A National Weather Service damage survey completed July 11, 2013 concluded a microburst caused straight-line winds estimated at 95 mph based on their damage survey.Six individuals were injured during this event.
A microburst occurs when a thunderstorm collapses. The collapse can be caused by a variety of factors that cause the warm, moist inflow that drives the storm to be cut off or weaken dramatically. With the updraft weakened or stopped there is no upward directed force to hold the cloud mass aloft.
Updrafts can also be weakened or made to collapse by evaporative cooling of rain and melting of hail falling from the storm. The cooled air is more dense than before cooling and the updraft energy becomes insufficient to maintain the storm.
The entire cloud mass crashes to the ground over several minutes. As the water drops and everything else within the cloud accelerate towards the ground under the influence of gravity a rapid burst of air is pushed ahead of all the cloud material.
When the air hits the ground it fans out and surface winds can exceed 100mph. Damage can be extensive at ground level and even worse is that the change of wind direction and speed can be a great hazard to aviation.
A microburst occurs when a thunderstorm collapses. The collapse can be caused by a variety of factors that cause the warm, moist inflow that drives the storm to be cut off or weaken dramatically. With the updraft weakened or stopped there is no upward directed force to hold the cloud mass aloft.
Updrafts can also be weakened or made to collapse by evaporative cooling of rain and melting of hail falling from the storm. The cooled air is more dense than before cooling and the updraft energy becomes insufficient to maintain the storm.
The entire cloud mass crashes to the ground over several minutes. As the water drops and everything else within the cloud accelerate towards the ground under the influence of gravity a rapid burst of air is pushed ahead of all the cloud material.
When the air hits the ground it fans out and surface winds can exceed 100mph. Damage can be extensive at ground level and even worse is that the change of wind direction and speed can be a great hazard to aviation.
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Artist's depiction of a microburst over an airport. As the air crashed to the ground it fans out and wind speeds can exceed 100 mph. Aircraft that approach the microburst experience a sudden and violent change of vertical wind. On approach or takeoff the aircraft is close to the ground an may not have time to adjust flaps and air speed to avoid a crash. Courtesy: NASA.
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A 3D (volume render) view of the thunderstorm that caused the Hilliard micoburst rendered in GRLevel2 Analyst. Notice how the volume of heavy rain (yellow and red) collapses, and, in approximately 18 minutes dissappears.
Text of the NWS ILN Local Storm Report on the Hilliard, OH microburst:
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE WILMINGTON OH
625 PM EDT THU JUL 11 2013
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0400 PM TSTM WND GST 4 SSE HILLIARD 39.99N 83.12W
07/10/2013 E95.00 MPH FRANKLIN OH NWS STORM SURVEY
*** 6 INJ *** A NWS STORM SURVEY CONFIRMED A MICROBURST
ABOUT 3 OR 4 MILES SOUTH-SOUTHEAST OF HILLIARD. BASED ON
OBSERVED DAMAGE...STRAIGHT LINE WIND SPEEDS OF UP TO 95
MPH WERE ESTIMATED.
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