• Akaeda, K., J. Reisner, and D. Parsons, 1995: The role of mesoscale and topographically induced circulations in initiating a flash flood observed during the TAMEX project. Mon. Wea. Rev., 123, 17201739, https://doi.org/10.1175/1520-0493(1995)123<1720:TROMAT>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Alpers, W., and B. Brümmer, 1994: Atmospheric boundary layer rolls observed by the synthetic aperture radar aboard the ERS-1 satellite. J. Geophys. Res., 99, 12 61312 621, https://doi.org/10.1029/94JC00421.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Barnes, S. L., 1978: Oklahoma thunderstorms on 29–30 April 1970: Part I: Morphology of a tornadic storm. Mon. Wea. Rev., 106, 673684, https://doi.org/10.1175/1520-0493(1978)106<0673:OTOAPI>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Blanchard, D. C., 1953: Raindrop size-distribution in Hawaiian rains. J. Meteor., 10, 457473, https://doi.org/10.1175/1520-0469(1953)010<0457:RSDIHR>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Bonner, S. F., 1966: Lucan and the declamation schools. Amer. J. Philol., 87, 257289, https://doi.org/10.2307/292851.

  • Bonner, W. D., 1968: Climatology of the low level jet. Mon. Wea. Rev., 96, 833850, https://doi.org/10.1175/1520-0493(1968)096<0833:COTLLJ>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Brandes, E. A., A. V. Ryzhkov, and D. S. Zrnić, 2001: An evaluation of radar rainfall estimates from specific differential phase. J. Atmos. Oceanic Technol., 18, 363375, https://doi.org/10.1175/1520-0426(2001)018<0363:AEORRE>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Branick, M. L., and C. A. Doswell III, 1992: An observation of the relationship between supercell structure and lightning ground-strike polarity. Wea. Forecasting, 7, 143149, https://doi.org/10.1175/1520-0434(1992)007<0143:AOOTRB>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Brown, R. A., 1980: Longitudinal instabilities and secondary flows in the planetary boundary layer: A review. Rev. Geophys. Space Phys., 18, 683697, https://doi.org/10.1029/RG018i003p00683.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Bryan, G. H., R. Rotunno, and J. M. Fritsch, 2007: Roll circulations in the convective region of a simulated squall line. J. Atmos. Sci., 64, 12491266, https://doi.org/10.1175/JAS3899.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Bunkers, M. J., B. A. Klimowski, J. W. Zeitler, R. L. Thompson, and M. L. Weisman, 2000: Predicting supercell motion using a new hodograph technique. Wea. Forecasting, 15, 6179, https://doi.org/10.1175/1520-0434(2000)015<0061:PSMUAN>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Businger, S., T. Birchard Jr., K. R. Kodama, P. A. Jendrowski, and J.-J. Wang, 1998: A bow echo and severe weather associated with a kona low in Hawaii. Wea. Forecasting, 13, 576591, https://doi.org/10.1175/1520-0434(1998)013<0576:ABEASW>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Cao, G., T. W. Giambelluca, D. E. Stevens, and T. A. Schroeder, 2007: Inversion variability in the Hawaiian trade wind regime. J. Climate, 20, 11451160, https://doi.org/10.1175/JCLI4033.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Caruso, S. J., and S. Businger, 2006: Subtropical cyclogenesis over the central North Pacific. Wea. Forecasting, 21, 193205, https://doi.org/10.1175/WAF914.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Coffer, B. E., and M. D. Parker, 2015: Impacts of increasing low-level shear on supercells during the early evening transition. Mon. Wea. Rev., 143, 19451969, https://doi.org/10.1175/MWR-D-14-00328.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Coffer, B. E., M. D. Parker, R. L. Thompson, B. T. Smith, and R. E. Jewell, 2019: Using near-ground storm relative helicity in supercell tornado forecasting. Wea. Forecasting, 34, 14171435, https://doi.org/10.1175/WAF-D-19-0115.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Davies-Jones, R., 1984: Streamwise vorticity: The origin of updraft rotation in supercell storms. J. Atmos. Sci., 41, 29913006, https://doi.org/10.1175/1520-0469(1984)041<2991:SVTOOU>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Dial, G. L., J. P. Racy, and R. L. Thompson, 2010: Short-term convective mode evolution along synoptic boundaries. Wea. Forecasting, 25, 14301446, https://doi.org/10.1175/2010WAF2222315.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Droegemeier, K. K., S. M. Lazarus, and R. Davies-Jones, 1993: The influence of helicity on numerically simulated convective storms. Mon. Wea. Rev., 121, 20052029, https://doi.org/10.1175/1520-0493(1993)121<2005:TIOHON>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Finley, C. A., W. R. Cotton, and R. A. Pielke Sr., 2001: Numerical simulation of tornadogenesis in a high-precipitation supercell. Part I: Storm evolution and transition into a bow echo. J. Atmos. Sci., 58, 15971629, https://doi.org/10.1175/1520-0469(2001)058<1597:NSOTIA>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Foote, G. B., and P. S. Du Toit, 1969: Terminal velocity of raindrops aloft. J. Appl. Meteor., 8, 249253, https://doi.org/10.1175/1520-0450(1969)008<0249:TVORA>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Foster, J., and M. Bevis, 2003: Lognormal distribution of precipitable water in Hawaii. Geochem. Geophys. Geosyst., 4, 1065, https://doi.org/10.1029/2002GC000478.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Foster, J., M. Bevis, Y. L. Chen, S. Businger, and Y. Zhang, 2003: The Ka’u storm (November 2000): Imaging precipitable water using GPS. J. Geophys. Res., 108, 4585, https://doi.org/10.1029/2003JD003413.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • James, R. P., and P. M. Markowski, 2010: A numerical investigation of the effects of dry air aloft on deep convection. Mon. Wea. Rev., 138, 140161, https://doi.org/10.1175/2009MWR3018.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Klemp, J. B., and R. B. Wilhelmson, 1978a: Simulations of right-and left-moving storms produced through storm splitting. J. Atmos. Sci., 35, 10971110, https://doi.org/10.1175/1520-0469(1978)035<1097:SORALM>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Klemp, J. B., and R. B. Wilhelmson, 1978b: The simulation of three-dimensional convective storm dynamics. J. Atmos. Sci., 35, 10701096, https://doi.org/10.1175/1520-0469(1978)035<1070:TSOTDC>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Knapp, D. I., 1994: Using cloud-to-ground lightning data to identify tornadic thunderstorm signatures and nowcast severe weather. Natl. Wea. Dig., 19, 3542.

