U.S. hurricane experts say all the weather ingredients, which normally fluctuate, are set on boil for the formation of storms. And it is going to stay that way for a while, they said.
Four named storms at the same time is a bit odd, but not unprecedented, meteorologists said. In 1995 five named storms lived simultaneously. And in 1998 there were four hurricanes at the same. But wait and see what happens next.
"Give us time, this is only Tuesday," said meteorologist Dennis Feltgren, spokesman for an all-too-busy hurricane center in Miami.
The peak of hurricane season is not until Sept. 10 and this season already has 10 named storms, which is the long-term average for an entire season.
"Normally in an active season, there are bunches of hurricanes and lulls. It just doesn't seem like there's been bunches of lulls. I sure hope we're not talking (hurricanes) Christmas Eve," said meteorology professor Hugh Willoughby at Florida International University.
Two hurricane prognosticators - including William Gray, who pioneered the field of storm season forecasts - predicted Tuesday that this month would be almost twice as busy as an average September. They forecast five named storms, four of them hurricanes and two of them major.
These latest predictions cover only September and are not a revision of the season-long forecast, which called for a total of nine Atlantic hurricanes through November.
The wind and water conditions that led to the September update will likely continue for the next month or so, said Phil Klotzbach of Colorado State University, co-author of the new report. But if history is any guide, those conditions should change sometime in October, he said.
Wind shear - wind coming from a different direction at high altitude - often weakens a hurricane or at least puts the lid on some developing storms. But at the moment, the only wind shear in the entire Atlantic hurricane region is around Hanna, Feltgren said. So a major factor keeping other storms from forming or strengthening is absent, he said.
Waves of clouds and thunderstorms this time of year head westward from northern Africa every couple days. Some become tropical storms and hurricanes and others just die down. Gustav, Hanna, Ike and Josephine all started as those waves. What's different right now is that all those waves from Africa head right into a brew of air and water conditions ideal for strengthening, Klotzbach.
First, in the deep tropics, certain winds are blowing from the west and in the subtropics they are coming from the east, creating a propensity for spinning in between - which is the main hurricane development region - Klotzbach said. The current "spin factor" is among the top 20 percent in history, he said.
Add to that the fact that water temperatures are slightly warmer than normal, Klotzbach and Feltgren said. Warm water serves as fuel for storms.
And finally, Klotzbach factored into his forecast how the season has already been so far this year: Extremely busy. That means the atmosphere is unstable, which is good for storm development. He said the atmospheric pressure in the hurricane formation area is among the lowest it has ever been and storms are giant low pressure systems.
So Klotzbach advises to keep watching those waves coming off Africa: "There may be one today or tomorrow. But certainly today we have enough to worry about with Hanna, Ike, Josephine and Gustav remnants to keep us all busy."