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How we do our Forecasting

Observations; how we do it

Meteorological observations of the weather are very client specific. CWI has done observations for the film industry for the past 8 years and has developed portable electronic data logging equipment (automatic weather station) in order to fulfill this need. The film industry requires an independent weather observer in order to monitor the weather for insurance purposes. CWI is recognised by a number of SA/European insurance companies, who insure film shoots.

  1. CWI is contacted by the Insurance Company/Production House, who inform CWI of time and location of shoot.
  2. CWI program the portable automatic weather and prepare the required instrumentation, mainly for wind, temperature, rainfall and cloud cover.
  3. The portable automatic weather station is then erected to international meteorological standards (as close as possible) at the film shoot location.
  4. The weather station is programmed to record the meteorological conditions every 10 seconds and to provide averages to the client’s requirements. Extremes are also recorded.
  5. To supplement the electronic readings, manual observations are done with respect to sunshine duration, cloud cover and rainfall, amount and duration.
  6. The CWI observer also provides the Production House with current trends in the local weather and is in constant contact with the main CWI weather forecaster. This enables the CWI observer to warn of any adverse weather conditions affecting the film shoot. Translations of the weather forecast to layman’s terms for the Production House and the overseas client is provided.
  7. At the end of the day CWI provide the Production House/Insurance Company with a detailed report of the weather monitored for that day. This report includes tables of data (Wind speed/direction, temperature, rainfall, cloud cover and sunshine), graphs and wind roses.

Forecasting, how we do it

While the general impression may be that weather forecasts are made by a quick glance at the latest satellite image and the current weather map, these two tools merely provide confirmation of what the forecaster has already, days ahead, predicted.

In producing weather forecasts in the medium term, CWI uses the output of the Global Forecasts System [GFS] model [USA], which actually produces prognoses for up to 16 days worldwide. The National Weather Service in the USA utilises the same model for their forecasts. However, our experience indicates that only up to 4 to 5 days can be expected to be realistically reliable for micro- scale prediction.

In particular, the following are the processes that occur to produce the GFS output and a final forecast:

  1. Worldwide observation and dissemination of weather data occurs every 6 hours, every day.
  2. These vasts amounts of data are ingested every six hours in an endless cycle of operational runs by some of the most powerful supercomputers in the world and processed to derive a current three-dimensional snapshot of the atmosphere.
  3. Then using sophisticated mathematical modelling, predictions are made of the expected changes in the atmosphere over an extended period.
  4. To representing space in the atmosphere, use is made of a three-dimensional grid and the various predicted weather elements such as pressure, temperature, wind etc are assigned to these grid points.
  5. Further computation generates finished prognoses maps which the forecaster can peruse to visualise a three-dimensional time series and to make decisions how the depicted weather pattern changes will influence a particular locality.
  6. Stability components twice a day for the following 6 days. CWI spends 2-4 hours daily evaluating numerous atmospheric parameters.
  7. The forecast is translated in layman’s terms and transferred to a pre-formatted form, which CWI has developed in Excel. In addition astronomical data i.e. sunrise, sunset, azimuth and angle of the sun during the day as well  as any lunar and marine conditions are added to the forecast form.
  8. CWI has bought software from the USA in order to give their clients a better service. This software predicts the path of the sun at any given place at any time
  9. This forecast is then faxed-emailed to the client at 06h00-07h00 on day of shoot and 13h00 – 14h00 for the next 4 days.
  10. CWI is able to forecast 4 days ahead. If a client wants a forecast for Friday then the forecast will begin on the Monday.

CWI, having issued forecast, continue to monitor the unfolding of the weather and will issue updates if we perceive that the original prediction was off the mark