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Circuito de Jerez – Angel Nieto Weather Analysis

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Ideal race conditions? Many would agree!
The mid spring months in Jerez present mild conditions, offering historically great weather for race week. Let’s lay it out as a chain reaction… Little moisture in the air results in little to no convective activity. These minor traces of moisture carried off the coast create below average humidity levels compared to the 19 circuits in the series. Due to mild average air temperatures, precipitation is not likely as the air is at an ideal moisture holding capacity. Now let’s talk circuit temperatures. To put it simply… HOT. The high detection of outgoing long wave radiation means there is a direct path for the incoming solar radiation to reach the Earth’s surface. The asphalt has a relatively low albedo, meaning it has a high absorption rate (opposed to some surfaces such as ice that reflect almost all insolation). As the circuit absorbs high amounts of shortwave radiation traveling from the atmosphere, it continues to collect energy until the Earth reaches its energy budget. Long wave radiation is then released in order to regain an energy balance between Earth and the atmosphere. Race weekend has historically offered amazing weather conditions with the exception of high surface temperatures. Tire choice will be an important part of each team’s preparation as they gear up for Sunday’s race.

Climate Factors of Study:

The following graphs track the average values of four different climate factors during April from 2012-2018. The Circuito de Jerez is identified on each map by a black pin point, allowing you to see where the circuit lies within the range of values. The color key on the right hand side of each graph portrays average values for this region. Colors located at the top of the key represent higher values while colors located at the bottom represent lower values.

To recap from our Weather & Racing page:

  • Outgoing long wave radiation:
    • The level of outgoing long wave radiation detects how much radiation is being released from the earth back to the atmosphere. Low levels of OLR detects higher moisture levels that have resulted in cloud formation which ultimately traps the OLR and reflects it back to the earth’s surface.
  • Humidity Levels:
    • Humidity is the level of water vapor in the air. Warmer air has a higher ability of holding moisture and creating the humidity effect that we are all too familiar with. When the relative humidity reaches 100%, this means the air can’t hold any more moisture and it can lead to precipitation.
  • Precipitation:
    • The condensation of atmospheric water vapor. (The stuff that makes you want some wet tires on your bike)
  • Average Air Temperature:
    • In our case, this will be the average air temperature for a specific location/circuit during the race season to track fluctuation and ties to to the other climate factors.


Circuit Values:

Average Outgoing Longwave Radiation (OLR) May 2012-2018  (~255 W/m^2)

The Circuito de Jerez experiences a higher level of OLR during its spring months compared to the average of all 19 circuits. A high detection level of OLR such as this suggests little convective activity meaning there is minimal moisture in the air. The chain reactions of these factors are reflected in the mild spring conditions that we see at this circuit.








Average Air Temperature May 2012-2018 (~20 degrees Celsius)

High OLR = little cloud coverage = increased amount of radiation reaching Earth’s surface. The Circuito de Jerez often presents warmer air temperatures with extremely elevated circuit temperatures. This is due to the little obstruction of insolation traveling through the atmosphere that is absorbed by the asphalt due it’s low albedo. When the Earth’s surface exceeds it’s radiation budget, it will release long wave radiation (hot hot hot circuit temperatures) in order to regain the Earth / atmosphere energy balance.








Average Surface Precipitation Rate May 2012-2018 (~1 mm/day)

Transitioning from a wetter winter into a drier summer season, May is an ideal month for racing as there is still moisture in the air but minimal rainfall. The circuit’s close proximity to the coast maintains a level of moisture but not enough to exceed the warm air’s water holding capacity. The average precipitation rate in Jerez during May falls below the average of all 19 circuits so rain races are not a concern!









Average Relative Humidity April 2012-2018 (~62.5%)

Humidity is not a big concern here! With an average humidity rate of around 60%, small amounts of moisture are carried inland from the coast. With warm air temperatures and elevated circuit temperatures, we are happy to see lower rates of humidity as muggy conditions present an added challenge to a rider’s stamina.