Monday, January 14, 2008

Will it snow in Alabama?

Will it snow? That is the question of the day in Alabama. Everyone wants to know whether we will see snow on Wednesday night or Thursday. Weather forecasts depend heavily on numerical computer models. These models do an excellent job with general trends but they do a poor job pinpointing exact locations and times.

Sometimes models have tendencies for errors. For example, models seem to do a poor job of predicting shallow layers of cold air. Another problem they have is the “wedge”, or cold air damming caused by the Appalachians. In addition, when there is a lot of snow on the ground to our northwest, the air does not heat as rapidly as it would without snow cover. As a result, with winds out of the northwest, our temperatures are sometimes colder than the models project. These local features sometimes make the model predictions a complete bust.

Also models do a poor job sometimes by underestimating the amount of moisture that can feed into the Southeast from the Pacific Ocean as it rides on a strong southern branch of the jet stream. This is where meteorology and weather forecasting become an art almost as much as a science. Forecasters have to account for variables and biases that come with the models.

As I write this on Monday evening we have two models with completely different solutions. The NAM is predicting snow will fall Wednesday night roughly along and north of a line from Hamilton in Marion County to Cullman, to Gadsden in Etowah County. It also shows snow continuing and intensifying during the day Thursday north and west of a line from Hamilton to Scottsboro in Jackson County. The GFS on the latest run is predicting rain across all of North Alabama throughout the period.

Why the radical difference between the model output? I am not certain but I suspect that the NAM is factoring in things that tend to keep north Alabama colder than the GFS. One thing to look for in models is consistency. Models that tend to predict a storm in the same location from runt to run, day to day tend to produce more accurate results. I suggest looking very closely at the Nam and GFS for all four runs during the next 24 hours. They are updated at 0Z, 6Z, 12Z, and 18Z very day. 0Z refers to Greenwich Mean Time which means that it is Midnight in London, or 6 p.m. in Alabama. After the model runs are examined during the next 24 hours we can get an idea as to which is more consistent.

As of now I will say this: Areas north of Hamilton, Cullman, and Gadsden may see snow. I would say that it is a 50/50 proposition at this time for those areas. There is a chance of some significant accumulation but there is an equal chance of nothing but rain. The best chance of significant accumulations would be in Northwest Alabama and the Tennessee Valley. Snowfall in areas to the south of that line is very unlikely. Any snow that falls in those areas will probably be limited to a few flurries as the storm exits the area and cold dry air enters from the north. Perhaps by Tuesday evening, which will be 24 hours from the event, I will have some better idea of what to predict.

13 comments:

MTWC said...

Nice write up Mike!
Clay in Nashville

Mike said...

Thanks Clay...what do you think?

Anonymous said...

Will it snow in Alabama? I don't know ask "Smith Lake Jake", that groundhog will know.

Mike said...

It did so if he said "yes" he was correct!

Anonymous said...

Yes I heard Smith Lake Jake predict on good day Alabama, on groundhoG'S day with Chris, and Ginger that there would be 6 more weeks of bad weather. And Smith Lake Jake predicted that we would have a few snow flakes before spring, and boy was he right, I LOVE THAT GROUNDHOG, AND HIS CUTE LITTLE HAT!

Mike said...

Well, if he said that, he was certainly right!!!!

Anonymous said...

Smith Lake Jake said that it would snow, and it did. We look foreward each year on groundhogs day to see what Smith Lake Jake will say, and I always have to make a video of his prediction for my children, And they watch it over and over again. Oh, and we LOVE the hat he wears.

Mike said...

I'd like to see the Smith Lake Jake video!

Anonymous said...

Myself and my family really enjoy groundhog's day, now that Alabama has "Smith Lake Jake. We love him, and his adorable little hats. My children watch him on the Suzuki Man commercials,as often as he is on there.

Charleane said...

you can type in "smith lake jake" and pull him up also. I also heard on the radio that Smith Lake Jake was going to be in the Mayberry Day parade in Graysville this saturday. You can find out more info. at the graysville city hall. or you can type in smith lake living and pull up his picture. He also can be seen on the Suzuki MAN T.V SHOW.WE ALL LOVE sMITH lAKE jAKE AND HIS LITTLE HAT.

Bobby said...

And also Smith Lake Jake has been named the worlds 2nd most famous groundhog. Punxsutawney Phil is of course number 1. I heard that on the national news on groundhoigs day. I have seen several videos of him. You can oull up a really cute one of him and mickey f. on groundhogs day, go under smith lake jake at fox 6 on groundhogs day.

Mike said...

Charleane and Bobby...
I have seen the Suzukiman but so far I have missed SLJ. I will try to find it. Thanks.

Anonymous said...

We watch Smith Lake Jake on the Suzuki man show all the time. ginger sings the cutest songs about him. And he does do a good job of predictinng.