Radar image Hurricane Laura

Hurricane Laura put on a phenomenal show of rapid intensification prior to landfall, increasing in strength by 65 mph in just 24 hours on August 26, 2020. That ties Hurricane Karl of 2010 for fastest intensification rate in the Gulf of Mexico on record. In the 24 hours prior to landfall, Laura’s winds increased by 45 mph, and the mighty hurricane made landfall in western Louisiana as a category 4 storm with 150 mph winds – the strongest landfalling hurricane in Louisiana history, and the fifth-strongest hurricane on record to make a continental U.S. landfall.

Laura’s rapid intensification was a disturbing déjà vu of what had happened just two years earlier.

Analysis

As Hurricane Michael sped northwards on October 9, 2018, towards a catastrophic landfall on Florida’s Panhandle, the mighty hurricane made an exceptionally rapid intensification. Michael’s winds increased by 45 mph in the final 24 hours before landfall, taking it from a low-end category 3 hurricane with 115 mph winds to catastrophic category 5 storm with 160 mph winds. And Michael’s performance echoed what had happened in 2017, when Hurricane Harvey rapidly intensified by 40 mph in the 24 hours before landfall, from a Category 1 storm with 90 mph winds to a Category 4 storm with 130 mph winds.

Human-caused climate change causing more rapidly intensifying Atlantic hurricanes

Unfortunately, not only is human-caused climate change making the strongest hurricanes stronger, it is also making dangerous rapidly intensifying hurricanes like Laura and Michael and Harvey more common.

According to research published in 2019 in Nature Communications, Atlantic hurricanes showed “highly unusual” upward trends in rapid intensification during the period 1982 – 2009, trends that can be explained only by including human-caused climate change as a contributing cause. The largest change occurred in the strongest 5% of storms: for those, 24-hour intensification rates increased by about 3 – 4 mph per decade between 1982 – 2009.

Led by hurricane scientist Kieran Bhatia of NOAA’s Geophysical Fluid Dynamics Laboratory – and titled “Recent increases in tropical cyclone intensification rates” – the study used the HiFLOR model to simulate intense hurricanes. HiFLOR is widely accepted as the best high-resolution global climate model for simulating intense hurricanes.

Dangerous scenario – rapidly intensifying hurricane making landfall

Rapidly intensifying hurricanes like Michael and Harvey that strengthen just before landfall are among the most dangerous storms, as they can catch forecasters and populations off guard, risking inadequate evacuation efforts and large casualties. A particular concern is that intensification rate increases are not linear as the intensity of a storm increases – they increase by the square power of the intensity.

Lack of warning and rapid intensification just before landfall were key reasons for the high death toll from the 1935 Labor Day hurricane in the Florida Keys, the most intense hurricane on record to hit the U.S. That storm intensified by 80 mph in the 24 hours before landfall, and it topped out as a Category 5 hurricane with 185 mph winds and an 892 mb pressure at landfall. At least 408 people were killed, making it the eighth-deadliest hurricane in U.S. history.

Another rapidly intensifying hurricane at landfall, Hurricane Audrey in June 1957, tracked on nearly the same course as Hurricane Laura. Audrey was the seventh deadliest U.S. hurricane, killing at least 416. Its winds increased by 35 mph in the 24 hours before landfall near the Texas/Louisiana border as a Category 3 hurricane with 125 mph winds. Lack of warning and an unexpectedly intense landfall were cited as key reasons for the high death toll.

With today’s satellites, radar, regular hurricane hunter flights, and advanced computer forecast models, the danger that another Audrey or 1935 Labor Day hurricane could take us by surprise is lower.

