Status:Ongoing analysisFinalized Material from: Linus, Fernando
Discussed in the following Daily reports:
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1. Impact
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On the 27 April 7pm local time (00UTC 28 April), tornadoes hit towns north and west of Little Rock, Arkansas killing approx 17 people (http://edition.cnn.com/2014/04/28/us/severe-weather/index.html?hpt=hp_c2). On the evening on the 28 April |
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fatal tornadoes occurred over Mississippi (http://www.bbc.co.uk/news/world-us-canada-27199071). |
2. Description of the event
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The picture above show the sounding from Little Rock at 28 April 00UTC, which should be very close in time and space to the worst tornadoes (from Uni. Wyoming). The CAPE calculation from the sounding gave a values value of 2115. We also see a strong wind shear in the lower troposphere.
Gallery includeLabel cape_efi_0 sort comment title CAPE EFI 0-24h
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We cannot expect the model to capture tornadoes, but the conevective convective environment. The figures above show the HRES forecast for CAPE (00+23h) and accumulated precipitation +23-24h. Little Rock is marked with an hourglass symbol. For this hour, the maximum precipitation exceeded 20 mm/h). If anything, the area of the strongest convection is shifted somewhat to the west.
3.3 ENS
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The figures above show the CAPE EFI (shades), precipitation (green symbols) and the ensemble mean of z500 (blue contours) valid for the 27 April Little Rock is marked with an hourglass symbol. This plots show the evolution of the weather situation. The large scale flow situation with a trough over western US was well captured for all lead times, leading to a southerly flow and enhanced risk of high CAPE values.
3.4 Monthly forecasts
3.5 Comparison with other centres
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- We cannot expect the forecast to capture tornadoes, but the convective environment.
- Good forecast of the flow situation in the medium-range
- High 1-hour precipitation values for the 27 April 00UTC run
- The tornado appeared around 00UTC, problem with the EFI accumulation period (00-00UTC)
6. Additional material
- Strong convection and heavy precipitation in U.S continued for a couple of days, see DR
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