Will Tropical Storm Bonnie Become a Hurricane?

(July 23) -- Tropical Storm Bonnie is heading for the warm waters of the Gulf of Mexico, but current conditions in the traditional hurricane breeding ground don't appear favorable for the cyclone to strengthen much before its expected landfall on Sunday.

The National Hurricane Center forecasts that Bonnie will remain below hurricane strength and, in fact, indicates that there is some possibility that Bonnie will weaken -- rather than strengthen -- as it moves northwestward through the Gulf of Mexico this weekend.

As of this morning, Bonnie's sustained winds were 40 mph; hurricanes have sustained winds of at least 74 mph.

NHC experts say Bonnie may be inhibited by a stronger than normal upper-level wind flow across the gulf. Since hurricanes grab their energy from the warm water below and not energy higher in the atmosphere, wind aloft slows development or weakens tropical storms and hurricanes.

In this case, the wind aloft is being created by the combination of a weak low-pressure system over the western gulf and a high-pressure system centered over the Carolinas. The result is a relatively brisk wind from the southeast over the gulf, which is not conducive to development.

The water in the Gulf of Mexico is certainly warm enough, being in the middle 80s, to allow the storm to strengthen, but it is not expected to be enough to counteract the interference from above.

These competing factors often exist when forecasters are attempting to predict the future strength of tropical storms and hurricanes, which is one of the reasons that forecasters have a better track record of forecasting the track of storms rather than the intensity.

The enhanced southeasterly flow does give forecasters confidence about the general track of Bonnie through the weekend, directing it toward the Gulf Coast after its path through southern Florida. But the flow might shift enough to push the storm on a more easterly track later in the weekend, and tropical storm watches extend from central Louisiana to the Florida Panhandle.

Weather dangers for the BP oil spill area, where cleanup work has been halted, will include strong winds, dangerous thunderstorms, very rough seas and an increased onshore flow -- regardless of the storm's classification. Sea levels will also be elevated along the Gulf Coast beaches as the storm approaches.

Even weak tropical systems have the potential to produce copious rainfall, and heavy rain will be a risk along the Gulf Coast as the storm approaches and then moves inland, most likely during the early-morning hours of Sunday. Isolated amounts of greater than six inches are possible, which could produce flash flooding. The storm will most likely be moving too quickly to produce rain amounts in excess of 10 inches.

The hurricane center is also monitoring a weather disturbance in the western gulf, but that system has drifted too close to the coast of eastern Mexico to be a concern in terms of development. The disorganized system, however, will continue to produce very heavy rainfall in eastern Mexico into the weekend, possibly resulting in life-threatening flash flooding.

Flash flooding unrelated to tropical weather occurred Thursday evening in Milwaukee. Slow-moving thunderstorms dumped 7.5 inches of rain in just two hours, resulting in a sinkhole that swallowed a car. The airport was temporarily closed, resulting in dozens of canceled flights, and two people were hospitalized after being struck by lightning.