Rather than yammering on and on about how a warmer atmosphere is a damper, but also more evaporation-inducing (and thus drying), and energetic atmosphere, and about how warmer air going over warmer sea water produces more and bigger storms globally, and all that, I’ll point you to some resources below.

But first I want to address two misconceptions: 1) that you can never attribute to a particular storm the effects of climate change THIS IS FALSE and 2) that climate scientists believe that Atlantic hurricanes will become less and less of a problem with climate change THIS IS ALSO FALSE.

On the attribution. Let’s say there is a disease with a 50% mortality rate. But then a treatment is invented that reduces that to zero. We use the treatment widely and nobody dies of it any more. Then, you get the disease, are cured, and go on a public speaking tour in which you espouse the greatness of this cure.

But one night, while you are speaking in front of a large audience, someone stands up and says, “Hey, wait one darn minute there! You might have been one of the 50% that would have lived! You can’t say that this cure did ANYTHING. Faker!”

The audience, realizing that the cure does not actually work, stands up and walks out.

Was that fair? Was what just happened in this scenario a honest, thoughtful turn of events?

With climate change it is a little like that. People who want to deny the importance of climate change, including journalists still stuck in the false balance mode (if there are Senators in the Senate claiming that human caused global warming is a hoax, then we must consider that as equally likely as what all the world’s scientists are saying), pull the attribution rabbit out of the hat all the time. Since you can’t yada yada. Even some climate scientists used to say this because the were badly trained in what to say.

Indeed, the binary (cure/not cured) I gave you above is not really like climate change. The fact that ALL the sea surfaces in the tropics and sub tropics — every single square centimeter — are on average (and in fact most of the time, for most of the seconds of most of the days, all year) anomalously warm, all of the tropical weather systems are affected all of the time. Fail to understand that at your peril.

The second falsehood, that Atlantic hurricanes will become less of a problem, is perhaps even more pernicious. There once was a study that seemed to show that some of the climatic conditions that would attenuate tropical cyclones, denying them the chance to form into hurricanes, would become more common in the Atlantic. This is probably true. However, the climatic conditions that cause tropical storms to form and advance to hurricane stage are also increased — different effects — and these effects have the added bonus of causing hurricanes to form much more rapidly and sometimes (perhaps often) grow much larger and, by the way, exist farther north. Indeed, if Florence does reach Category 5 for a short time today or tomorrow, it will be the farthest north Cat 5 hurricane ever in the Atlantic.

Here’s the thing. We will see periods of time when hurricanes that might have formed, say, 20 years ago, won’t. But we will also see periods of time when more and bigger and worser hurricanes form. The actual average number of hurricanes in the Atlantic has not gone down, but rather, stayed fairly stable, over recent decades. The frequency of large and dangerous hurricanes globally has gone up, and that trend is probably observable in the Atlantic.

Point is, we are not seeing a decrease in Atlantic hurricane activity or impressiveness, and we are seeing records being broken with respect to time to formation, size, strength, etc.

Climate Signals has a page on Hurricane Florence. They point out that sea level rise and coastal storms are a significant coastal erosion threat. warmer waters make for more and bigger hurricanes, keeping the hurricanes big longer, and making them form faster. These hurricanes are wetter.

Indeed, we have replaced the term “Biblical Flooding” with “Harvey Size Flooding” since we no longer have to imagine it.

Here is a helpful video:

This graph showing the relationship between sea surface temperature and hurricane activity.

Finally, an interview with Michael Mann, author of The Madhouse Effect: How Climate Change Denial Is Threatening Our Planet, Destroying Our Politics, and Driving Us Crazy, on Florence in which Mann points out ways in which climate modeling predicted greater severity of hurricanes. That set of predictions included, by the way, an increased tendency for Atlantic hurricanes to hit the US:

Florence is now likely to stall on the coast longer. This is very bad news for people on the coast. I had suspected this, and intimated it earlier and now others are realizing as well. How did I know that? Random lucky guess. I also noted earlier the possibility that Florence would degrade from major hurricane to tropical storm while it’s eye was still off shore, and thus, never make eye landfall. That would allow Roger Pelike (Junior or Senior, either one) to leave Florence off the list of landfalling hurricanes, and thus, continue to claim that climate change is not a problem. But I digress. Here’s the skinny on the storm.

How strong will Florence be?

Florence is going to be a mid range Major Category 3 hurricane as it sidles up to the coast. As it makes landfall it will weaken to a strong Category 2 hurricane. That’s the important part. Florence may well reach Category 5 status while still out over the very warm Atlantic waters, and is now a Category 4 hurricane.

Where will Florence hit?

This is one of the things that has changed over the last day. Florence is now projected to shift a bit to the south. Bulls eye (the center of the range of possible landfalls) has moved from the Greenville area down to Willington, shifting from the middle of the North Carolina coast south to the North Carolina-South Carolina border. And, it is possible that as Florence comes ashore, it will shift even further to the left, heading straight west along the northern part of the Carolina coat.

