Hurricanes, Global Warming and Rainfall Risks

Hurricane Humberto Weather Underground First, I suppose, the good news: The third official hurricane of the Atlantic season did not follow in the footsteps of its two predecessors and reach Category 5 intensity. While Hurricane Humberto did strengthen quite rapidly (see radar loop) after forming yesterday and managed to become a strong Category 1 storm before striking near the Texas/Louisiana border, it ran out of ocean much too quickly to become a major hurricane.

Both Houston and New Orleans should consider themselves very, very lucky that Humberto didn't have another day to intensify (and possibly change course) over the warm, hurricane-friendly Gulf of Mexico. But while Humberto won't deliver sustained hurricane winds above around 85 miles per hour at its landfall point, the slow eastward forecast track across the Gulf Coast states poses a serious rainfall risk. It's important to remember that hurricanes don't just cause damage through wind and waves -- they also dump massive amounts of tropical moisture. A storm that moves slowly over land or, even worse, stalls over a particular place, can create tremendous and often life-threatening flooding. A little noticed aspect of how global warming ought to change hurricanes is relevant here, incidentally: Because a warmer atmosphere retains more water vapor, hurricanes and tropical storms are expected to rain more in the future, and indeed, are probably raining more already on average. It's just another way in which climate change could be potentially increasing the damage caused by these storms.

Your "Storm Pundit" has a personal stake when it comes to Humberto, by the way -- I head to my hometown of New Orleans, Louisiana, on Friday to celebrate my 30th birthday and, supposedly, the various achievements of my twenties (like, say, writing a book on hurricanes). But now I can't help wondering whether Humberto's remnants will be either in the path of my airline flight or, perhaps worse, partly hanging over the city itself.

Ah, ironies.

New Orleans probably won't experience the bulk of the rainfall, of course. The National Hurricane Center is much more worried about other parts of Louisiana, southwest and northeast of the city -- some of which could experience over a foot of precipitation. And also, let's face it, the experts may be worried about this fact: Some respected hurricane models (see below) suggest Humberto could pull a big loop over land and eventually come back out over the Gulf of Mexico -- potentially even traversing waters with far higher heat content in a second incarnation: Weather Underground While these scenarios are not yet the part of the official forecast, they could be trouble. Stay tuned.

Tropical Storm Ingrid Today?

Tropical Depression 8 Weather Underground It's around the traditional peak of hurricane season, so we ought not to be surprised that there's also a storm brewing out over the central Atlantic, possibly on its way to a point just north of the Caribbean over the next five days. However, the experts don't foresee a strong storm developing here within the forecast period -- while waters are warm, atmospheric conditions aren't expected to be very conducive. Nevertheless, we may get Tropical Storm Ingrid today -- the ninth named storm of the 2007 Atlantic season. At this rate, and especially in light of La Nina, the forecasts of 15 to 17 named storms this year may turn out to be right on target.