I’ve sat out Sandy in an area about 100 miles inland and on the periphery of the real wrath of the storm. I experienced some moderate to heavy rain and a lot of wind gusts. The rain was nothing like Irene last year.
So where I’m at we have wind chimes and bird feeders that give you a pedestrian sense of the force of the wind. Today, the sky was clearing with some break in the clouds but there were severe wind gusts. Same thing last evening. Why? They would only last maybe a minute.
Wind is air moving against air. Why isn’t there consistency in the storm system? How long does a wind gust last? Does it just keep moving or is it something I was experiencing on a local, immediate basis and wouldn’t continue down the road while everyone else in the area is experiencing their own personal wind gusts? Shouldn’t most if not all of the air within the system move consistently?
Stand along side a stream or a river, note how there are eddies, flows and boils along the surface. Few, if any, of these stay in the same place, with the same intensity, for long. Air does the same stuff, but on a much larger scale.
chacoguy has it right - the “whitewater” analogy is useful. The point is that there’s a lot of turbulence in the atmosphere - most especially when something like Sandy comes along - and this results in a lot of variation in the wind measured at any one place.
I’m not quite getting it. Where there are rapids in a river the water rushes on a continual basis depending on volume because of narrowing or a drop in elevation. It doesn’t rage and then calm within minutes. Same thing at a bend or a narrowing of a river. The water isn’t swirling one minute then passing calmly the next. My location hasn’t moved so why the sudden severe changes in wind velocity? I’m not getting the analogy.
I also go back to the question as to whether everyone in the area (lets say a 20 mile radius) is getting the effect of a single gust or a lot of small gusts. Is the severe gust that is trying to rip down my wind chime the same gust that is trying to get rid of the someone’s bird feeder 10 miles away?
Your location doesn’t move but the location of the hurricane is constantly moving and the direction of the wind is constantly changing with it. Eddies and currents within the storm are not fixed in place the way they are in a river system, instead they move and change. Basically the weather is much more dynamic than a river. Hurricanes also contain thunderstorms that create their own little wind system of updrafts and downdrafts. The downdrafts in a mature thunderstorm can be felt as a very strong gust front at the leading edge of the storm. This might be a situation where, with a large thunderstorm, people 10 miles apart could be feeling the same gust front.
To add to what has already been said, the air functions more three dimensionally than a river, (which although affected by gravity, is more of a 2 dimensional plane) and unlike a river, is fueled by the buoyancy of warm air; that is the powerful phenomenon, warm air’s tendency to rise. When air is warmed it rises, surrounding air rushes in to fill that void. This creates more complex eddies and currents than in a comparatively simple river system.
As well as the thermal effects mentioned, a lot of turbulence is caused by surface roughness (on the scale of trees and buildings, as well as on the scale of hills). An observer at one point on the ground experiences this turbulence as variations in wind speed (gusts).
To apply the river analogy, don’t think of the whole river speeding up and slowing down. Think instead of how it would be experienced by a tiny observer at one point on the river bed. From the point of view of that observer, the eddies are experienced as temporary changes in the water speed; these “gusts” are small-scale and local; the overall flow rate of the river remains constant.
My experience of this from sailing is that no, they are different gusts. Someone 10 miles away may be having similar gusty conditions to you, but it wont be exactly the same. Sometimes when we are sailing, the same gust will hit the whole fleet, stretching out over 100-200 yards, and sometimes a gust will hit just one or two boats. Maybe Sandy has some really wide gusts, but Im guessing not 10 miles.
Sometimes when I want to know how the wind is going to develop over the day, I check the weather station 20 miles or so upwind, since that is the weather we will be getting soon. But the buildings and terrain between here and there mean that we wont get the exact same sequence of gusts and lulls that they got there. It changes all the time.