*For the ins and outs of hurricanes and other information in this blog, continue reading. However if you just want to read the forecast, jump down to "Florence: Where, When, How Strong?". I apologize for my long-winded writing as it has been a while since I have written a post and I am out of practice with succinct writing.*
Why Wind Speed?
Great question! Above is our equation for the geostrophic wind, or the wind that is balanced with respect to Pressure Gradient Force (caused from a difference in atmospheric pressure at two locations) and the Coriolis Force (the force enacted on an object as a result of our Earth spinning on it's axis), While each hurricane can have it's own major impacts, may it be flooding, wind damage, long-term power outages, or coastal erosion, the Saffir-Simpson Hurricane Wind Scale is a fantastic way to determine the strength and potential hazards of a hurricane. Diving shallowly into our dynamical equations for the atmosphere, the horizontal wind is related to the horizontal pressure gradient, or the change in atmospheric pressure over a given distance. A hurricane is essentially a localized, very strong low pressure system, with extremely low pressure at the surface. The lowest pressure recorded in a hurricane was the Labor Day Hurricane of 1935 that struck the Florida Keys with 892 millibars of central pressure. Generally pressure at the surface ranges from 980 millibars to 1040 millibars in North Carolina depending on the season and the location in a weather pattern. A bar is the metric unit of pressure and is equivalent to the weight of the atmosphere above a location at sea level, hence the surface pressure being ~1000 millibars. In essence, the stronger the pressure gradient force, the faster the geostrophic winds will be, and the more opportunity the storm has to have more devastating impacts.History of 'F'-Named Hurricanes in North Carolina
While in recent memory, Hurricanes beginning with the letter 'F' have had an incredible impact on North Carolina (Hurricane Fran in 1996, Hurricane Floyd in 1999, Hurricane Florence in 2000, Hurricane Fabian in 2003, and Hurricane Frances in 2004), the only one of that list to actually be a major hurricane upon landfall was Hurricane Fran. If you have lived in North Carolina for a while and remember these storms, you may recall that Fran was the only storm of that list in which major destruction was caused by wind. Floyd and Frances both caused catastrophic flooding from record-shattering rainfall totals, and Florence and Fabian both affected the coast with rip currents and beach erosion (Fun Story: Hurricane Fran is how I gained my interest in meteorology. The dream and fascination with the weather began back in 1996). With the exception of Fran, all the major hurricanes to make landfall in North Carolina had names that did not begin with 'F' (Emily 1993, Diana '84, Donna '60, Helene '58, Ione '55, Connie '55, Hazel '54, Great Atlantic Hurricane '44...). The complete list can be found here if you're interested.
Florence Again?
You may have noticed from the above paragraph that a hurricane named 'Florence' made landfall in 2000. Why is there another Hurricane named 'Florence'? The World Meteorological Organization implemented a list in 1953 of six years worth of names starting with 'A' to 'W' and with the exception of 'Q', 'U', 'X', 'Y', and 'Z' because names beginning with those letters are generally difficult to pronounce. The WMO implemented these lists because prior storms were referred to based on their coordinates in longitude and latitude, making it difficult to differentiate storms both during the event and in historical archives. The National Hurricane Center also mentions that a name can be removed from the lists in the event that the "storm is so deadly or costly that the future use of its name on a different storm would be inappropriate for reasons of sensitivity." Sandy, Katrina, Irma, Andrew, Hugo, Fran, Floyd, Hazel, and others have been removed from this list.
Florence: When, Where, How Strong
Hurricane Florence is one of three named tropical Cyclones in the Atlantic basin: Florence, Isaac, and Helene (Gordon formed in the Gulf and made it's way up through the belly of the United States as a Tropical Storm last week). As of 11:00 p.m. AST (Atlantic Standard Time, analogous to Eastern Daylight Time), Hurricane Florence was located at 24.6°N 57.7°W moving west at 7 mph with a minimum pressure of 974 mb and max sustained winds of 90 mph. Over the course of the next 4-5 days, it will move over warmer waters and into an area of lower wind shear, both conditions favorable for strengthening. Florence is expected to increase in strength to a major hurricane prior to making landfall. 
Levi Cowan, meteorologist and owner of "Tropical Tidbits" posted this latest GFS Ensemble track for Florence. As is apparent, most of the ensemble members show a trend for Florence to become a major hurricane and make landfall somewhere in North Carolina. While it is still too soon to determine exactly where landfall will occur, it is safe to say that the coasts of North Carolina, Virginia, and likely South Carolina will be affected by strong winds, heavy rains, and storm surge.
At this point, North Carolina Governor Roy Cooper has wisely declared a state of emergency in order to allow for numerous days of preparation ahead of a potentially devastating storm. The National Hurricane Center believes that the most likely path for Florence to take will be into the southern beaches of NC, which could mean direct landfall in Wilmington, however it is still too soon to pinpoint an exact beach as to where the biggest impacts will occur. At this point the best thing to do is prepare for the worst. Once Florence makes landfall, interaction with the land will cause the storm to weaken substantially, however even with weak winds this storm will still have an impact
Expected Hazards
1. Wind: As Florence will likely be a Category 3 or stronger storm at landfall, winds in excess of 110 mph can be expected within a couple dozen miles of the storm center. These winds could easily cause downed trees, power outages, damage to roofs and other structures, and damage from flying debris. The best thing to do would be stay away from windows (or even board up windows at the coast) and remain in interior rooms of the home throughout the initial stages of the event.
2. Rain/Flooding: This storm is moving relatively slowly right now, but will pick up speed as it rounds the south end of the High pressure system establishing itself over the New England States. However, once the storm makes landfall, it will slow down substantially and the moisture nearby will be converted to rain within the storm. Some early precipitation forecasts show over 12" of rain to fall through the event in some areas (but still too early to tell exactly how much and where). Flooding could also lead to pollution of water used by the city, so be sure you have bottled water stocked up.
3. Power Outages: Hurricane Florence might not produce as widespread or long-lasting power outages that Fran did back in 1996, however I suspect that due to the nature of this storm there will be extensive, widespread power outages along the coast and inland along the path Florence inevitably takes. Be sure you have your batteries and external batteries charged, flashlights at the ready, and candles where you can easily access them.
4. Beach Impacts: Ahead of Florence, due to the expected wind direction and increased wave action along the beach, it would be wise to stay out of the water due to possible rip currents. In addition, through Florence's trip, I would expect some beach erosion along the the Carolinas and Virginia.
*I will have a subsequent post early this week as Florence continues it's west-westnorthwest path toward the east coast.*
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