Monday, July 23, 2007

Big Predictions, So Why No Storms Yet?

Back in late May, forecasters from Colorado State University and NOAA/National Hurricane Center issued their predictions for the 2007 hurricane season. Both groups came to the same conclusion that this hurricane season was going to be very active.

The Colorado State team predicted 17 named storms, 9 hurricanes and five major hurricanes, while the group from NOAA and the National Hurricane Center forecast 13 to 15 named storms, 7 to 10 hurricanes and 3 to 5 major hurricanes.

And, right on cue, the 2007 hurricane season started with a bang when Tropical Storm Barry formed on June 1, the first day of the hurricane season (Sub-tropical storm Andrea was the first named storm of the season when she formed in May). Barry, however, turned out to be more of a blessing and less of a curse when he brought beneficial rains to the Florida peninsula.

Yet, since Barry swept across Florida during the first weekend of June the tropics have been very quiet. No other named storm has formed and, frankly, no other tropical disturbance has gained much attention from forecasters at the National Hurricane Center.

So, where are all those tropical storms and hurricanes forecasters predicted back in May? The answer is pretty simple: it is quiet in the tropics now because it is supposed to be quiet.

Historically, July is a relatively inactive month. On average, one tropical storm will form in July every two years. Last year, Tropical Storm Beryl formed on July 18 several hundred miles east of Jacksonville, Florida. The storm moved north staying well offshore of the eastern seaboard before dissipating on July 21st.

High wind shear, an abundance of dry air and even Saharan dust are all fairly common across the tropical Atlantic during July. All three factors-especially wind shear-prevent tropical systems from developing.

Still, the hurricane season is far from over. Once the calendar turns to August, that high wind shear tends to disappear, along with the dry air and Saharan dust. The number of tropical waves sweeping off the coast of Africa increase, and sea surface temperatures warm into the 80 degree range throughout the Atlantic Basin.

August, September and October are the peak months of hurricane activity with 90% of all tropical storm and hurricane activity taking place during that three month period. From a historical perspective, the hurricane season is about to begin.

Posted at 10:59 AM