Also see: Video: Jeff Masters on 2019 Hurricanes

But all of that sophisticated technology didn’t help much for 2007’s Hurricane Humberto, which hit Texas as a Category 1 storm with 90 mph winds. Humberto had the most rapid increase in intensity, 65 mph, in the 24 hours before landfall of any Atlantic hurricane since 1950. A mere 18 hours before landfall, the National Hurricane Center (NHC) in 2007 had predicted a landfall intensity of just 45 mph, increasing its forecast estimate to 65 mph six hours later. It’s fortunate that Humberto was not a stronger system, as the lack of adequate warning could have led to serious losses of life.

Historical records show that since 1950, the eight storms have intensified by at least 40 mph in the 24 hours before landfall. It is sobering to see three of those storms, below in bold face, occurred in the past four years:

Humberto, 2007 (65 mph increase);
King 1950 (60 mph increase);
Eloise 1975 (60 mph increase);
Danny 1997 (50 mph increase);
Laura 2020 (45 mph increase);
Michael 2018 (45 mph increase);
Harvey 2017 (40 mph increase); and
Cindy 2005 (40 mph increase).

Extreme rapid intensification rates just before landfall to become more common

In a 2016 study – “Will Global Warming Make Hurricane Forecasting More Difficult?” from the Bulletin of the American Meteorological Society – MIT hurricane scientist Kerry Emanuel used a computer model that generated a set of 22,000 landfalling U.S. hurricanes between 1979 and 2005. Emanuel then compared their intensification rates to a similar set of hurricanes generated in the climate expected at the end of the 21st century.

For the future climate, he assumed a business-as-usual approach to climate change – the path we are currently on. Emanuel found that the odds of a hurricane intensifying by 70 mph or more in the 24 hours just before landfall were about once every 100 years in the climate of the late 20th century. But in the climate of the year 2100, these odds increased to once every 5 – 10 years.

What’s more, 24-hour pre-landfall intensifications of 115 mph or more, essentially nonexistent in the late 20th-century climate, would occur as often as once every 100 years by the year 2100. Emanuel found that major metropolitan areas most at risk for extreme intensification rates just before landfall included Houston, New Orleans, Tampa/St. Petersburg, and Miami.

Figure 1
Figure 1. VIIRS image of Super Typhoon Haiyan at 1619 UTC November 7, 2013. Haiyan at that point was about to make landfall near Tacloban in the Philippines with 190 mph winds, the strongest land-falling tropical cyclone in recorded history. (Image credit: NOAA/CIRA)

Eight-fold increase in ultra-intense hurricanes predicted

The same HiFLOR high-resolution global climate model for simulating intense hurricanes referenced above produced some rather startling findings detailed in a 2018 paper, Projected Response of Tropical Cyclone Intensity and Intensification in a Global Climate Model.

The scientists who authored that paper forecast a dramatic increase in the global incidence of rapid intensification as a result of global warming, and a 20% increase in the number of major hurricanes globally.

For the Atlantic, the model projected an increase from three major hurricanes per year in the climate of the late 20th century, to five major hurricanes per year in the climate of the late 21st century.

The HiFLOR model also predicted a highly concerning increase in ultra-intense Category 5 tropical cyclones with winds of at least 190 mph – from an average of about one of these Super Typhoon Haiyan–like storms occurring once every eight years globally in the climate of the late 20th century, to one such megastorm per year between 2081 to 2100 – a factor of eight increase.

Even more concerning was that the results of the study were for a middle-of-the road global warming scenario (called RCP 4.5), which civilization will have to work very hard to achieve. Under the current business-as-usual track, the model would be expected to predict an even higher increase in ultra-intense tropical cyclones.

One technique for computing hurricane damage uses ICAT’s damage estimator to review all contiguous land-falling U.S. hurricanes between 1900 – 2017. That technique computes the amount of damage they would do currently and corrects for changes in wealth and population. It finds that while Category 4 and 5 hurricanes made up only 13% of all U.S. hurricane landfalls during that period, they caused 52% of all the hurricane damage.

