What developed from a typical Cape Verde tropical wave is quickly becoming a disaster in the making for the Southeastern US…. In particular, North Carolina and to a lesser extent, South Carolina and Virginia as well. Early on in it’s formation, it seemed a fairly cut and dry forecast. Florence would develop, curl out to sea, and nothing would come of it….. However, A typhoon in the Western Pacific had other ideas… Super Typhoon Jebi made landfall in Japan nearly a week ago, and the strong low pressure system that Jebi spawned as it transitioned into an extra tropical storm, created a chain reaction that has led to a nearly record breaking ridge forecast to develop over the Northeast and Western Atlantic over the next couple of days…….
This could not be worse timing as this ridge has caught Hurricane Florence, turning it west and creating one of the more unusual tracks a hurricane could take in the Atlantic. Indeed, every single hurricane that has developed and moved in the areas that Florence has… besides Florence herself, have harmlessly moved out to sea….
This is further exacerbated by a tropical wave and Upper level low currently situated over the Central Gulf of Mexico. These two features combined have removed much of the dry air from Florence’s path, and the ridge, has eliminated the wind shear….. The only question then remains surface temperature of the ocean..Which is the only place in the Atlantic that is anomalously above normal at this time of the year.
A terrible combination of events, with even worse timing, has led to what can only be described as a terrifying situation. Florence took advantage of this atmosphere starting last night, and rapidly intensified to a Category 4 storm with winds of 140.
Tonight, the storm has wavered a bit, combating some internal core issues. Most notably, the hurricane is undergoing an Eyewall Replacement Cycle, in which a secondary ring of storms forms around the inner eyewall, and chokes it off, eventually leading to the inner eyewall’s collapse, and the outside ring taking over as the new eye. During this, the overall wind and pressure gradient spread out, which weakens the winds, but enlarges the storm. The new eye will then begin to contract, and the wind speeds will likely again rise. This is terrible news for the people of North Carolina, as it is highly likely to see a Category 5 Florence moving in their direction tomorrow afternoon and evening, maybe even through Wednesday. Wind shear will begin to pick up as Florence makes it’s approach to the coast, which may serve to weaken the system a little… However, at this point, it would be like throwing a dart at a rhino, and would be too little, too late. On Thursday, the forecast, which up to this point had been very straightforward, suddenly becomes much much more difficult.
The upper level ridge mentioned earlier in this discussion, begins to break down, with a new ridge forming over the Ohio Valley. Unlike previous storms with the names of Hazel, Gracie, Floyd, and Hugo, Florence will not be pulled away by an incoming trough. Instead, what seems likely at this time, is that Florence will stall either inland… or just offshore, in what may an even worse incarnation of Harvey from last year. With a high to the north, east, west, and south of Florence.. There is simply no where else for her to go. It is important at this point to note that a difference of 50 miles in any direction, will have a MAJOR impact on what happens to the storm during this time. 50 miles to the south or east, and Florence could sit and spin offshore of the north carolina coast. This would create a terrible storm surge for much of the coastline, with beach erosion being nearly complete. 50 miles to the North or West, and Florence could then move inland, dumping heavy rain over much of the area, and at the same time, quickly weakening the system.
Should this weakening occur, Florence will start moving as it becomes guided by trade winds lower in the atmosphere, whereas a stronger Florence offshore will be guided by winds higher off the ground, and will likely remain stalled for several days before the Ohio valley ridge moves it west back into the coastline anyways. It’s very much a case of pick your poison as it seems very unlikely, though not impossible, for Florence to entirely miss the US coastline at this time.
Regardless of either of these, the fact remains that you have a landfalling organized tropical system sitting and stalling out over an area for several days. Rainfall will be torrential, will build up quick, and in areas that have already seen more rain than average during the summer. Flooding will quickly become another big issue, even for those who have moved inland to escape the coast… It should be further noted that even where Florence goes once it’s inland, IF it gets inland, will also be a major issue. Move west and Florence will run up against the Appalachian mountains where upsloping and terrain will work as the proverbial wringing of the sponge, working more and more moisture out of the atmosphere which could create rockslides in areas that get a lot of rain. Should some of the models be correct, rain may be measured not in inches, but feet. Needless to say, it’s all around just a terrible situation….. And it may only be the first of more to come.