More importantly, the likely landfall location of the CENTER of the very wide hurricane has shifted from somewhere near Cape Hatteras to central South Carolina to the south, and is now projected as somewhere between the middle of the North Carolina coast down to the Georgia-Florida border. Yes, it is possible that a half million of those evacuated are out of the woods and a whole bunch of people in Georgia who may have not bothered to evacuate are now looking into the maw of the beast.

Note: This could all change again over the next 24 hours. People tell you that you can’t predict what a hurricane is going to do several days out. That is true, but it is not that important to know. Here is what is important to know: When a Hurricane gets near land, all the things that influence the storm’s direction, strength, and forward motion change in highly unpredictable ways. You’ve heard the expression, “Don’t like the weather? Wait an hour, it will change!” Everybody says that everywhere, but it actually was invented along the Atlantic coast of the US, because of all the places in the world, that is where it is the most true, owing to various factors. That coastal effect in combination with the fact that the exact geography of the storm in relation to the land and human settlement determine the nature of the storm caused death and destruction means that even as the storm is plowing into land, it is hard to predict what will happen next.

Timing

Tropical storm force winds will start to come ashore on the barrier islands of the Carolinas during the night tonight. By tomorrow morning, sunup, there will be barrier island erosion well underway, and tropical storm force winds will be well inland.

Outer hurricane-strength bands of Florence could start to come ashore mid afternoon on Thursday. Since the coast juts out to the north and the hurricane may be making a move to the left (south), that could really vary.

All afternoon and night on Thursday, tomorrow, we will see the bad parts of the storm coming to land somewhere, with the powerful front right quadrant in contact with land near the eye before sunup on Friday.

Then, the storm may sit there from the wee hours of the morning on Friday until the wee hours of the morning on Saturday. There may be a period of 24 hours of hurricane right there somewhere near the North/South Carolina border.

Some time between the wee hours of the morning Saturday and early morning Sunday, the storm will degrade to a tropical storm, but it will not have moved very far inland. Then, over the next 24 hours, Florence should speed up and spread out bringing flooding rane inland in South Carolina, Georgia, and elsewhere.

Flooding Rains: The Big Difference

Yesterday we were talking about flooding rains across Virginia, North Carolina, and some or all of neighboring states. Virginia will still experience flooding rains, but not as much, according to current forecasts. Rather than a large widely dispersed rain accumulated rain patter, Florence now seems likely to dump huge amounts of rain in a smaller area. Southwestern North Carolina is now expected to receive over 10 inches everywhere, with two feet right along the coast.

Storm Surge

The storm surge is probably more of a problem with a stalled hurricane. Don’t be distracted by the actual amounts, though. Areas where there is expected to be a 7 or 8 foot storm surge have higher topography, while areas that are expected to have 3-5 feet of storm surge are low lying areas, where a 5 foot storm surge could overtop barriers or rework coastal landscape features.

Also, with two or more feet of rain coming from above, regions that back against the coast AND are expecting a high storm surge, may experience a sort of double whammy the likes of which are really seen, so we don’t really know what the are going to look like.

As always, this is all subject to revision.

From the National Hurricane Center:

Key Messages:

1. A life-threatening storm surge is now highly likely along
portions of the coastlines of South Carolina and North Carolina, and
a Storm Surge Warning is in effect for a portion of this area. All
interests from South Carolina into the mid-Atlantic region should
complete preparations and follow any advice given by local
officials.

2. Life-threatening, catastrophic flash flooding and significant
river flooding is likely over portions of the Carolinas and
Mid-Atlantic states from late this week into early next week, as
Florence is expected to slow down as it approaches the coast and
moves inland.

3. Damaging hurricane-force winds are likely along portions of the
coasts of South Carolina and North Carolina, and a Hurricane Warning
is in effect. Strong winds could also spread inland into portions
of the Carolinas.

4. Large swells affecting Bermuda and portions of the U.S. East
Coast will continue this week, resulting in life-threatening surf
and rip currents.

FORECAST POSITIONS AND MAX WINDS

INIT 12/0900Z 29.0N 70.1W 115 KT 130 MPH
12H 12/1800Z 30.3N 72.1W 120 KT 140 MPH
24H 13/0600Z 32.0N 74.4W 125 KT 145 MPH
36H 13/1800Z 33.2N 76.1W 120 KT 140 MPH
48H 14/0600Z 33.8N 77.3W 105 KT 120 MPH…NEAR THE COAST
72H 15/0600Z 33.8N 78.2W 85 KT 100 MPH…NEAR THE COAST
96H 16/0600Z 33.6N 79.7W 45 KT 50 MPH…INLAND
120H 17/0600Z 34.2N 82.7W 25 KT 30 MPH…INLAND

Timing

The best estimate for timing of events is as follows.

