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I post weather updates and other interesting tidbits throughout the day. 
February Review
February has been quite the month of ups and downs in Kentuckiana! As we begin March I thought I'd share some of the numbers that were recorded in Louisville last month.
Highest Temperature: 67° Days in the 60's: 2 Days at 40° or lower: 8
Lowest Temperature: 9° Days in the 50's: 10 Snow: 3.2" Rain: 1.92"
The thing that stands out the most is the 58 degree temperature difference between the highest and lowest temperature during the month. What a contrast! Not only that, but both temperature readings happened within a week of each other, the 67° high on the 1st and the 9° low on the 7th. It's also worth mentioning that the month ended up 1.15" lower than average in liquid precipitation. No monster snows happened in February obviously since we counted up a paltry 3.2" of snow. But what about March, the beginning of meteorological spring? The latest data says we could be in for a forecast challenge to start off the month...
Something to Watch: Next Week's System
A system diving into the Eastern US on Tuesday will be one to watch as it could bring us some wintry weather in Kentuckiana. It's still not clear how exactly this will play out since the various forecast models are having difficulty figuring out the track and temperature setup as it moves through. Yesterday both the GFS and European forecast models had this storm tracking so far south that it would give Kentuckiana little to no precipitation. Now, both models (right) have come into line with a more northerly solution that could potentially bring us some wintry weather. The European is a hair further north by Tuesday night than the GFS but the overall look of the system is fairly similar similar between the two models. I must caution that there is a very high degree of uncertainty with this entire setup given the model shifts that are going on.
If we back up a little bit to Tuesday morning on the GFS you'll see that it has the low about where we would need it to be to get a good snow. The problem is that it's weak and isn't pulling in enough cold air to give us much snow during this snapshot in time. Given how far out we are from this event and model uncertainties, it's not even worth looking at exactly who gets rain and snow yet. Below is a graphical representation of when the GFS thinks we'll have snow and rain in Louisville during this system's passage. A snow to rain to snow scenario here, but again it's too early to even place bets on this one.
Let's throw a third model into the mix now. Or rather, I should say, multiple versions of one model. To the left you'll see the Canadian model's ensemble mean. Basically what is going on here is that multiple variants of one model (the Canadian in this case) are run with various things tweaked. The data from all of those "tweaked" versions of the one model are then put onto one map so that meteorologists can tell if there's agreement or disagreement among them. This helps in situations when the main model has an issue or if you're looking for a second opinion. The red characters you see in the ensemble mean map are where each "tweaked" run of the Canadian thinks the low for our storm will be on Tuesday morning. Notice how most of the ensembles are clustered in the vicinity of St. Louis while the operational GFS (mentioned earlier) has the low at the same time near Nashville. This more northerly track of the Canadian ensembles would mean little to no snow for us compared to the GFS/Euro's idea. Just goes to show what kind of uncertainty we're dealing with.
So, the question all of us have: Will it snow next week? It's just too early to say. No model I've seen has a good snow for us right now. This is more of a situation where you have the elements to create a storm fairly close by and need just the right blocking setup and cold air to get it. Both of those may be hard to come by. We'll see how it pans out on the models over the weekend. Brian Goode called this system a "booger" on Twitter yesterday and I wholeheartedly agree. In fact, I see his booger and raise him a "bogey," the British equivalent of the word booger! :) BOTS!
Ryan Hoke
Great explanation of the differences in models and differences in runs of single model.
Posted by: Jeremy Radford | March 01, 2013 at 01:50 PM