Entries by robertdill (15)

Monday
Feb132012

Wild Weekend 

Truck in 12 feet of water near Alburg Vermont. Went through at a pressure ridge. The ice within a couple feet of the center of the ridge was two layers, each about 4-5" thick. Note the track leading to the hole.  

Late last week many new spring techtonic cracks and fold down ridges formed in some areas of lake champlain.  Early Saturday an inch or snow fell and then blew accross the ice where it collected in the exposed water of the ridges and formed wide slush bands.  Many vehicles went in.  All but two were either made it out on their own or were pulled out within a couple hours. 

More later.

Bob

 

Tuesday
Feb072012

Lots of Ice, Lots of Swimming

A person skated onto this rotten snow ice filled folded ridge and stumbled for three steps before breaking through just short of the far side. At least four people have fallen through this ridge even though there are several easy ways around it.

New England has been enjoying a warm and, at least recently, low snow winter.  There has been lots of good ice and lots of dodgy ice.  Here in Northwestern Vermont we have had several weeks of very good skating and sailing.  Malletts Bay has had very good ice over two weeks.  The Inland Sea, just to the north has been full of holes, areas of thin ice and open water.  So far I know of eleven people who fell through.  In all cases, with the benifit of hindsight, they could have/should have recognized problems. 

 

Tuesday
Jan242012

Ice Forecast for Skating

Jan-Erik Gustafsson  forecasts skating ice in Sweden and he has set up forecasts for a few cities in the US. The forecast takes into account temperature, wind and radiational cooling, solar heating, cloudiness as well as snow.  Click here for his forecast page.

The forecast for Burlington VT 1-24-12

Jan-Erik's forecast projects ice growth from a thin skim (pink line).  He also estimates the rate a two inch ice sheet will change in thickness (blue and red bars).  If you average the four bars for a day you get how he expects the ice to change from two inches in a day.  Dark blue bars indicate growth rate with no snow cover.  The much smaller light blue bars show the dramatic insulating effect of an inch of snow.   Red bars indicate melting which is hard to predict with reasonable certainty. 

Skaters typically are looking for black ice that is at least two inches thick (sometimes thicker if weather is warm, if the lake is large or for a variety of other reasons).  Once it gets near 8" it is much thicker than it needs to be for most skating locales.  The forecast starts from a thin skim as that indicates when  the body of water is cool enough to grow an ice sheet.  Jan-Erik's forecast does not predict when open water is likely to catch.  Local history of the 'first ice dates' combined with a idea of how much-warmer or colder the season has been in freezing-degree-days should give a reasonable idea of when it will come in.  Obviously cold, clear, still nights are the most likely time to catch.  Ice grows more slowly as it thickens.  For example at 10 deg F a 2" sheet may add an inch in a day.  Starting at 6" it will add about half as much.   (More on growth rates)

As with all predictions based on something as complex as the weather,  this one should only be used as an estimate of what will happen, particularly as the forecast gets out more than a couple days.  As always, the ground truth on the ice is what really counts.  For that you need to carefully check the ice out yourself (see the November 23, 2011 blog entry below for more discussion of ice checking).

All this is made possible by data provided by NOAA.

Monday
Jan162012

Slush Ball Mystery mostly resolved

In the previous post we were unsure what is the source of slush that occasionally creates slush balls along beaches and on downwind ice edges.  A bit of cold weather wading has demonstrated one formation mechanism for this interesting form of lake ice. A review of the new information can be found at the end of the Slush Ball page.

Saturday
Dec242011

Slush Balls

 

 Ardmore Beach Ontario. Photo by Richard Bramwell

Slush balls are an unusual and interesting ice formation that occurs on beaches under specific (but not fully understood) conditions.  To read an article on them click here.

Bob