat, but at this point, I am leaning towards mostly snow for the entire area, with maybe some freezing rain mixed in at times towards far South Central and Southeastern Indiana. If the storm tracks farther East, then Western and parts of West Central Indiana will likely get far less snowfall then I am currently going to forecast, and that is a possibility, as one of our better forecast models does have a farther East solution. If the storm system travels farther Northwest, a larger and more significant area of freezing rain could affect the area, and southeast Indiana could stay all rain. But at this time, I do think the majority of the area will see mostly just snow.

Now the BIG QUESTION?!? How much snow is going to fall. Well that is a tough question to answer, and I hate to start “hyping” this storm too much, but two forecast models are forecasting over 2 inches of liquid precipitation. If temperatures are between 29-32 degrees, and there is a 1:10 ratio (1 inch of rain equals 10 inches of snow), then some parts of the area could be talking about snowfall amounts WELL over a foot. If temperatures are 24-29 degrees, then there is a 1:15 ratio, which means even more snowfall. This is going to be a longer duration event, and at this point, it looks like we will start out with a 1:10 ratio and end with a 1:20 ratio towards the later part of the storm. At this point, I am going to be conservative with amounts and say that most areas will see 6 inches, BUT this has the possibility to be a HUGE winter storm. Again, if our forecast models are taken literally, parts of the area will see over 2 feet of snowfall, which is more snow than I can ever imagine. But remember, forecast models are not meant to be taken completely literally and require analysis. At this point, I do not think anyone will see over 2 feet, but there is a good possibility that someone in the Ohio Valley will see double-digit snowfall amounts. To be completely honest with you, I haven’t even bothered to check about wind speeds, but with a system that could drop over a foot of snowfall on someone, I would bet money it will be strong enough to produce some very gusty winds.

One last thing for tonight. I noticed on the latest version of the ETA forecast model, what appears to be a favorable pattern for a second storm to develop by Christmas Day. Whether this storm does develop and if so, where it goes is yet to be determined, but please stay tuned!

Brandon Redmond
http://www.indianaweatheronline.com
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#18 Postby Scorpion » Sun Dec 19, 2004 6:58 pm

Under none of the circumstances currently being portrayed do I see JAX getting snow - it'll definitely be cold next weekend, but after all precip is out of the area. Lows will be in the teens or low 20's in outlying areas of the city and a hard freeze should make it down to the orange groves...I think.


Any idea if it might get into the 30's down here? Im kinda waiting for it to get cold, tonight was supposed to be the coldest but its only getting down to 44 :grr: .
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First Guess

#19 Postby IndianaWxOnline » Sun Dec 19, 2004 7:31 pm

I know this is kinda early for a first guess map, but I was anxious, haha.

My first guess map is on the frontpage of my website, http://www.indianaweatheronline.com Let me know what you guys think.
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#20 Postby jkt21787 » Sun Dec 19, 2004 8:46 pm

Purdue, a nice write up there.

I've been looking at recent models (12 and 18z) and they show pretty good chances of wintry weather in my area (Memphis). Do you think that is on track, or too far south. If it happens, would it be ice or snow, or perhaps even a mix as I heard one say.

The HPC keeps the heaviest band to my NW as per the 12z GFS (surprise for them :wink: ), but recent trends suggest further south and east.

I have really closely been monitoring the models and cant wait for the 00z data.
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