November 2, 2011 | By Eric Sorensen | No Comments »
Categories: Agriculture, Earth sciences
Tags: AgWeatherNet, Eric Sorensen, Flickr, forecast discussion, Gerrit Hoogenboom, Kamiak Butte, meteorology, National Weather Service, Nic Loyd, Palouse, Roger Lynn, snow, Washington State University, wind, WSU
The crack weather observers employed by WSU Discovery noticed an odd phenomenon this morning: a biting wind blowing from the east outside our Pullman field station, while forecasters say our first snow of the year could come out of the west.
It did not make sense that weather would move into the wind. Seeking clarification, we first went to the National Weather Service’s forecast discussion, a consistent source of wonky weather detail. No luck.
So we tapped Gerrit Hoogenboom, the relatively new director of Washington State University’s Agricultural Weather Network, AgWeatherNet. He passed our query to Nic Loyd, AgWeatherNet meteorologist. Here’s his ‘splanation, with a bonus comment on today’s forecast:
Yes, there is a storm system and a trough of low pressure approaching from the west today. However, winds are out of the east and southeast in many places such as Pullman this morning. Often in Washington during the late fall and winter, as low pressure approaches the coast from the west, the winds have an easterly component since wind at the surface often blows toward lower surface pressure. Also, in eastern Washington during the late fall and winter, the surface land is cooler than the air near the warmer offshore water, especially in the morning, and so cold, heavy air moves toward the warmer, lighter, rising air to the west. Behind the cold front, the winds often switch to westerly or southwesterly.
Another way to look at it is that during November when the atmosphere is often stable with a weaker sun, winds behave differently at different heights, and surface winds do not always mix with winds higher in the atmosphere, especially at night. Therefore, winds aloft will be out of the southwest today, but winds were out of the southeast and east this morning in the lowest levels of the atmosphere only.
By the way, it does look as if the weather pattern will be cooler during the day through at least the weekend, but little if any snow is expected in the eastern Washington lowlands. There is not a lot of moisture with tonight’s weather system, however, the mountains should receive a few inches of snow.