Thursday, November 24, 2022

Environment Agency rainfall data now available in WOW!

The Met Office and Environment Agency have a long history of working together in partnership. One of the many things that unites the two agencies is our involvement in citizen science, and our networks of voluntary observers, such as those that contribute to WOW.

 Alongside their manual rainfall observers, the Environment Agency operate a network of approximately 1000 automatic telemetered rain gauges across England. These automatic rain gauges measure the amount of precipitation falling at their given location. The data from these gauges is used by the Environment Agency to provide flood warnings and forecasts, and to manage other water resources.

A Rainfall API* from the Environment Agency is now available, providing accumulated rainfall totals from this network at 15-minute intervals.

Environment Agency automatic rain gauge site in Devon

This data, provided under Open Government Licence is now routinely uploaded to WOW as it becomes available on the API. It is displayed in hourly accumulations on the WOW map. The rainfall data can be visualised by specifying the time and date of interest, selecting the ‘hourly rainfall’ layer on WOW, and ensuring that the ‘EA Rainfall Sites’ filter is selected.  


If any rainfall has been reported in the specified hour, then it will be displayed on the map.

By selecting an individual site from the map, more detail can be seen, with the hourly total separated into 15-minute accumulations.

The data can be analysed further in a tabular view by selecting ‘view’ or ‘view full observation’. Please note that there are three rainfall parameters available in WOW, see below for their definitions. It is the ‘Rainfall (mm)’ parameter that is used for this particular data set.

Rainfall (mm) - Accumulated rainfall since the last observation. In the case of this Environment Agency data this is a 15-minute accumulation.

Rainfall Amount (mm) - Rainfall accumulated in a 24-hour period, this parameter is provided by some automatic weather stations.

Rainfall Rate (mm/hr) - An instantaneous rainfall rate, this parameter is provided by some automatic weather stations.

Hourly rainfall accumulations are used by Meteorologists, and Hydrometeorologists, such as those in the Flood Forecasting Centre (another Environment Agency and Met Office partnership). Rainfall observations on the ground are used in combination with rainfall radar data. Monitoring rainfall is essential to inform future weather and flood forecasts and warnings.

Since this data set has become available, the number of observations received by WOW has increased significantly from 1.2 million observations per day in September 2022, to 1.35 million observations per day in October 2022. The EA automatic rainfall data accounts for roughly 150,000 of those daily observations. 


Thursday, February 24, 2022

Using WOW observations to capture high impact weather events

 Weather observations recorded by the WOW community are extremely valuable to research and development work at the Met Office, particularly for what we call “nowcasting” (0-2 hour forecasting). One application that directly uses your [BC1] WOW observations is our Mesoanalysis system. This system produces a rapidly updating UK-wide picture of current weather variables (such as pressure and temperature). This is useful to forecasters for situational awareness and as a tool to understand how the environment is evolving and where high-impact weather such as thunderstorms and strong winds may be likely to develop.

WOW observations are quality-controlled and bias corrected before being interpolated to produce a best estimate of current weather over the UK. The high volume and density of the network of WOW sites allows us to capture regional weather features more accurately than using conventional weather observations alone. Over the last year the mesoanalysis system has been developed to combine WOW observations with Numerical Weather Prediction (NWP) model data. Using model data allows us to extend the domain over the sea and help fill the gaps and give more confidence over regions with sparser observations.

Here we give a recent example where WOW data were found to add value during a high impact event over England last Halloween.

On the morning of 31st October 2021, a small low pressure system developed along a cold front off the south coast of England, with high wind speeds to the south of the low pressure centre. This so-called ‘mesolow’ made landfall over Dorset around 8am and tracked north-eastwards across England, passing over the North Sea off the Yorkshire coast around 12 noon. It brought with it significant wind damage to trees and property and disruption to the public transport network (Holley et al., 2022).

Although this mesolow was apparent in NWP model output, there was some uncertainty in the intensity and exact positioning of the feature. By making use of WOW observations, the mesoanalysis system was able to produce an accurate representation of both the location of the low pressure centre and the high wind speeds associated with it, as seen in the figure below.

