What forecasters are worried about with Hurricane Florence

Hurricane Florence is set to strengthen over the next 24 hours, and according to CBC, the intense Category 4 hurricane is predicted to make landfall by tomorrow, somewhere between North and South Carolina.

Hurricanes are inherently dangerous, and Florence is no different. Weather forecasters, however, have some particular concerns they’re paying attention to.

Florence is moving slowly

With maximum winds of 225 km/hr, Hurricane Florence is moving at a leisurely pace of 28 km/hr as of 2 a.m. this morning. Forecasters are predicting that speed will lessen dramatically, slowing to between 5.5 km/hr to just 9 km/hr.

This snail’s pace could spell total loss for structures in its way. Hurricanes are defined as Category 4 when they reach a “sustained wind” speed of 209-251 km/h, according to the U.S. National Hurricane Center (NHC). Category 4 storms produce “catastrophic” damage.

“It looks like as soon as it gets to the coast, there’s a good chance it’s going to stall right out. So [it will] end up getting cut off from the main jet stream flow that normally carries systems quickly up the coast” said Johanna Wagstaffe, CBC meteorologist. “Instead, it’ll just sit and spin.”

The danger involved in a sitting hurricane is clear. When high- and low-pressure systems are stuck, a blocking pattern occurs, preventing the storm from moving on and dissipating.

Flash flooding

Residents in the Carolinas and adjacent mid-Atlantic states are being warned that “catastrophic” and “significant” flash flooding and river flooding is likely. The NHC expects “38 to 63 centimetres of rainfall” from Hurricane Florence.

The slow pace of the storm has a higher chance of significantly flooding its territories once it hits land, producing prolonged periods of rain. Grounds are already saturated, “unable to absorb extra moisture.”

Storm surge

Storm surges come along with any hurricane disrupting ocean water. If Florence remains at sea, the storm surge is “minimal”. Once it touches the coastline, “the storm encounters shallower water, and the displaced water has nowhere else to go but forward.”

The portion of “the continent's crust that is underwater” – called the continental shelf – is particularly shallow in the Carolinas. A higher surge could be created along with high tides for late tomorrow and into Friday.

Extremely strong and sustained winds

Hurricane Florence is expected to produce “potentially deadly” winds.

“Because [Florence is] such a large storm, as well as such an intense storm, by tomorrow afternoon, the coastline will probably start to feel tropical storm-force winds. That radius extends out much farther than hurricane-force winds do,” continued Wagstaffe.

The region in and around the Carolinas could see damage as early as tomorrow afternoon.

The “tropical storm-force” winds stretch out and extend nearly 300 kilometres from the centre of the storm; “hurricane-force” winds extend out nearly 100 kilometres from the storm's centre.

As you get closer to the centre, you get closer to feeling the catastrophic forces of a Category 4 storm.

Surf, riptide

Even with a sunny day, blue skies and a hurricane expected many days in the distance, the riptide can strengthen making normally safe waters extremely dangerous for swimming.

Florence has, according to CBC, “already demonstrated” strong riptide power, pulling people out to sea. At Wrightsville Beach in North Carolina, over 24 water rescues were undertaken by authorities last weekend.

Will Canada be threatened by Florence?

This past Monday, parts of southerwestern Ontario were wet and gloomy, absorbing pieces of Tropical Storm Gordon moving in from the east coast.

The Great Lakes may see something similar over the long-term forecast, due to the slow pace of Florence. Weathercasters are “uncertain” how much moisture will remain in the system as it approaches the US-Canada border.