To describe the large-scale atmospheric circulation on a given day, we often use patterns. An example pattern is the North Atlantic Oscillation (NAO), which I’m going to focus on here. In general, the NAO is a measure of the pressure difference between the Azores high and Iceland low, and is thus intrinsically related to the… Read More The many faces of the NAO
I’ve recently added some additional products from the NCEP Climate Forecast System version 2 (CFSv2) to my site — namely, forecasts of the weekly-average 500 hPa geopotential height anomalies for the next 4 weeks, and forecasts of the monthly-mean 700 hPa geopotential height anomalies over the next 6 months. These sit alongside the 44 day… Read More CFSv2 ain’t that bad: tips on using long-range forecasts
The atmosphere is a chaotic system with an infinite number of configurations – the weather pattern on any specific day has never before been exactly the same everywhere. Thus, it is extremely difficult to link a specific weather event to climate change. And yet, when significant weather occurs, discussion immediately jumps toward climate change –… Read More Weather and climate records are not mutually exclusive
This article originally appeared in the February 16th 2020 edition of The Sunday Times, and was co-written with Shingi Mararike. Every winter Britain gets hit by a series of storms. Ciara and Dennis are just the latest — but with two key differences. The first is their strength. Our storms get their energy from temperature… Read More The link between climate change and Britain’s winter storms
In the UK, it’s currently mild – very mild. Provisional data through the 9th shows the mean Central England Temperature (CET) is running at 7.5°C, which is 3.9°C above the 1961-1990 average. The large-scale pattern during the month so far (Fig. 1) has been characterised by a ridge extending from the Azores to Europe, and… Read More January 2020: Memories of January 2007
The title might seem rather obvious – or a surprising statement coming from me! But what I seek to achieve in this short blog post is provide a simple reminder that historically cold weather has indeed happened without a sudden stratospheric warming (or significant stratospheric polar vortex disruption). The role of the stratosphere can sometimes… Read More There’s more to the UK winter than the stratosphere
Lee, S. H., P. D. Williams, and T. H. A. Frame, 2019: Increased shear in the North Atlantic upper-level jet stream over the past four decades. Nature, https://doi.org/10.1038/s41586-019-1465-z. What is the key result of the study? Our study shows that the annual-mean vertical west-to-east (zonal) wind shear over the North Atlantic at aircraft cruising altitudes (within the… Read More 10 FAQs on “Increased shear in the North Atlantic upper-level jet stream over the past four decades”
May 23rd, 2019. Day 4 of our 2019 chasecation. Only a few days after the infamous and frustrating “high risk bust” in Oklahoma on May 19th (which remains the worst chase day I’ve had), we found ourselves in the Texas Panhandle under a Moderate risk – having driven all the way from Missouri the preceding… Read More Canadian, TX tornado – May 23 2019
If I followed up every time Donald Trump opened his mouth on climate change with a blog post pointing out where he was wrong, I’d have no time left to do anything else – but this one is a bit more special. This week, Trump visited the U.K., and part of that visit involved a… Read More Trump on climate change: what he should have said
The stratospheric Polar Vortex is currently at record-strong levels, based on the metrics of 10 hPa 60°N zonal-mean zonal-wind and 60-90°N average temperature. This is likely to be due to a combination of the timing and duration of the major Sudden Stratospheric Warming (SSW) in January: the duration of easterlies (most of January) shielded the… Read More Final Stratospheric Warmings