On Wednesday morning, Hurricane Florence will likely be looming just off the Carolina coast, with winds of about 140 mph (making it a Category 4 Hurricane).

Tropical storm strength winds will come ashore Wednesday night. Strong surf will have already developed.

The strongest part of Florence will be pounding the Carolina coast at sunup on Friday, and the storm may sit right on the coast for several hours as it winds down to a tropical storm. Landfall and this rapid weakening may happen at about the same time. It is remotely possible that the eye wall will not pass over the coast, thus causing weather reporters and climate disaster deniers to become stupified.

Storm surge

It is important to understand how storm surge warnings work. There are two kinds of estimates that can be made. One is to assume exactly where the eye will come ashore, exactly when (to include the contribution of tieds), estimate the wind speed and forward speed of the storm, and the angle of movement, then use all these variable together with the topography of the coast to estimate how high flooding will be at any given point.

The second is to look at where the storm may go, and how strong it might be, and how those other variables will pan out, but with uncertainty in location and timing being much larger, and produce a map of coastal regions indicating where there might be high flooding, and how high that might be.

The former is generally not what you are looking at when you see a storm surge map. For example, right now there are estimated storm surges of over 9 feet near Kinston and Greenfille North Carolina, but only one foot in and around Albermarle sound. This is based on a combination of the likely track and behavior of the storm but considering that we don’t know exactly where the storm is going to hit. The difference between Greenville and Albermarle sound is a combination of where we think the storm is going and what the storm might do. The two topographies are greatly different, accounting for most of the difference in possible flood height.

In other words, most of the flood levels indicated in most storm surge maps are not going to happen. Only some of them. But, we don’t know which ones.

Anyway, there are storm surges expected to be greater than 9 feet in some places. Even three foot surges are a lot if it is high tide along very low lying barrier islands. If Florence does plow into North Carolina as expected, it is quite likely that the configuration of the barrier islands along that coast will change. Some lines may become dotted lines. Some inlets may be filled, some new inlets created, many tidal channels in the estuaries will shift. Places like the town of Ocracoke may suffer very sever damage, as they lie below the maximum possible food surge.

Flooding

Aside from storm surge, flooding happens inland with hurricanes. The special feature of East Coast hurricanes, especially in “Hurricane Alley”, between Northern Georgia and southern Virginia, is that behind the coastal plain there is a mountain range. So, if tropical storm carried water dumps on that mountain range, a two or three inch rainfall over a very large area can cause significant flooding.

Rainfall of over four inches is expected to fall over most of Virginia, and about half of North Carolina. Delaware, DC, Delmarva, Maryland, southern Pennsylvania, and parts of West Virginia and South Carolina will also get lots of rain. The area of expected landfall, and a few areas in land (like in south-Central Virginia) may see rainfall totals of over 15 inches, maybe two feet right along the coast.

A lot of roads and bridges will be wiped out, immortal doods in large pickups will be obviated, and low lying villages will be flooded. Unless the storm does a zany (and very unlikely) turn to the north before coming ashore, this may be the biggest problem, since it is hard to evacuate five or six states.

Washington DC could get up to a foot of rain. Note: The White House lies on much lower terrain than the Capitol. I’m not promising you a Rose Garden flood, but it could happen.

What if

Florence is just like any other storm of the day: Enhanced by global warming. But note this. Florence will weaken from a strong Category 4 storm to a strong Category 3 storm as it gets near the coast. This will happen because the warm waters on the surface will be churned by the storm itself into the colder water at depth, weakening the storm. Over recent years, however, we’ve seen storms fail to weaken, or even strengthen when they would normally have weakened, because the deeper water is still at “hurricane-strength” temperature. Katrina, Haiyan, and some of last year’s Atlantic storms exhibited this behavior.

With increased warming of the sea, this will eventually start to happen in the US East Coast littoral. Florence ten or twenty years from now would build to Category 5 strength and keep that level of intensity, or nearly, before reaching the shore. And, in ten or twenty years from now, sea levels will be higher. And, by then, a few other hurricanes would have smashed up the barrier islands. In 20 years, North Carolina and Virginia are not likely to be very well protected by those sand features. James Hansen was right.

There are now very few models that show Hurricane Florence not hitting the east coast of the US.

Florence is fairly likely to come ashore on the east coast somewhere between the Georgia-South Carolina border, north of Savannah, and Chesapeake Bay south of the Maryland-Virginia border. The current bull’s eye is near Wilmington North Carolina.

If the storm turns way to the north, regions including Maryland and Southern Delaware would likely be affected. If the storm turns way to the south, regions in Georgia would be affected. In all cases, how far the storm heads inland, over what time, and now wet it is, will have an impact on interior flooding, which is very likely to be be significant.

