NEW RELEASE Series of Video Lectures based on the Instrument Rating Study Guide (14 Mar 2019)

Individual topics are available for purchase through PayPal starting at $10


or Contact Maree in the Office This email address is being protected from spambots. You need JavaScript enabled to view it. or 0732040965 if you wish to purchased the entire Course for $675

× Welcome to the CPL Meteorology question and answer forum. Please feel free to post your questions but more importantly also suggest answers for your forum colleagues. Bob himself or one of the other tutors will get to your question as soon as we can.

Synoptic charts and measuring QNH

  • Posts: 15
  • Thank you received: 0

rodcarey created the topic: Synoptic charts and measuring QNH

Hi all,

Just wonder where on the synoptic chart you take the QNH measurement Ie in the middle of either a low or high is the QNH measurement, each gradient line after that has a value which is on the line. I have attached a sample for Melbourne, the high is 1024, and the next gradient line is 1016. Melbourne sits north of the Gradient line, between 1016 and 1024. I would assume the gradient line 1016, and the area between this and 1024 is all a QNH of 1016, and once you hit the gradient line around the high, then it would become 1024?

Please Log in or Create an account to join the conversation.

  • Posts: 1902
  • Thank you received: 98

bobtait replied the topic: Synoptic charts and measuring QNH

Because it's called a gradient, it's useful to imagine that you are looking at contours on a map of a hill that is 1024ft high. As you leave the top of the hill, the spacing of the contours is 4 but only every second contour line is given a value to avoid making the map too cluttered. So the line between the 1016 and 1024 would be 1020. It is quite valid to interpolate between the contours, although, in practice, it would be normal not to go further than half way between two lines (2Hpa).
The following user(s) said Thank You: rodcarey

Please Log in or Create an account to join the conversation.

Time to create page: 0.548 seconds