Have questions about Hurricane Florence? Ask the Capital Weather Gang.

Sep 12, 2018

The Capital Weather Gang answered your questions about Hurricane Florence Wednesday at noon.

The chat is now over but the transcript is below. You can track the storm's current path here. Be sure to follow the Capital Weather Gang on Twitter for updates.

Read The Post's coverage on the storm:

Hey everyone -- thanks for joining! Sorry for the late launch. We've got a lot of things to watch with Hurricane Florence and everyone is asking really important questions, so I want to dive in as quickly as possible. Let's get started.

All of the reporting appears to focus on the location of landful but should not the concern be on the location of the northern outer bands of wind?

This is a good question to start with because it touches on what I keep stressing -- don't focus too much on where "landfall" will happen. Landfall is a very specific thing. It's where the eye of the hurricane comes ashore. Yes, that's where the worst storm surge and winds will be, but the impacts of Florence will be so much more widespread than that.

I was just looking at the storm size, and from one end to the other, Florence measures 300 miles wide. Across that entire area, winds could be at least 40 mph and rain will be torrential at times. Storm surge will be significant well away from the eye. And with 12-30+ inches of rain falling inland, flash flooding and river flooding will be life-threatening.

Landfall is interesting but it's only a small part of the story.

With Florence appearing to move slightly south are we in DC out of danger?

Earlier this week it looked like Florence could dump a lot of rain on Washington. Fortunately for the capital, those projections have changed. Now that the forecast is farther south, it looks like D.C. will have a typical grey, showery weekend. Beyond that, we'll have to see what the moisture from Florence does early next week. I wouldn't rule out getting some rain from the storm after Monday. Too early to talk about that in much detail, though

Read the latest forecast for the D.C. area: Continued cloudy and clammy, as we keep an eye on Florence

NC had a dam emergency this summer. How many high hazard dams are in the area of forecast heavy rains? Do people downstream know about it?

I'm not sure how many of the dams are technically high-hazard, but I can say with certainty that any dam that's at risk of overflowing is a high hazard. With this much rain in the forecast, people who live downstream from dams should be watching the weather closely. If you're evacuating from the coast, I recommend making sure the place you're staying isn't in a flood zone. You don't want to evacuate from one emergency into another. 

Will Hurricane Florence pose a threat to the State of Maryland?

Maryland is at low risk, especially inland. Some of the rain Maryland gets next week could be associated with the remnants of Florence. All year the D.C., Maryland and Virginia area has been dealing with heavy rain and flooding, and that will continue next week. We just have to watch and see where the heaviest rain falls.

On the Maryland coast, high waves could lead to coastal erosion. 

It's Tuesday lunchtime as I submit this question. I just crossed the 14th St. Bridge, and saw much more than usual flooding over East Potomac Park. Is this related to the storm? Or is it just a bad sign that things are likely to get much worse when the storm flooding actually does arrive?

The coastal flooding we had earlier this week was due to a combination of high tide and winds that were pushing the water toward the shore. North of the Virginia Beach area, there will be very little coastal flooding impact from Florence, if at all. Definitely not on the Potomac. Depending on how much rain we get next week, we could see some localized flooding but it's too soon to say exactly where that will occur.

Everyone keeps talking about the rain that we will receive, but I have not seen any reports about the wind gusts in terms of what the DMV will receive. Are there any estimates of Tropical Storm winds or Hurricane Cat 1 for example (75mph to 100 mph)?

There was a chance, earlier this week, that Florence would impact the region with heavy rain, but it was never going to be a big wind threat. Even less so now. This weekend looks pretty dreary in the Washington region, but that's about it.

Hello Jason and Angela: My mother and I enjoy following the CWG. I live in the Wheaton area and our storm drains often back up when the rain comes down in large quantities all at once. A sump pump wouldn't help because there's no place to drain the water; we live near the bottom of a hill. It would just flow back towards our basement steps. We already know by following the CWG that our area is expected to get ~6 inches. But will this accumulation be spread over several hours and not drop on us all at once? Thanks for the work you do to keep the people of the DMV area informed during severe weather.

