Update - December 16, 2015 - Viral social media posts

In the post I did on the 8th (click here), I mentioned how computer forecast models, that attempt to predict various weather elements, often fail even 12 to 24 hours out.  By changing initial conditions (perhaps temperatures) just a tiny bit, there are often huge differences several days out.  These models are run with these different initial conditions to come up with what we call ensemble forecast solutions.  Often, 5 to 10 days out these different ensemble solutions overlaid on a map look like spaghetti. The following is an ensemble of 20 solutions at 384 hours out using 20 different initial conditions:

 

What the map shows is that 16 days out, the jet stream configuration could be just about anything. Each different possibility was arrived at by plugging in an initial condition with a small difference.  Essentially what this tells us is that computer forecast guidance that far into the future cannot account for small changes in those initial conditions and should not be used for decision making.  Often the "control" output or solution is plotted instead of the ensemble members.

That "control" solution often changes from run-to-run (computer forecast is generated every six hours), especially in the later periods.  It's nothing new, this has been going on since models have been developed.

Unfortunately, because of the access of this output via the internet and because of social media, these varying solutions can be posted and often are posted.  Take for instance what occurred Tuesday, December 15.  A person on Facebook (his page name is Oklahoma Weather Network) posted output from just ONE computer run from the Global Forecast System (GFS), which has a tendency of exaggerating output elements.  The solution was "off the charts" and he posted it as if it might really happen.  The post has gone viral being shared (as of the 16th) over 10,500 times and likely reaching 100's of thousands of unsuspecting persons.  I've been answering a bunch of e-mails, Facebook posts and text messages inquiring about this "storm".

The following should shed some light on what we're dealing with:

First - the "solution" at 324 hours out valid for 12 PM Monday, December 28 that went viral:


 

When the same computer model was run 12 hours later the solution for the date was completely different!
 

Then, it was run 12 hours later and now look!  NOT A BIT OF SNOW!



This is a common occurrence with these long range models!

If you have followed my blog, you know that I look for a cyclic pattern and look for areas of forcing (areas of latent heat releases from the oceans and others) to produce these weather patterns.  I'm close to nailing down the cycle length (48 to 52 days I think) but with intermediate cycles embedded in the overall pattern.  Using this information, there actually "could" be a storm around the 28th.  More on that at the end of this post.

December 12-13 storm

Several posts ago I discussed changes in the pattern that would favor storminess starting as early as December 12.  Due to personal obligations (nothing big - just a daughter getting married :-)) I didn't have time to post anything specific.  As you are aware the storm that impacted the center of the country on the 12th and 13th brought a variety of weather.  There was even one tornado reported in the Texas Panhandle!  The amount of rainfall with the storm was epic for December and I saw a couple of 5 inch amounts in central and north central Kansas!

The snowfall was limited to elevation and the temperature profile.  Had the temperatures been just 3 to 4 degrees colder there would have been over 2 feet of snow in some locations!  In Dodge City there was 8 to 9 inches and if the temperature had been just a degree colder and a little sooner there would have easily been 12 to 15 inches!  What a storm!  The following is the snowfall map and a map of the water equivalent or rainfall:




 

There are areas of southwest Kansas that have recorded over 40 inches of precipitation since the first of the year!  Unreal!  Parts of southeast Oklahoma and northeast Texas are approaching 90 inches for the year!

Here is the latest satellite image:



The green lines/arrows represent the jetstream.  This is actually a-typical of an El Nino!  The strongest and most moisture laden stream of air is slamming into the Pacific Northwest while a typical pattern would be pointed towards California.  I talked about this for months in this blog and to me it's not surprising.  (I still see it possibly changing over the winter).

This afternoon there was a small disturbance over Idaho (not depicted on the satellite map).  It will move southeast and head rapidly towards the central plains  early Thursday and should help to bring more snow to Colorado and perhaps a little bit to western Kansas.  It shouldn't amount to a lot.

There are other systems across the Pacific.  With the cycling pattern, I do see at least a small chance of a minor system around Christmas that could bring some rain or snow to the region.  The bigger storm may be between Christmas and the last days of December.  Then based on the pattern, an even bigger storm could occur the first week of January followed by a "brief" Arctic outbreak.

I'll try and nail down specifics in the next post that I hope to do this weekend or early next week.