Although it’s the peak time of the year for strong storms in the North Atlantic…
What’s been especially noteworthy about the winter’s weather is the frequency and intensity of the storms spawned in the North Atlantic. Yes, it’s the third extraordinarily intense North Atlantic bomb cyclone in 10 days. And that’s unprecedented!
This is the peak time of year for bomb cyclones in the North Atlantic due to the insane power of the jet stream and intense air mass differences that tend to move over moisture-rich waters.
But, what’s been especially noteworthy about the winter’s weather is the frequency and intensity of the storms spawned in the North Atlantic.
Normally, just a few of extratropical cyclones see their minimum air pressure drop to 930 millibars or lower.
Energized by an unusually powerful jet stream — a highway of air at about 30,000 feet that is powered by the thermal contrasts between air masses — these weather systems are developing rapidly and reaching extraordinary intensities in a region already known for strong winter storms.
Winds in the core of the jet stream are forecast to be as strong as 240 mph late Friday, which could lead to another record for the fastest transatlantic flight, first broken Sunday.
The Arctic Oscillation
The Arctic Oscillation (AO) is a climate pattern characterized by winds circulating counterclockwise around the Arctic at around 55°N latitude.
When the AO is ‘positive’, a ring of strong winds circulating around the North Pole acts to confine colder air across polar regions.
In its negative phase, the AO is weaker and more distorted, allowing southward penetration of colder, arctic airmasses and increased storminess into the mid-latitudes.
We are currently in a positive state, with a very strong jet stream, low pressure predominating near Greenland and a ridge of high pressure to its south in the northeastern Atlantic.
That ‘positive’ Arctic Oscillation is one of the main reasons winter has been absent in much of the eastern United States and parts of Europe, and it’s helping to turn the North Atlantic into a virtual bomb cyclone express lane.
The wind and rain may steal the headlines as #StormDennis batters north-west Europe this weekend, but the temperature anomalies will be truly staggering.— Scott From Scotland (@ScottDuncanWX) February 15, 2020
Overnight temperatures in the mid-high teens Celsius for Central Europe and reaching 25°C in southern France?
In addition to the deaths and damage from Ciara, the winter’s North Atlantic storms have also affected North America.
Last month, for example, Newfoundland and Labrador were buried by one of their worst blizzards on record, when a storm underwent rapid intensification and piled snow up to the second and third stories of buildings in downtown St. John’s.