Why So Cold? It’s the Jet Stream
[Via Booman Tribune]
Yes, we are having record cold snaps here in the East and Southeast. Global warming must be bunk then, right? Not so fast. Out West, its nice and toasty with unusually warm temperatures. Take a look at this map from the National Weather Service.
So why the big divide between East and West? Isn’t the temperature gradient between colder and warmer supposed to be more a North and South thing? Well, maybe once upon a time. Unfortunately, we are experiencing dramatic changes to the pattern of one of the biggest drivers of our climate on the North American Continent – the Jet Stream -and the rapid rate of the warming in the Arctic is the cause.
The map up top shows the areas of the US where the highs (red) and lows (blue) were different from the average January weather. The lows allowed cold air from Canada to spill into the US.
And here is a map showing the departure from the average temperature for January (red is warmer):
All due to where the jet stream falls.
This is pretty much what the models have been saying for much of the last decade. The Arctic warms at a faster rate than the temperate latitude. As the Arctic warms, it alters the shape of the jet streams, making them wavier, like hitting a key on a piano makes the sound louder.
Here is a larger version of picture at top where you can see the other strong ridge from the Atlantic that squeezed the cold air further down.
This means that cold air from the Arctic now dips down further into the US (for those who want more in depth information).
And the same models show more high ridges off the coast of the western US, keeping our skies clear.
So we get a very cold East while the West is warmer than normal. Plants are already starting to bloom. The skies have generally been clear and when it does rain, it pours, because of atmospheric rivers from Hawaii.
These rivers bring intense but pretty localized rain. The rest of the West still sees drought conditions. Several of them saw some of the warmest, driest months on record.
This low jet stream also kept a lot of Gulf Coast moisture from coming end, keeping Texas drier than normal.
This also fits the models which have suggested that the Seattle area will get about the same amount of rain as before, just all at once rather than in a long drizzle.
Every once in a while, these strong jet streams are disrupted and we return to the normal pattern of west to east cold fronts. Seattle gets cloudy and rainy, the rest of the country sees a mostly mild drop in temps.
But for now, the new normal may well be like this, with Seattle clear and dry and much of the rest seeing a large drop in temperatures.