Spring 2025 rainfall anomalies (03xxx stations, 68 sites, with >=57 obs, and >=20 years in climate).
Sum of 24 hour precipitation reports at 0600Z. Anomalies with respect to end of month climate.
Season/Year:
24 hour ppn 06Z-06Z:
24 hour ppn 00Z-24Z: 		Plot Anomalies:
Plot Percentiles:
Plot with respect to:
*current season only		Whole Season:
Part Season*:
Reduce required ob count by:
Num years in site climate:>=
Wettest 10
Milford Haven Conservancy Board86.1 %
Culdrose74.8 %
Aberdaron73.1 %
Camborne71.9 %
Baltasound No 267.9 %
Plymouth, Mountbatten67.6 %
Islay: Port Ellen57.9 %
Fair Isle54.5 %
Pembrey Sands53.5 %
Stornoway Airport53.5 %

Driest 10
Middle Wallop11.5 %
Boscombe Down12.7 %
Lyneham13.3 %
Benson13.3 %
Leeming15.1 %
London, St James's Park16.1 %
Warcop Range17.0 %
Thorney Island17.5 %
Wight: St Catherines Point17.9 %
Heathrow17.9 %

Data courtesy of MetOffice and OGIMET

Usage
This map will show you seasonal rainfall anomalies or percentiles with respect to a climatology calculated from Open MIDAS data provided by the Met Office. Only seasons which have a complete record are used to create the climatologies. At present, you are only able to access rainfall data from 2021/2022, extracted from daily SYNOP reports (you can select the 24 hour total reported at 06Z, or a 00-24Z value constructed from 6/12 hour rainfall reports on the main synoptic hours). But in the future, I plan to add the entire MIDAS Open dataset.

You can choose to plot site specific anomalies, which is the percentage of either the mean seasonal rainfall, or, should you select "Part Season", the percentage of the mean value up to the point in the season for which data is most recently available. You can only select "Part Season" for the current season, as previous seasons will have a complete set of observations. Or you can choose to plot percentiles, which shows the position of the measurement relative to the climate max and min. If the measurement was equal to the median, this would equate to the 50th percentile for example.

The final options which you can select are to reduce the required observation count for the season you are plotting - if you are happy to accept sites where the record is incomplete, and you can also filter for sites which have a climate record equal to or longer than a certain length. This is useful if you want to see only sites which have a long period climate record; climate is much more likely to be exceeded for sites with just a few years data, but this of course is less significant than for a site which has many decades.

Clicking on a point on the map will bring up a pop-up with further statistics, and a link to a second page which has more detailed information about the site climate, and how the plotted measurement compares.


Additional information about percentiles.
Climatology percentiles have been calculated for every day of every complete month, season, and year available in the Open MIDAS dataset. They have been calculated at a resolution of 1%, with current values falling between percentiles assigned a weighted mean percentile between each integer percentile value. Where current values exceed climate, an "excess" percentile is calculated, this represents the distance above the maximum as a proportion of the climate span (distance between climate max and climate min). A similar approach is taken with current values that undershoot the climate min.


CAVEAT EMPTOR
Current data is calculated using non-quality controlled SYNOP data. With this being cumulative rainfall, both missing data, and incorrect data if present on the SYNOPs, will affect the overall totals and percentages shown. This will also feed into the climatologies for the site in question, if the season is complete. So please be careful and use your judgement at all times when interpreting the maps and graphs.


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