Instant Replay: Storm radar loop

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Twin Cities radar loop 1:30 am to 7:30 am December 9th. Note widespread moderate snow, and heavy snow band in the east metro. Also note snow rotating around the vorticy or "pivot point" near Austin in southern Minnesota.

Check out this cool radar replay courtesy of the Twin Cities NWS and their excellent storm recap. There are several interesting features evident on the loop. It's a great illustration of why it's difficult to pinpoint snow amounts in a storm, and how snow totals can vary over even short distances.

-Notice how the individual snow bands seem to have a life cycle of anywhere from a few minutes to a few hours. They also are in constant motion, even though they may linger over an area for a period of minutes or hours.

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-Notice the vorticity or "spin" center in southeast Minnesota just east of Austin. The circulation around this feature helped throw moisture back toward the Twin Cities.

-Watch the heavy snow band set up in the eastern metro, then slide southeast. It's a great example of how dynamic these storm systems are. The band is also pretty narrow, that's why one community can get several inches more than another spot just miles away.

-Note the ragged western edge of the snowfall west of the metro. This is drier air eating away at the west edge of the storm. That's why snowfall totals were much lower in places like St. Cloud and Willmar.

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GOES 14 visible image shows snow covering the Midwest landscape today. Note the rivers clearly visible and the sharp cut off on the southeast edge of the snowfall. Image courtey OSEI Image of the Day.

The computer forecast models we look at have improved dramatically in the past 10 years. Still, there is nothing that even comes close to portraying the detail and intricacy of what you can see on the radar loop. That's why there's still so much art and forecaster interpretation in weather forecasting

Pretty cool stuff for a weather geek like me!

PH