On the evening of April 15, 1999, one of the most bizarre and unusual supercell thunderstorms ever observed roared across southeastern North Carolina. It produced several damaging tornadoes, one killer tornado, non-tornadic wind damage reports, and a measured gust to 165 mph. At one point, as it was producing a tornado with a 30 mile damage track across portions of Duplin County, the thunderstorm cluster assumed a hurricane-like shape (above, and in this filtered image), even forming an eye-like "hole" in the reflectivity field just east of the mesocyclone. [The mesocyclone -- parent circulation to the tornadoes -- is evident in this storm-relative velocity image off Morehead City's Doppler radar.]
The storm moved out of northern South Carolina as a heavy-precipitation (HP) supercell, moving east-northeast close to the intersection of a warm front and a surface trough. It then moved ENE across southern NC, producing a gust front on its rear flank on which more thunderstorm cells formed. That gust-frontal band, and the forward flank of the original storm, began to curve into spiral bands -- eventually assuming the hurricane shape. This structure was the result. The evolution of this storm from HP supercell to "tornadocane" to bow echo is shown and described in more detail here.
The 165 mph gust was recorded just north of Trenton NC in Jones County, at about 0220Z (10:20 pm EDT). At the time, the original HP storm and the cells along its gust front had largely separated; and the gust corresponded well to the track of the gate-to-gate shear maximum in the mesocyclone. So this gust may have resulted from a tornado strike to the anemometer, or an intense eddy in the downburst. There was also a more typical signature of an HP supercell well offshore over the Atlantic E of Myrtle Beach SC (not shown).
Javascript reflectivity loop of the "tornadocane"
