Datums

You can't have data without a datum. This is my choice for measuring the intesnsities of geo phenomena. …

The first image comes from a late January computer run of the weather over the North Pacific.

The second is a nice example of vortice behaviour. The 'plane looks like a crop duster, not built for speed so no streamlining effect. Not that I expect it to differ, overmuch.

Now then, back to the upper image: The cut off line for pressure change in the vortex is on the 1016 millibar line. In the North Atlantic there is less clarity over where the cut off line lies. It appears to predominate on the 1008 line but this may be anything within a range of 1016 to 998 or so.

But the idea is that one exists. It is the line of isobars that seeks to blend most accurately the overall coutours of the high and the low pressure areas it lies between.

That would be an obvious conclusion even if you had never seen an isobar chart. The median line would follow both sides as best it could, that is logical. What is less easily seen is that this line also travels in between successive air pressure systems. The higher and lower lines curve aroud their respective regions.

The 1016 isobar tends to travel over both oceans.

More examples of vortices and of isobar charts can be found in my albums.

I'll be putting all of January's North Pacific and North Atlantic FNMOC Ensemble charts (Computer model runs) up there too in a few days so you can run them all past you and see what I mean.

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This is likey to build into quite a long thread starter so don't forget to come back to it from time to time. I would suggest adding it to your bookmarks if it interests you.

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This thread is more or less a restart of this one:
http://my.opera.com/Weatherlawyer/blog/2009/01/22/some-earthquake-chasing
Which had so many iteresting directions come out of it that I lost track.

I wanted to write something about clouds. But before I could, I felt that I had to check out what was known about air behaviour. So I went to the UK.sci.weather Usenet FAQs and down loaded about ten or so pages on Vortex stuff. http://weatherfaqs.org.uk/node/63

One page lead the next and eventually I ended up with about 4,000 words, most of which I uderstood but not in the order that they arrived in. The basic problem is that I have one concept and everyoe else doesn't. Or they are wrong. And sometimes both.

Here is my idea:

Clouds are an example of a vortex. Not just the obviously twisting clouds that produce downbursts, derechos, tornadoes and hurricanes. Clouds are a part of the global cyclone/anticyclone effect. The visible part.

I was looking for stuff online about a behaviour in fluids called "shedding", hoping this would explain how clouds occur. It mostly deals with the interaction of fluids on soldid obstruction. Containers ducting and fish mainly. But there must be an interaction between positive and negative rotating gas masses. (Positive and negative are terms for cyclones and anticyclones -it probably helps the computing)

As a fluid there is virtually no friction in gasses. Instead compression and expansion occurs and this is proportional to the amount of heat transferred in the process. As air is compressed it affects the way that it holds moisture. Look ast the way that it occurs or precipitates in the top picture. The clouds form inside that 1016 millibar barrier, as the pressure changes. <<<I'd like to edit this but it is what I believe and adding "seems to" …form inside… just doen't cut it for me.>

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Here is a picture of a jet just breaking the sound barrier.

One on video: http://uk.youtube.com/watch?v=wHrwgRsX0BI
An explanation of sorts on here: http://urbanlegends.about.com/library/bl_sonic_boom2.htm

I don't think the conensation produced was long lasting. Not like condensation/vapour trails from high flying aircraft. They push out tremendous amounts of dirt and heat into rarefied air that is relatively still. Air seems to be sucked down from above them from quite a distance and depsited below them at abo the same distance.The passage of 300 tons of aircraft makes quite a long term impact. And I dare say the pressure changes caused by the winds shown in the top picture must also have some sort of impact. I dare say they are the source of clouds in nature. It certainly looks the part.

The green and white aerofoils presented, by the way, in that weather model run is speculative for wind speed not cloud development.

Have fun.

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