mb heights photo

[SouthFloridawx]

Here is a photo that I refer to from time to time that shows the mb to feet conversion.

[linkerweather]

This is not really a good "conversion" from height in feet to mb as these numbers are anything but constant. ONe of the challenges of forecasting is determining at which height significant pressure levels will be at. For example if the 500 mb height is low then that could mean some kind of upper low pressure or colder pocket aloft, or the level may be high indicating a ridge or warm air. Of course the thickness between pressure levels is also a good indicator of the temperature profile of the layer in the atmosphere. It is very important to NOT use those levels as a constant.

[SouthFloridawx]

This is not really a good "conversion" from height in feet to mb as these numbers are anything but constant. ONe of the challenges of forecasting is determining at which height significant pressure levels will be at. For example if the 500 mb height is low then that could mean some kind of upper low pressure or colder pocket aloft, or the level may be high indicating a ridge or warm air. Of course the thickness between pressure levels is also a good indicator of the temperature profile of the layer in the atmosphere. It is very important to NOT use those levels as a constant.

I totally agree, I found it and used it as a general thing so I knew where I was looking at something in the atmosphere. Is this chart totally inaccurate?; or is it generally a useful thing for a person, like myself that doesn't have a formal education in atmospherics.

One question that I have regarding the bold section above. How dramatically higher or lower can, lets say for instance... 500mb Height... What is the Mix/Max Feet in the atmosphere will you see, High pressure vs. Low pressure. I realize that it varies, and there is no exact answer to that question... I would like to get a better Idea of levels measurement and how high and low pressure are measured and determined.

If this is not very clear I apologize.

[wxman57]

It's a good representative of the pressure/height relationaship in a standard atmosphere (outside of high and low centers).

[SouthFloridawx]

So let me see if I am understanding this at all...

Looking at the 12Z GFS as shown below...

The ridge in the Atlantic Labeled 588; this would equal out to 588mb and the isobars for the 588 are all equal to that measurement of pressure?

When looking at tropical system forecasting, what is the typical height, that one would look at... to represent where the system would travel around? Is there an height @ the 500mb region, that typically a Hurricane or Tropical Storm would not be able to penetrate?

[wxman57]

That map you posted is a constant pressure map. The numbers represent the height of the 500mb pressure surface in tens of meters. So the "588" means that the height of the 500 mb surface there is 5880 meters.

[linkerweather]

It's a good representative of the pressure/height relationaship in a standard atmosphere (outside of high and low centers).

I agree with this, and after reading my earlier post, I didn't intend to belittle the initial poster. I hope it wasn't construed that way. In any event, I was responding to the "conversion" word in the first post. Your 500mb map is a contour of heights at that pressure level.
Edited to add, I see that second part was already addressed)

[Aslkahuna]

It's a first guess height and a rounded off one at that since under standard conditions, the standard heights for the various pressure levels is not a rounded height (H7 for example is actually found a bit below 10000 ft and H85 is less than 5000 ft.).

Steve