Lake temps/ ice in

[This'nThat]

Originally Posted by Grady223

Only needs to be 39 degrees to freeze?

No, water freezes at 32 degrees. However, the lake can't freeze until all water underneath is at 39 degrees (4 degrees C). Water is most dense at 39 degrees, so water at that temperature sinks, and warmer lake water rises to the surface -- which also must be cooled to 39 degrees -- which sinks, is replaced by warmer water, and so on until everything is at 39 degrees. When that temperature is reached, there is no more warm water to rise to the surface. Therefore, the surface water can now begin to freeze and ice begins to form and stay on the lake.

This "water density at 39 degrees" also explains why shallow lakes freeze quicker than deep lakes like Winni. Deep lakes have much more water that needs to be cooled to 39 degrees. It also explains (in part) why Alton Bay can freeze before the rest of the lake, or even other parts of Alton Bay (as mentioned by another poster here) -- because it is more shallow and gets to 39 degrees a lot quicker.

[BoulderBronco]

Thanks guys and gals. Looks like the lake temps are a solid 2-4 degrees colder than this time last year. Now I am no expert but seems to me that is a note worthy difference for water temps. Of course a warm spell can ruin all that but at 2-4 degrees the lake COULD freeze earlier than usual by a week or two. Good enough for me. I am tired of these winters with thin ice. I want to see 24" this year in Meredith bay.

[Lakegeezer]

The water depth averages 30' around here and the earliest I've walked on the ice is December 17'th. That year was weird as it melted a few days later. For my first fourteen years here, the local ice was safe to walk on for New Years day. Three of the last four years, that has not been the case. Its too bad we don't have a way of measuring ice-in like we do ice-out in the spring. It would be interesting to see the history, along with knowing if there was any correlation between the two dates.

[Blue Thunder]

Originally Posted by This'nThat

No, water freezes at 32 degrees. However, the lake can't freeze until all water underneath is at 39 degrees (4 degrees C). Water is most dense at 39 degrees, so water at that temperature sinks, and warmer lake water rises to the surface -- which also must be cooled to 39 degrees -- which sinks, is replaced by warmer water, and so on until everything is at 39 degrees. When that temperature is reached, there is no more warm water to rise to the surface. Therefore, the surface water can now begin to freeze and ice begins to form and stay on the lake.

This "water density at 39 degrees" also explains why shallow lakes freeze quicker than deep lakes like Winni. Deep lakes have much more water that needs to be cooled to 39 degrees. It also explains (in part) why Alton Bay can freeze before the rest of the lake, or even other parts of Alton Bay (as mentioned by another poster here) -- because it is more shallow and gets to 39 degrees a lot quicker.

Nice job TNT. I was gonna take a crack at explaining it after I posted it, but I knew someone else with a better way of explaining it would come along. I remember former Channel 4 meteorologist Bruce Schwoegler talking about the 39 degree principle on TV when I was a kid. He always made references to Winnipesaukee during "ice in/out" season.

BT

[nj2nh]

Thanks for all the information on the lake freezing and the whole 39 degrees thing. You learn something new everyday!

I am going to pass this along to my kids.

nj2nh

[This'nThat]

Originally Posted by nj2nh

I am going to pass this along to my kids.nj2nh

NJ2NH, the 39 degree water temperature also explains why the whole lake doesn't freeze down to the bottom, and why the fish also don't freeze. The bottom layer of the lake ice is always in danger of being melted by the 39-degree temperature water underneath, which actually limits the thickness of the ice in our NH climate. Think about how much heat is in the massive body of water at a uniform 39 degrees! To put it in perpective, if you had a heat pump at your house, when the air temperature is 39 degrees outside, the heat pump can completely warm the entire house and keep it at a comfortable 68 degrees F inside -- that's a lot of heat at 39 degrees.

And of course, 39 degrees isn't freezing, so the fish are happy to be swimming in this relatively "warm" water -- given that they are a cold-blooded species and don't need to stay warm.

[Grady223]

Originally Posted by nj2nh

Thanks for all the information on the lake freezing and the whole 39 degrees thing. You learn something new everyday!

I am going to pass this along to my kids.

nj2nh

I agree, thanks for the info.

[Grady223]

Looks like we are about one week behind last year - we are at 49 degrees, last year we made it there by 11/9. Of course some teen temps this week may catch us up in a hurry.

[CanisLupusArctos]

Originally Posted by Grady223

Looks like we are about one week behind last year - we are at 49 degrees, last year we made it there by 11/9. Of course some teen temps this week may catch us up in a hurry.

I think you're right. We're at 47 for lake temp now, only the second cold night in a row and more to come.

[Mink Islander]

And now it's down to 44 degrees at Lakeport.... C'mon winter!

[chipj29]

I have seen ice on some of the smaller ponds in Southern NH. There is even ice on parts of the Shawsheen River down here in Andover, MA. Certainly is early for ice, but a good sign nonetheless.

[Merrymeeting]

The small pond that I pass on my way to work here in central MA was fully skimmed over for the first time this morning...

[BoulderBronco]

Bring it on. I just looked at the forecast for the Meredith area and it looks like a good cold spell has a hold on you guys. Come on winter!

[Resident 2B]

Looking at the data for the past 5 years, it looks like 45 degrees, plus or minus a degree, is the normal for November 20th in this era. Yesterday was November 20th and the lake was at 44 degrees.

With the cold weather here and looking to hold for some time, I would guess that will put the lake a few degrees below normal in a week or so, so it is approaching the magic temp of 39 degrees for transition rather quickly. I realize the water freezes at 32 degrees, but there are specific gravity reasons why 39 degrees is so magical, and important.

It looks like there are about eight weeks to get the sleds and bob houses ready for the big lake, maybe less in the coves if the cold holds.

R2B

[BoulderBronco]

My brother was just up there (Meredith Bay) yesterday getting the sleds fired up and ready. I would love it if the lake froze by Christmas, but that might be too optomistic He said it was pretty burly out there. I don't think he was out on the water but he said it was nasty!

[Lakegeezer]

There is a bunch of skim ice on Winnipesaukee by the Lago resturaunt. It extends from the guest docks to the western shore and about 100 feet south of the north shore. Woo-hoo! Maybe its time to think about getting the docks in.

[Merrymeeting]

I was at the lake yesterday. It was miserably cold and windy. Smaller ponds are all skimmed over, even some of the coves showing signs of ice.

What surprised me the most was to see the Merrymeeting Marsh and River around the Alton circle completely skimmed over. With the water temps and movement, I wouldn't have expected this.

Flip should occur any day now, if not already.

http://www.squamlakes.org/sla/ecology.htm

[Mink Islander]

41 degrees at Lakeport this morning per the recorded message. Getting close to that magic 38.2 degrees....

[Grant]

Check out the Ossipee cam...Broad Bay appears to be entirely skimmed over.