Tornadocane is a
portmanteauof the words " tornado" and " hurricane" given to certain Mesoscale Convective Systems that develop a weather radarsignature in the shape of a hurricanein low levels. These storms have a central "eye" free of precipitations with surrounding arms of strong echoes but are really associated with a supercell thunderstormdeveloping a squall line. These storms are not in any way related to a hurricane other than the fact that they are shaped similarly to one. The only use of the term "tornadocane" occurred on April 15, 1999over Duplin County, North Carolina, Storm Prediction Center. [http://www.spc.noaa.gov/coolimg/nc_storm/ncloop.htm North Carolina "Tornadocane" from 1999.] Retrieved on 2008-01-08.] and the term does not exist in any standard dictionary or glossary.
These unusual thunderstorms complexes begin as the
rear flank downdraftof a supercell thunderstormand generate a vigorous gust frontat the base of the hook echoregion. If the instability and humidity of the air ahead of the front are conducive, a squall linedevelops from the supercell toward the southwest ( northern hemisphere) closing the gap of the bounded weak echo region(BWER) and curving into spiral bands seemingly rotating around the BWER. The supercell itself is often associated with tornadoes while the squall line produces microbursts.
North Carolina case
This tornadocane began as an HP (Heavy Precipitation) supercell on April 15, 1999, and moved across
North Carolinawhile assuming a hurricane shape. It exited the State as a Bow Echoas the parent supercell decayed and the squall line took over. One tornado spawned from this supercell was .8-1.6 km (.5-1 mi) wide, caused major damage and injured 11 people along a 48 km (30 mi) long damage track.
One death and a 265 km/h (165 mph) wind gust were also reported with this storm. This wind gust is thought to have come from a direct hit to an
anemometerby a tornado, which is in the F3 windspeed range. However, since only damage can be used to rating of a tornado, that recorded wind speed is ineligible for determining the F scale rating of this tornado.
Another case of tornadocane happened across the Midwest on
July 21, 2003. An area of convection developed across eastern Iowanear a weak stationary/warm front at 0302 UTCand moved to the east along it. By 1203 UTC, the convective system had matured, taking on the shape of a wavy squall line across western Ohioand southern Indiana. The system re-intensified after leaving the Ohio Valley, starting to form a large hook, with occasional hook echoes appearing along its eastern side. A surface low pressurebecame defined and became more impressive later in the day. By 2244 UTC, a squall line took shape along its band to the south. This began to starve the inner convection and by 0126 UTC, daytime heating had ceased. The squall line ran out ahead of the low, causing the entire convective structure to weaken. [ David M. Roth. [http://www.hpc.ncep.noaa.gov/research/roth/landcane.html MCS with Eye - July 21, 2003.] Retrieved on 2008-01-08.]
Heavy rainfall and straight wind damages were the main effect of this system. It left a maximum of 102 mm (4 inches) of rain along the path of the system and numerous reports of violent winds. A few weak tornadoes have been reported too.
* [http://www.spc.noaa.gov/coolimg/nc_storm/index.html Report on the North Carolina Tornadocane of 1999]
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