1. Meteorological charts

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

3. Salient features
Surface pressure pattern dominated by highs and lows, on a scale ~ 103 km. We call this the synoptic scale

4. Salient features
Surface pressure pattern dominated by highs and lows, on a scale ~ 103 km. We call this the synoptic scale
Pressure excursions around ± 30 mb – much smaller than the total pressure of ~1000 mb.

5. Salient features
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
Wind is in knots – 1 knot = 0.5 ms-1. The arrow points along the wind direction. This symbol is called a wind fleck.

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
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

11. European radiosonde stations (launch 00 and 12 UTC)
Vaisala RS80
Vaisala RS92
European radiosonde stations (launch 00 and 12 UTC)
Launching a
radiosonde
Data available from:

12. vertical wind shear  horizontal T gradient
300 mb,
~ 9 km
700 mb,
~ 3 km
Smoother patterns than at the surface; fronts not marked on these charts
700 and 300 mb charts show a similar pattern – synoptic scale features are generally coherent throughout the troposphere. That is, vertical scale of synoptic-scale features ~ 10 km
Winds closer to geostrophic – no surface friction
Very strong winds at 300 mb denote the jet stream. Jet stream is related to fronts, either at the surface or in the upper troposphere.
Westerly winds increase with height: thermal wind equation
vertical wind shear  horizontal T gradient