Past IEM Features tagged: talltowers

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Derecho Profile

19 Aug 2020 05:37 AM
The featured chart is a preliminary plot of height profile horizontal wind speed from the ISU "Talltower" facility in Story County (north of Ames). This tower is outfitted with many sensors at various heights and records wind speeds at one second refresh intervals. The chart uses this one second data along with six sensors at various heights to construct a two dimensional analysis of horizontal wind speed during the passage of the most gusty portion of the derecho at that location. Please note that sampling winds at this time resolution more represents gusts than sustained winds. You can see lots of crazy things happen including an initial gust front that rocketed near surface winds to near 90 MPH (11:23 - 11:24 AM) to only subside for a brief moment before the most intense winds arrived. This plot indicates 90+ MPH gusts got very close to the surface with 120+ MPH gusts briefly recorded some 375 feet above ground level.

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Tags:   2020derecho   talltowers  

Undular Bore

02 May 2017 05:35 AM
The powerful storm system that brought tornadoes, heavy snowfall, and flooding rains to the US this past weekend also produced an undular bore over Iowa on Sunday evening. These events are not atypical of strongly forced storm systems and typically are harmless only producing neat cloud features and shifts in wind speed, direction and air pressure. The featured plot presents 1 second interval data from the "Hamilton County" ISU Tall Towers site whose data will be featured on this website more prominently soon. The data shown is for the 10 meter above ground sensor and shows the jump in pressure associated with the bore and then oscillation afterwards. The drop in wind speed and shift to southwesterly is interesting to see.

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Tags:   bore   talltowers