The dark blue area is open water created by high winds ripping out the ice a day before this picture was taken.
A rip-out occurs when the wind is strong enough to start breaking the ice at a pressure ridge, wind hole, big new ice hole, etc. Once it gets started the wind and waves break a band of ice out down wind with an accumulation of ice pieces at the end. Often these plates are stacked on top of each other or tipped vertically and stacked. A blow out is a rip-out that is as wide as the lake. Rip-outs are more hazardous as they may not be as visible from shore and they tend to occur on ice that otherwise would be excellent for sailing or skating.
Conditions when a rip out is likely
- Ice less than 3" thick (the thinner, the less wind it takes)
- Ice in a moderate state of thaw but they can occur in cold ice as well
- They tend to occur after a frontal passage. This can be because of increased wind speeed or shifting of the ice sheet from the change in direction of the wind pressure.
- Most common on new ice. Spring ice tends to be too thick while it still has some strength.
The following outlines the probable ice evolulation on northern Lake Winnipeasaukee (NH) in late Janurary and early February 2013. Based on Modis Stellite images, temperature and winds the ice came in on most of the lake on January 23. A brief but intense warm up on January 31 along with high winds blew most of the ice back out leaving bands of ice rubble in the lower right of the picture. The open water caught again on the early morning of Feb 3. It was cold enough to grow to a couple inches (maybe more) before the next wind event arrived around mid day on Feb 4. This event was strong enough to create the rip-out
Graphs for Laconia NH and are from www.weatherunderground.com
the view seen in the picture above (Google Maps)