The heat wave in Atlanta continues. Today’s high temperature of 103 degrees recorded at 12:46 PM at Hartsfield-Jackson airport beat the previous record of 101, set back in 1980. Meanwhile, here in Lawrenceville, the temperature on Thursday also crossed the century mark, to 101.5 degrees, the highest temperature I’ve recorded since I started keeping records in 2002. It could be worse…you could be playing at the PGA Championship in Tulsa, Oklahoma, where it’s currently 97 degrees with a heat index of 105, and expected to stay very warm.

Speaking of records, Brooklyn, New York recorded its first-ever tornado on Wednesday morning—one of three to hit New York City since recordkeeping began. The F2 storm, along with the associated torrential rainfall ground the NYC morning commute to a halt, flooding subways and stalling buses. Central Park recorded 2.5 inches of rain, while 3.47 inches of rain fell at Kennedy Airport in Queens.

With all the heat and drought in Georgia, we could certainly use some of the rain that fell on New York yesterday, and the Weather Service has come through with its updated hurricane forecast. Similar to last week’s predictions by Dr. Gray, the Weather Service is still calling for a stronger than normal season, but has dropped the number of storms by one from its original forecast.

The prediction now is for 13-16 named storms, instead of 13-17, and 7-9 hurricanes, rather than 7-10. The number of predicted intense hurricanes remains at 3. Overall, there’s an 85 percent chance of an above normal season in 2007. Forecasters say that they are more confident of their prediction now because of a favorable climate leading to storm development.

As the above chart shows, the peak of the tropical season isn’t until after Labor Day. Typically, there are one or two storms during June and July, and things don’t really start to pick up until mid-August.

Despite a relatively cool July —the mean July temperature was actually cooler than the mean June Temperature, both here in Lawrenceville and in Atlanta— it looks like August is going to be our hottest month of the year.

The short range, medium range, and long range forecasts are all calling for warmer than normal temperatures, and it looks like we may not get much rain to help out, at least until the middle of the month.

Temperatures will be approaching the 100 degree mark all this week in North Georgia. To make things worse, we’ll likely be seeing high dew points as well. That means that the humidity will be approaching the unbearable range. Take a look at the forecast dew points in Georgia for 2 PM Thursday:

If this forecast validates, we’ll see the heat index above 105 degrees, the danger level, several times this week.

Ultimately, it’s the moisture in the air that determines how we feel when we go outside. Although relative humidity is the measurement most people use to measure moisture content, the dew point temperature can provide a better measure of how uncomfortable conditions are. When the dew point rises to near 70 or above, most people are unlikely to want to be outside for very long.

The heat index also measures the apparent temperature. For more detail, take a look at this table showing the relationship between relative humidity, temperature, heat index, and dew point.

The reversal from the cool and wet July conditions to the hot and dry conditions for August isn’t going to do much to help the drought conditions in Georgia. Over the last month, the drought levels in Georgia haven’t changed very much. While the rain has kept lawns green in the short term, we will see a quick return to brown lawns without more rainfall.

As I’ve said before, tropical weather will probably be the key to breaking the drought. Despite the relatively quiet season so far, the latest forecast by Dr. Gray at Colorado State University is still calling for an above average hurricane season. The researchers are predicting 15 tropical storms for the season, down 2 from their May forecast, and eight hurricanes, down from nine in May. There’s also an above average chance of a major hurricane striking the US coast.

You’ve probably heard this on the news: the Climate Prediction Center has weighed in with its predictions for the 2007 hurricane season, which starts June 1st. The Atlantic Hurricane Outlook calls for a 75% chance of an above normal season, and only a 5% chance of a below normal season. Overall, they predict between 13 and 17 named storms, of which between 7 and 10 will become hurricanes. The predict between three and five of those hurricanes will be category three or greater.

These predictions are in line with what Bill Gray and the Colorado State University center are calling for, and slightly above what Accuweather forecasts. Dr. Gray will update his forecast at the end of the month. The weather service bases its predictions on the current above-normal cycle of activity for hurricanes that has gone on since 1995, and the probability of a La Nina pattern developing later on this summer.

In terms of the numbers, they look very similar to the predictions for the 2006 season, with the main difference being the possibility of La Nina conditions developing. La Nina and El Nino are terms used to describe the Pacific Ocean variances in sea surface temperatures, which are warmer than normal in El Nino years, and cooler than normal in La Nina years. Last year, forecasters failed to see the El Nino conditions that developed in late summer, causing a fairly normal hurricane season. This year’s forecast says that if a La Nina pattern does indeed develop, we are likely to see a hyperactive season, similar to what occurred in 2004 and 2005.

