Hurricane Florence: Monday 11 PM Update

Infrared Satellite Image of Hurricane Florence. This satellite measures the temperatures of cloud tops (the more red, the colder the cloud top).

As of the 10:00 PM CDT update, Hurricane Florence is maintaining her intensity as a Category 4 Hurricane with sustained winds of 140 mph and gusts up to 165 mph. However, recent satellite data and soundings have indicated that Florence may have actually weakened slightly.

At 4:00 PM CDT her pressure was at 939 millibars (mbs), but as of 10:00 PM CDT her pressure had risen to 944 mbs. When it comes to a low pressure system (i.e., a hurricane) the lower the pressure, the stronger the storm. Florence's pressure over the past 6 hours has risen slightly, but that does not mean that Florence is completely weakening.

There are some indications that Florence may be undergoing a process known as an "eyewall replacement cycle" in which she exchanges 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 encompass 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.

If Florence undergoes this process, there is the possibility that her overall intensity may weaken a little bit, but once the new eyewall is in place, Florence would regain her intensity.

In the meantime, it is entirely possible for Florence to near the threshold necessary to attain Category 5 Hurricane status, but there is a strong possibility that she will not be at her strongest when she makes landfall, rather she may reach peak intensity a day or so before landfall.

To add to the forecast, Florence is expected to remain in a low shear environment (hurricanes favor an atmosphere with little wind shear). However, this may change slightly as Florence approaches land.

An area of high pressure over the extreme Northwestern Atlantic should cause Florence to start turning a bit more to the northwest, and a building area of high pressure over the Great Lakes will work to slow her forward speed down as she approaches land (an area of low pressure cannot move an area of high pressure, so the high pressure generally wins out when it comes to picking a location). Thus, Florence is expected to make landfall either late Thursday Afternoon or during Thursday Evening, as a Category 4 Hurricane (or possibly a high-end Category 3 Hurricane should the wind shear be enough).

Florence is not the first hurricane to strike North Carolina or pass near it. Since 2010, there have been two major hurricanes pass within 150 miles of where Florence might make landfall, these hurricanes were Irene and Matthew. However, Florence may be one of the "stronger" ones (that we know of) to strike North Carolina head on, but we will have to wait until after her landfall to see where exactly she will rank.

The main hazards, at this time, are still a little uncertain as it will depend upon exactly where and when Florence will make landfall. However, high surf and strong gusty winds - especially right along the shoreline - are to be expected.

As of 11:00 PM CDT, there are no current watches or warnings in effect along the East Coast in regards to Hurricane Florence; however, watches and warnings may start being issued as early as Tuesday Morning.

This time of the year, the Atlantic Ocean gets active with hurricanes and tropical storms, and this year is no exception. 

-Timothy Albertson.