Hurricane Florence: 2:00 PM Tuesday Update

As of 1:00 PM CDT, Hurricane Florence remains a low end Category 4 Hurricane with sustained winds of 130 mph and gusts up to 160 mph. Florence had weakened slightly overnight, due to an "eyewall replacement cycle" in which she exchanged her old eyewall for a new one. The eyewall of a hurricane is where the strongest winds are located, and usually where the most damage occurs from a hurricane. Eyewalls tend not to cover the entire hurricane, rather they usually extend no more than 40 miles from the center of the hurricane.

During the eyewall replacement cycle, a hurricane may temporarily weaken slightly (sometimes an entire category). During the eyewall replacement cycle, an "outer" eyewall develops and intensifies, and slowly moves inwards towards the "inner" eyewall. This process weakens the inner eyewall, and eventually the outer eyewall takes over.

An area of high pressure over Bermuda is causing Florence to move in a west-northwest fashion; strong hurricanes like to turn right, but the high pressure is preventing her from doing so. This places her on course for a landfall on North Carolina. But will she be a Category 4 Hurricane at landfall?

Recent atmospheric conditions suggest that it is possible that Florence may end up being a Category 3 Hurricane at landfall. She is going to slow down as she approaches land, due to a high pressure moving over the Great Lakes. As mentioned in the previous article; an area of low pressure cannot move an area of high pressure (the high pressure always wins it comes to picking a location). This means that Florence is going to slow down rapidly as she approaches land on Thursday Night, and this could add some shearing which may (as well as other atmospheric details that I spare you details of) start to weaken Florence.

If you remember from a previous article I wrote yesterday about the wind fields of a weakening hurricane, this weakening may mean that Florence's wind field will expand outwards a bit more as she nears land (although the strongest winds will not be as strong as they were before the hurricane weakened).

Her time of arrival on Friday will play a notable role in her exact intensity at landfall. Hurricane Florence is expected to make landfall as a high-end Category 3 or low-end Category 4 Hurricane on Friday Morning. If she is able to advance quicker (and make a landfall on Thursday Night, she will be stronger than if she makes a landfall late, say on early Friday Afternoon).

In addition, her slow movement may mean that she will not make a landfall until possibly Friday, despite being very close to land for most of the day on Thursday. This means that heavy rain falls will be present in eastern North Carolina for a while, and rainfall amounts will be in the inches for several spots across the eastern portion of North Carolina.

Tornadoes are also another hazard when it comes to landfalling hurricanes. Due to the low level shearing present with a hurricane, the outer rain bands tend to rotate and, especially with stronger hurricanes, can produce tornadoes. This is not an uncommon event with a landfalling hurricane (perhaps you remember Hurricane Harvey's tornadoes last year, or the record setting number of tornadoes from a hurricane by Hurricane Ivan in 2004).

Hurricane Watches are in effect for most of the coast of South Carolina and North Carolina. 

-Timothy Albertson