Cityscapes Could Impact Hurricane's Path, Study Says

A team of researchers at the University of Hong Kong developed a computer model to track the movement of a simulated tropical cyclone traveling across varying terrain, and found that big cities such as New York, Miami, New Orleans and Houston could act as magnets for hurricane landfalls.

How so? The results of the research, which will soon be published in the Journal of Geophysical Research, indicates that tropical cyclones tend to be attracted towards areas of higher friction. Therefore rough areas of land, including city buildings and naturally jagged land cover might actually attract what would ordinarily be passer-by hurricanes.

To obtain that conclusion the team modeled the effects that different terrain has on these storms to determine how cities that lie in the path of a hurricane change the storm's motion. They found that rough cityscapes (and forests alike) trap and compresses air, forcing it up into the atmosphere, which translates to added energy in the storm and a pulling of the center of circulation towards the rough region. Their model suggests that a city can cause a hurricane to swerve from its predicted path by as much as 20 miles.

Interesting, but not a concept I haven't heard before. Just look at that last-minute easterly jog of Charley right before landfall in southwest Florida! Friction all the way!

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Northeast Tornadoes Fail this Weekend. Why?

This past weekend featured two solid days of severe weather in the northeast accompanied by torrential rains and scattered violent storms containing damaging winds, hail and even funnel clouds. That's right... funnel clouds! Tornado watches were posted for a good part of the day Saturday for New England, and those watches extended southwards into the mid-Atlantic on Sunday. But while tornado activity was heightened in the cornfields of the rural midwest this past weekend, not too much actually materialized for the hilly terrain of the northeast or along the city-sprawling I-95 corridor.

OK, why the descriptive detail? Well, I've been reading several blogs about the subject this weekend and even this morning, and I want to set something straight about the myth (yes, it's a myth) that tornadoes don't occur, or are hard to form, in both mountainous terrain and cities alike.

While topography does influence how often tornadoes form, other stronger atmospheric processes determine where and when tornadoes form, meaning even those is rugged mountainous terrain are at risk. Storm systems that generate tornadoes over the midwest often rely on large amounts of moisture from the Gulf of Mexico and high quantities of atmospheric energy which aren’t always available once systems cross the Appalachians. However, if those systems remain intact, these areas, such as the Northeastern United States, are equally susceptible.

Tornadoes in cities? I can easily recall several U.S. cities being hit by a tornado in the last decade or so... Oklahoma City, Fort Worth, St. Louis, Miami... even Salt Lake (both urban and mountainous)! But in the northeast? Not so much. While it is possible, the atmospheric dynamics explained above typically do not support the development of tornadoes reaching cities like New York, Boston and Philadelphia, per se. However, the fact is tornadoes have a long history of hitting big cities and when they do, they usually cause a great amount of damage because a lot more debris is generated.

In conclusion, the severe weather threat is long gone now and the weather is gorgeous! Sadly, residents in Ohio and Michigan were not so lucky as tornadoes there as strong as EF-3, have caused extensive damage and loss of life.

Mild days and cool nights are the rule this week in the northeast... enjoy it!