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Weather Forecast Air Temperature Range Accuracy Research
Article
Author : Perić Željko ( home page ) ( mail adress )
Date : 04.07.2017
Article Title
Weather Forecast Air Temperature Range Accuracy Research
Overview
Several years ago I have published article called Meteorology - Current Weather And Forecast Observations. The purpose of that article was to share knowledge about developing computer program for downloading and displaying specific meteorological data from a remote Internet server. At that article are shown results of one month research of weather forecast accuracy of four randomly selected Internet weather forecast services. The purpose of that was to find out the actual usability of developed computer program, that collects and presents meteorological data from those services.
The purpose of this article is to show results of another similar research compared to those from above mentioned article, with possibility to determine changes in weather forecast accuracy over passed years, and to confirm or deny previously established computer program usability.
Accuracy Notice !
This research and all research results shown in this article are based on the data collected from the Internet servers of listed weather services. For accuracy of those data there is no any kind of guarantee, so the results are declared approximate and it should be taken with reserve.
Research Methods
Main research method was based at periodically collecting air temperature range data of weather forecast for selected Earth location determined by its longitude and latitude, from selected Internet weather forecast service, for the next four days from selected date, and comparing those data with actually measured and officially published data for the same location, from referent Internet weather service. For collecting weather forecast data was used computer program " Current Weather&Forecast Observations ". For gathering measured temperature data was used computer program " Air Temperature History in Serbia ".
Selected location :
decimal latitude 44.8000
decimal longitude 20.466667
altitude 133 m
Selected Internet forecast weather services :
Aeris Weather ( former HAM Weather )
Selected weather forecast dates :
13.06.2017
20.06.2017
26.06.2017
02.07.2017
08.07.2017
Selected reference Internet weather service :
Two different accuracy calculation methods are applied to collected data:
Percentual accuracy calculation I Falling out from the announced temperature range
Percentual accuracy calculation II Absolute temperature range differences
Percentual accuracy calculation I method is simple, compare two temperature ranges and for each 0,1 °C of measured air temperature range that is out of forecast air temperature range, accuracy is decreased for 1% out of 100%.
Example :
Announced temperature range for observed day is 10 °C/30 °C.
Actually measured daily min and max temperature is 12.2 °C / 31.5 °C.
Calculated accuracy is 85,00%, since that measured max °C temperature is out of announced temperature range for 1.5 °C.
Measured min °C temperature is inside announced temperature range, and calculated difference is 0 °C.
This calculation method shows how accurate is weather service at predicting min/max temperature range.
Main flaw of this method is when weather service starts predicting temperature range with enlarged difference between announced min and max temperature. For example announced temperature is from 10 °C to 40 °C and measured temperature is from 20 °C to 30 °C. With 30 °C difference between predicted min and max temperature, weather service shall " always be 100% accurate :) " . This error can be avoided by second accuracy calculation method.
Percentual accuracy calculation II method is similar to previus one, for each 0,1 °C difference of measured min and max air temperature and announced min and max air temperature, accuracy is decreased for 1% out of 100%.
Example :
Announced temperature range for observed day is 10 °C / 30 °C.
Actually measured daily min and max temperature is 12.2 °C / 31.5 °C.
Calculated accuracy is 63,00% since that measured min °C temperature, is different from announced min temperature for 2,2 °C, and max °C temperature is different from announced max temperature for 1,5 °C. Absolute difference is 3,7 °C.
This calculation method shows how accurate is weather service at predicting min/max temperature.
By combining results of those two calculation methods , we can make hi quality decision on weather service accuracy.
Collected Data and Accuracy Calculation
Collected data and accuracy calculation with comments are attached to this document as PDF archive.
Weather Forecast Air Temperature Range Accuracy Research Data
Research Results
Percentual Accuracy Calculation I
Comparative Average Percentual Weather Forecast Air Temperature Range Accuracy Research Results
As shown at Percentual accuracy calculation I graph, the approximate average accuracy of predicted temperature range for the four day weather forecast of selected Internet weather services is increased from 77,75% to 87,16%. Individually, greatest improvement was made by World Weather Online, then by Weather Underground and then by Yahoo! Weather. Unfortunately Aeris Weather has drop down its weather forecast accuracy and it seems that changing the name of the service did not make it more accurate. To be honest I really liked their previously name HAM Weather.
Percentual Accuracy Calculation II
Comparative Average Percentual Weather Forecast Air Temperature Range Accuracy Research Results
At the second graph can be spotted before mentioned main flaw in Percentual Accuracy Calculation I method. Observe World Weather Online result and compare it with result at previous graph. It explains exactly how this weather service became so accurate at predicting temperature range. The average approximate accuracy is 65,55%. Any way, results are excellent considering that they are related to four day weather forecast, especially for Yahoo! Weather service, where approximate average temperature deviation of predicted min/max temperature compared to actual one is not larger than 3 °C.
Conclusion
Accordingly to research results, and tankfully to impressive weather services accuracy,
final conclusion is that computer program " Current Weather&Forecast Observations " has excellent usability.
Article Copyright
Copyright © 2017, Perić Željko, periczeljkosmederevo@yahoo.com
Article Licence
This article and attached PDF document archive is Public Domain Dedication.
All the best,
Author
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