|
#1
|
|||
|
|||
Gust fronts and microbursts
Rick
I have one piece of equipment in my plane that I won't fly without. It's a Garmin 396 GPS that has XM satellite weather. It's not as up-to-date as on- board real time radar, which is quite expensive, but it does give relatively timely Nexrad radar information which is usually updated every couple of minutes. In addition it gives winds aloft, lightning strikes, cell movement, cloud levels, and individual reporting station weather, as well as severe weather alerts. Apart from the initial cost of the unit, the XM weather is 9.95/month. I can also get XM radio with it, just in case I get bored. It can function on battery power alone, and could be used quite easily on the beach. I think the most worrisome thing that we as kiteboarders might have to deal with are microbursts and their associated gust fronts. Gust fronts happen to some degree with every mature thunderstorm, and it's the increase in a cooler wind that we feel in the face of an approaching TS. However, it emanates in a radial pattern from the cell and can be felt even if the storm is moving away from us. Normally the increase in wind is usually in the 10mph range. But with an entity called a microburst, conditions within the cell accelerate the downdrafts and the wind increase can be quite significant. Some gust fronts have been clocked at 168mph, but typically they are more in the range of 60mph with this type of phenomenon. As the gust front moves outward, friction from the ground or base causes the leading edge to roll upward causing a severe wind shear. How would you like to get lofted by a 60mph updraft? Microbursts were once thought to only occur with supercells, but now are known to occur with your run of the mill airmass thunderstorms that make up our summertime pattern here in Florida. Airmass TS are the result of the differential heating and cooling of the surface, and are not usually associated with a frontal line. The safe rule of thumb in flying is to give all thunderstorms a 20 mile buffer zone. They bring down Jumbo jets, so imagine one measly kiteboarder. |
#2
|
||||
|
||||
Thanks for your detailed input, good stuff! There was a particularly notable microburst involving a kiteboarder in Utah a few years back. I recall it was his sixth or seventh microburst while he was riding. Dry microburst may be even more common in the western states than the wet variety in our area. They have some fairly sophisticated warning measures in place out that way. In this case, the rider thought he could handle this extreme weather events and would ride with them going off around him. Not sure if he realized they could boost up to around 170 mph or not if a good sized one struck nearby. Out there the dust columns show them up from a fair distance away. He landed his first jump from perhaps 70 ft. high after burst hit but failed to carry the remaining ones off. More about this at: http://fksa.org/showthread.php?t=631
There was another severe lofting in Portugal in 2005, one I have learned little about unfortunately. One newspaper account puts the height of the lofting at over 325 ft. and distance downwind of over 1750 ft.. I have no details about the weather that contributed to this tragic event. I have to wonder if it might not have been some form of burst. It happened to a well experienced commercial airline pilot out kiteboarding.
__________________
FKA, Inc. transcribed by: Rick Iossi |
|
|