Figure of the wind (arrows) and pressure (contours) fields from the mesoanalysis over Dorset on the morning of 31st October. This is overlaid by radar data to help show the accurate positioning of this feature.

By using WOW observations forecasters are able to improve their situational awareness of features like the one seen in this example. This information can be used to improve warnings and provide advance notice to areas likely to be impacted. The more observations we have, the better this mesoanalysis system can be, so thank you for continuing to submit your data on WOW!

Holley, D. and members of TORRO (2022), Halloween windstorm and tornadoes in England, 31 October 2021. Weather. 

Tuesday, November 2, 2021

One Million Observations a Day!


This month, WOW has hit a major milestone in that we are now receiving 1 million observations every day from weather enthusiasts around the world!

WOW was launched in June 2011, with support from the Royal Meteorological Society and the Department for Education, for weather observers across the UK and now the world. The main purpose of WOW is to provide a platform for the sharing of current weather observations from all around the globe, regardless of where they come from, what level of detail or the frequency of reports. Now, the observations we receive are playing an even more vital role in forecasting as they are fed into Nowcasting to produce our very short-range forecasts.

These observations come from a range of sources including from our voluntary climate observers, weather enthusiasts with weather stations in their gardens that connect to WOW automatically and those who input their observations manually.

We would like to say a huge thank you to our dedicated users who have helped us to reach this milestone and we hope to continue to grow our user base and daily observation totals as WOW progresses.

Friday, June 11, 2021

WOW Updates Blog


We have some very exciting changes planned for WOW over the next few months which we would like to share with you.

The first change is updating Mapbox, which is the main map on the landing page, so that we have a map that is optimised for handheld devices such as phones and tablets. We are hoping this will enable more people to interact with WOW and be encouraged to submit data and impact observations to the website.

The next thing that we have planned are some user experience updates. A couple of years ago, the WOW team ran a small user experience project that identified several areas on the website that needed improvement to make them easier for our users.

These will include a new landing home page for the WOW website, providing more clarity on how to connect a weather station, improving the ‘create site’ entry form, a new ‘how to contribute’ page, improvements to ‘My site dashboard’ and to the ‘Enter an Observation’ page. The ultimate aim for these improvements is to make the site easier to use and to also attract new users who may want to get involved with WOW but aren’t sure how to do that in its current form.

Finally, we have identified that the logging in process can be seen as a pain point by some users and we are currently investigating ways that this process can be made easier. Once we know more, we will post an update on the blog.

                                        An example of how the new home screen might look.

If you have any questions regarding the updates, please email

Thursday, April 29, 2021

Is St Harmon really the coldest place in Wales? Or the whole of the UK?

By John Adams, current observer at St Harmon 2. 

When we first arrived in St. Harmon the local farming community were very quick to inform us that  we had moved to the coldest place in Wales, if not the whole of the United Kingdom. Some of them even sounded proud of the fact, but it was certainly not something we had given any consideration to ourselves before coming here. Being keenly interested in meteorology since a young child I was curious. A little investigation revealed that there used to be a Met Office climate and auxiliary observing station in the village during the 1980’s. On searching through the records on the Met Office website it soon became apparent that St. Harmon featured far more frequently in the list of coldest nights than one would normally expect. At the same time I had also observed from WOW that there was a hole in the observing network around Mid Wales, even in respect of personal weather stations. This is the story of my quest to establish whether St. Harmon really is the coldest place, and to try and fill the hole in the observation network, first with my own personal weather station and subsequently establishing St. Harmon no.2 voluntary climate station under the auspices of the Met Office.

Thursday, August 13, 2020

Record Breaking Temperature recorded at Cambridge University Botanic Garden: One year On

Just over a year ago, on Thursday 25th July 2019, a temperature reading of 38.7°C was recorded at Cambridge University's Botanic Garden. It was the highest temperature ever officially recorded in the UK, which made international headline news. Sally Petitt, Head of Horticulture, explains how weather is recorded at the Garden and the significance of these exceptional readings.

Activities within the Garden are varied and constantly evolving, but there is one daily task which has been part of our routine for over 100 years, and that is taking meteorological readings.

