We suffered from a microburst storm early Friday, that did extensive damamge. We were without power until today.
Please accept our appoligies for any packages that are shipped later than expected. The storm has caused us much troubles, damage & delays.
Luckily we were all safe.
Microburst
Illustration of a microburst. Note the downward motion of the air until it hits ground level, then spreads outward in all directions.
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A microburst is a very localized column of sinking air or downburst, producing damaging divergent and straight-line winds at the surface that are similar to but distinguishable from tornadoes which generally have convergent damage. Microbursts can generate wind speeds higher than 75 mph that can knock over full grown trees. They are completely opposite to a tornado. |
A distinction can be made between a wet microburst which consists of precipitation and a dry microburst which consists of virga. They generally are formed by precipitation-cooled air rushing to the surface, but they perhaps also could be powered from the high speed winds of the jet stream deflected to the surface in a thunderstorm (see downburst).
Wet microbursts
Wet microbursts are downbursts accompanied by significant precipitation at the surface which are warmer than their environment. These downbursts rely more on the drag of precipitation for downward acceleration of parcels than negative buoyancy which tend to drive "dry" microbursts. As a result, higher mixing ratios are necessary for these downbursts to form (hence the name "wet" microbursts). Melting of ice, particularly hail, appears to play an important role in downburst formation, especially in the lowest one kilometer above ground level. These factors, among others, make forecasting wet microbursts a difficult task.
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Characteristic |
Dry Microburst |
Wet Microburst |
|
Location of Highest Probability |
Midwest/West |
Southeast |
|
Precipitation |
Little or none |
Moderate or heavy |
|
Cloud Bases |
As high as 500 mb |
Usually below 850 mb |
|
Features below Cloud Base |
Virga |
Shafts of strong precipitation reaching the ground |
|
Primary Catalyst |
Evaporative cooling |
Downward transport of higher momentum |
|
Environment below Cloud Base |
Deep dry layer/low relative humidity/dry adiabatic lapse rate |
Shallow dry layer/high relative humidity/moist adiabatic lapse rate |
|
Surface Outflow Pattern |
Omni-directional |
Gusts of the direction of the mid-level wind |
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