    • Search Google Scholar
    • Export Citation
  • Kodama, K. R., and G. M. Barnes, 1997: Heavy rain events over the south-facing slopes of Hawaii: Attendant conditions. Wea. Forecasting, 12, 347367, https://doi.org/10.1175/1520-0434(1997)012<0347:HREOTS>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Kodama, K. R., and S. Businger, 1998: Weather and forecasting challenges in the Pacific region of the National Weather Service. Wea. Forecasting, 13, 523546, https://doi.org/10.1175/1520-0434(1998)013<0523:WAFCIT>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Kulie, M. S., and Y. L. Lin, 1998: The structure and evolution of a numerically simulated high-precipitation supercell thunderstorm. Mon. Wea. Rev., 126, 20902116, https://doi.org/10.1175/1520-0493(1998)126<2090:TSAEOA>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Kumjian, M. R., 2013: Principles and applications of dual-polarization weather radar. Part II: Warm- and cold-season applications. J. Oper. Meteor., 1, 243264, https://doi.org/10.15191/nwajom.2013.0120.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Kumjian, M. R., and A. V. Ryzhkov, 2009: Storm-relative helicity revealed from polarimetric radar measurements. J. Atmos. Sci., 66, 667685, https://doi.org/10.1175/2008JAS2815.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Lemon, L. R., 1976: The flanking line, a severe thunderstorm intensification source. J. Atmos. Sci., 33, 686694, https://doi.org/10.1175/1520-0469(1976)033<0686:TFLAST>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Lin, Y. L., S. Chiao, T. A. Wang, M. L. Kaplan, and R. P. Weglarz, 2001: Some common ingredients for heavy orographic rainfall. Wea. Forecasting, 16, 633660, https://doi.org/10.1175/1520-0434(2001)016<0633:SCIFHO>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Loney, M. L., D. S. Zrnić, J. M. Straka, and A. V. Ryzhkov, 2002: Enhanced polarimetric radar signatures above the melting level in a supercell storm. J. Appl. Meteor., 41, 11791194, https://doi.org/10.1175/1520-0450(2002)041<1179:EPRSAT>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Lyman, R. E., T. A. Schroeder, and G. M. Barnes, 2005: The heavy rain event of 29 October 2000 in Hana, Maui. Wea. Forecasting, 20, 397414, https://doi.org/10.1175/WAF868.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Maddox, R. A., and C. A. Doswell III, 1982: An examination of jet stream configurations, 500 mb vorticity advection, and low-level thermal advection patterns during extended periods of intense convection. Mon. Wea. Rev., 110, 184197, https://doi.org/10.1175/1520-0493(1982)110<0184:AEOJSC>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Markowski, P. M., and Y. Richardson, 2010: Mesoscale Meteorology in Midlatitudes. Wiley-Blackwell, 430 pp.