Today this task is carried out by Katie Martyr, Experimental Section Assistant, who succeeds a long line of dedicated weather observers, including John Kapor (Supervisor, Systematics). The role entails recording a range of readings including maximum and minimum temperatures, ground temperatures, rainfall, cloud cover, and wind speed and direction. Readings are taken at our weather station located in the Experimental Plots, at 9.00am Greenwich Mean Time (so 10.00am in summer), and capture data from the preceding 24 hours.

The station is monitored by the Met Office to ensure that it meets their requirements, and that there have been no changes to the site, such as new buildings or tree growth, which can influence microclimates. The ways of taking readings are relatively low tech, with most observations made using standard thermometers, measuring cylinders and visual observations. The maximum temperature is charted electronically on a thermometer housed in a louvred Stevenson Screen to ensure consistency of measurements. Readings from this thermometer are charted on to a computerised data logger. The reading is then taken by looking for the peak temperature in the preceding 24-hour recording period. All data is logged at the Garden and also with the Met Office which uploads the information on to their publicly accessible Weather Observers Website (WOW). It is this thermometer which took the record 38.7°C reading on 25 July.

In late July, forecasts indicated exceptionally high temperatures. During the week beginning 22 July, the temperature began to rise, and on Thursday 25 July it was evident that the temperature was abnormally high. Plants were wilting and being scorched, glasshouses and ticket offices had to be closed as they were too hot to bear, and staff were flagging - with some resorting to standing in buckets of cold water while potting up plants in the shade!

As usual, the readings for 25 July were not read until 10.00am on 26 July, when Katie excitedly measured a temperature of 38.7°C. This was noted and uploaded onto WOW. It was only later that afternoon the Met Office indicated that this might be a record temperature for the UK. We then waited for the Met Office to check our station before confirming that this was officially a new record. On 29 July they visited the site to calibrate the maximum thermometer computer, and to verify that the weather station and that none of the equipment had been tampered with. It was not until that afternoon that the Met Office declared that we had officially recorded a new maximum temperature for the UK of 38.7°C.

Inevitably this created a great deal of media interest and headlines. From our perspective, the real significance of this chance occurrence was not in reaching this temperature, but in knowing that our continued monitoring of weather here at Cambridge University Botanic Garden was valuable in defining this heatwave.  The University holds readings from our weather station dating back to 1904, though Met Office records show that we have been gathering valuable and continuous data for them since 1891. It is the historical significance of this data which is of real value to the Met Office and climate researchers as they are able to use this to establish how weather patterns are changing over time.

It also acts as a caution about what is happening to our environment, the inevitable consequences for the plants and animals around us, and the impact on our collections. If these new weather patterns become ‘the norm’, then we may need to adapt what we grow in the future. Mediterranean plants do well in our local conditions and there may be scope with changing weather to extend their representation. Conversely, we may also need to review whether we continue to bring in more moisture-loving, temperate species. 

Written by Sally Petitt, Head of Horticulture at CUBG


Monday, June 8, 2020

Attention UK Weather Enthusiasts

You may have noticed the two new links that have appeared at the top of the WOW Blog. These may be of particular interest to UK weather observers and enthusiasts, we hope you will find both interesting and useful;-

Daily Weather Summary

As the name suggests 'Daily Weather Summary' holds daily weather summaries from 1860 up to current day. Note these are a monthly publication and are usually available on the website around 6 weeks after the end of every month.
Each summary provides an overview of the weather conditions across the UK for each day based on observations from the network of Met Office synoptic and climate stations, including from our official network of Voluntary Climate sites. Each day includes a table of daily extremes for the UK for key climate variables including temperature, rainfall, sunshine and gust speeds.

 UK Climate Maps and Data

Here you will find a host of fascinating information relating to the UK climate, again all reliant on our network of official observing sites including Voluntary Climate sites, some of which have been recording weather information on behalf of the Met Office for in excess of 100 years. A particular highlight here is the UK Actual and Anomaly Maps section which takes you to a collection of gridded maps derived from Met Office and official Voluntary Climate site data which is interpolated to provide coverage across the UK of up to 1kmx1km resolution. Maps are available for daily, monthly, seasonal and annual timescales, as well as long term averages.

For more information about how the data from our Voluntary Climate Network, usually submitted through WOW, is used please see this blog post.