Floridians are looking at an unusual storm system moving onto the peninsula from the Atlantic Ocean today, the first official day of the 2011 Atlantic hurricane season. This weird disturbance actually began as a squall in Michigan.

The concentration of thunderstorms and gusty winds turned up Tuesday about 200 miles off the Jacksonville coast, and is moving south and west toward a Wednesday landfall in Central Florida. It's an area that badly needs rain, so the storm is not at all unwelcome. Better still, it won't have time to develop tropical characteristics and grow to more dangerous levels.

AccuWeather.com notes that much of Florida has received barely a quarter to a half of its usual rainfall this spring.

While we're on the topic of hurricanes, AccuWeather.com has posted a start-of-season update to its hurricane forecast. The only change is the addition of one major storm to the spreadsheet. So they're calling for 15 named storms, of which 8 are predicted to become hurricanes, and 4 will reach Cat. 3 status (sustained winds of 111 mph or more).

"We believe the highest potential for early season development will be near and off the southeast U.S. coast and from the southern and southeastern Gulf of Mexico southward over the western and southern Caribbean," the statement said.

"For the middle of the hurricane season, we see the greatest threat for the U.S. from the Texas coast eastward along the northern Gulf coast, as well as all Florida and Carolina coastal areas. Areas north of the North Carolina coast have a lower chance for direct impacts. We caution that just because this area has a lower chance does not imply no impact. There could also be indirect impacts from storms making landfall well to the south or even from the Gulf of Mexico. Those indirect impacts would include the potential for heavy flooding rainfall."

Out at Colorado State University, hurricane forecasters William Gray and Phil Klotzbach have updated their forecast, but they have not changed their forecast numbers.  

They do offer some landfall probabilities, however. "Based on our historical analysis along with our current forecast, the probability of a major hurricane making landfall along the U.S. coastline is approximately 72 percent," Klotzbach said. They're assuming that a more active season will mean more landfalls. But last season was one of the most active on record for the Atlantic, and there were no U.S. landfalls at all.

Breaking that down a little farther, Gray and Klotzbach say the chance of a major storm making landfall on the East Coast, from Florida northward, is 48 percent. The long-term average is 31 percent.

Both forecast teams base their expectations for an active season partly on the same factors: Persistent warm surface water temperatures in the Atlantic, especially in the hurricane "nursery" zones; "neutral" La Nina/El Nino conditions in the Pacific, which reduce the westerly Atlantic wind shear that can stifle hurricane formation; low air pressure in the hurricane development region of the Atlantic and westward into the Caribbean, and off West Africa.