1. Surface Meteorological charts
Maps of sea-level pressure

2. Surface weather chart for 3 January 2007 (UK Met Office)
1° lat = 111 km

3. Salient features 1
Map shows sea-level pressure. Over land the measured pressure is adjusted to what it would be at sea level.

4. Salient features 1
Map shows sea-level pressure. Over land the measured pressure is adjusted to what it would be at sea level.
Surface pressure pattern dominated by highs and lows, on a scale ~ 103 km. We call this the synoptic scale

5. Salient features 2
Isobars give an indication of the wind speed by the geostrophic relation: wind tends to flow along isobars and its strength is proportional to pressure gradient

6. Salient features 2
Isobars give an indication of the wind speed by the geostrophic relation: wind tends to flow along isobars and its strength is proportional to pressure gradient
Pressure excursions around ± 30 mb – much smaller than the total pressure of ~1000 mb.
Pressure is the weight of air above you

7. Time scale
00 h
3/1/07
Weather system takes ~ 1 day to pass over the UK – so synoptic timescale is around a day (105 s)
00 h
4/1/07

8. Fronts: areas of cloud and rain
AVHRR IR image /1/07

9. Cold and warm fronts Motion of front Warm air Cold Air Warm air
Cold front: narrow (~100 km), steep, can get line convection particularly on leading edge
Warm front: broad (~300 km), layer cloud due to gentle upglide. Convection unusual.

10. Occluded front
Warm air
Cold, unstable air
Cold, stable air