Florence: Storm Surge And Rainfall Of More Consequence Than Category

Sep 13, 2018

Meteorologist Steven Pfaff from the National Weather Service provides a late morning update on Hurricane Florence. He says the category of the storm is nearly inconsequential--when the ground is saturated, the wind can be destructive at lower speeds.

WHQR's Gina Gambony spoke with Pfaff; listen above and see our full transcript below.

Steven Pfaff is the Warning Coordination Meteorologist for the National Weather Service in Wilmington, North Carolina.

Gina:      We're hearing a lot about the flooding, about the water. Can you tell me about that?

Steven:   Yeah. Unfortunately, since the storm is expected to continue to slow down, in fact, with the 11 am advisory it has to be done to do so. We're looking at rainfall totals as a result with this thing in the area in the next couple of days, of 20 to 30 inches across the Cape Fear area. So, just a phenomenal amount of rainfall. We wouldn't be surprised if there are isolated higher amounts closer to 40. We hope that the storm can keep moving on and off to the West and pick up some speed, but it's not looking likely.

Gina:      The precipitation that's falling into the rivers and streams upstream from us-- is all that coming to us and then we'll increase the flooding in areas around bodies of water?

Steven:   Yeah, and some of the longer developing river flooding that typically follows, or develops during and then persisted for a week or two afterwards, looks like it will be coming into the picture here. It's possible we could have major flooding along the Northeast Cape Fear River at Burgaw. Possibly along some of the other rivers into the area as well. The Lumber River, Waccamaw River and anything connected to it. Fortunately, the, you know, the river levels were low because it's been so dry in August and September thus far, so we can take a little bit, but they're not going to be able to take 20, 30 inches of rainfall. They'll get to major flood levels as a result.

Gina:      Do you think it's possible for areas that don't usually flood, to flood?

Steven:   Yes. Looking at the amount of rainfall, it is possible that some areas that didn't receive flooding during Floyd, or with Matthew for the folks further inland, they, they could see flooding with this event. It has the potential to be a catastrophe on the large scale in our part of the country. I think another thing to consider too, flooding is very complex. It's not just the amount of rainfall that's going into the area, but also we have to deal with storm surge. So the higher water levels that the storm is bringing right into the coast, that could counter any of the normal flow down through our creeks and streams and everything tidally connected like the Cape Fear River, as it tries to flow out normally and runs into the storm surge, everything backs up. So we got a lot of rainfall coming, a slow moving storm. This is a recipe for disaster in terms of flooding.

Gina:      Are the tide's going to come into play at all?

Steven:   Yeah, they will in some, in some places the tidal influences will significantly cause rises or falls and the flooding impacts that we're seeing especially there's a lot of closer to the coast. Well upstream Cape Fear River, Northeast Cape Fear River, the tidal contribution is very nominal at that point, but it's very large as you get to the tidal creeks, Bradley Creek, Virginia Creek, and all the other little tributaries and small we have in the area of Brunswick River. Those things are very tide modulated.

Gina:      Of course, we also are going to have hurricane force winds in our area. Are we expecting hurricane force winds for two or three days?

Steven:   Yeah. Yeah. This, this event is a multi spectrum type of storm. When we talk about the individual hazards and we discuss the storm surge parts, we talked about the flooding component part and we can't forget the winds too. I mean, there are certainly going to be some hurricane force winds in the area. We think the strongest winds fortunately may be more limited to the coastal areas, like we typically see. But since this is such a large storm in the area, of tropical storm force winds is expected to be very expansive. We will have wind impacts, especially as the ground becomes saturated over time, the trees and the roots don't have anything to hold onto. The ground gets liquification and it doesn't take as much wind to knock over trees, trees down on power lines, onto homes, those sorts of things. Long term power outages. And this is going to be a tough recovery.

Gina:      Right now I'm talking to you at about 16 minutes past 11:00 AM. If there's anyone who is still considering leaving the Wilmington area, is it still safe to do so? And if they leave, where should they go?

Steven:   It's a very difficult question to answer because of the expansiveness of this storm. Certainly anybody in a low lying storm surge area, you know, along the tidal creeks, along the ocean front-- now's the time to get out. That first band is not far off shore. As the storm gets closer tonight into tomorrow, the storm surge is going to pick up. And also anybody who has experienced flooding from Floyd and matthew, it's likely going to happen again. So if you had low lying areas near the rivers, you don't want to get cut off. You want to be able to take action now. And again, time is running out. We don't have too much time here.

Regardless of the intensity changes in the forecast with Florence, if it is going to be a Cat 1 or Cat 2, at landfall or as it approaches the coast, I think is going to be pretty much inconsequential at this point with the storm surge aspects and with the heavy rainfall. We've got to continue to take this seriously. Don't take the bait, given the weakening. Be prepared.