Meanwhile, Accuweather has released its summer forecast. Also citing the possibility of developing La Nina conditions, it calls for warmer than normal weather in the Northeast US, and makes a parallel with the ‘dust bowl’ conditions that occurred in the middle of the 20th century.

For the southeast, the forecast calls for near normal conditions, including precipitation. However, forecasters note that there is likely to be little long-term drought relief until hurricanes or tropical storms arrive later this summer.

110 Degree Summer Temperatures in 2080?

You may have read the banner headline at the top of Thursday’s Atlanta Journal-Constitution — NASA Predicts Scorcher for Atlanta. The article focused on the potential for daily high summer temperatures of 110 degrees in Georgia by 2080, 15 to 20 degrees above what we typically see now. The article was based on a press release from NASA’s Goddard Space Flight Center, which in turn was based on a peer reviewed article that appeared in the American Meteorological Society’s Journal of Climate. I tried to read the original article, which unfortunately is only available to subscribers, but was able to locate the article’s abstract.

The interesting thing to me is that the focus of the research seemed to be the effects of colder sea surface temperatures on precipitation probabilities in the eastern US. While the abstract says nothing about carbon dioxide levels or global warming, it appears that the bottom line is that if CO2 levels continue to increase by 2% per year, and you get a summer with extreme low eastern Pacific sea surface temperatures, which would result in fewer storms in the eastern US, then daytime temperatures could range between 100 and 110 in cities like Atlanta.

Kirk Melhuish Weighs In on Global Warming

WSB Radio meteorologist Kirk Melhuish released a position paper this week that reflects his observations on global warming. The four page missive is well worth a read, both for his opinions on the subject, and for his command of English literature. He cautions readers to be wary of the extremists on both sides of the global warming debate, but acknowledges that there does appear to be strong evidence of some human-caused effects in the rise of temperatures.

He questions our current ability to correctly model Earth’s climate such that we can make accurate predictions about what the climate will be like 100 years from now, and thinks that it may take another 20 years before the competing scientific theories are analyzed properly to determine whether what is being predicted now is correct.

AccuWeather Releases 2007 Hurricane Projections

Hurricane expert Joe Bastardi and the weather forecasters at AccuWeather put out a press release this week with their predictions for the 2007 hurricane season. They forecast between 13 and 14 named storms, and 3 intense hurricanes category 3 or higher. While still a season with greater than normal hurricane activity, they are predicting fewer storms than Dr. Gray at Colorado State University, who is calling for 17 named storms, and 5 intense hurricanes.

AccuWeather thinks that the area most likely to be hit by hurricanes this year is the Gulf Coast, with the most danger from Cape Hatteras, North Carolina, through Florida, and west to the mouth of the Mississippi.

If the predictions hold true, it will be bad news for an area that got clobbered in 2004 and 2005. However, it could mean an end to the drought that is affecting Georgia, since there is a good likelihood that storms in the eastern Gulf end up bringing rain to Georgia. Dr. Gray will update his forecast one more time, just before the tropical season officially starts on June first.

The team at Colorado State University has released its updated forecast for the 2007 hurricane season, which starts on June 1st. Primarily due to the rapid dissipation of the winter’s El Nino conditions, the number of predicted hurricanes has increased from the forecast made last December.

In many ways, the forecast is strikingly similar to the one made a year ago for the 2006 season. The prediction is now for 17 named storms, and nine hurricanes. Five of those are expected to be major category 3-5 hurricanes.

The difference between this year and last is where the storms might strike. While last year, there was a 64% chance of a storm striking the east coast, this year, the chance is down to 50%. There is also a 49% chance of a storm hitting the Gulf coast, and above average chances of a major hurricane landfall in the Caribbean Sea. Overall, Dr. Gray and his team expect that the season will be almost twice as busy as the long term average.

Dr. Gray admitted that last year’s forecast fell short, primarily because of the unseen El Nino when the forecast was made. In fact, no hurricanes made landfall in the United States during 2006 (although there were a few tropical storms that some forecasters, including Joe Bastardi, thought should have been classified as hurricanes. There have only been two periods since 1945 where no hurricanes made landfall in the US over two consecutive years, and the forecast team doesn’t expect to break that record in 2007.

I’ll report on other hurricane season predictions as they become available.