    • Crossref
    • Export Citation
  • Markowski, P. M., and N. Dotzek, 2011: A numerical study of the effects of orography on supercells. Atmos. Res., 100, 457478, https://doi.org/10.1016/j.atmosres.2010.12.027.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Morrison, H., J. M. Peters, A. C. Varble, W. M. Hannah, and S. E. Giangrande, 2020: Thermal chains and entrainment in cumulus updrafts. Part I: Theoretical description. J. Atmos. Sci., 77, 36373660, https://doi.org/10.1175/JAS-D-19-0243.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Morrison, I., S. Businger, F. Marks, P. Dodge, and J. A. Businger, 2005: An observational case for the prevalence of roll vortices in the hurricane boundary layer. J. Atmos. Sci., 62, 26622673, https://doi.org/10.1175/JAS3508.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Mulholland, J. P., S. W. Nesbitt, and R. J. Trapp, 2019: A case study of terrain influences on upscale convective growth of a supercell. Mon. Wea. Rev., 147, 43054324, https://doi.org/10.1175/MWR-D-19-0099.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Murphy, M. J., Jr., and S. Businger, 2011: Orographic influences on an Oahu flood. Mon. Wea. Rev., 139, 21982217, https://doi.org/10.1175/2010MWR3357.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Nielsen, E. R., and R. S. Schumacher, 2018: Dynamical insights into extreme short-term precipitation associated with supercells and mesovortices. J. Atmos. Sci., 75, 29833009, https://doi.org/10.1175/JAS-D-17-0385.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Nielsen, E. R., and R. S. Schumacher, 2020a: Dynamical mechanisms supporting extreme rainfall accumulations in the Houston “Tax Day” 2016 flood. Mon. Wea. Rev., 148, 83109, https://doi.org/10.1175/MWR-D-19-0206.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Nielsen, E. R., and R. S. Schumacher, 2020b: Observations of extreme short-term precipitation associated with supercells and mesovortices. Mon. Wea. Rev., 148, 159182, https://doi.org/10.1175/MWR-D-19-0146.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Nielsen, E. R., G. R. Herman, R. C. Tournay, J. M. Peters, and R. S. Schumacher, 2015: Double impact: When both tornadoes and flash floods threaten the same place at the same time. Wea. Forecasting, 30, 16731693, https://doi.org/10.1175/WAF-D-15-0084.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Perica, S., and Coauthors, 2011: Precipitation-Frequency Atlas of the United States. Vol. 4, version 3: Hawaiian Islands, NOAA Atlas 14, NOAA, 103 pp., https://www.weather.gov/media/owp/hdsc_documents/Atlas14_Volume4.pdf.

