Friday, November 15, 2024

1000 Year Rainfall Claims Are Poppycock – Watts Up With That?

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From NOT A LOT OF PEOPLE KNOW THAT

By Paul Homewood

This is not just BS, but fraudulent BS!

Officials called Hurricane Helene’s deadly rainfall and floods “biblical” and “generational.” But weather forecasters used another term: “once in 1,000 years.”

Helene was actually the second once-in-a-millennium storm to strike North Carolina in a matter of days. Less than two weeks before Helene made landfall, an unnamed tropical storm brought 1,000-year rains to communities on the opposite side of the state, inundating homes along the coast.

The idea of two such rainfall events occurring back-to-back might seem confusing. After all, it sounds like they should only occur every 1,000 years. But in reality, it’s all about probability. Understanding the odds — and how climate change is shifting them — is more important than ever for communities and infrastructure managers.

Researchers were able to definitively identify these two extremely rare deluges in North Carolina based on rainfall frequency estimates. Using years of precipitation measurements for a specific place, scientists extrapolate what constitutes a hundred-year storm, for example, for that location.

Add in the effects of climate change — which are not included in current estimates — and the likelihood of catastrophic rains increase, said Daniel Swain, a climatologist at the University of California Los Angeles. A hotter atmosphere can hold additional moisture, which is driving more frequent and intense downpours.

Take Helene’s rains. While they were a 1,000-year event using statistical estimates based on the historic record, a rapid analysis in the wake of the storm found that rains as severe as Helene’s now occur about once every 70 years due to global warming.

https://www.bnnbloomberg.ca/investing/2024/10/18/what-it-really-means-when-a-1-in-1000-year-rainstorm-hits

So, North Carolina had two “one-in-1000 years “ rainstorms in two weeks? Really?

Sorry but this must be called out for the absolute fraud it is.

Let’s start with Helene.

Storm rainfall in the worst affected part of North Carolina was for the most part below 20 inches, although a small handful of high altitude sites recorded slightly higher than that.

http://web.archive.org/web/20240930152623/https://www.wpc.ncep.noaa.gov/discussions/nfdscc4.html

However these total were steadily accumulated over three days, for instance at Asheville:

Hurricane Helene Update

However in 1916, we know that 22 inches fell in exactly the same area in just 24-hours, still a record for the whole of the US.

Plainly the Helene floods were not unprecedented.

And what about that other storm:

This refers to the small rainstorm which dumped 10 inches of rain on a short length of coast around Southport, NC on 17th September. I covered the story here.

http://climod2.nrcc.cornell.edu/

But again, ten inches in a day along the coast of the Carolinas is pretty much par for the course, when a tropical storm passes by.

The 24-hour record for South Carolina, for instance, stands at 14.8 inches during Hurricane Floyd in 1999:

But North Carolina was even more badly affected by Floyd, according to Wikipedia:

North Carolina received the brunt of the storm’s destruction. In all, Hurricane Floyd caused 51 fatalities in North Carolina, much of them from freshwater flooding, as well as billions in damage.

The storm surge from the large hurricane amounted to 9–10 ft (2.7–3.0 m) along the southeastern portion of the state. The hurricane also spawned numerous tornadoes, most of which caused only minor damage. Damage to power lines left over 500,000 customers without electricity at some point during the storm’s passage.[2]

Just weeks prior to Floyd hitting, Hurricane Dennis brought up to 15 in (380 mm) of rain to southeastern North Carolina. When Hurricane Floyd moved across the state in early September, it produced torrential rainfall, amounting to a maximum of 19.06 in (484 mm) in Wilmington. Though it moved quickly, the extreme rainfall was due to Floyd’s interaction with an approaching cold front across the area.[2]

Extensive flooding, especially along NC Hwy 91 and the White Oak Loop neighborhood, led to overflowing rivers; nearly every river basin in eastern North Carolina reached 500 year or greater flood levels.[33] Most localized flooding happened overnight; Floyd dropped nearly 17 in (430 mm) of rain during the hours of its passage and many residents were not aware of the flooding until the water came into their homes. The U. S. Navy, National Guard and the Coast Guard performed nearly 1700 fresh water rescues of people trapped on the roofs of their homes due to the rapid rise of the water. By contrast, many of the worst affected areas did not reach peak flood levels for several weeks after the storm, as the water accumulated in rivers and moved downstream (see flood graphic at right).

The passage of Hurricane Irene four weeks later contributed an additional 6 in (150 mm) of rain over the still-saturated area, causing further flooding.

