Harvey has been a stunning hurricane, in its raw power and natural beauty. Scientists have been able to capture some incredible shots on the ground and above from satellites.
Mesovortices within the eye
Exceptionally strong hurricanes often develop miniature vortices within their eyes. These smaller spin-ups rotate within the eye, and can bend the eye’s structure into a wavy, flowerlike pattern.
While scientists are unsure about the way these form, there is speculation that a greater number of pinwheeling eddies correlates to a stronger hurricane. In extreme circumstances, like when Hurricane Harvey was making landfall near Rockport, Tex., these vortices can be responsible for repetitively thrusting some locations into and out of the eye because of irregularities in the edge of the eyewall.
As a general meteorological rule, low-pressure systems like to house smaller concentric lows within them. This pattern within Harvey’s eye is a stellar example of such.
When a cyclone develops quickly enough, its eye clears out, and convection (showers and thunderstorms) within the eyewall tend to lean outward with height. It produces a breathtaking phenomenon known as the “stadium effect,” and those within the eye of the most intense hurricanes have reported witnessing this spectacle.
Last night, extreme storm chasers Simon Brewer and Justin Drake captured an otherworldly shot while inside Harvey’s eye of lightning illuminating the eye wall. Meanwhile, clear skies above permitted the viewing of stars, betraying the fury that would return after the eye passed overhead.
It was electrifying
Most of the time, tropical storms and hurricanes produce very little lightning.
This is due to the nature of the storm’s shear, since thunderstorms require vertical shear to yield the charge separation that gives rise to lightning. Hurricanes, on the other hand, feature mainly horizontal shear, and their convective plumes normally tower to less than 30,000 feet.
But Hurricane Harvey touched off several lightning strikes within its eye wall and outer rain bands. On occasion, hurricanes have been known to feature extremely high electric fields, such as Emily in 2005 — within which NOAA scientists measured an absurd 8 kilovolts per meter, on par with what would be found within the most monstrous supercell thunderstorms on the Great Plains.
Matthew exhibited similar characteristics in October 2016 as it passed south of Puerto Rico, as did Hilda in 2015. During both of these storms, “sprites,” a rare type of upper-atmospheric electrical discharge, flashed above the hurricanes like fleeting red fireworks reaching to space.
Residents of coastal Louisiana, southern Texas and coastal eastern Texas may be able to spot a few sprites dancing above Harvey on Saturday night.
The vigorous updrafts within Hurricane Harvey punctured the “atmospheric equilibrium level” at which they should stop rising, and instead continued to oscillate about this vertical benchmark as they propagated outward from the eye. Akin to ripples, these “gravity waves” southeast of the eye yesterday afternoon show the rising and falling motions in the atmosphere as the waves passed through. Many folks forget the atmosphere is, in fact, a fluid, and behaves as a compressible one in all respects.
Birds trapped in the eye
Using the “correlation coefficient” feature of the dual-polarization WSR-88D weather radar, we’re able to probe inside Hurricane Harvey to gather information about the hydrometers (particulates of precipitation) being tossed around inside the storm’s core.
Marked by very low correlation coefficient values (meaning jagged, rough, or unusual shapes are detected), it appears that thousands of birds became trapped within Harvey’s eye by the converging winds. In the past, this has lead to forced migrations of several tropical species northward to the mid-latitudes, noted by many ornithologists following the Great New England Hurricane of 1938.
An old forecaster’s wives’ tail rules that storms with greater symmetry tend to be more intense, since they are able to “balance” by drawing in reliable amounts of warmth and moisture from all sides. Harvey is a classic example, becoming progressively more uniform in shape as it intensified over the past 48 hours.