The storm surge near the point of landfill is expected to be significant.

Almost all Atlantic hurricanes reach a maximum strength while still at sea, then slow down a bit as they head inland. I believe this is in part because the warmest waters are usually a bit off shore, as well as other factors. Florence will be passing over waters that are quite a bit warmer than normal, due to global warming. It may also be the case that those waters are warm at depth, a feature of climate change that enhances storms. So, we can expect Florence to become a very strong storm, then reduce in strength to be merely a very strong storm.

In other words, there will be breathless reporting that a Category Four storm is heading for the US but the US will actually be hit by a strong Category 3 storm. Don’t be fooled that this storm is not going to be powerful.

One of the things Florence is likely to do is to curve northward as it approaches the bulging Carolina coast. The exact angle at which the storm makes landfall, and the exact location, will make the difference between a very bad hurricane and an epic disaster the likes of which have not been seen since whenever. The front right quadrant of the storm could push a huge storm surge into a restricting estuary with a city on it. One way or another, someone’s gonna lose themselves some barrier island.

Timing

By late evening Wednesday or a bit later, tropical storm force winds are likely to be on shore somewhere along the east coast. That will make being at the beach dangerous, and damage from winds and waves will commence here and there.

Early in the morning on Thursday, September 13th, Florence will be off shore and close enough to be having a strong effect on land. At that point we’ll know a lot more about where the most dangerous places to be are, but evacuations will have hopefuly already been started over a larger area. By the next morning, Friday, Florence will likely have made landfall somewhere. Starting in the wee hours of the morning on Friday and extending for the next few days, inland flooding will be severe, somewhere.

However, the forward speed of the storm can change quite a bit, so maybe this will all happen a bit earlier. Or later.

Estimates of intensity show the storm peaking in about 96 hours at 125 knots (144 mph), putting Florence in the middle of the Category 4 range. There is a very good chance the storm will be just transitioning from Category 4 to strong Category 3 at about the time of landfall.

The National Hurricane Center says:

There is an increasing risk of two life-threatening impacts from Florence: storm surge at the coast and freshwater flooding from a prolonged heavy rainfall event inland. While it is too soon to determine the exact timing, location, and magnitude of these impacts, interests at the coast and inland from South Carolina into the mid-Atlantic region should closely monitor the progress of Florence, ensure they have their hurricane plan in place, and follow any advice given by local officials.

FORECAST POSITIONS AND MAX WINDS

INIT 09/1500Z 24.4N 56.3W 65 KT 75 MPH
12H 10/0000Z 24.5N 57.4W 80 KT 90 MPH
24H 10/1200Z 24.9N 59.3W 95 KT 110 MPH
36H 11/0000Z 25.6N 61.7W 105 KT 120 MPH
48H 11/1200Z 26.4N 64.5W 120 KT 140 MPH
72H 12/1200Z 29.0N 70.8W 125 KT 145 MPH
96H 13/1200Z 32.2N 75.8W 120 KT 140 MPH
120H 14/1200Z 35.0N 78.5W 85 KT 100 MPH…INLAND

However, all of these models have the storm still a couple days minimum from hitting something (if it hits something) FIVE DAYS in the future. The collection of models suggesting a tropical storm or hurricane’s track are very accurate, at the level of something the size of a US state, for a couple/few days. Five days out is a long way to predict. If Florence were to hit the US coast, it would be in perhaps six days from now or later.

There is a very high probability that the storm will turn right, north, and entirely avoid the US.

The full range of possible landfalls IF if makes landfall runs from Miami to New Jersey.

So, it is undoubtedly too soon to say anything clear about Florence.

Nonetheless there are two things that compel me two write this premature post. First, the major media are starting to report Florence. I assume this is in part because the Atlantic Hurricane season has been quiet so far and weather-oriented reporters and editors are getting jumpy. I know I am.

The other reason is more important. Just as there are many predicted tracks that have Florence hitting the US, there are also predictions of Florence being rather strong. Most of the intensity predictions suggest that in about 100 to 120 hours from now, the storm will reach Category 3 or possibly Category 4 status.

So, if this is going to be a thing, it might be a big thing.

The intensity predictions don’t say what happens after that, and it is not uncommon for a Category 4 storm out in the middle of the ocean to weaken before it gets near land. So, the news headlines will read “Category Five Storm Heading For Virginia” while what is really happening is “Category Five Storm Will Weaken To Category 3 Storm Before Maybe Hitting Virginia.” The breathless over reporting of strength is dangerous, because the actual Category 3 storm is bad enough, still a major hurricane. But if everyone hears “The Cat Five Weakened to a Cat Three” all they may see is the word “weakened.”

When will we know if Florence is going to hit land? Maybe Tuesday or Wednesday of next week. Stay tuned.