Freezing Fog...whaaa?

Posted by MTF at 1/20/2010 9:10 AM
Categories: uncategorized
Breezers,
   I hope everyone is enjoying the week and got out and about a bit on MLK weekend.  JAMIE, I hope Cancun was a blast.  Talk about an MLK excursion!

   I've received a few questions about freezing fog.  The last week has been riddled with fog across a large portion of the country.  Basically the entire central U.S. has seen fog.  There has been little west to east flow across the mid-section of the country, with the jet stream being confined to the far south and well north in central Canada, typical of an El Niño pattern.  The milder temperatures have led to gradual snow melt and sublimation, which has increased the air moisture.  This combination has led to fog.  It has been so persistent including during the days because of a temperature inversion aloft.  This is where the temperature warms  with height.  This is due to primarily the snow cover on the ground, acting to keep the near surface air chilled.  Thus it is more dense, underneath warmer air that is less dense.  Little vertical moition ensues because of this stable pattern.  So the fog and particulates stick around.  Hence for you runners (not me thus far in 2010), you may notice the air not being so clean when out for the jog.  More about temperature inversions can be read on this link below, which is from one week ago today and here in Minneapolis where the temperature was 58° at 4,600 ft, yet we were only 27° at the surface!

http://www.crh.noaa.gov/news/display_cmsstory.php?wfo=mpx&storyid=46523&source=2

   So back to the freezing fog.  Freezingfog is a dense fog that generally has just a little movement in it, that is the air is not completely still like most dense fogs, over a groundthat is cooler than freezing. This causes riming, which is iced epositing on surfaces, often making roads slick.  This has been the case off and on during this dense fog stretch.

Annual number of dense fog days:  http://www.sweetcornforecast.com/climate/images/DenseFog.jpg


When will this foggy and "non-clean air" pattern break?  There is so significant Canadian or arctic air push the next week which will do it.  However, precipitation is likely as the week ensues, including a mixed bag of freezing rain, sleet, and even snow up here in Minnesota (go figure, for late January?!)  Precipitation can "scour out" the atmosphere of a lot of the particulates, so that may help somewhat.  It will really take a strong cold front though to truly scour it out.  This has been a serious pain in the butt for aviation forecasting, so I cannot wait either!

   On another note, my next weekend off in late February has been hashed out over the past month to take a little excursion.  I am about to book tickets to join Luke, Miles, Cozzy, and 'Vis in Las Vegas for two days.  Big mistake?  Possibly, especially if you hear what happened to Luke this past weekend!  But, I had one night in Vegas with Luke and Cozzy two years ago that I am still recovering from because it was a blast.  Might I add, on the tail of a huge OC venture in Cali with B-Mengler and Foul-Mouthed James.  So I am fortunate enough to be heading out west once again.  Hopefully we survive.





Watch the Aussie Open Breezers...ESPN at nights.

From the 'Sota to the 'Dota...
MTF

 

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