The Tar River suffered the worst flooding, exceeding 500-year flood levels along its lower stretches; it crested 24 ft (7.3 m) above flood stage. Flooding began in Rocky Mount, as much as 30% of which was underwater for several days. In Tarboro, much of the downtown was under several feet of water.[34] Nearby, the town of Princeville was largely destroyed when the waters of the Tar poured over the town’s levee, covering the town with over 20 ft (6.1 m) of floodwater for ten days.[35] Further downstream, Greenville suffered very heavy flooding; damages in Pitt County alone were estimated at $1.6 billion (1999 USD, $2.81 billion 2022 USD).[13] Washington, where the peak flood level was observed, was likewise devastated. Some residents in Greenville had to swim six feet underwater to reach the front doors of their homes and apartments.[36] Due to the heavy flooding in downtown Greenville, the East Carolina Pirates were forced to relocate their football game against #9 Miami to N.C. State‘s Carter–Finley Stadium in Raleigh, where they beat the Hurricanes 27–23.[37]

The Neuse RiverRoanoke RiverWaccamaw River, and New River exceeded 500-year flood levels, although damage was lower in these areas (compared to the Tar River) because of lower population densities. Because most of the Cape Fear River basin was west of the peak rainfall areas, the city of Wilmington was spared the worst flooding despite having the highest localized rainfall; however, the Northeast Cape Fear River (a tributary) did exceed 500-year flood levels. Of the state’s eastern rivers, only the Lumber River escaped catastrophic flooding.[33]

Rainfall and strong winds affected many homes across the state, destroying 7,000, leaving 17,000 uninhabitable, and damaging 56,000. Ten thousand people resided in temporary shelters following the storm. The extensive flooding resulted in significant crop damage. As quoted by North Carolina Secretary of Health and Human Services H. David Bruton, “Nothing since the Civil War has been as destructive to families here. The recovery process will be much longer than the water-going-down process.”[13] Around 31,000 jobs were lost from over 60,000 businesses through the storm, causing nearly $4 billion (1999 USD, $7.02 billion 2022 USD) in lost business revenue.[38] In much of the affected area, officials urged people to either boil water or buy bottled water during Floyd’s aftermath.[39]

In contrast to the problems eastern North Carolina experienced, much of the western portion of the state remained under a severe drought.[13

https://en.wikipedia.org/wiki/Hurricane_Floyd#Southeastern_United_States

Floyd dumped 19 inches on Wilmington, and this was not untypical of the wider area.

Note also the reference to Hurricane Dennis, which dropped 15 inches on the same region just weeks earlier. This certainly gives the lie to Bloomberg’s story that two such events are just not supposed to happen.

NOAA published the rainfall totals for the 33 days encompassing both storms. Wilmington, for example, received 28 inches:

.

https://web.archive.org/web/20170109112928/https://www.ncdc.noaa.gov/oa/climate/extremes/1999/september/Sep99rn2.txt

https://web.archive.org/web/20170109113605/https://www.ncdc.noaa.gov/img/climate/extremes/1999/september/ncrain3_pg.gif

In Wilmington, 18 inches fell in two days during Floyd.

Dennis, meantime, had already dropped 19.91 inches, mostly in the last two days of August:

https://www.wpc.ncep.noaa.gov/tropical/rain/dennis1999.html

Floyd and Dennis were both exceptional, but many other tropical storms have dropped as much rain as that seen in Southport last month.

So where do they get this “one in a thousand year” nonsense from?

Yes, I realise that it does not literally mean once every thousand years – it is merely a statement of probability. You can win the lottery, but that does not mean there is no chance of winning it again.

But nevertheless, there must be something fundamentally wrong with their models, if they are coming up with such results.

Indeed, even the scientists who came up with this crock of nonsense admit that the claims are based on “the historic record”. Plainly the “historic record” does not support their claims. They are no more than statistical jiggery-pokery, intended to mislead.

If it is based on the historical record, they can only tell us about the situation in the last hundred years or so. In other words, the once every 70 years they mention, which given that these are based on individual locations is probably accurate. It also implies that the US will likely see this sort of event somewhere every year.

But, based on the historic record, they have no way of knowing how frequent these events were before “global warming”. And this is where the models are twisted to provide whatever results the authors are looking for – that is, a 1000-year event.

The whole objective is to frighten the public into believing that weather is any worse than it has always been:

It is not just poor science, it is deliberate disinformation.

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