500hpa v 850 on GFS charts

[moses]

Could anyone please explain what these figures mean on the top of weather models eg GFS/ECM etc

and what thrie significance is - why two separate readings

Thanks Guy

[Nick F]

850 hPa and 500 hPa are pressure levels above the earth's surface where winds, temperature and geopotential heights for finding highs and lows (ridges and troughs) can be found at different levels. The 850 hPa level is roughly around 1500m above sea level, the 500 hPa level is roughly about 5700m above sea level.

The 850 hPa level is often useful for seeing if the air will be cold enough for snow, 850 hPa temps below -10C often indicates snow is likely if pressure is low with fronts, troughs around or the air is moving over warm SSTs.

500 hPa level can also be used for it's thickness levels to determine if snow is possible, air which is sub 528 DAM thickness suggests snow is possible, above 528 DAM (i.e. 528-546 DAM) then snow is unlikely. Also this level is usefull for spotting more colder drier air arriving aloft -as this steeepens lapse rates if warm moist air is present below and indicates increasing instability if pressure is low and helps in convective forecasting.

[BrickFielder]

500hPa is mid level in the troposphere at about 18000 feet and the temperatures at this level give a fair view of the synoptic pattern. You should be able to get a rought idea of where the jet stream ought to be by looking at the steepest temperature gradients. You should be able to get a feel for how air is moving and from that the general synoptic pattern.

Heres a quick first look at a 500hPa chart.

Not too far out when looking at the more detailed charts at that level.

Note that where the 500hPa winds are strongest is where rain is likely to occur most.

850hPa is a lower level in the troposphere at about 4500 feet. This gives a reasonable indication of low level temperatures with -8C at this level equating to about 0C at ground level. It also is a good level to get of feel of where the frontal systems are. Warm air and strong temperature boundarys being likely places for fronts.

Here is another quick interpretation of a chart.

A little out but not too far off the detailed chart.

As easy quick glance charts these charts give a lot of information and really cannot be beaten ,however delving into some of the other charts will tell you a lot more if you are so inclined.

[moses]

500hPa is mid level in the troposphere at about 18000 feet and the temperatures at this level give a fair view of the synoptic pattern. You should be able to get a rought idea of where the jet stream ought to be by looking at the steepest temperature gradients. You should be able to get a feel for how air is moving and from that the general synoptic pattern.

Heres a quick first look at a 500hPa chart.

Not too far out when looking at the more detailed charts at that level.

Note that where the 500hPa winds are strongest is where rain is likely to occur most.

850hPa is a lower level in the troposphere at about 4500 feet. This gives a reasonable indication of low level temperatures with -8C at this level equating to about 0C at ground level. It also is a good level to get of feel of where the frontal systems are. Warm air and strong temperature boundarys being likely places for fronts.

Here is another quick interpretation of a chart.

A little out but not too far off the detailed chart.

As easy quick glance charts these charts give a lot of information and really cannot be beaten ,however delving into some of the other charts will tell you a lot more if you are so inclined.

Cheers mate!!