    • Search Google Scholar
    • Export Citation
  • Pessi, A. T., and S. Businger, 2009: The impact of lightning data assimilation on a winter storm simulation over the North Pacific Ocean. Mon. Wea. Rev., 137, 31773195, https://doi.org/10.1175/2009MWR2765.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Peters, J. M., C. J. Nowotarski, and H. Morrison, 2019: The role of vertical wind shear in modulating maximum supercell updraft velocities. J. Atmos. Sci., 76, 31693189, https://doi.org/10.1175/JAS-D-19-0096.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Peters, J. M., C. J. Nowotarski, J. P. Mulholland, and R. L. Thompson, 2020a: The influences of effective inflow layer streamwise vorticity and storm-relative flow on supercell updraft properties. J. Atmos. Sci., 77, 30333057, https://doi.org/10.1175/JAS-D-19-0355.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Peters, J. M., C. J. Nowotarski, and G. L. Mullendore, 2020b: Are supercells resistant to entrainment because of their rotation? J. Atmos. Sci., 77, 14751495, https://doi.org/10.1175/JAS-D-19-0316.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Peters, J. M., H. Morrison, A. C. Varble, W. M. Hannah, and S. E. Giangrande, 2020c: Thermal chains and entrainment in cumulus updrafts. Part II: Analysis of idealized simulations. J. Atmos. Sci., 77, 36613681, https://doi.org/10.1175/JAS-D-19-0244.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Ramage, C. S., 1995: Forecasters guide to tropical meteorology (AWS TR 240 updated). AWS/TR-95/001, Air Weather Service, U.S. Air Force, AWSTL, 392 pp.

  • Raymond, D. J., 1978: Instability of the low-level jet and severe storm formation. J. Atmos. Sci., 35, 22742280, https://doi.org/10.1175/1520-0469(1978)035<2274:IOTLLJ>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Robinson, T. E., and S. Businger, 2019: A novel method for modeling lowest-level vertical motion. Wea. Forecasting, 34, 943957, https://doi.org/10.1175/WAF-D-18-0064.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Rosenfeld, D., D. B. Wolff, and D. Atlas, 1993: General probability-matched relations between radar reflectivity and rain rate. J. Appl. Meteor., 32, 5072, https://doi.org/10.1175/1520-0450(1993)032<0050:GPMRBR>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Rotunno, R., and J. B. Klemp, 1982: The influence of the shear-induced pressure gradient on thunderstorm motion. Mon. Wea. Rev., 110, 136151, https://doi.org/10.1175/1520-0493(1982)110<0136:TIOTSI>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Sachidananda, M., and D. S. Zrnić, 1987: Rain rate estimates from differential polarization measurements. J. Atmos. Oceanic Technol., 4, 588598, https://doi.org/10.1175/1520-0426(1987)004<0588:RREFDP>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Said, R., and M. Murphy, 2016: GLD360 upgrade: Performance analysis and applications. 24th Int. Lightning Detection Conf. 2016/Sixth Int. Lightning Meteorology Conf., San Diego, CA, ILDC/ILMC, https://training.weather.gov/wdtd/courses/woc/severe/data-fusion/lightning/sat-ltg-prod/story_content/external_files/Said_Murphy_2016.pdf.

  • Schroeder, T. A., 1977: Meteorological analysis of an Oahu flood. Mon. Wea. Rev., 105, 458468, https://doi.org/10.1175/1520-0493(1977)105<0458:MAOAOF>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Stolz, D. C., S. Businger, and A. Terpstra, 2014: Refining the relationship between lightning and convective rainfall over the ocean. J. Geophys. Res. Atmos., 119, 964981, https://doi.org/10.1002/2012JD018819.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Thompson, R. L., C. M. Mead, and R. Edwards, 2007: Effective storm-relative helicity and bulk shear in supercell thunderstorm environments. Wea. Forecasting, 22, 102115, https://doi.org/10.1175/WAF969.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Trenberth, K. E., 1978: On the interpretation of the diagnostic quasi-geostrophic omega equation. Mon. Wea. Rev., 106, 131137, https://doi.org/10.1175/1520-0493(1978)106<0131:OTIOTD>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Uccellini, L. W., and D. R. Johnson, 1979: The coupling of upper and lower tropospheric jet streaks and implications for the development of severe convective storms. Mon. Wea. Rev., 107, 682703, https://doi.org/10.1175/1520-0493(1979)107<0682:TCOUAL>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Uccellini, L. W., and P. J. Kocin, 1987: The interaction of jet-streak circulations during heavy snow events along the East Coast of the United States. Wea. Forecasting, 2, 289308, https://doi.org/10.1175/1520-0434(1987)002<0289:TIOJSC>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Warren, R. A., H. Richter, H. A. Ramsay, S. T. Siems, and M. J. Manton, 2017: Impact of variations in upper-level shear on simulated supercells. Mon. Wea. Rev., 145, 26592681, https://doi.org/10.1175/MWR-D-16-0412.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Weisman, M. L., and J. B. Klemp, 1982: The dependence of numerically simulated convective storms on vertical wind shear and buoyancy. Mon. Wea. Rev., 110, 504520, https://doi.org/10.1175/1520-0493(1982)110<0504:TDONSC>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Weisman, M. L., and J. B. Klemp, 1984: The structure and classification of numerically simulated convective storms in directionally varying wind shears. Mon. Wea. Rev., 112, 24792498, https://doi.org/10.1175/1520-0493(1984)112<2479:TSACON>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Weisman, M. L., and R. Rotunno, 2000: The use of vertical wind shear versus helicity in interpreting supercell dynamics. J. Atmos. Sci., 57, 14521472, https://doi.org/10.1175/1520-0469(2000)057<1452:TUOVWS>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Whiteman, C. D., X. Bian, and S. Zhong, 1997: Low-level jet climatology from enhanced rawinsonde observations at a site in the southern Great Plains. J. Appl. Meteor., 36, 13631376, https://doi.org/10.1175/1520-0450(1997)036<1363:LLJCFE>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
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The Anatomy of a Series of Cloud Bursts that Eclipsed the U.S. Rainfall Record