Earlier this week, we thought there might be heavy rain in the D.C. region -- something in the neighborhood of 6 inches -- but fortunately that forecast has changed. There's some indication we could get some Florence-related rain next week, but we need to keep watching how it plays out over the weekend. Still too soon to talk about amounts.

Hey! I am visiting Charleston this weekend and was wondering when I should leave DC to make sure I get there before the storm hits! Thanks.

I hate to be the bearer of bad news, but you probably don't want to go to Charleston this weekend. In fact, I suspect Charleston's hurricane watch is about to change to a hurricane warning this afternoon. They might not even let you into the city if evacuations are ordered.

Once Florence reaches the Carolina coast, it's just going to sit there all weekend. Winds are going to be destructive, surge will be catastrophic and flash flooding will be life-threatening. Stay in D.C., where the weather will be boring.

Hi - traditionally we see hurricanes hitting the coast and then moving up the eastern seaboard. It looks like this one is projected to go inland (west) and then fizzle. Why is this storm different? Does it have anything to do with the current flow of the jet stream?

You're exactly right, it has everything to do with the jet stream. Really strong high pressure developed just north of Hurricane Florence this week, which is preventing it from doing what hurricanes usually do -- curve north and then out to sea. Instead, it's forcing Florence toward the coast. The path has been really strange... we've been having a hard time finding other storms like it. 

What is the probability in next 4 days there will be any "Nice Days" in SC?

As close to zero as possible.

If hurricanes generally pick up a lot of their steam traveling through warmer water temperatures, hypothetically couldn't someone figure out a way to "super cool" the ocean so that the storms wouldn't have as much fuel? (I know the sheer vastness of the ocean would make it difficult, but don't most hurricanes during the seasonal period all start around or near a general "band" area?)

You're not the first person to suggest a way to make hurricanes weaker, or prevent them from forming at all. It's a noble effort, these thought experiments. 

There are a number of problems, though. Like you say, we don't always know exactly where a hurricane is going, so that makes it hard to figure out what part of the ocean to cool. Also, the amount of energy required to cool that much ocean water is ... unimaginable. Water has a very high specific heat, meaning it holds on to heat very well. Here's some thermodynamics, if you dare. This is all to say that it might actually be impossible to do what you're suggesting, even if it were a really good idea.

The other issue is that the planet needs hurricanes. Hurricanes take heat from the tropics and transfer it to the poles. If Earth didnt have hurricanes, the tropics would be uninhabitably hot and the poles would be giant glaciers and there would be very little livable climate in between.

Hurricanes are a necessary evil. I think we're better off spending our money on making our coasts and communities more resilient and adaptive so when they strike, they don't do as much damage.

How much water does a hurricane like Florence hold?

It varies, but check out how much water Hurricane Harvey dumped on Texas last year. We estimated around 33 trillion gallons. Obviously it's impossible to measure, but this gives you an idea of what Florence is capable of.

Although there is no doubt that storms as of late appear to be worse than what we have seen historically it seems every storm is now labeled as worst in a generation, catastrophic, etc. Similarly, giving worst case scenario's would seem to be prudent but I can think several situations of the top of my head in which the outlooks was grim only to have low impact for something that was deemed as a catastrophic storm. Any concern that by using such terms for every storm it will lead to people ignoring or dulling of the sense of severity of storms?

Totally valid point.

Hurricane Irma is a good example of that. The forecast shifted so many times with Irma that people had no idea what to expect. All they were left with was the memory of "catastrophic" and "life-threatening" damage. 

Sometimes the forecasts are going to be really bad, like they were in Irma. Other times, like Florence, we're going to have several days' notice that it's going to be a historic storm. Given how long it takes for people to evacuate the coast, I think (like you say) it's prudent to prepare for the worst-case scenario, knowing that it might end up better than expected.

Hi! What kind of effects do marine life feel from a hurricane? Do they feel the rotation of the hurricane under the surface, or is it just a normal Wednesday for Nemo?

I like thinking about this stuff.

