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Weather Logistics Ltd - WeatherLogistics.com (Provider of regional-seasonal weather forecasts for the UK and Ireland)

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View Details of the Summer Weather Forecast & Winter Products

How Our Seasonal Weather Forecasts are Made

View our Seasonal forecast code

How Seasonal Temperatures affect your Energy Bills

Please see Heating_degree_days

How does Weather Logistics Ltd produce seasonal forecasts?

Red box.png A jet stream perturbation model is employed by Weather Logistics Ltd (1), which simulates the diversion of the air streams in the upper atmosphere. Atlantic air flow modelling is simulated by combining a monthly jet stream climatology input calculated at 20 to 30°W, with different blocking high patterns. These climatic states are then ranked in order of likelihood in their position and intensity, a blocking index system that is linked to the state of the North Atlantic Oscillation (NAO). The jet stream input is generated by thermal wind balance calculations at 316 mbars (6 to 9km aloft) in the mid-latitude range from 40 to 60°N. Long term blocking patterns are determined by the weather forecaster, who identifies the likely position and strength of North Atlantic highs from synoptic charts, the North Atlantic Oscillation (NAO) and El Niño-Southern Oscillation (ENSO) patterns. The model is based on the knowledge that low pressure systems at the surface are steered by the fast ribbons (jet streams) of air in the upper atmosphere.

The jet stream - blocking interaction model simulation examines the Sea Surface Temperature (SST) field using data from National Oceanic and Atmospheric Administration (NOAA) tracked along the ocean on a path to the British Isles. The principal theory suggests that long term weather patterns act on longer time scales, so large blocking patterns are thought to appear in a similar locations repeatedly over several months. With a good knowledge of blocking high patterns, the model performs with an impressive accuracy that is useful to the end user.

The version 3 weather forecast product was produced for winter 2010/2011 and demonstrated clear success when validated against UK Met Office data. It predicted below average temperatures and precipitation for all the UK regions. The results are consistent with knowledge of a strong blocking pattern (with a maximum index of 10 on our scale).

The modelling undertaken at Weather Logistics Ltd produces regional-seasonal predictions that are probabilistic in nature. Two different blocking sizes are used for the modelling, located at two different locations. The four possible blocking diversions are then ranked in an order, to be combined by logistic regression and generate the appropriate likelihoods of weather events on seasonal time-scales. The raw output consists of 24 different weather conditions for each season that are compared to the average atmospheric conditions. A global warming bias and 1961-1990 climatology of British Isles temperatures are added to the anomaly value to produce a final temperature prediction. The seasonal weather forecasts at Weather Logistics Ltd comprise of several additional weather components (derivatives) including: precipitation anomalies, storm tracks, air flow trajectories, heating degree days for household utility bills, cooling degree days, heat wave and the snow days odds.

External links + Seasonal Weather Forecast Downloads

Red box.png * Weather Logistics Ltd: Jet stream - Blocking interaction model (5 to 9km) jet stream - blocking interaction to simulate large scale and long term air flow for the British Isles. Designer Weather Climate / Heating Energy Demand (.xls) Code for "Jet Stream Blocking" Model (wiki) Autumn Forecast A Cold Winter? Business Forecasts Twitter: @cjnankervis

References

Red box.png 1. 'http://www.weatherlogistics.com/wordpress/?p=740' overview of jet-stream / blocking interaction model, March 2011, 'http://www.weatherlogistics.com/?p=740'

2. 'http://www.weatherlogistics.com/Seasonal.pdf' The Technophobes Guide to Seasonal Forecasting in the 21st Century, August 2009, 'http://www.weatherlogistics.com/Seasonal.pdf'

3. 'http://www.weatherlogistics.com/Software_Outputsv3.pdf' Validation of jet-stream / blocking model, Winter 2010/2011 (Version 3)
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