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  • 1 a University of Hawai‘i at Mānoa, Honolulu, Hawaii
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Abstract

A series of extreme cloudbursts occurred on 14 April 2018 over the northern slopes of the island of Kaua‘i, Hawaii. The storm inundated some areas with 1262 mm (∼50 in.) of rainfall in a 24-h period, eclipsing the previous 24-h U.S. rainfall record of 1100 mm (42 in.) set in Texas in 1979. Three periods of intense rainfall are diagnosed through detailed analysis of National Weather Service operational and special datasets. On the synoptic scale, a slowly southeastward propagating trough aloft over a deep layer of low-level moisture (>40 mm of total precipitable water) produced prolonged instability over Kaua‘i. Enhanced northeast to east low-level flow impacted Kaua‘i’s complex terrain, which includes steep north- and eastward-facing slopes and cirques. The resulting orographic lift initiated deep convection. The wind profile exhibited significant shear in the troposphere and streamwise vorticity within the convective storm inflow. Evidence suggests that large directional shear in the boundary layer, paired with enhanced orographic vertical motion, produced rotating updrafts within the convective storms. Mesoscale rotation is manifest in the radar data during the latter two periods, and reflectivity cores are observed to propagate both to the left and to the right of the mean shear, which is characteristic of supercells. The observations suggest that the terrain configuration in combination with the wind shear separates the area of updrafts from the downdraft section of the storm, resulting in almost continuous heavy rainfall over Waipā Garden.

© 2022 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Steven Businger, businger@hawaii.edu

Abstract

A series of extreme cloudbursts occurred on 14 April 2018 over the northern slopes of the island of Kaua‘i, Hawaii. The storm inundated some areas with 1262 mm (∼50 in.) of rainfall in a 24-h period, eclipsing the previous 24-h U.S. rainfall record of 1100 mm (42 in.) set in Texas in 1979. Three periods of intense rainfall are diagnosed through detailed analysis of National Weather Service operational and special datasets. On the synoptic scale, a slowly southeastward propagating trough aloft over a deep layer of low-level moisture (>40 mm of total precipitable water) produced prolonged instability over Kaua‘i. Enhanced northeast to east low-level flow impacted Kaua‘i’s complex terrain, which includes steep north- and eastward-facing slopes and cirques. The resulting orographic lift initiated deep convection. The wind profile exhibited significant shear in the troposphere and streamwise vorticity within the convective storm inflow. Evidence suggests that large directional shear in the boundary layer, paired with enhanced orographic vertical motion, produced rotating updrafts within the convective storms. Mesoscale rotation is manifest in the radar data during the latter two periods, and reflectivity cores are observed to propagate both to the left and to the right of the mean shear, which is characteristic of supercells. The observations suggest that the terrain configuration in combination with the wind shear separates the area of updrafts from the downdraft section of the storm, resulting in almost continuous heavy rainfall over Waipā Garden.

© 2022 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Steven Businger, businger@hawaii.edu
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