It’s not happened yet that one of the new-style extra-large hurricanes arrives late in the season to collide with a deep cold trough.
The pictures being drawn must be confusing a lot of people.
But now most of the models are saying it will land. Why should a vigorous jet heading northeast “pull” a storm to the west?
That’s the wrong way to think of it. A vigorous jet stream is associated with a steep temperature gradient, i.e., a front. What happens with a front is that it is a battle between the rotation of the earth trying to keep winds going round in circles and not mixing, versus the temperature differential that tries to mix everything up. And then fronts develop a kink, a spot where the cold air stops advancing. warm air starts riding up over the kink. This is a midlatitude baroclinic storm. It’s what drives most of the weather in spring and fall in the northern US and southern Canada (and the southern US’s weather in winter). It’s similar over other landmasses at comparable latitudes, but for various reasons North America is particularly good at doing this.
So the main thing about the kink is that warm, surface air rides up over it. And on Monday, such a kink looks likely to develop somewhere near Rochester NY, where the red line meets the blue:
The warmer the surface air, and the colder the front, the more spectacular and energetic the collision. If this occurs near the coastline, it can be especially spectacular because of the extra boost in warmth of the warm sector provided by the gulf stream. And if there’s some spin (vorticity) around, the spectacular class of storm called a nor’easter results. These are generally responsible for blizzards.
Which brings us to our peculiar situation right now. Everything seems to be falling into place for a nor’easter-hurricane combination. I’m not sure if there’s any precedent for this, and it’s beyond my abilities to get much further here, but the experts and the models seem to be saying that these phenomena will reinforce each other. A warm-core nor’easter? A frankenstorm? A blizzacane?
People get pretty worked up about weather predictions these days and it’s little wonder. But the scariest model runs are, in fact, pretty darned scary:
The winds in that scenario are not enormous for a hurricane, but they are extremely widespread. And the cold air behind the storm could even lead to a combination of tropical storm winds and snow; a spectacular blizzard.
Please note – this is just a scenario, not a prediction. But it seems to be in the realm of possibility.
Climate related? Well, Sandy is one of the new breed of very
geographically large, err, very wet (see comments below) tropical storms. And the jet stream is in one of its wamdering moods, also associated with climate change, where what little cold air there is finds its way more than ordinarily far south. As usual with an individual event, theer’s no direct causality. But if something like this pans out it certainly will be perceived as an example weather weirding. And it’s another sort of event that the ever-more-wobbly system manages to serve up to us for our consideration.
Those of us who were in Chicago in the late 70s can remember an election turning on a bad response to severe weather. Risks of power outages and other forms of chaos just before an election could have some effect on people’s moods, and on the logistics of running an election. And the trajectory of the election is also unfortunate, toward a close election, where issues of fraud and vote suppression and miscounting become important.
It’s hard to imagine exactly what will come out of this witches’ brew, but there’s plenty of ways that hopes for an uneventful couple of weeks might not pan out.