senorpepr wrote:mempho wrote:On this question...doesn't shear hurt the vertical development of overland storms? I know some of our hail producing storms can get very, very high. It's hard to imagine that shear would help those storms.
No... shear helps to vent the storm and introduce more dry air, which helps an overland tstm. Actually, during a tstm that is producing hail, usually the shear is VERY high. It helps in the hail development process.
The highest-sheared storms will be the ones that produce tornadoes, if I remember correctly.
wxmann_91 wrote:Yet another question, what makes hurricanes larger or smaller? Is it just random chance or does something create the size?
There is a theory which a met presented on here that if a hurricane is exposed to shear in their formative stages, they might start out larger than the average cane, thus develop into bigger canes. Examining the satellite loops of Katrina and Rita, one can notice that at first, there are TUTT's near them that hinder them in the beginning, only to move away, but still provide good UL divergence. This allowed them to fan their clouds freely and become big and fat.
Time also has to do with it too. More time, the more time for fanning of the clouds, and the storm keeps getting larger during ERC's. Of course, 2005 being an exception. Ivan went through a ton of ERC's, allowing its windfield to expand each and every time, thus it became huge.
Speed of the storm, IMO, has something to do with it too. Think about it: if a hurricane travels at an extremely fast rate of speed, the storms on the outer fringes never develop because they will lag behind, sheared apart by the storm's outflow
(BTW, when I mention "fanning of the storm" I mean development of convection on the outer rainbands. That is key to bringing TS force winds to the sfc and thus expanding the windfield. How large a storm looks on sat is a poor indicator of the actual windfield.)
The surrounding atmospheric environment is important too. We had low atmospheric pressures across the basin in 2005, so thunderstorms easily developed on the outer fringes of the hurricane. If there were high pressure, the storm would be sort of suppressed, squeezed. Good example would be Andrew of 1992, which was kept small by a huge area of high pressure to the north (which of course drove Andrew into FL in the first place).
Just my thinking here.
Sat loop of Lenny: http://vortex.plymouth.edu/hur_dir/1999 ... 9_sum.html (scroll down to bottom)
Don't forget that eyewall replacement cycles may also lead to the hurricane expanding in size, as we saw with Katrina.