The Facts About Florence

Hurricane Florence may do a great deal of damage and bring major flooding, but the system has weakened some in the days before hitting the east coast and even the storm surge may not be as devastating as advertised.Dr. Tim Ball taught climatology at the University of Winnipeg.  He is also the author of "The Deliberate Corruption of Climate Science."  Two days ago, forecasters expected Florence to come ashore as a Category Four hurricane, meaning maximum sustained winds were thought to be 130-156 miles per hour.Florence is now a Category 2 storm, with wind speeds now expected to be between 100-110 miles per hour.  That's still capable of causing plenty of destruction, but how did forecasters miss the downgrade?Dr. Ball says they shouldn't have.  He says as the storm moved north in the Atlantic Ocean, it was guaranteed to hit colder water, which weakens the power of hurricanes.  "Hurricanes are driven by the water that's evaporated off the surface, and the heat energy that's used to evaporate that water is released back into the storm when it condenses.  That's called the latent heat of condensation," said Ball.He also says the storm is further hampered moving north by the tropopause, the layer of our atmosphere between the troposphere and the stratosphere.  The tropopause is twice as big at the equator than it is at either pole, so a reduced tropopause going north also weakens Florence."As they move north, these systems get squeezed, get flattened out.  As they get flattened out, that means that they spin less rapidly, which  reduces the wind speed," said Ball.He also says while the storm surge may cause significant peril along the coast and even further inland, that too will likely be less significant than advertised.Ball says atmospheric pressure pushes down on the ocean but the low pressure accompanying hurricanes allows the ocean to bulge up and surge into land.  It can get even worse if the storm strikes at high tide and depending how the wind from the hurricane is acting at landfall.However, Ball says the 955 millibars (the measure of atmospheric pressure) is not particularly low, so that ocean bulge will hopefully be less catastrophic than most are reporting.Listen here for more of Dr. Ball's hurricane analysis, his explanations of why the the forecast is now shifting, and his larger thoughts on the climate debate.