A few quick weather ideas today …

The hurricane season starts tomorrow, and Drs Gray and Klotzbach of Colorado State University have updated their hurricane forecast for the year … somewhat. They haven’t changed their ideas at all from their original forecast last December, calling for 17 named storms, and 5 intense hurricanes. That’s slightly over what the National Hurricane Center is calling for, and more than what Accuweather’s Joe Bastardi is calling for, with 3 major storms making landfall, with the most activity in the Texas area early in the season, and the Carolinas and East Coast late in the season.

Meanwhile, protesters are at the headquarters of NOAA in Maryland calling for the resignation of National Hurricane Center Max Mayfield because he refuses to endorse the idea that global warming is causing the increase in tropical activity. Mayfield’s view is that the uptick in hurricane activity is the result of a multi decade cycle that has repeated itself over the years, and happens to be in a strong phase now. He does not believe that global warming has anything to do with it. Accweather’s Bastardi has a similar opinion in his article from the Durham Herald Sun.

Metro Atlanta may get its first real chance of significant rainfall since back on May 10th on Thursday and Friday. After spending the last two weeks dominated by a high pressure ridge, the trough that had been further west is moving east, and could bring some rainfall, although it appears the worst of it will be further north. After all the heat over the last ten days, I’ll be glad for some rain.

And, the weather service has updated its forecast for June. They predict that warmer than normal temperatures will dominate much of the southern plains states, from Arizona, New Mexico, and west Texas north to the Canadian border. Below normal rainfall is predicted in an oval centered over Nebraska, and extending southeast to the Tennessee-Alabama border. For Georgia, the weather service is calling for equal chances of above or below normal temperatures and precipitation.

The shorter term forecast is for below normal temperatures and normal to below normal rainfall in north Georgia from the 6th to the 14th. They have been advertising this drop to below normal temps for the last few days, and it seems like they’re pushing it back much the way they kept predicting the current warm spell to start in early May, and then pushed it back until it finally got here. We finally got the above normal temperatures, and I suspect that we will see the cool spell as well.

With the start of the 2006 hurricane season less than two months away, Dr. Gray of Colorado State University has released his 2006 hurricane predictions. If Dr. Gray and his team are right, we’re in for another volatile weather season.

For the season, which runs from June 1 through November 30th, Dr. Gray predicts 17 named storms, with 9 hurricanes, 5 of which will be intense, or categories 3-5. In comparison, last year, the center predicted 13 storms, and 7 hurricanes, well under what actually happened. Overall, the probability of hurricane landfall in the United States is 55% above average.

The center predicts an 81% chance of a hurricane striking the US Coast, with a 64% chance of striking the east coast, and a 47% chance of a strike on the Gulf coast. This is strikingly similar to early predictions by Joe Bastardi of Accuweather, who also believes that the east coast is likely to get hit in 2006.

Dr. Gray also addresses the issue of the effects of global warming on the large number of hurricanes we’ve seen over the last several years. Like other hurricane experts, including Dr. Max Mayfield of the National Hurricane Center, he believes that we are at the middle of a long range pattern of greater than normal hurricane activity that began in 1995. This pattern, called the Atlantic Ocean thermohaline circulation. This phenomenon is driven by the salinity of the Atlantic, and is believed to have nothing to do with global temperature change.

By now, I think that most people have had a chance to understand the devastation that Hurricane Katrina caused in Louisiana and the Gulf Coast. After watching the news tonight, I am amazed not only at the destruction in Mississippi and Alabama that the storm caused, but at the fact that the predictions made by the weather service for New Orleans seem to have come true.

While the country will have to deal with the effects of Katrina (and everyone is encouraged to contribute to the Katrina Relief effort), there are a few weather-related observations that need to be made:

• The effects of a hurricane can be measured not only by wind speed, but by the barometric pressure at the eye of the storm. When the storm hit New Orleans, the barometric pressure was 915 millibars, or 27.02 inches of mercury. It had been as low as 902 millibars, or 26.64 inches of mercury. With pressure as low as this (“normal pressure” is about 30 inches), it’s no wonder that the storm had such a damaging effect.
• The intensity of the hurricanes this season in general, and Hurricane Katrina in particular, was not caused by global warning, and there wasn’t anything anyone could ‘do’ to prevent it. Hurricanes are Nature’s way of equalizing the temperature differences between the heat of the tropics and the cold of the Arctic. Essentially hurricanes move the heat of the oceans up into the upper atmosphere. As David Chandley explained in a talk at the NFL Luncheon today, were it not for hurricanes, the tropics would be even warmer, and the polar regions would be solid ice.

If there’s any good news to be had on the weather front, it’s that the weather in Atlanta for Labor Day weekend is expected to be wonderful. The heat and humidity of summer is losing its grip. By the weekend, we could be seeing temperatures in the low to mid 80s during the day, and lows in the low to mid 60s, with low humidity.

On the tropical storm front, Tropical Depression 13 has become Tropical Storm Lee as of 5 PM today.

It continues its slow moving path, and is not expected to affect the United States.