Why? How? Read here for a reasonably recent review of the phenomenon. It has to do with changes in the way heat built up at the equator makes its way across the surface of the globe. The change is caused by the Earth warming more at the poles than at the equator. It seems that the rate of Arctic warming has exceeded expectations of a couple of decades ago, and this higher degree of warming at the poles caused a previously suspected but generally not appreciated phenomenon, the formation of giant wave in the jet stream, that in turn stall out weather systems and make the effects of global warming worse than otherwise likely. So this is an example of both a worsening and an unexpected worsening.

Not all the stalls are in the form of major rainfall events. Droughts can also occur. The so-called “ridiculously resilient ridge” that caused the recently ended California drought was one of these stalled systems.

And now, we are starting to see stalled hurricanes, for, probably, similar reasons.

In this recent Yale Climate Connections video by Peter Sinclair, Angel Adames-Corraliza, Jeff Barardelli, James Kossin, Jeff Masters, Allison Wing, Kerry Emanuel, and Michael Mann, talk about hurricanes moving more slowly, meandering, or just plain stalling, and thus causing much more damage and death and other bad things because of the enormous amounts of rainfall this phenomenon brings. Witness recent such hurricanes Florence, Harvey, Dorian.

Here is the article referenced in the video.

Irma is a new named storm in the Eastern Atlantic. See this post for details, eventually.

UPDATE (Aug 29th)

There is a system currently raining on Cabo Verde, off the West Coast of Africa (nee Cape Verde) that is expected to develop. It is on the verge of becoming a tropical depression. The National Hurricane Center has estimated that there is a high probability of this stormy feature becoming a tropical storm in a couple of days or so. If it gets a name, it will be Irma, unless some other large rotating wet object takes that name first.

UPDATE (Aug 29th)

How is the Atlantic Season doing so far, in relation to most hurricane seasons?

Using data from NOAA, we can say that on average (using the 1966-2009 baseline) we reach the eight named storm in the Atlantic (Harvey is the eighth) on September 24th. So, we’re having more named storms than average.

This year so far we’ve had 3 hurricanes. Normally one reaches that number of hurricanes on September 9th. That’s a week and a half from now, so we can declare this year a bit above average in this measure, but not spectacularly so.

So far this year we’ve had one major hurricane (Category 3 or above). There are some years with zero major hurricanes, but on average one major hurricane occurs by September 4th. So, we’re close to average now.

UPDATE (Aug 29th)

The following posts discuss various aspects of Harvey

Harvey The Hurricane: Truly Climate Change Enhanced

Is Harvey a failure of the assumption that we’ll adapt to climate change?

Harvey’s effects on petroleum pricing and related things

UPDATE:

I’m writing up Harvey here on its own post. This is going to prove to be an important hurricane. If you are in Texas get caught up right now.

UPDATE:

Well, finally, something interesting happened in the Atlantic! Tropical Depression Harvey is heading for Texas and in a very short amount of time is going to whip up into a hurricane and hit the Lone Star State right on the coastline.

From the NWS HPC:

1. Harvey is likely to bring multiple hazards, including heavy
rainfall, storm surge, and possible hurricane conditions to portions
of the Texas coast beginning on Friday.

2. Heavy rainfall is likely to spread across portions of eastern
Texas, Louisiana, and the lower Mississippi Valley from Friday
through early next week and could cause life-threatening flooding.
Please refer to products from your local National Weather Service
office and the NOAA Weather Prediction Center for more information
on the flooding hazard.

3. A Storm Surge Watch is in effect from Port Mansfield to High
Island, Texas, indicating the possibility of life-threatening
inundation from rising water moving inland from the coast during the
next 48 hours. For a depiction of areas at risk, see the Storm
Surge Watch/Warning Graphic at hurricanes.gov.

4. The Potential Storm Surge Flooding Map is available on the NHC
website. This product depicts a reasonable worst-case scenario –
the amount of inundation that has a 10 percent chance of being
exceeded at each individual location. Because the Flooding Map is
based on inputs that extend out only to about 72 hours, it best
represents the flooding potential in those locations within the
watch area.

