Quote:
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.