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Hurricane Harvey In Perspective

August 31, 2017

By Paul Homewood



Thankfully it’s stopped raining in Houston, so time for a round up on Storm Harvey.

Total rainfall from the storm peaked at 51.88 in at Cedar Bayou, just outside Houston.



This beat the previous record rainfall from a single storm over the contiguous US. The previous record was 48 in from Storm Amelia in 1978, also in Texas. However, most of that fell over just four days, from Aug 2nd to 5th.

Rainfall from Harvey was less intensive, as it was spread over five days.

Neither event was close in intensity to Storm Claudette, which dumped 43 in on Alvin, Texas in July 1979 in a single 24-hour period.



Texas Hurricane Trends

In 2010, David Roth of the NWS published his “Texas Hurricane History”, which gave this list of Texas landfalling cyclones:




Since 2010, there have been three tropical storms, Alex, Hermine and Bill, and no hurricanes (prior to Harvey of course).

The 1940s was by far the busiest decade.

Roth goes on to explain why the weaker tropical storms tend to carry the greatest flooding risk:


He also includes the full list of hurricanes:





Based on this list, and including Harvey, we can tabulate the number of major hurricanes by decade:




Clearly there is no trend towards more powerful hurricanes, and Harvey was the first Cat4 since Gilbert in 1988. (I have seen it incorrectly reported that Harvey was the most powerful Texas hurricane for “more than 50 years”).

Roth also has an account of one the worst Texas floods on record, San Antonio’s Great Flood of 1921:


The rainfall recorded over 18 hours in Williamson County was far greater than anything experienced around Houston during Harvey.



Jet Stream Behaviour

The usual suspects have attempted to claim that global warming has made Harvey more intense than it would have been otherwise, for instance Mann and Trenberth here.

However, comparison with earlier storms, such as San Antonio, Amelia (1978) and Claudette (1979) discredits such claims.

As we know, the only reason why so much rain fell on Houston was because Harvey was stuck between two high pressure systems for five days. So step forward Michael Mann to claim that this weather event was due to climate change!

“The kind of stalled weather pattern that is drenching Houston is precisely the sort of pattern we expect because of climate change,” climatologist Michael Mann explained in an email to ThinkProgress.

Earlier this year, Mann co-authored a study explaining how human-caused warming is changing our atmosphere’s circulation, including the jet stream, in a way that leads to “increase in persistent weather extremes” during the summer.

“I agree with Mike [Mann] that the weak steering currents over the south-central US coincident with Harvey are consistent with our expectations for a warmer world, which of course includes effects of a very warm Arctic,” Jennifer Francis, a climate scientist at Rutgers University, told ThinkProgress.

Francis is a leading expert on how global warming and the related Arctic amplification affect the jet stream and extreme weather. A study she co-authored that appeared in the Journal of Climate in June, concludes, “Over the central United States during summer, the weaker and wavier flow” of the jet stream favors “more intense summer weather.”

A 2012 study led by the National Oceanic and Atmospheric Administration (NOAA), and coauthored by Francis, concluded global warming was driving changes in extreme weather in North America. “Our research reveals a change in the summer Arctic wind pattern over the past six years,” lead author James Overland of NOAA explained at the time. “This shift demonstrates a physical connection between reduced Arctic sea ice in the summer, loss of Greenland ice, and potentially, weather in North American and Europe.”

“Enhanced warming of the Arctic affects the jet stream by slowing its west-to-east winds and by promoting larger north-south meanders in the flow,” NOAA said in a press release. “The researchers say that with more solar energy going into the Arctic Ocean because of lost ice, there is reason to expect more extreme weather events, such as heavy snowfall, heat waves, and flooding in North America and Europe but these will vary in location, intensity, and timescales.”



Only one problem with Mickey Mann’s theory!

HH Lamb found exactly the same phenomenon back in the 1960s and 70s, when the Arctic was getting much colder and the sea ice was expanding. In 1982, he wrote:

Such worldwide surveys as have been attempted seem to confirm the increase of variability of temperature and rainfall [since 1950].’’

In Europe, there is a curious change in the pattern of variability: from some time between 1940 and 1960 onwards, the occurrence of extreme seasons – both as regards temperature and rainfall has notably increased.

These variations, perhaps more than any underlying trend to a warmer or colder climate, create difficulties for the planning age in which we live. They may be associated with the increased meridionality of the general wind circulation, the greater frequency of blocking, of stationary high and low pressure systems, giving prolonged northerly winds in one longitude and southerly winds in another longitude sector in middle latitudes.

Over both hemispheres there has been more blocking in these years… The most remarkable feature seems to be the an intensification of the cyclonic activity in high latitudes near 70-90N, all around the northern polar region. And this presumably has to do with the almost equally remarkable cooling of the Arctic since the 1950’s, which has meant an increase in the thermal gradient between high and middle latitudes.

And he was not the only one. CC Wallen of the WMO wrote:

The principal weather change likely to accompany the cooling trend is increased variability-alternating extremes of temperature and precipitation in any given area-which would almost certainly lower average crop yields.

During cooler climatic periods the high-altitude winds are broken up into irregular cells by weaker and more plentiful pressure centers, causing formation of a “meridional circulation” pattern. These small, weak cells may stagnate over vast areas for many months, bringing unseasonably cold weather on one side and unseasonably warm weather on the other. Droughts and floods become more frequent and may alternate season to season, as they did last year in India. Thus, while the hemisphere as a whole is cooler, individual areas may alternately break temperature and precipitation records at both extremes.

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In other words, these proper scientists found the exact opposite of what Mann and Francis are claiming now.

  1. Joe Public permalink
    August 31, 2017 3:57 pm

    “Neither event was close in intensity to Storm Claudette, which dumped 43 in on Alvin, Texas in July 1979.”