We still hear the yammering that climate change has not affected storms. “They said there would be more storms. There’s no more storms,” they say.

They are wrong in so many ways. For example, the total energy observed in tropical storms around the globe is up. There have been several big huge scary storms in the tropics in recent years, some of which are unprecedented in their size, strength, rapidity of forming, when they formed, where they went, and what they messed up. Other types of storms show either likely increases or, if not clearly increased yet, still show strong liklihood of increasing in the future based on models. Models that are good.

This is from Emannuel 2005, showing his “Power Dissipation Index” over time and sea surface temperatures.

This shows the long term up and down swings in total tropical storm activity, and an overall upward trend exactly as expected with effects from global warming.

This is from “Increasing destructiveness of tropical cyclones over the past 30 years” by Kerry Emanuel, Nature 436:686-688.

See also this post for more details.

Roger Pielke Jr. is one of those yammering fools (I used to try to be nice to him until he accused me of horrible things a few months back and almost none of them were true!) who will tell you this. Roger says, there have bee no more landfalling Atlantic Hurricanes in the US recently than ever before. But trying to figure out what is occurring on the Earth by only considering what the smallest of the Hurricane basins produces, and only counting the small subset of those hurricanes that hit the US (and, by thew way, ignoring some of them such as Hurricane Sandy in order to fudge the numbers) is like trying to get a handle on the frequency of major train derailments by watching the 100 mile length of track you drive along five times a year on the way up north fishing. Nobody would do that. Except Roger.

The normal number of named Atlantic storms is 12.1 of which 6.4 are hurricanes, and 2.7 major hurricanes, in a given year. The record high is 28 named storms, and the record low, is 4.

There have been various predictions for how much storm activity we expect this year. The predictions that are most recent and most reliable call for 11, 12, 11-15, 14, 11-17, and 15.3 storms. So, generally, close to average plus.

The prediction I watch most closely is from PSU’s Earth System Science Center. PSU has been making very accurate predictions for a number of years. For this year, they predict 15.3 +/- 3.9 named storms this year (i.e., about 11 to 20 with the best guess being 15). Their prediction will drop a little if there is a mild El Niño this year, but that seems increasingly unlikely. Also, PSU has a second alternative model that produces a lower estimate, of around 12.4.

So, in short, barring an El Niño, we can expect a near average but slightly above average year for Atlantic hurricanes. And no, that does not mean that global warming is not happening. It means that no derailments are expected along a particular section of recently maintained rail track.

Anyway, for the second year in a row, IIRC, we got cheated on our A storm. Below, I’ve put the official list of storm names for the Atlantic 2017 season (as headings, we’ll fill in info as the year progresses), but the first tropical storm to talk about today, 19 days into the season, is Bret (one ‘t’). Arlene happened last April.

Tropical storms don’t happen in the Atlantic in April. ‘Cept for Arlene. Generally, it seems like the boundaries are becoming enfuzzied. Expect more “extraseasonal” storms over the next few years, and expect eventually, perhaps a decade from now, for the National Hurricane Center crew to be asked to start watching year round, because a tropical storm that hits your fleet in April is still a tropical storm. Even if Roger says it doesn’t exit.

Bret

Bret formed near the very southern edge of the Atlantic Hurricane basin.

This is the earliest far south forming hurricane in the Atlantic Basin. So, our first storm of the season happened months early, the second storm hundreds of miles south, compared to normal. Roger that.

Bret will menace the northern edge of South America, then in a few days from now it will be gone. Bret is not expected to strengthen and will not be a hurricane. Nor will it hit the United States of America. Therefore, according to Roger, Bret, as novel as it is, does not exist.

Cindy

The next storm, to be named Cindy, is very likely to form from a disturbance now seen in the south-central Gulf of Mexico. This is fairly typical place to see a tropical storm or hurricane form this time of year. Cindy will likely become a north-moving tropical storm, and will likely stay just at tropical storm strength, coming ashore somewhere between Houston, Texas and Morgan City, Louisiana. The chances of Cindy wetting down NOLA is very good, but again, this will not be a hurricane. This will happen some time late Wednesday, most likely.