Given that assessment, it’s very concerning that the HiFLOR model, the best model for simulating current and future behavior of Category 4 and 5 hurricanes, is predicting a large increase in the number of these destructive storms. Even more concerning is the model’s prediction of a global factor of eight increase in catastrophic Category 5 storms with winds of at least 190 mph by the end of the century – and that under a moderate global warming scenario.

All of which leads to the regrettable conclusion that the prospects for quickly intensifying storms as they approach landfall are likely to increase in a warming world.

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Posted August 27, 2020, at 3:56 p.m. EDT.

Jeff Masters, Ph.D., worked as a hurricane scientist with the NOAA Hurricane Hunters from 1986-1990. After a near-fatal flight into category 5 Hurricane Hugo, he left the Hurricane Hunters to pursue a...

288 replies on “Climate change is causing more rapid intensification of Atlantic hurricanes”

    2. The wave West of the AOI mentioned in the TWO looks to be more organised and has more vorticity it is located at 13N 39W. This area of disturbed weather is also moving west

  6. Japan Meteorological Agency
    Tropical Cyclone Advisory #11 – 9:00 AM JST August 29 2020
    SEVERE TROPICAL STORM MAYSAK (T2009)
    =================================================
    Sea East of the Philippines

    At 0:00 AM UTC, Severe Tropical Storm Maysak (985 hPa) located at 16.5N 129.6E has 10 minute sustained winds of 55 knots with gusts of 80 knots. The cyclone is reported as almost stationary.

    Storm Force Winds
    ===================
    30 nm from the center

    Gale Force Winds
    ===================
    180 nm from the center in southwestern quadrant
    90 nm from the center in northeastern quadrant

    Dvorak Intensity: T3.5-

    Forecast and Intensity
    =======================
    24 HRS: 17.8N 129.5E – 80 knots (CAT 3/Strong Typhoon) Sea East of the Philippines
    48 HRS: 22.7N 128.8E – 100 knots (CAT 4/Very Strong Typhoon) 410 km southeast of Naha (Okinawa Prefecture)
    72 HRS: 26.8N 126.4E – 100 knots (CAT 4/Very Strong Typhoon) East China Sea

  8. that haiyan/yolanda pic in the article, about to cause so much heartbreak. That was nasty personified.

    My future ex and my kids were in Manila and Cebu at the time, they were lucky to just see a lot of wind, I was white knuckling it.

    Then, they were in Hawaii, on the big island, when Lane came by – fortunately they were on the Kona side, unbelievable!

    1. Oof
      a friend of mine who moved my way after Katrina just left today to help her folks out after this
      Her sister lost their house completely,
      Her Dad got flooded out

  12. Skye glad to see you here….I’ve been on WU since 2014….been using the bootleg Disqus thread thus far…miss Grothar and Cariboy on here though

  13. So happy to find this blog. I miss you all at WU. Lurker and lover of all things weather for many years. Is there a way to add this site to my home screen?

  14. Tropical Weather Outlook
    NWS National Hurricane Center Miami FL
    800 PM EDT Fri Aug 28 2020
    For the North Atlantic…Caribbean Sea and the Gulf of Mexico:
    The Weather Prediction Center is issuing advisories on Tropical
    Depression Laura, located inland over western Kentucky.
    A tropical wave located about 800 miles east of the Windward
    Islands is producing a disorganized area of showers and
    thunderstorms. Some gradual development of this system is possible
    during the next several days while it moves westward at about
    15 mph toward the Lesser Antilles.
    * Formation chance through 48 hours…low…20 percent.
    * Formation chance through 5 days…low…30 percent.

