• Kauai's 2018 record-setting rain caused

    From ScienceDaily@1:317/3 to All on Thu Apr 21 22:30:48 2022
    Kauai's 2018 record-setting rain caused by a series of supercell
    thunderstorms

    Date:
    April 21, 2022
    Source:
    University of Hawaii at Manoa
    Summary:
    A record-setting rainstorm over Kaua'i, Hawai'i in April 2018
    resulted in severe flash flooding and estimated damage of nearly
    $180 million. The deluge damaged or destroyed 532 homes, and
    landslides left people along Kaua'i's north coast without access to
    their homes. Atmospheric scientists have now revealed that severe
    supercell thunderstorms were to blame.



    FULL STORY ==========================================================================
    A record-setting rainstorm over Kaua'i, Hawai'i in April 2018 resulted in severe flash flooding and estimated damage of nearly $180 million. The
    deluge damaged or destroyed 532 homes, and landslides left people
    along Kaua'i's north coast without access to their homes. In a recently published study, atmospheric scientists at the University of Hawai'i at
    Manoa revealed that severe supercell thunderstorms were to blame.


    ==========================================================================
    The rainstorm inundated some areas with nearly 50 inches of rainfall in
    a 24- hour period, smashing the previous 24-hour U.S. rainfall record
    of 42 inches set in Texas in 1979. An interesting finding is that the
    rainstorm described in this paper was associated with a kona low and
    not a tropical cyclone as featured in previous U.S. rainfall records.

    Terrence Corrigan, a doctoral candidate, and professor Steven Businger,
    both in the Department of Atmospheric Sciences at the UH Manoa School of
    Ocean and Earth Science and Technology, sifted through copious weather
    radar data from NOAA's National Weather Service to unveil the factors contributing to this historic event. Their analysis revealed large changes
    in the direction and speed of the winds in the lower atmosphere. When
    these shifting winds collided with Kaua'i steep cliffs, thunderstorms
    with rotating updrafts were triggered.

    The scale of rotation seen in radar data, and the strength of rainfall
    seen as reflectivity echos are consistent with supercell thunderstorms.

    "This finding was a surprise, which has interesting implications for
    other mountainous areas of the world," said Businger.

    "Updrafts with rotation are more intense and longer lived, and have
    been observed to produce large hail and tornados in Hawai'i," said
    Businger. "In this case, the updrafts were forced by Kaua'i's steep
    mountain cliffs, with the result that the thunderstorms were more
    vigorous and anchored to the terrain, thus setting a new US 24-hour
    rainfall record!" Although supercells thunderstorms are the least common
    type of thunderstorm in Hawaii, they have the greatest likelihood of
    producing severe weather, including large hail, tornados, and strong straight-line winds.

    "Understanding the dynamic interaction of our tropical atmosphere
    and steep mountains will help weather forecasters better anticipate
    severe weather events and flash floods in our state and elsewhere."
    Businger and Corrigan's next steps are to use computer models to simulate
    the interaction between various wind flows and terrain configurations
    to further shed light on the interaction of mountains and severe
    thunderstorms.


    ========================================================================== Story Source: Materials provided
    by University_of_Hawaii_at_Manoa. Original written by Marcie
    Grabowski. Note: Content may be edited for style and length.


    ========================================================================== Journal Reference:
    1. Terrence J. Corrigan, Steven Businger. The Anatomy of a Series
    of Cloud
    Bursts that Eclipsed the U.S. Rainfall Record. Monthly Weather
    Review, 2022; 150 (4): 753 DOI: 10.1175/MWR-D-21-0028.1 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2022/04/220421181205.htm

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