Global map data and layers

Contents

Dates and times

Data sources

  1. Data models
  2. Met Office Global model
  3. ECMWF IFS model
  4. NCEP GFS model
  5. Met Office radar
  6. Satellite observations

Map layers

  1. Accumulated precipitation
  2. Mean sea level pressure
  3. Total cloud cover
  4. Low cloud cover
  5. Medium cloud cover
  6. High cloud cover
  7. Temperature
  8. Relative humidity
  9. Wind speed
  10. Wind gusts
  11. Freezing level
  12. Visibility
  13. Convective Available Potential Energy (CAPE)
  14. Dew point temperature
  15. Visible composite

Dates and times

Dates and times on the global map are shown in your local timezone. This is set by your computer or mobile device settings.

Data sources

Data models

Data models are computer programs run by forecasting centres, like the Met Office.

Every model produces forecasts in a different way. As a result, the same weather layer may look different, depending on the data model.

It is useful to compare the same weather layer across data models. Any differences between models shows where the forecast is uncertain.

Met Office Global Model

The Met Office Global Model will give you a forecast across the whole globe.

This model will show you the 'bigger picture' of how the weather is moving and evolving. This model is available in 10km and 17km resolution. 

More information:

ECMWF IFS model

The European Centre for Medium-Range Weather Forecasts (ECMWF) produces the Integrated Forecasting System (IFS).

This model shows us how weather is moving and evolving across the globe. This model is sometimes referred to as the 'European model', to distinguish it from the NCEP GFS model.

NCEP GFS model

The National Centers for Environmental Prediction (NCEP) produce the Global Forecast System (GFS).

Like the ECMWF IFS model, the GFS shows us global weather patterns.

Met Office radar

The Met Office radar is not a forecast model. It shows where we have observed rainfall across the UK, at any given time. This is why you can only see data in the past.

We detect rain by using an instrument called a radar. There is a large network of radars across the UK, scanning for rain in the surrounding areas.

More information:

Satellite observations

Satellite observations are not a forecast model. Instead, it shows us where clouds were across the globe, at any given time. This is why you can only see data in the past.

A satellite in space captures our cloud observations.

More information:

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Map layers

Accumulated precipitation

Accumulated precipitation shows the amount of precipitation expected to build up over the course of a specified time period. We classify precipitation as all types of water falling from clouds. This includes rain, snow, drizzle, and hail for example.

More information:

Mean sea level pressure

Mean sea level pressure shows areas of high and low pressure across the globe.

As a rule of thumb, high pressure often leads to more settled weather (lighter winds and less rain). Low pressure often brings wet and windy conditions.

More information:

Total cloud cover

Total cloud cover shows the amount of cloud expected, as a percentage of the sky.

For example, 50% cloud cover would mean there are roughly equal amounts of blue sky and cloud.

This map includes all types of cloud: low, medium and high.

More information:

Low cloud cover

Low cloud cover shows us the amount of low cloud expected, as a percentage of the sky.

We define low cloud as any cloud below 6,500 ft in altitude.

50% low cloud cover means that half of the sky has low cloud, and the other half has medium, high or no cloud.

More information:

Medium cloud cover

Medium cloud cover shows us the amount of medium cloud expected, as a percentage of the sky.

We define low cloud as any cloud between 6,500 ft and 20,000 ft in altitude.

50% medium cloud cover means that half of the sky has medium cloud, and the other half has low, high or no cloud.

More information:

High cloud cover

High cloud cover shows us the amount of high cloud expected, as a percentage of the sky.

We define high cloud as any cloud above 20,000 ft in altitude.

50% high cloud cover means that half of the sky has high cloud, and the other half has low, medium or no cloud.

More information:

Temperature

We show temperature in degrees Celsius, at varying altitudes.

Temperature is usually measured at 2 metres above ground level. This is a good height to use for a general forecast.

You can also see temperatures much higher up in the atmosphere. These altitude layers are selected in hectopascals (hPa) rather than in metres, which is a more useful way to view temperature this high up.

Relative humidity

Relative humidity measures water vapour in the air and tells you how close it is to becoming saturated.

If temperatures are high, high humidity can make it feel even warmer. In low temperatures, low humidity can make it feel even colder.

More information:

Wind speed

Wind speed shows the average wind speed in miles per hour. In reality, the wind will strengthen and lull above and below this value.

The gust layer will show you what the highest possible wind speeds could be.

You can also view winds at different altitudes. Wind is usually measured at 10 metres above ground level, which you can use for general forecasts.

The jet stream is usually found at around 300 hPa. Weather systems tend to follow the path of the jet stream, so this can help to see where they might travel to.

Wind direction

The wind direction is given in degrees clockwise from north. For example an easterly wind (blowing from east to west) will be around 90 degrees. 

More information:

Wind gusts

Wind gusts show the highest wind speed to expect at that time, as the winds peak and then lull again.

Freezing level

Freezing level shows you the height at which the air temperature reaches zero degrees. 

Visibility

Visibility shows how far you can expect to see in metres. Where there are no colours on the map, the air would be clear and you would have good visibility.

The colours show where the air may be a little more hazy (blue) to where there is likely to be thick fog (red).

Convective Available Potential Energy (CAPE)

Convective Available Potential Energy (CAPE) measures how much energy is available for convection. Convection is when air rises upwards, sometimes forming clouds or showers.

A higher amount of CAPE (red colours) means you are more likely to see clouds forming or showers developing.

Dew point temperature

Dew point temperature shows the temperature the air must fall to in order for it to become saturated.

More information:

Visible composite

Visible composite is a satellite picture, showing where clouds are across the globe.

The satellite records the image in a similar way to our eyes, using the visible part of the electromagnetic spectrum.

This means that the satellite cannot capture images of the clouds during the night. The image begins to fade at dawn or dusk.

That is why there is always a large section of the earth 'in the dark', with no clouds showing.

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