Not sure about Nemo, but here's something interesting. Inside a truly violent hurricane (Category 4 or 5) the boundary between sea and sky doesn't exist. Where the two meet becomes a slurry of rain, waves and spray. 

As far as the fishes go, the turbulence from the hurricane extends 500 feet deep in the ocean, give or take depending on the strength of the storm. It can be devastating to marine ecosystems near the shore.

Are the OBX out if danger now that the storm has shifted???

Yes -- storm surge, damaging winds and torrential rain will still be an issued for the Outer Banks. As long as an area is still in a hurricane warning, it's not out of the woods.

Would a bomb being dropped into a hurricane possibly break it up?

No. A bomb would be like a sneeze to a hurricane. I'll refer to a story my friend and CWG colleague Jack Williams wrote on this:

"Hurricane Andrew struck South Florida in 1992, the eye and eyewall devastated a swath 20 miles wide," NOAA writes. "The kinetic energy of the wind at any instant was equivalent to that released by a nuclear warhead."

In other words, in any given moment, the power of a Category 5 hurricane is as much as a nuclear warhead. A bomb would be a pinprick to a hurricane.

In fact, lobbing a nuclear bomb into a hurricane would do nothing but create a radioactive hurricane. All of the rain would be radioactive, and the storm surge would be radioactive too. Not to mention the ocean itself — lots of radioactive marine life.

People would need shelters not only from wind and rain, but from fallout.

How do eyewall replacement cycles work? What triggers them?

Great question -- this is a huge x-factor in hurricane forecasts, something we still don't understand. We can observe them happening: An eyewall forms as the storm strengthens, then it weakens and widens, which allows for a new stronger eyewall to take its place. This can happen over and over again until the storm makes landfall. But we still don't know how it happens, and we can't really predict it. It certainly has to do with a hurricanes' purpose -- to take heat (energy) from the tropical areas and transfer it to the colder areas (the poles). It certainly has to do with angular momentum. Scientists still haven't figured out how all the pieces fit together, at least not well enough that we can forecast when it will happen.

What steps, if any, have the affected states taken to prevent storage lakes of hog excrement from being washed into downstream lakes and rivers that supply drinking water? NC--home to one of the largest industrial hog farm systems in the country--has had this problem before.

Hurricane Matthew did a number on hog and chicken farms when it struck in 2016. We looked into it back then and had a hard time wading through (punny!) the back and forth between scientists, regulators, advocacy groups and the pork council to find the truth about what the environmental impact actually was. 

My colleagues are out in front of this story with Florence. From their reporting, we know hog farmers are already reducing lagoon levels to mitigate flooding. The spillover will depend on how high the water rises and in what areas. Like you say, it's a problem N.C. has faced before and it will continue to face as long as the lagoons exist.

If hurricane names are in alphabetical order, why is it we had Gordon last week and only now Florence?

Good question! Storms are named in the order they develop. Florence formed way out in the Atlantic Ocean on September 1. Two days later, Tropical Storm Gordon formed just off the coast of Florida and made landfall before Florence.

I have a family member in North Myrtle Beach, SC, who is in the evacuation zone and lives very close to the intracoastal waterway. She is refusing to evacuate, despite repeated warnings on the news and pleas from family. Any advice for how to convince people in vulnerable places (with the means to evacuate) that it's in their best interest to leave now?

We haven't seen a storm like this since at least Hugo, 25 years ago. It's probably been a while since people have been exposed to a really dangerous hurricane, and they are hesitant to leave, but they're going to have to get out one way or another. If they leave now, it will be easy and low risk. If they leave later, it will be life-threatening for themselves and emergency responders.

Thanks for joining me and for asking thoughtful questions. If you're in the path of the storm, be smart. Do what the local officials are asking you to do. Check on your neighbors. Don't leave your pets behind. Don't evacuate into a flood zone and never EVER drive into flood water. 

Stay safe.

In This Chat
Angela Fritz
Angela Fritz is an atmospheric scientist who is currently serving as the Washington Post’s deputy weather editor.
Jason Samenow
Jason Samenow is chief meteorologist with the Capital Weather Gang.
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