Irreconcilable differences

Posted at 7:12 AM on December 19, 2007 by Paul Huttner (2 Comments)

The Weather Lab models don't seem to agree about much when it comes to our chances for snow this week.

Take the GFS. Uncertain, quirky and mercurial. Not really able to settle on a particular track for the surface low. Not sure of two split storm centers or one. If we are to believe the GFS, it will snow, some, on Friday and into Saturday. The split pattern of two upper low centers usually produces lighter snow amounts for southern Minnesota, with more up north in the northern stream and more to the south.

GFS model forecast 6am Saturday

Then there's the NAM. Bold, certain, loud and quite possibly wrong. It keeps the storm center more compact and together as it tracks into Iowa late Friday night. This kind of a solution generally produces a band of heavier snow in southern Minnesota and western Wisconsin.

NAM forecast for 6am Saturday

The NAM has seemed to move just a little toward the GFS solution over the past 24 hours.

When meteorologists try to forecast snow storms, we watch for (and hope for!) day to day and run to run consistency in the computer output. No such luck this time.

Suffice to say if you are planning pre holiday travel Friday afternoon through Saturday, be ready for some snow. How much? We'll have to let the NAM, GFS and friends fight that out for a while longer.

PH

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Comments (2)

Has the NWS ever done a study on which computer model was right more of the time?

Posted by Curt | December 19, 2007 1:01 PM

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Hi Curt:

Yes, NWS keeps track of model performance and bias. Problem is, model performance can vary from season to season, even day to day.

Most forecasters know which models beahve better in certain situations, and we all have our favorites.

Check this link out for recent model performance. It's complicated.

http://www.emc.ncep.noaa.gov/modelperf/

PH

Posted by Paul Huttner | December 20, 2007 7:58 AM

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