How many times have you seen the weather on TV and are totally blind when it comes to trying to understand what the presenters are showing on those screens behind them and what those symbols and lines mean. On this page is your chance to understand what is meant by Symbols on Weather Maps in the UK, many of which are used in TV broadcasts worldwide today.

FIGURE 1 SYNOPTIC CHART

1. HIGH PRESSURE shown as HIGH on a Weather Map.


High pressure on a Weather Map is defined as an area where air pressure is higher than the air that surrounds it. Winds around a High pressure located in the Northern Hemisphere moves clockwise while in the Southern Hemisphere winds blow counter clockwise around it. They are usually associated with fine weather but are very seasoned dependent with cold and frosty weather experienced in Winter and very warm and sunny conditions possible in summer. There are many factors though that can alter this general rule of thumb definition but it is a good bench mark description. See Figure 1 above.

2. LOW PRESSURE shown as LOW on a Weather Map.
Low pressure on a Weather Map is defined as an area where air pressure is lower than the air that surrounds it. Winds around a Low pressure located in the Northern Hemisphere moves counter clockwise while in the Southern hemisphere winds blow clockwise around it. They are usually associated with areas of rain or snow and windy weather though there is a complex structure that make up a low pressure area or 'Depression' as it is commonly known. The basics of these are made up of Warm and Cold Fronts and Occlusions all of which are described below. See Figure 1 above.

3. ISOBARS shown as Contour like lines on a Weather Map.
These are lines that are drawn on a Weather Map which join places with equal barometric air pressure in the same way that Contour Lines join all places with equal height above sea level on an Ordnance Survey Map. Isobars that appear close together indicate strong surface winds while widely spaced ones indicate lighter wind. See Figure 1 above.

4. FRONTAL SYSTEMS associated with Low Pressure areas and shown on a weather Map as indicated below

THE JET STREAM AND HOW IT INFLUENCES OUR WEATHER

WORLD AIR MASSES

SATELLITE CLOUD IMAGERY

PRECIPITATION RADAR

SOME DATA ON THIS PAGE IS SUPPLIED FROM THE UKMO at metoffice.gov.uk