Major hurricane drought

[OnlinePoker]

I was just curious to know when the last major Atlantic hurricane (Cat 3 or higher) hit the U.S. and found it was Wilma in October 2005. I then found this interesting study from last May when the drought record was beaten. There's an interesting figure in it (figure 1) that has a logarithmic scale for the number of years you would have to wait for a similar drought to happen. If we make it to October without one hitting, that will be a once in 500 year event. If we go another year to year 12, that will be a once in 900 year event. What is keeping strong hurricanes from reaching the U.S.? Is this concrete evidence of the IPCC predictions of fewer tropical cyclones but more intense in some locations?

http://onlinelibrary.wiley.com/doi/10.1002/2015GL063652/full

[teach1st]

1. Changing patterns?

Hurricanes’ Centuries-Old Patterns May Be Shifting
May 2015

One emerging theory is that hurricanes appear to be reaching peak intensity farther north, he said. Tropical cyclones around the globe are reaching peak intensity closer to the poles, he said, meaning in the Northern Hemisphere, farther north and in the Southern Hemisphere, farther south.

What this means for the Atlantic hurricanes is that they are gathering strength farther north over open water and could increasingly take aim at targets north of Florida, from the Mid-Atlantic to New York and Massachusetts.

“That means that the Caribbean may see a decline in hurricanes,” Eman­uel said.

Full article

[Warpy]

2. I wouldn't bet on that

The pattern for the last few years seems to be that they develop father west and hit farther south.

This year, the African storms seem to be falling apart just off the coast. The Pacific season has been fairly active so far.

[localroger]

3. The jet stream has shifted further south

The biggest pattern change is that Gulf storms are getting blown out into the Atlantic instead of hitting the Gulf Coast. Sometimes they are looping back and hitting the east coast, but by this time they are further north and weaker; Sandy was bad but it wasn't even technically a hurricane any more when it hit land. This seems to be related to the collapse of the circumpolar vortex which is also the reason we've had a few wicked cold snaps in the deep south and eastern seabord; air which normally stays trapped over the Arctic ocean is moving further south, and warmer air moves up to replace it melting the ice faster, which reinforces the destabilization of the polar vortex.