Category Archives: weather

Storm Ulysses

On 27th February 1903 a major windstorm hit the UK and Ireland, known as Storm Ulysses.

The 20th Century Reanalysis (20CRv3) includes a modern reconstruction of the storm, created by assimilating available observations of surface pressure into a state-of-the-art weather forecast model.

There is a problem however. The number of available observations over north-west Europe is limited as most have never been digitised from the original hand-written paper sources. Recently, the WeatherRescue.org project rescued millions of observations, allowing us to examine the value of this new data by rerunning 20CRv3 with the new data added.

The animation below shows Storm Ulysses in the original version of 20CRv3 (left) and an improved version (right) with added observations (black dots). The contours are of sea level pressure and the colours are the wind speed at 10m, with blue arrows showing the wind vectors. The new rescued observations have reduced the minimum pressure, which is also simulated with more confidence.

But, is this an improvement? The wind ‘footprint’* for Storm Ulysses shows an increase in simulated wind speed when adding the new pressure observations, and this is now a far more credible simulation given the known damage that occurred during this storm (also see this photo).

* This figure shows the maximum wind speed from the 3-hourly simulated data so is probably an underestimate of the maximum sustained wind speed.

Weathermen of Ben Nevis

For twenty years between 1883 and 1904, three intrepid weathermen lived at the top of Ben Nevis – the highest mountain in the UK – experiencing some of the worst weather the country has to offer.

Every hour, day and night, winter and summer, and whatever the weather, one of them would step outside and check the meteorological instruments, diligently recording the observations.

This was a uniquely Victorian-era endeavour. Science for the sake of science. Rather than exploring the world’s polar regions like some of their contemporaries, these Weathermen were exploring the atmosphere.

There was simply no other way of learning in detail about how the atmosphere changed with height without living at the top of a mountain. So that is what they did.

Continue reading Weathermen of Ben Nevis

U.S. Deep Freeze, December 2016

There had been speculation that record low temperatures would be coming to the United States in early December, and this had been framed as either evidence against global warming in general or that cold air outbreaks are increasing due to climate change.

World Weather Attribution (WWA) presents a quantitative study of this cold air outbreak. WWA researchers compute how rare the outbreak was and how it is affected by human-caused greenhouse gases. The analysis uses the same methods as WWA used in the peer-reviewed analysis of the cold extremes in the Midwest in the winter of 2013 – 2014 (van Oldenborgh et al, 2015). Continue reading U.S. Deep Freeze, December 2016

Extremes of 2014 in review

Was last year really the warmest on record? As soon as NOAA published its official announcement in January, this question invaded the web feeding blogs, online newspapers and forums with passionate discussions. Relevant or pointless? The question is not so much knowing whether or not a new record was broken. Should 2014 rank second or third, this wouldn’t change the big picture: last year, temperatures on our planet continued the existing long-term positive trend. On top of that, the story is a bit thicker than the one single number obtained when averaging near-surface air temperatures in time and space. So, 2014: year of extremes or warm year in a changing climate?

Guest post by François Massonnet, Université Catholique de Louvain, Belgium / Catalan Institute of Climate Sciences, Spain Continue reading Extremes of 2014 in review

Improving the weather from 96 years ago

Ideally, we would have observations of past weather everywhere for several centuries to reconstruct the state of the atmosphere and learn about its variability. But, we don’t.

Instead, all the observations ever taken would, ideally, be available digitally for everyone to use. But, they aren’t. Many past observations are buried in hand-written journals and logbooks, gathering dust in libraries and archives all over the world. Rescuing this data would be of great benefit to reconstructing past weather, as this example will show. Continue reading Improving the weather from 96 years ago