science question?

Question

what are local breezes and how does it affect weather? and what is an example?

Answer 1

Good question - During the day land heats up faster than the water. The air over the land warms and rises creating low pressure. Cool air from the water than blows in under the warm air. This is called a sea breeze because it comes in from the sea during the day, generally in the afternoon when the land has reached its max heating.

At night the land cools faster than the water. A reverse process is established and a land breeze forms with a breeze from land to sea. Cooler air always has a higher pressure. This land and sea breeze phenomena is not a deep layer phenomena and is only perhaps a 1 km or less deep.

Mountain slopes and valleys also experience diurnal breezes. When the slopes are heated by the sun during the day the air rises up the slope from air at the same altitude over the valley which is cooler, but at night when the slopes cool more quickly than the valley, there is a breeze that comes down the slopes.

I hope this helps.

Answer 2

There are numerous examples out in nature where local winds can cause forecast to be way off. It usually takes two years of experience before a forecaster can recognized these local effects. Here are a few examples:

Wind flowing through a river canyon. At certain speed and directional shear, winds can become erratic. This is difficult to forecast, but can mean the life of a wild land fire fighters if not forecasted.

Wind flowing at a angle can help increase the low level barrier jet the blows parallel next to a high mountain range. This can cause temperatures in the foothills to be much higher at night near the boundary level.

Down slope winds at night mixed with an onshore flow will produce "surprised" late evening thunderstorms over the valley region. To this day, this is rarely forecasted by any of the high resolution models.

Strong onshore winds mixed with strong barrier jet and complex terrain of the adjacent foothill region can produce strong speed and directional shear at the low levels. Mixed that with shallow instability (low CAPE environment and you can get a "surprise" very low top supercells (echo tops to `12,000 ft) tornadic thunderstorms in the California valley regions around sunrise.

These are the local non-textbook breezy wind event that you can find around the country that only a local forecaster may learn from experience and can be critical to predict.