TOP 6 DATES TO PICK
2. April 23
3. April 28
4. May 10
5. April 27
6. April 21
TOP 6 DATES TO AVOID
2. April 30
3. April 18
4. April 20
5. May 6
6. May 12
The easiest technique to choose an ice-out date is to open a calendar to April/May and throw a dart. However, if you want to improve your chances of winning you might review the ice-out facts and throw a dart at a smaller number of dates. Or you can review the same ice-out data and look at the dates to pick/avoid (shown above) and choose a date based on the theory that the actual ice-out percentages will, over time, match the normal (Bell) curve. This is happening with each passing year but it's certainly not foolproof for any given year, although the above dates improve your chances over the dart technique. Are you wondering why May 8, 9 and 10th are in the top picks?
Answer: Over 10% of the ice-outs have occurred after May 10th. There is only 1 ice-out date for May 8,9,10th combined, around 1%. This creates a hole in the distribution. There should be 3-4 "ice-outs" on these dates to fill in the hole and match the Bell curve shape.
We had a fairly early ice-out in 2015 so the overall average ice-out is now April 28th but it is within a couple of hours of April 29th, the DNR reported average ice-out date, so no evidence of climate change on this data point.
We are half way through the 10 year cycle when the overall average for the decade is recorded and compared to previous 10 year cycles and a new 'normal' for 30 years is established. During the past 5 years we have had a record breaking early ice-out and some very late ice-outs. The average for the first 5 years of this decade is the same as the overall ice-out average date-April 28th. The record breaking ice-out occurred on April 2, 2012 and the latest ice-out in the last 5 years happened on March 17, 2014. That is a spread of 45 days within a 2 year period! That is one reason why it is so hard to predict the ice-out in a given year.
Someone asked what the standard deviation was around the average April 28th date? The standard deviation is 9 plus (9 days, 3 hours, and 27 minutes to be exact) days. This means that 67% of the time the ice will go out between April 20th and May 8th. The spread mentioned previously causes the standard deviation to be what it is and is another reason why predicting ice-out is so difficult to do with this high variability. In the industrial world this kind of variability would render the process to be out-of-control.
We had a brutal February 2015. The high and low temperatures were both significantly lower than the average of the last 96 years. The snow fall totals in March and April were much less than normal so the higher temperatures in March/April had less of a snowpack to melt and worked on the ice thus causing a 10 day earlier than normal ice-out. By mid-March the snowpack on the lake was gone and then even higher March temperatures started the thaw. March continues to be the key month in predicting how soon the ice will go out. Colder high and low temperatures and additional snow in March will push the ice-out into late April or May.
Good luck with your 2016 ice-out prediction.
© Iceman - January 2016