Surface low and upper level low

[ckmc]

I`m begininning to understand upper level charts, and have a fairly good understanding of and upper level low, and a surface low.

My question, what is the best way to tell them apart on a satellite image. There are so many available, from visbible to IR, to colored to Water Vapour and more.

So do I tell an upper level low from a surface low on satellite imagery??

I apologise for my English, it is my third language

 

[wxmanjerry]

Hello

Analysing an upper level low on satellite images that are available to the public is very difficult, but they have improved enormously in the last decade Your best way to analyse upper level lows is look for troughs instead of upper level lows. Depending on what height level your looking at, especially during summer its much less frequent to have an upper level low than a surface low. Sometimes even with a deep and active surface low pressure upper level charts (300mb) only show a trough and not an actual low pressure.

Water vapour imagery is certainly one of the best images for analysing upper troughs. Firstly find the surface low pressure on a surface weather chart, or on an IR or VIS image. If the low pressure is deep and active enough look for what are called dark stripes within the water vapour. These signal regions of high vorticity, commonly associated with jet streams and jet max's.

Hope that helps

 

[ckmc]

Thanks wxmanJerry, that was my thinking that water vapour imagery would be better suited.

My guess, becuase I`m unsure whether I have this right. An upper level low is basically an upper level trough that has been cut-off?

 

[wxmanjerry]

The words 'cut-off' are the wrong words to use in essence, but I see what your trying to get at...

As you know if you look on a surface weather chart you can get a low pressure, but you can also just get a trough in the isobars. If that trough develops and frontal zones are associated then a low pressure will develop. When I say low pressure I mean a system that has a closed circulation.

The same applies to the upper atmosphere, but it takes more for a closed circulation to appear, especially in the mid to upper level atmosphere. Upper level lows usually start out as troughs within the mean flow, if the surface low develops and deepens than there is a chance that the trough will develop a closed circulation.