Updraft: July 7, 2011 Archive

Short term uncertainty

Posted at 6:56 AM on July 7, 2011 by Craig Edwards
Filed under: Climate, Climate change

With the weakening jet stream in the summertime, meteorologists are frustrated with the uncertainity of forecasting precipitation due to lack of a clear triggering force. Thus the broadbrush of low end precipitation probabilities for the next twenty-four hours.

What a difference a day makes. At this time on Wednesday morning much of Minnesota was cloud free. Here's a look at the 630AM visible satellite that shows south central Minnesota enjoying sunshine. Notice the bumps in the cloud cover along the South Dakota/Minnesota border where showers have more gitty-up.

Indications from tracking last night's model output support more forcing and vertical lift in the atmosphere on Friday night into Saturday night. Exactly where the potential for heavier showers might be is difficult to pin-point. See the output from the GFS model for a bulls-eye of significant rain on Saturday evening. Is this just an outlier or will this become reality? The next model run may confirm or overrule the downpour potential.

Yes that's a total of nearly two inches in central Minnesota. An example of what meteorologists examine to craft a forecast for your weekend.

You may have heard that the NWS has released and as of July 1st is now using the updated thirty year normals. As we learned over time normals are the output of the collection of the extremes. The numbers currently used have tossed out the relatively cold temperatures in the 1970s and incoporated the warmer winter temperatures of the past ten years.

I was speaking with the chief meteorologist for NOAA in the Twin Cities last evening and we agreed that the long range outlook for the winter, posted by the Climate Prediction Center is now impacted by the change in the normals.

See the graphic from NOAA on the change/warmer minimum temperatures in our neck of the woods. Most of this warming in the new normals comes from the winter season.

Based on the new normals, here's the Climate Prediction very long range outlook for the months of December 2011 to February 2012. There are several more factors that will come into play by the time we approach the winter season. Use outlooks with caution.

Equal chances of above or below temperatures for the upcoming winter; not necessarily breaking news. But you did read it here.
CE