While possible-Cindy would transform from a tropical storm to a depression with landfall, the storm will track up the Mississippi and cause lots of rain.

Don

Emily

Franklin

Gert

Harvey

Irma

Jose

Katia

Lee

Maria

Nate

Ophelia

Philippe

Rina

Sean

Tammy

Vince

Whitney

The Atlantic storms are getting interesting.

Two different systems are poised to become named storms, but it is not clear which one will be awarded the name Hermine, and which one Ian. If the storm recently near Cuba develops as expected, it could become a weak hurricane before making landfall along Florida’s Gulf coast. This will not likely be a very impressive hurricane, but it will be big and wet, and the area is already experiencing too much water. Flooding will ensue.

A third system is moving off of Africa, with 40% chance of forming into a storm over the next several days. This system looks really promising for a hurricane.

Hurricane Gaston is still hanging out in the middle of nowhere, but it will likely menace the Azores.

Update (Wednesday AM):

Gaston is at present a Major Hurricane, and will continue heading east, weakening to a tropical storm before arriving in the Azores.

There are three other systems of interest. The Cuban storminess that has been on everyone’s mind for a while refuses to get organized into a namable storm. Another, in the Atlantic, is also developing slowly. Both disturbances are likely to become sufficiently organized and strong to become named tropical storms, and that is likely to happen before sunset today. Which one will get organized first to claim the name of Hermine? Which one will become Ian? Neither is likely to spin up to hurricane strength.

The more southerly of the two storms, in the area of Cuba, is likely to sweep across the base of the Florida Peninsula and cause a mess (but as a tropical storm, not a hurricane). the other is likely to stay out to sea, in the Atlantic.

Meanwhile, the disturbance off the African Coast (to the right of the map) retains a certain amount of ambiguity as dry air reduces its chances of formation. But, it will reveal its will over the next several days as it moves west. We will see.

It is possible that we could see four names storms churning away simultaneously in the Atlantic. That is probably not a record, but it could be. My impression is that this happens now and then. Do you know? There have been as many as 8 storms formed in a given month (but not necessarily extant at the same time) a few times. So, four at the same time may be highly unusual.

ADDED:

OK, I found this about simultaneous storms:

Four hurricanes have existed simultaneously twice: August 22, 1893 and September 25-27, 1998 with Georges, Ivan, Jeanne and Karl as hurricanes. In 1971 there were 5 tropical cyclones simultaneously, but only 2 were hurricanes. [source]

Note, that refers to hurricanes, not named storms. So it is not an answer to the question.

Update (Wed PM):

Hermine exists and is expected to strengthen over the next two days or so, but not to full hurricane strength, before hitting florida near the base of the peninsula. After that, it will come out the other side, and hug the coast until at least North Carolina. Then it will go off to sea.

The second disturbance in the Atlantic will turn into a named storm, perhaps within a day or two, and Gaston will still be a named storm, so there will be three named storms at the same time. Gaston will be on or near the Azores by the end of the day Friday. The fourth stormy event, off the coast of Africa, is looking less likely to turn into a named storm any time soon.

We are approximately in the middle of the 2016 Atlantic Hurricane Season, by calendar time. The number of named storms (tropical storms plus hurricanes) predicted for this year is about 14, taking the average of all the predictions made so far, and there have been 7 storms including one currently brewing in the middle of the Atlantic. So, perhaps we are right on track.

But, the first of those seven storms actually happened last year, but after the Hurricane Prediction Center had closed the book on the 2015 season, so Hurricane Alex got dumped into the 2016 season. (It happened in Janurary.) So, we are a bit behind in the total number of named storms.

But, we are not really half way through the hurricane season. It starts on June 1 and ends on November 30th, though as was the case with Alex, individual storms sometimes fail to get the memo. But, more importantly, the peak of the season tends to be around September 10th, and the distribution of Atlantic hurricanes over they year tends to be a bit skewed, with the latter half of the season being more active.

