ASOS-HFM is a series of low precision but high frequency readings from ASOS weather stations. These values are currently rounded to a whole decimal Celsius value and transmitted in this fashion. Without the decimal digit in the data, the accurate Fahrenheit conversion cannot be made.
We’ve made improvements to the Climate Sight’s chart to show you accurately the possible values in a range.
The Precision Problem
Some whole digit Celsius values have smaller ranges that the original Fahrenheit could have been because of the way F to C conversions work. Some have as much as ±1.5°F range, while others have as little as ±0.5°F range when converted back to Fahrenheit.
You can now hover over the chart to see these ranges. The actual dots on the chart represent ASOS (METAR) high precision readings, while the ranges represent the ambiguity of the low-precision data.
25°C has a lower range of possible values than 24°C or 26°C, this is reflected in the chart.
SPECI Support
We’ve also added support for SPECI METAR readings, whether they are transmitted in low or high precision, and you’ll see that reflected on the chart.
Since we cannot accurately discern the value of a low precision reading, we have chosen not to show the midpoint as other sites do (including NWS) or show an incorrect conversion. Instead, we just show the range of possible values which correlate well typically with the higher precision ASOS readings available.
There are certain instances where it becomes evident how the ASOS-HFM value being misinterpreted due to rounding errors can throw off Prediction Climate Markets. You can read more in our rounding guide.
Next steps
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