Monday, December 17, 2012

A Christmas Day Storm System?


1:40 PM Monday Update... First thing, I can't thank all of you enough for getting your weather information here on the Arkansas Weather Blog.   This marks 6 years I have been doing this and I love seeing the numbers grow and grow.  It just confirms my belief you love the weather as much as I do. 

Now onto what the computers are saying and what I believe.  If you get a chance, make sure your read the original blog post today.  It does look like a storm system will influence Arkansas weather Christmas Day and on the 26th.  While I show you the specific model information, take it with a grain of salt.  This far out in the forecast, it's going to be wrong!  However, I want to show you the things we look at when making forecasts so you know what we're watching and the possibilities that exist down the road.  With that said, here's an update from the European model run this morning.

This is the 26th at midnight.  The surface low pressure according to this is in northeastern Arkansas.  Remember that low pressure has a counterclockwise flow into it in the northern hemisphere.  This indicates cold northwesterly winds on the back side getting wrapped around the west side of the circulation.  Upper atmospheric conditions would be favorable for snow production as the precipitation comes to an end.  The green blobs are precipitation amounts over the previous 6 hours.  This is NOT an ideal set up for significant snow in Arkansas!!!  However, this track COULD bring a quick change over to snow showers before the rain ends late Christmas day into Wednesday morning.  Again, don't count on this being correct.  Let's have fun watching how all this plays out.
 
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You will see  Let's get ready to ruuummmmmmbbbbbbbllllleeeeee.  We actually have something to watch Christmas week!  Before you get too excited, this storm has been on the computer models for awhile and they all show mostly rain.  HOWEVER, let's dream okay?  We can do this because the overnight run of the European model does show something interesting happening late Christmas Day here in Arkansas, but the GFS is just a rain maker.

Remember, take these computer models with a grain of salt!  If you recall, last week I showed you data which pointed to snow in portions of northern Arkansas on Tuesday morning and that was completely wrong.  So getting these models to accurately predict a storm more than a week away is absolutely impossible, but like I said, let's dream.  It will be interesting to follow this as we go into Christmas week. 

This is the European model valid Christmas Day at 6 PM.  There's an area of low pressure at the surface in the Gulf with the upper level storm located in the southern plains.  Cold high pressure is oozing cold air into the storm from the north.  That's the black closed line in Canada with 1044 on it.  The green, yellows, red, and purples are precipitation areas.  Remember, the blue dashed line is a good indicator of the rain/snow line.  According to the first glance of this it's a cold rain across the state with BIG snows across north Texas into Oklahoma and Kansas.  However, I want you to look at the next map.
This is the Euro again valid at the same time showing you the 850 mb temperatures.  This is about 5000 feet up.  Look at the solid black line running through portions of western and northern Arkansas.  This is the freezing line at that level of the atmosphere.  This is telling me that north of this line, something frozen COULD fall depending on surface temperatures.  As the storm system develops and moves away, the rain could change to something else as it cold air wraps around into Arkansas.  PLEASE REMEMBER, THIS IS 10 DAYS OUT!!!!!!!!   I'M DREAMING HERE AND THIS WILL CHANGE, BUT HEY, IT'S CHRISTMAS!!!!!!!!!!!!!!! MAYBE SANTA WILL MAKE IT HAPPEN.
Here's the latest GFS valid Christmas day at noon.... Rain, Rain, Rain, and more rain.  There's snow, but it's well north over Kansas, Nebraska, the Dakotas, etc.  The surface low is further north and therefore we're in the warm sector.
So what should you take from this?  The models have been hinting at a system around Christmas time and as you would expect, the models vary greatly on how this will play out.  Remember, the purpose of this blog is not to make official Channel 7 forecasts, but to show you the things we are looking at in the weather center. 

I have seen the models show storms in the long range and then days later, it's gone and nothing happens.  Let's just stay patient and see what happens.  I'll keep you updated!

1 comment:

Will said...

Hey Todd and fellow bloggers.....

Glad to see you finally coming around to my idea of a possible Christmas present that I mentioned a few posts ago! The models continue to suggest a trend to a much stormier and colder pattern beginning next week. The models are continuing to do their normal waffling but are definitely trending in the right direction for snow / cold lovers. It appears from my amateur's vantage point that as the PNA transitions to a more positive state later this month that will allow for the cold in NW Canada to finally come southward. In addition it looks like the NAO is going to remain negative, (slightly) which should give us some shots of some winter-like weather.

I would love to hear SnowBirdBob's and Ninja's take on this as well as yours.