During the period 1851 to 2015 there were 1619 Atlantic tropical storms or hurricanes recorded. 609 of them happened prior to the end of August. The remaining 1010 happened in September, or later, with September and October having most of them.

So, roughly speaking, if we are half way to the predicted 14 named storms now and still in late august, one could guess that we’ll slightly exceed average expectations, but likely fall within the range of those expectations. We’d have to have over 20 or so named storms to raise the eyebrows of most of the predictors.

I get the impression that the percentage of named Atlantic storms that made landfall this year has been on the high side, though there has been no catastrophic landfall to date.

Katrina made landfall in about four days from now (in 2005). Among the deadliest, Sandy (which was a Hurricane that ate another storm and became too big and powerful to maintain its status as a hurricane by landfall, thus dubbed a “super storm” and enigmatically left off most hurricane lists) was later in the year, as were Stan, Jeanne, Mitch, Gordon, Fifi-Oriene, Flora, Jeremie, several other storms. Of recent deadly storms, Katrina was relatively early, and only 1979’s David came close (formed August 25th, fizzled out on September 8th).

So, speaking just of the more powerful storms, that is generally a phenomenon of September or October and now and then November.

Gaston is the currently active named storm. It is likely to form into a hurricane over the weekend, veer right before coming too close to Bermuda, and remain pretty far out in the Atlantic. There are no clear predictions of what it will do by mid week, but it is likely to weaken a bit on Wednesday. Gaston will be in hurricane-hostile territory at that time, so may be it will just go away.

Hermine is the name that would be given to what is now a tropical disturbance, should it form a tropical storm. The changes that it will do so are not small. If Hermine forms up into a reasonable storm, the chances that it would miss already-water-logged Florida are very small. I expect Hermine to be a significant weather event for the southern US.

South Carolina Floods

I haven’t said much about this partly because there is so much good coverage, but South Carolina’s floods, still ongoing, are going to get on the list of worst weather events of 2015. Since these floods are amounting to a one in 1,000 year event, they are actually on the list of worst weather events since Vladimir the Great died, Cnut the Great invaded Enlgand (unrelated event), Eric Haakonsson outlaws berzerkers in Norway, and Olaf Haraldson declared himself King of Norway.

And yes, that event was climate change enhanced in at least two ways, maybe three. With global warming there is more moisture in the atmosphere and in large parts of North America it seems that this moisture is often clumped up into longer term slow moving rain systems. That was going on in the region for days. Then, the strength, size, and wetness of hurricane Joaquin, which indirectly fed moisture into the system, was enhanced by very high sea surface temperatures in the Atlantic. Also, those sea surface temperatures have generally increased the punch from Atlantic based storms. All in all, it is likely that South Carolina, the neighbor of the state that is famous for making climate change illegal, and who’s congressional delegation refused to help the victims of Super Storm Sandy, got walloped by climate change.

Fortunately for the good people of South Carolina, our federal government does not act cynically and help is on the way. But next time we are called to help a storm impacted region, we expect South Carolina to put their big kid pants on and step up to the plate.

Oh No, Oho!

The storm formerly known as Oho, a Category 2 eastern Pacific hurricane, is in the process of doing something that does not happen very often: Slamming into British Columbia and Alaska. I’m told this is only the second time a tropical storm, in a post-tropical state, has followed a track like this.

Probably not a big deal for a region where serious windy and wet storms are common. But this is yet another case of the tropics breaking out of their usual pattern as a result, likely, of climate change combined with this year’s ongoing El Nino. Certainly, warm sea surface temperatures (which are everywhere there is sea) have helped this system maintain strength as it has moved north.

Here in Minnesota, famous for winters that start in October, we will be experiencing a summer like weekend. Global warming plus El Nino has exacerbated an ongoing trend of warming falls. Too bad some of our garden plants respond more to changes in sunlight than to changes in temperature, or we might not be eating fried green tomatoes for dinner tonight.

More hurricanes to come?

Meanwhile keep an eye on the Eastern Pacific. Two more disturbances are developing with reasonable (though not certain) chances of becoming tropical storms. 18-E is very likely to become a hurricane by early Sunday morning, and if so it will be called Pali. Disturbance Number 1, just getting going, has about a 50% chance of becoming a tropical storm over the next five days. All quiet in the Atlantic, the rest of the Pacific, or the Indian Ocean.

