Does Colder Water Mean Better Thermals??

[robertovillate]

Originally Posted by Unimog Bob

The water is SO cold... lol... it is chilling the air down at the surface and up a little bit, as well.
The warmer air (the air with wind) passes over this colder air, creating a wedge.

Go inland, and that wedge disappears and the winds blow good.

This is what we call a "marine layer"
The cold air sits on the cold water like a blanket
The warm air flows thru faster at slightly higher altitude
There can also be "sheer" where the wind direction at water level and 50' off the water are different, which makes trimming sails very confusing sometimes.

In the example of Sunday at PAG, Sam was probably into the warm air (would be interesting to have a thermometer on the kite at 75m and at 25m). Once it died enough where my 13m on 25m lines was not cutting it, Sams kite was still clearly powered enough to ride.

At Picnic Island the marine layer could not be as strong , or exist at all, after air had flowed over the Pinellas Peninsula which eliminated the m-layer from the picture at least partially.

This effect is common up on Lake Michigan during the spring sailing season and sometimes in mid-summer/fall during the thermocline turnover days where the water temp might go from 70F to 48F overnight due to a wind shift.

There are lots of other things that effect a seabreeze, but I think the "marine layer" was the phenomenon on Sunday. For Picnic Island the "thermal" effect was almost definitely a factor with lots of warm asphalt surfaces over there.

[Steve-O]

That makes sense. The colder air is denser while the hotter air is traveling above it. Kind of like water and oil.

[robertovillate]

Originally Posted by Steve-O

That makes sense. The colder air is denser while the hotter air is traveling above it. Kind of like water and oil.

probably a good analogy, very similar I would think to the oil/water comparison...although a real meteo guy might have a better explanation.

My guess is - The colder air on the water surface is less "viscuous" and will not flow as easily, especially with very little surface wind flow. The warmer air above has to go somewhere and usually heads for other heated areas of flow (and less resistance). The other day there wasn't really any "pressure" to move the cold air mass.

in addition...this "marine layer" situation probably does not happen around here very often since the water temps rarely go below 55F and then only for a few days (normally anyway )...

at any rate we need some wind!!!!!!!!!!! please don't downgrade Thursday...please!

[Steve-O]

Nice Seabreeze today and yesterday N. County.

Easterly flow in the am
Just had a passing front
Clear blue skies (high pressure)
Big temperature change throughout the day.

All things I look for.

[jaco]

"When the dew is on the grass
Rain will never come to pass.
When grass is dry at morning light
Look for rain before the night."

Dew forms when the air is cooled to its dew point, when it overflows with moisture. At night this happens in clear, cloudless weather, which (as it did in Sausalito last month) allows the day's heat to escape into the atmosphere. If a cloudless night cools the air, a cloudless day heats it and creates thermals. A heavy dew at dawn, therefore, may promise a fresh sea breeze that afternoon.