This is a discussion concerning the December 20th Winter Storm.
The above image portrays an average predictability of something happening by combining all the NCEP ensembles into one average. The more oranges and reds you see indicates a higher predictability the ensembles believe that atmospheric feature will come to happen. There are some very important factors involved here.
•Ridge in the Southeast
•Disturbance in the South Plains
•Jet Stream
On the image above, there is a spot of orange in Florida, where the 500mb height isobars are positioned at an arcing angle. This is a typical position a ridge of high pressure takes. It appears that the NCEP ensembles are more open to this ridge in the Southeast, as per the darker colors around the arcing isobars. The consequences of this ridge, should it be strong enough, would direct the jet stream north, along with other disturbances following the jet stream.
The second atmospheric feature we are looking at is a disturbance in the South Plains. Ultimately, as this disturbance ejects from the Southwest, this would be our storm system for December 20th. The ensembles are latching onto this disturbance's presence, characterized by a valley formation in the 500mb isobars. This is a feature you will find is associated with troughs, or disturbances. The placement of this disturbance appears to be somewhat debated, but there is an indication that the system will be present in the Texas Panhandle region.
The third feature that is worth watching is the jet stream. The jet stream can be thought of as a highway- low pressure systems follow the jet stream as they make their way west to east. The jet stream can be disrupted and moved around by disturbances and ridges. The ridge in the Southeast, if present, would direct the jet stream more northward, likely where the isobars on the image get really tight in the Northeast. An interesting feature that may be enhancing this jet stream is a proposed other atmospheric feature farther north, judging by the continued tight isobars into Canada. The jet stream will be a big player in this storm, as will the ridge- the ridge's placement/presence essentially determines the storm track, among other factors.
Side notes: The ECMWF did come back south, determining the low placement will be in Central Illinois with the 12z run. This would bring the heaviest snowfall to Chicago north to around a Madison-Milwaukee line westward.
13 comments:
Hello Andrew.So this system as of now is basically going to effect the chicago area on northward and northwest of there.I understand that the JET is a huge player where storms will go.This one will pretty much miss my area.Do you see any other heavy hitters in the near future? Also,do you see any signs of a major pattern change or not?
I forgot to mention the Christmas eve or day storm.Do you still see signs of this on the scope or not?
So Valparaiso won't get a big one out of this?
Were will the heaviest snowfall possibly be right now?
So with the low being over central Illinois I guess that means no snow for the area then? :\
Would Detroit get snow
And also when do you think the NAO will turn negative if it does
Mike: Your area might get some snow if the low travels at a strictly WSW direction, possibly along the jet stream. We haven't had time to look at the Christmas Day storm too closely.
AJ: The models will still shift. It would be N. IL to S. WI with the heaviest snowfall. ECMWF predicts upwards of 4 inches for them.
Eddie: It's certainly possible. The NAO should start a more negative trend soon, with the warming stratosphere and tanking QBO.
How much will Valparaiso currently get?
Way too early for amounts and still too early to determine anything. Just cause this run of European gives you snow, that doesn't mean it will happen. Towards Saturday, I would pay more attention to the models, still too early.
Exactly anonymous.It's way,way,way too early.These models are not very accurate this winter.We all better hope that they get better at projecting these storms or we will be in TROUBLE.Like for instance,we might get a huge snowstorm that the models don't forecast.This could happen.Models do not control the weather,only predict it.
I realize that this is early. That's why we base this off of ensembles and trends. The ECMWF is getting a handle on a solution that would give the Midwest snow. It's never too early to mention a storm- waiting until the last minute takes all the 'fun' out of forecasting.
For the record, if you are ever going to use a model for winter, use the ECMWF.
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