Abstract/Summary

During the early hours of Easter Monday, 28 March 2016, the passage of a very rapidly-deepening depression across central England resulted in a rare inland gale, followed by a succession of squally showers during the afternoon in the polar maritime air behind the cold front. During one of these showers, two anemometers (at 2 m and 10 m above ground level) located in the Atmospheric Observatory at the University of Reading recorded gusts exceeding 30 m/s (60 kn), the highest recorded at the site for almost 20 years. Although these were well in excess of other local gust speeds, the meteorological situation was favourable for very high squally gusts, and this taken together with records from a well-maintained site with impeccable site and instrument metadata initially suggested the observations were beyond reproach. However, it soon became clear that wind speeds from other anemometers on the site (one on the same mast) did not support these extreme gusts. A careful investigation into the circumstances concluded that both anemometer outputs were temporarily incremented by rapid pulses resulting from coronal discharge (St Elmo’s fire), even though observed electric fields were not sufficiently large to result in lightning. Other instances of observed high wind gusts from similar instruments, apparently genuinely recorded but lacking supportive evidence in terms of substantive infrastructure damage or confirmation from a second instrument, may now warrant retrospective re-examination.