Supercell Thunderstorms Produce Super-Size Hail in Hawaii

Powerful thunderstorms in March were unusual – and dangerous

As the end of the winter rainy season approached in the northern Pacific Ocean, severe supercell thunderstorms hit Oahu, Hawaii on March 9, 2012. According to the National Oceanic and Atmospheric Administration (NOAA), these large and violent storms produced hailstones as large as grapefruits (fortunately not as large as pineapples), setting a new record for the state of Hawaii. Figure 1 shows a satellite animation of the event.

Figure 1. Infrared (IR) brightness temperature animation of the Oahu, Hawaii hail event on March 9, 2012. Cyclonic rotation of the thunderstorm clouds is visible. The data set, Global Merged IR from geostationary weather satellites, is archived at the NASA Goddard Earth Sciences Data and Information Services Center (GES DISC). The data can be accessed through the Hurricane Data Analysis Tool for visualization, or Mirador to download this data set. (Click to see the full-size image).

Data and services at the GES DISC can be used to analyze atmospheric conditions for this event, as well as other similar events, because of their global coverage. In particular, the Global Merged IR product, an ancillary product of the Tropical Rainfall Measuring Mission (TRMM) with spatial coverage from 60° S - 60° N, provides IR imagery every 30 minutes at 4-km spatial resolution. NASA GEOS-5 model assimilated products provide hourly analysis of global atmospheric conditions. Visualizations which overlie these two products can facilitate data analysis, as shown in Figure 2. Users can access the related data products of GEOS-5 through Giovanni's MERRA Hourly 2D or MERRA Hourly 3D portals for data analysis and visualization and Mirador to search and download the MERRA data.

Figure 2. Brightness temperature from the Global Merged IR product overlain by the GEOS-5 sea-level-pressure and surface wind at 10 m, showing a low level trough formation in the lee of the Hawaiian islands and a wind shear zone between the northeasterly and easterly winds. (Click the image to see it full-size.)

March is not the peak month for convective weather activity, according to lightning climatological data observed from the Lightning Imaging Sensor (LIS, http://thunder.nsstc.nasa.gov/lis/index.html). Therefore, it is unusual to have such violent supercell thunderstorms during March. The formation of such thunderstorm requires a combination of basic atmospheric conditions, such as warm, moist air in the boundary layer to provide energy to fuel the storm development and updrafts to lift this moist air into a colder, drier upper atmosphere.

From the animation of GEOS-5 sea-level-pressure analysis (Figure 3), a high pressure system between the Aleutian Islands and Hawaii is visible, moving toward the east. As the system passed through, a low pressure trough was formed in the leeward area of the islands, due to the blocking effect of the island land masses (see Figures 2 and 3), lifting the moist boundary air to higher altitudes. With the help of a passing upper level trough and a cold and dry environment (Figure 4), the uplifted moist air quickly developed into intense supercell thunderstorms (Figure 1). As the system waned, it moved to the northwest away from Hawaii toward the northwest (Figure 3).

Large hail can be destructive and dangerous to human health. This video from May 2012 shows baseball-size hail hitting cars and homes in a suburb of St. Louis, Missouri and breaking a few windshields: http://www.youtube.com/watch?v=WijrCC3rSoo

Figure 3. Animation of GEOS-5 sea-level-pressure and surface wind at 10 m altitude, showing the movement of the high pressure system, the blocking effect of the Hawaiian Islands, and the northwest movement of the low pressure trough.

Figure 4. Time-series analysis for the Hawaiian area. March 9, 2012 is circled in red. (a) Geopotential heights at 500 and 250 hPa, showing passage of an upper level trough. (b) Air temperatures at 500 and 250 hPa, revealing a cooling before the event on March 9. (c) Specific humidity at 500 and 250 hPa, showing a steep drop in humidity in the upper atmosphere before the event. (d) Wind speeds at different levels, showing increasing and decreasing wind speeds in the lower and upper atmosphere, respectively, resulting in reduced wind shear conditions in the atmosphere during the event. (Click on the image to see if full-size).

Acknowledgments

Text and images by Dr. Zhong Liu. Reviewed by Bill Teng and Chris Lynnes, editing and Web formatting by James Acker.

The Modern Era Retrospective-analysis for Research and Applications (MERRA) and GEOS-5 model are projects of the Goddard Modeling and Assimilation Office (GMAO).

The GES DISC is a NASA earth science data center, part of the NASA Earth Science Data and Information System (ESDIS) Project.

Questions or comments? Email the NASA GES DISC Help Desk, gsfc-help-disc@lists.nasa.gov.