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The National Centers for Environmental Information (NCEI) calculated climate normals every ten years for the previous 30 years, so the next time normals are calculated will be in 2031 for the period 2001-2030. If you were not one of the CoCoRaHS stations for which either provisional or pseudo-normals were calculated, here is what you can do to be sure that your CoCoRaHS station makes the cut in 2031. A station with as little as two years of complete data can qualify for pseudo-normals. Pseudo-normals are estimates of monthly precipitation totals and month-to-date and year-to-date totals scaled to match them. To qualify for pseudo-normals a station must: - Each calendar month is complete with daily observations in at least two years. Zeroes need to be recorded. For example, if a station has six years of observations, and each calendar month is complete in at least two of those six years, the station qualifies.
- No more than ten days in multi-day accumulations in any year/month
- Multi-day accumulations no longer than five days
- Multi-day accumulations must not cross over the start/end of a month
To qualify for provisional normals, a station must meet the following criteria: - Each calendar month is complete with daily (not multi-day) observations in at least 10 years. NCEI requires daily values for this criterion in order to be able to calculate daily normals.
- It does not have to be the same 10 years that are complete in different months. For example, if an observer always goes on vacation in July and either accumulates or misses observations during that month, the station will not qualify, even if every other month is sufficiently complete.
- No more than ten days in multi-day accumulations in any year/month
- Multi-day accumulations no longer than five days
- Multi-day accumulations must not cross over the start/end of a month
In 2031 it’s possible that many CoCoRaHS stations could qualify for World Meteorological Organization (WMO) standard normals. That would mean that every calendar month is complete in at least 24 years (80% of 30).
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