By insideSail
Automated technical check · version 1 ·
A bulletin has more than one time
Separate issue, validity, observation and forecast to understand what you are reading.
In this guide
Original schematic illustration. Read the explanation and limitations in the lesson.
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A screenshot can preserve numbers while losing crucial information: when they were produced and when they apply. Before interpreting a forecast, learn to read its accompanying information. This makes a weather discussion more precise.
| Field | Question |
|---|---|
| Issue | When was the bulletin produced? |
| Validity | Which time or interval do the values concern? |
| Area | Which area is described? |
| Type | Observation, analysis or forecast? |
UTC and local time
UTC is an international time reference. Local time and UTC should not be mixed without identifying the conversion for the place and date. This lesson does not apply a fixed offset to every European country: the labels remain attached to the information.
A forecast is not an observation from the future
An analysis represents an estimated state at a time; a forecast estimates future development. Uncertainty is part of interpretation, especially as the horizon grows. A map colour or a value with decimal places does not establish certainty. Without a legend, time and area, a display’s apparent precision can mislead.
Learning starts with identifying the product and reading its official explanation. Weather passage planning, interpreting warnings and decisions in adverse conditions belong in reviewed application lessons.
The concept in a few words
Forecast validity
The time or interval to which forecast data refers; distinct from issue time.
Sources and references
- Coordinated Universal Time: an overview ↗
ITU / BIPM · 31 July 2023 · UTC as international time reference
Version: 31 July 2023. Jurisdiction: International.
Checked on - Surface pressure charts ↗
Met Office · Analysis versus forecast; uncertainty at longer ranges
Version: Institutional page. Jurisdiction: International.
Checked on - Coast and sea forecast guide ↗
Met Office · Forecast issue, validity and UTC
Version: Institutional page. Jurisdiction: United Kingdom forecast product.
Checked on
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