Help me understand the winds on the Rathdrum Prairie. (Arco: how much, community college)

[volosong]

I've been teaching 'Weather and Climate' part-time at the local community college for the past twelve years and am always interested in web sites with weather data, charts, and graphs. Ran across an interesting one yesterday and the below snap is from the CdA page, (data monitored at the airport).



After I retire to the Rathdrum Prairie next March, one of the activities I will be doing frequently is road cycling. Those of you who cycle know how important wind is in determining an enjoyable ride. The ideal is no wind at all, but that is unrealistic. Otherwise, most of us would rather 'fight' the wind on the way out to the turn-around point and have a nice 'assist' on the return leg when we're a bit tired.

The winds on the Rathdrum Prairie, as measured at the airport, come predominately from the northeast and from the south/southwest. There seems to be much only a slight seasonal variation. What I would like to ask, for those of you who live on the prairie, and have noticed the winds . . . is the change in wind direction something that changes on a regular basis throughout a day; for example, out of the south in the morning and out of the northeast in the afternoons? Or, is it more governed by weather systems that enter the area from elsewhere? Anybody know?

p.s. from: https://weatherspark.com/averages/29...-United-States

[elousv]

That probably does not take into account what most people would call windy. If it is barely a breeze then you may not even notice the direction. By and large, when it is windy, like annoying Antelope Valley forever blowing it is westerly. If you have become hyper-windified as I have by living in Pompton, then you may reconsider sticking yourself out on the prairie. My anecdotal evidence includes the flags at Stateline Speedway on Beck road. When it is blowing, they are more than likely to be pointing east. At least you don't have to dodge hundreds of tumbleweeds like on Rancho Vista Blvd.

[banjomike]

Hi, vovlo…
I know nothing about the winds of the prairie, but it seems to me that you are asking 2 different questions which would be answered by different sets of data.

Daily winds often shift directions due to smaller factors than seasonal shifts. The daily winds may be affected by more subtle factors than seasonal winds, due to the fact that the shifts happen faster and more often.

Comparing the shifts in wind direction between the middle of summer and the middle of winter may give you an answer on the seasonal shifts.

I think the daily shifts would be more difficult to deduce from logic alone because there are so many factors.

A few:
temperature of the hour
location
elevation
humidity
relative flatness of the terrain
… and there must be many others. These are only the first that come to mind.

Location can be a surprisingly big factor; things like mountain shadows can cool down the air much faster than in an area that isn't shadowed and along the line of sun and shadow, those temp differences can start a wind blowing, as the air always wants to average itself out in temps. A few difference of feet in elevation can cause a dust devil circular wind during the heat of summer.
And then the bigger seasonal wind pattern has to be figured in, and that's where humidity starts to become a factor.

So it gets really complicated when thinking about daily winds. I think talking to a local weatherman might be a big help.

[banjomike]

We used to own a wheatfield on a local sidehill. Whenever I would farm it, I could look out on the Arco desert with about 1500 feet of elevation, and one year, I began paying attention to the prevailing winds for the week or so it took to work the land with a tractor.
Once, day after day I watched cumulus clouds from and rise from the summer heat, elevating high enough to begin blowing in a particular direction. That direction during that time span was generally due east across the desert, and then, as the winds began reaching the east edge of the Snake River valley, which is part of the bench that rises to the great divide, the wind would bend northward.

As that week progressed, those winds would begin to collect moisture. Day after day, I watched thunderheads form as the wind bent, and then a shower line would begin and it would move north with the wind direction. Lightning always formed inside the storm line.

I never got wet except for one day. For whatever reason, the winds became stronger, and the overall direction of the wind changed into a straight line headed due east. All of a sudden, I could feel the stronger wind that was pushed ahead of the storm front. It was definitely cooler and moister. My back was turned away from the long view at that time, because I was driving the tractor east.

It happened quickly. All of a sudden, boom, boom, boom! Lightning began snapping all around me, and though the tractor, a D4 Cat, was never struck, I could feel the electricity in the ground through the steel floorboard of the tractor in my feet, which were insulated by rubber soled boots. My hand were insulated by the hard rubber grips on the steering levers, and my butt was insulated by the leather seat and the horsehair padding, but each strike still felt like a hammer blow on my entire body.

I had a dog name Nervous with me. Nervous rode atop the fuel tank to watch for rabbits or mice, and he had no insulation. The first bolt made his muscles contract so much it was like he elevated about 4 feet straight up until he hit the bottom of the shade cab on the tractor.
While he was in midair, all four legs were already trying to find traction. He was moving before he even came down, and I wasn't far behind.

We both scampered off the tractor as fast as our legs could take us, and I ran to a nearby shallow swale in the field and laid as flat as I could with Nervous cuddled up to me as close as he could go. We both got soaking wet in about a minute, while 2 lightning strikes hit the field we were working.

And then, in less than 6 minutes later, the entire storm petered out and became just a breeze. Still headed due east. I climbed back on the tractor, put it in gear and finished the field. Nervous spent the rest of the day under the truck.

It was one of the more remarkable days of my life. I still remember vividly how the underside of Nervous looked, with all his feet running like crazy in midair.

That dog was a lightning magnet. So was my uncle. The dog was struck twice more, once with my uncle, and he was struck a total of 5 times during his lifetime.

[AK76]

I offer this based on weather observation. The trend in wind direction is typically seasonal and is primarily dependent on the path of the jet stream and the systems- high pressure and low pressure -which are moved along it. Consider that high pressure systems rotate in a clockwise fashion, low pressure rotate counter-clockwise as they move west to east. For example; looking at today's forecast and satellite for the Spokane/CDA area one can see low pressure moving west to east across the zone as it rotates counter-clockwise, the current wind speed and direction as I type this 12mph from the SW (if it were a high pressure system the wind would likely be from the NE). Keep in mind that whichever system that is passing may be more miles to the N, or the S, and as such would affect how much E, or W influence there would be on a predominately N, or S, wind.

During the spring/summer months the weather trend is predominately high pressure systems, during the fall/winter months, low pressure is more frequent, generally speaking.

So, imagine a disk if you will, rotating one direction or the other while sliding it across a map of the PNW to get an idea of how the wind may affect the area.

[javatom]

There are not a lot of trees on the rathdrum prarie. Hence, not much to abate the wind.

[volosong]

I think I might be overthinking this a bit. Even though the wind direction is highly variable at the air terminal, the velocity is not all that great and should not affect most riding experiences.



Below are the conditions where I am used to riding. You can see that the velocity is quite high, but at least the direction is fairly consistent, so makes route planning pretty simple. The winds in the Antelope Valley are caused by several factors, among them are the intense local pressure gradient created between ocean/land and elevation differences, influenced by the topography of the transverse mountain range, the high albedo of the desert floor and relatively low albedo of the heavily vegetated mountains to the west and south, and the lack of low-level height variability to create surface friction. All adds up to a perfect place to sail a catamaran . . . if there were only some water around.

[elousv]

Originally Posted by volosong

All adds up to a perfect place to sail a catamaran . . . if there were only some water around.

Nonsense, you can "sail" all you want:

https://www.youtube.com/watch?v=O1LgavwsdEs