Brace for heavy rain, because forecasters have upped the odds for a tropical depression

Subtropical storm Alberto forms in Gulf

National Hurricane Center forecasters say Alberto has formed in the Gulf of Mexico, a rare preseason subtropical storm, a week before hurricane season starts.
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National Hurricane Center forecasters say Alberto has formed in the Gulf of Mexico, a rare preseason subtropical storm, a week before hurricane season starts.

UPDATE: Subtropical storm Alberto, first named storm of the season, forms in the Gulf

A tropical system threatening to become Alberto, the season's first named storm, continued to become better defined early Friday.

In a morning advisory, National Hurricane Center forecasters upped the odds of a depression forming to 90 percent over the next 48 hours and warned that storm surge and tropical storm force winds could reach the Gulf Coast by late this weekend or early next week. A hurricane hunter plane is scheduled to fly into the storm later today.

Because the system is sucking so much moisture from the Caribbean, much of Florida, the north Gulf Coast and western Cuba should brace for heavy rain.

"Regardless of the development of the system, there will be a surge in tropical moisture over South Florida beginning today and lasting through Memorial Day weekend," Larry Kelly, a meteorologist at the National Weather Service's Miami office, said Friday morning.

Flooding is possible in Miami-Dade and Monroe Counties after weeks of rain that in some locations pushed total rainfall to more than two and three times usual May amounts. Gusty winds and rough seas should increase Saturday, with tornadoes possible Saturday and Sunday. Rip currents are also expected on both coasts, the Miami weather office said.

No flood advisories for South Florida have been issued, but Kelly said they're possible.

"It's something we'll definitely continue to monitor," he said.

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NOAA forecasters are calling for heavy rain over Florida and the north Gulf Coast over the next five days. Source: NOAA Weather Prediction Center

Forecasters said the system continued to become better defined early Friday and will likely form in the northwestern Caribbean sea or southeastern Gulf. They've been watching the messy, slow-moving system for more than a week now after a swirl of low pressure appeared off the coast of Belize. Strong upper level winds had kept the system in check. But as it moves north, those winds are expected to dramatically weaken, allowing the system to become better defined over warm, hurricane-fueling Gulf waters.

While some models show the storm intensifying to a Cat 1 hurricane, forecasters have been more hesitant to call it while the system remains close to the Yucatan peninsula.

"I take the intensity with a huge grain of salt at this point," said University of Miami hurricane researcher Brian McNoldy.

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Forecasters say the wettest side of the storm will fall to the east, where this satellite image taken Friday shows water vapor concentrated. Source: National Hurricane Center

Models show the storm making landfall along the north Gulf Coast between the Florida Panhandle and Louisiana. But without a center, making an accurate forecast track remains difficult.

There's also a chance that the lopsided storm becomes a subtropical system. Subtropical systems pack the same hazards — heavy rain and wind — but lack the warm center of a tropical system. Stronger winds also wrap around the storm's edges, rather than at its center.

There’s a hurricane coming, and you have questions. How much food should you stock up? What needs to be moved out of your yard? And what room of the house is the safest? Here are five things you definitely should do if there’s a hurricane warning.

Follow Jenny Staletovich on Twitter @jenstaletovich
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