    During a 24-hour period!

  2. August 31, 2017 4:00 pm

    “So step forward Michael Mann to claim that this weather event was due to climate change!”

    Shouldn’t that be “slither forward?”

  3. August 31, 2017 4:03 pm

    No trends in hurricane activity 1945-2014

  4. Mack permalink
    August 31, 2017 4:48 pm

    Bingo! Well done Paul for yet another clinical, evidence based appraisal of a ‘seemingly natural’ event that was neither extraordinary, unusual or even unprecedented in recent Texas history, never mind in the millennia before when humans weren’t around to record the impacts of such hurricanes. What was particularly interesting for me was a report on last night’s ITV evening news in the UK about the flooding in Houston that clearly attributed the intense urban impacts on poor town planning, unregulated construction along vulnerable watercourses and inadequate flood defences, not climate change. Is that a first for a channel that, like Sky, BBC and Ch4, almost always prefaces any report of a natural disaster with the climate change mantra? Is the worm beginning to turn perhaps?

  5. Athelstan permalink
    August 31, 2017 4:49 pm

    Seriously, a great read educating too. Thanks Paul and the stuff from HH Lamb I can’t get enough of that.

    I won’t wax on lyrical about storms, I’ve had me face slapped ’bout that and a couple of times but I can console myself in that, I probably know more than does Mickey mouse Mann, having said that – maybe “console” is probably the wrong word.


  6. Sunsettommy permalink
    August 31, 2017 5:42 pm

    Significant Houston Area Floods

    The record starts in 1837.

  7. Sunsettommy permalink
    August 31, 2017 5:45 pm

    Jo Bastardi replies to Mann overboard:

    Bastardi: No Michael Mann — Climate change did not cause Hurricane Harvey

  8. A C Osborn permalink
    August 31, 2017 6:22 pm

    One slight error Paul, “Clearly there is no trend towards more powerful hurricanes, and Harvey was the first Cat4 since Gilbert in 1988”
    it wasn’t really a Cat 4 when compared to the previous ones was it?
    As you know it only attained Cat 4 by them using Satellite high altitude wind speed values.
    The ground speeds say it was a Cat 2 and possibly a Cat 3 for a short period.

    • dave permalink
      September 1, 2017 6:59 am

      After a bit of confusion between knots and mph the following becomes clear:

      ‘Harvey’ briefly attained 100 knots (=115 mph) when it reached the barrier islands near Corpus Christi – and then quietened, although still giving widespread rain.

      ONLY speeds at 10 meters local elevation count.

    • September 3, 2017 10:07 pm

      What I’ve been thinking as well. At most this was a Cat3 storm, which declined really fast once it made landfall and maintained its Tropical Storm strength\pattern over the weekend.

    • Nomoregore permalink
      September 4, 2017 12:51 am

      The Weather Channel were reporting the CAT 4 designation was ‘Estimated’ from winds at altitude. Looking up the History, the declaration of CAT 3 was ~10 hrs prior to landfall. This lasted for only 4 hours, when CAT 4 was declared SURPRISE! 1MPH over the line. This designation only lasted 6 hrs. But surface measurements were commonly seeing GUSTS in the 110 range. I saw a single location that claimed a gust of 132.

      It was most likely just peeking into CAT 2 territory at landfall. But all the lefty heads explode, and there is green vomit everywhere if you mention this in most forums.

  9. A C Osborn permalink
    August 31, 2017 6:25 pm

    The current floods in Asia also put this Hurricane in perspective, as Paul’s data showed Asia gets a lot higher rainfall totals than the USA.
    The great flood of China is another one as well.

    • Nordisch-geo-climber permalink
      August 31, 2017 11:13 pm

      I can not produce the words of admiration for all the effort you put in, in telling the truth.
      Thank you so much.
      I’m sure we can all do our best to spread the words of common sense.
      This is a massive issue for our contemporary political and scientific contemporary society and establishment, and they are on very thin ice indeed.
      The evidence is against them.

  10. Philip Hurst permalink
    August 31, 2017 10:17 pm

    On Thu, 31 Aug 2017 at 17:44, NOT A LOT OF PEOPLE KNOW THAT wrote:

    > Paul Homewood posted: “By Paul Homewood Thankfully it’s stopped raining in > Houston, so time for a round up on Storm Harvey.Total rainfall from the > storm peaked at 51.88 in at Cedar Bayou, just outside Houston. > This ” >

  11. September 1, 2017 4:16 am

    Reblogged this on Climate Collections.

  12. Coeur de Lion permalink
    September 1, 2017 7:01 am

    I noticed that our famous biased BBC took some time to mention ‘ ‘climate change’ in its coverage and then only as a third party quote.

  13. Gerry, England permalink
    September 1, 2017 12:51 pm

    So meridional Jetstream is related to cooling which is what competent scientists have been predicting in relation to declining solar activity.

    • RAH permalink
      September 1, 2017 1:35 pm

      yep, seems that when the sun gets quiet the jet stream gets loopy.

  14. Dermot Flaherty permalink
    September 1, 2017 4:23 pm

    Paul, I am lost in admiration for your clinical analysis of Hurricane Harvey and the completely expected rush by the usual suspects to blame Climate Change.
    I was listening to the Today programme a few days ago when the presenter talked to some official in Houston and within a couple of questions, the Today guy wanted to know if the Houston guy blamed Climate Change.
    I really must stop listening to Today since its diet of soundbites and opinions has long since replaced news and it doesn’t do my blood pressure any good.
    Thank goodness for people like you who take the time to discover and present the facts.
    The BBC seems unable to do anything remotely like that these days.

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