In case you were wondering about the climate change – hurricane link, this might be of interest to you:

A large typhoon (hurricane) is heading for China and is expected to make landfall in the vicinity of Shanghai. The image above is from the Japan Meteorological agency, and the image below is from JAM via Jeff Masters Blog.

Apparently Chan-hom will make landfall in a region that very rarely sees typhoons. Chan-hom will be, according to Masters,

… one of the strongest typhoons on record for a portion of the country unused to strong typhoons. Of particular concern is Chan-hom’s storm surge, which has the potential to bring the highest water levels ever observed into Shanghai, China’s most populous city, with 23 million people in the metro area.

This is all going to happen Saturday US time, in the wee hours of the morning, but PM locally. The storm, now a category 4, will likely be a category 2 at the time of landfall, which is still a problem.

The region has real tides, so a storm surge of several feet during low tide may be not such a big deal, while a storm surge on top of high tide could be devastating. In 1956 a storm came through with a nearly 6 foot storm surge but the normally 7+ foot tide was not high. In 1997, Winnie, a mere Category 1, struck near Shanghai. According to Jeff Masters,

the storm surge from Winnie was only 5.5″ (14 cm) below the top of the 19.2-foot (5.86 meter) Suzhou Creek floodgate that protects downtown Shanghai on the Huangpu River, which flows through the center of town. This floodwall was rated to protect against a 1-in-200 year flood, and was overtopped by about one foot (30 cm) along a 8.5 mile (13.7 km) section inland from the downtown area, flooding over 400 homes

The tied, therefore, will make a huge difference, and it is probably too early to say much about the co-occurrence of high tide and Chan-hom’s landfall.

Jeff has a LOT more on this storm and several related issues such as sea level rise in the area at his post.

In addition, there are three other tropical cyclones extant in the Pacific.

Nathan is just on the Tropical Storm-Hurricane boundary and is heading for Cape York, Australia. Olwyn is a fully formed tropical cyclone (hurricane) with sustained winds at 85mph, and is busy menacing the west coast of Australia, which it will scrape over the next several hours, reaching Sharks Bay very soon and passing off the southwest corner of OZ over the weekend. But since that is so many time zones away we really have no idea when any of this will happen. Bavi is a tropical storm out in the Pacific heading roughly west by northwest. This storm may reach hurricane strength in a few day, but the forecast I saw is very uncertain.

And yes, there are views of the Earth that allow you to see all four storms at once. Here is one from the Climate Reanalyzer. The storms are marked but you should be able to spot them:

This one, that I got of Twitter, has the storms marked:

You don’t see this every day.

Tropical Storm Polo is currently south of Mexico and is expected to stay away from the coast, and it is not clear that it will reach Hurricane strength. If so, only for a brief time.

Hurricane Iselle was the strongest tropical cyclone to hit Hawaii (the big island).

Hurricane Marie was the first Category 5 Pacific hurricane in the region in four years.

Hurricane Genevieve was the first hurricane to pass through all three defined Pacific hurricane basins since 2003.

Including Polo, there have been 17 named storms in the Eastern Pacific so far this year. Eleven have been hurricanes. The average Eastern Pacific hurricane season has 15.4 (range 7-25) storms with 8.4 hurricanes (range 3-16). Officially the season ends on November 30th. So, this is clearly an exceptional year.

Warm ocean waters combined with light wind shear will allow the storm to remain well organized through Friday as it approaches Hainan Island. Rammasun will likely bring widespread winds of 100 mph to northern Hainan Island on Friday afternoon and Friday night with higher gusts. Widespread wind damage is expected across northern Hainan, as well as the Leizhou Peninsula to the north.

Jeff Masters has a detailed analysis here.

UPDATE Friday AM: The typhoon is battering the coast in Hainan and Guangdong provinces in southern China China, and the Chinese have classified this as a “red alert” typhoon, the highest category for them.