  15. Tropical Weather Outlook
    NWS National Hurricane Center Miami FL
    800 PM EDT Fri Aug 28 2020
    For the North Atlantic…Caribbean Sea and the Gulf of Mexico:
    The Weather Prediction Center is issuing advisories on Tropical
    Depression Laura, located inland over western Kentucky.
    A tropical wave located about 800 miles east of the Windward
    Islands is producing a disorganized area of showers and
    thunderstorms. Some gradual development of this system is possible
    during the next several days while it moves westward at about
    15 mph toward the Lesser Antilles.
    * Formation chance through 48 hours…low…20 percent.
    * Formation chance through 5 days…low…30 percent.
    Another tropical wave is located over the eastern Atlantic Ocean
    near the Cabo Verde Islands. This system is expected to move very
    slowly for the next several days, and some development is possible
    early next week over the eastern or central tropical Atlantic.
    * Formation chance through 48 hours…low…near 0 percent.
    * Formation chance through 5 days…medium…40 percent.

  17. Thanks for the great read Dr. Masters, i believe that we all need to get used and acomodate to the new type of storms we will keep getting.

  18. Japan Meteorological Agency
    Tropical Cyclone Advisory #9 – 3:00 AM JST August 29 2020
    SEVERE TROPICAL STORM MAYSAK (T2009)
    =================================================
    Sea East of the Philippines

    At 18:00 PM UTC, Severe Tropical Storm Maysak (990 hPa) located at 16.6N 129.6E has 10 minute sustained winds of 50 knots with gusts of 70 knots. The cyclone is reported as almost southwest slowly.

    Gale Force Winds
    ===================
    180 nm from the center in southwestern quadrant
    90 nm from the center in northeastern quadrant

    Dvorak Intensity: T3.0-

    Forecast and Intensity
    =======================
    24 HRS: 17.4N 129.8E – 70 knots (CAT 3/Strong Typhoon) Sea East of the Philippines
    48 HRS: 21.8N 129.7E – 90 knots (CAT 4/Very Strong Typhoon) Sea South of Okinawa
    72 HRS: 26.2N 126.9E – 100 knots (CAT 4/Very Strong Typhoon) East China Sea

    1. NOTES: close to 105 knots means Intense Typhoon status

      100 knots (JMA 10 min) should be west Naha, Okinawa or nearby Kume Island

  20. We obviously follow the Atlantic most closely. But typically the Atlantic averages only about 14% of global ACE. The typical Western Pacific ACE average is almost triple the Atlantic and the East Pacific also historically has higher ACE than the Atlantic. However in recent years the Atlantic seems much more active than the East Pacific, and the West Pacific has an almost nonexistent typhoon season so far in 2020.

    What the reason for the lull in East and West Pacific activity? Shouldn’t all basins experience the hyperactivity the Atlantic has been having?

    2. Yeah. it also, not all that surprisingly, leads to droughts in the SW US
      I haven’t seen more than the barest teaser of rain in months this year
      EPAC storms keep me wetter than currently for sure

    3. no, it tends to shift basins from year to year
      El Niño patterns have some to do with it, there is also the PDO, AOI, the IOD, the temporal alignment of the MJO, and the Kelvin Waves to consider
      this year, it is seriously favoring the North Atlantic Basin

    1. amazing how the areas with the biggest heat anomalies are also in positions to be least tapped by storms
      Great Lakes excepted

  23. All of this is exactly why I decided about a decade ago to close up the house with the approach of any hurricane I suspect may undergo rapid intensification and predicted to landfall within 100 miles in any direction. I’ll take the family, the critters, any irreplaceable photos, documents, or heirlooms and GTFO.

    I decided that I’d rather feel silly than sorry.

    2. I am definitely rethinking my escape plan. Of course my spouse must report to work or lose his job so I really don’t like the idea of leaving him.

  25. Testing….I made a post 5 minutes ago that isn’t showing and said “awaiting approval”….I’ve never seen that message before….Testing

    1. It’s been approved:) This issue is resolving. The more everyone posts the better it will get.

      4. I guess it depends on the device. On MacBook pro it’s command + R.
        Here’s what I found by googling “how to refresh a page on android” — hope it helps:

        On Android, you must first tap the ⋮ icon in the top-right corner of the screen and then tap the “Refresh” icon at the top of the resulting drop-down menu.Feb 17, 2020

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