Producing your own synoptic chart

Without a prepared forecast synoptic chart, any attempt at DIY forecasting for more than a few hours ahead needs to begin with the preparation of your own forecast synopsis. Obviously this is unlikely to be as accurate as one prepared by a professional meteorologist with high-tech resources at his disposal, but it can still be a valuable guide.

Ideally, you need to be able to visualise the swirling mass of the atmosphere – it may help if you can imagine the ripples and eddies created if you stir a basin of water – but there are a few general rules of thumb which can help.

Depressions, around us and Europe, usually…

1. Move in an easterly or north-easterly direction, parallel to the line of the isobars in the warm sector.
2. If a depression has been moving in a particular direction for 12 hours, it is likely to go doing so for another 12 hours unless it meets land or a large anticyclone.
3. Lows slow down and fill up when they meet land, or when their fronts occlude.
4. If the barometer is rising more quickly behind a depression then it fell when the depression approached, the depression is probably filling and slowing down (and vice versa.)
5. When a large depression occludes, a smaller ‘secondary’ depression often develops somewhere along the trailing cold front.
6. If two similar lows are close to each other they may merge to form a complex low, with two centres that rotate anticlockwise around each other.

Fronts

1. Each section of a front moves at right angles to the line reprenting the front itself.
2. Each section of the cold front moves at about the speed of the geostrophic wind behind it. Warm fronts typically move about 30% slower.

next