The 86th Anniversary of the “Big Wind”
2020-04-10 15:57:06.000 – Eric Kelsey, MWO Lead Research Scientist
Eighty-six years ago, five men holed-up in a small wooden structure atop Mount Washington contemplated the question, “Will they believe it?”
These five men, alongside three cats and a litter of five kittens less than a week old, witnessed the fastest wind speed ever recorded on Earth: 231 mph.
The storm that came through on that historic day, 12 April 1934, surprised everyone with its incredible power. The skies just two days before were crystal clear and the winds were unusually light. Around sunset offered the first harbinger of the storm to come: reddish cirrus clouds to the west and a pair of sundogs. Those cirrus clouds were advancing eastward from an extratropical cyclone of moderate intensity tracking eastward through the Great Lakes. On 11 April, it moved into southern Canada while a stronger secondary low developed off the mid-Atlantic coast. Concurrently, a high pressure center retreating northeastward from Maine into the Canadian Maritimes also strengthened and became stationary over Labrador, which increased the pressure gradient between the coastal low and the high.
Figure 1: Sea-level pressure analysis valid 9:00 a.m. EST on 12 April 1934 just hours before the 231 mph gust. A low pressure system centered just south of New England intensified and tracked slowly northwestward during the day. From the U.S. Weather Bureau (now the National Weather Service).
A third feature became involved and may have been the critical disturbance to intensify the summit winds to over 200 mph. A weak low pressure system just northwest of Bermuda tracked northwestward and was absorbed by the developing coastal cyclone south of New England. The merging of these two cyclones increased the strength of its circulation and the southeast winds to its north across New England. With the blocking high pressure over Labrador preventing the typical northeast advancement of the cyclone, the pressure gradient tightened across New England and produced over 24 hours of winds over 100 mph at the summit Mount Washington. The “Heated Number 2” anemometer that recorded the record-breaking winds was fortuitously positioned to measure the full, uninhibited force of the winds on the southeast side of the summit.
Figure 2: The Heated Number 1 (left) and Heated Number 2 (right) atop of the Mount Washington Carriage Road Stage Office roof.
Sal Pagliuca, Alex McKenzie, and Wendell Stephenson (“Steve”) were the three Mount Washington Observatory (MWO) Observers who were on the summit that day. Sal invited two close friends to the summit too, Arthur Griffin, an artist and photographer, and George Leslie. Around 4 a.m. on the morning of 12 April, Steve awoke to a loud shuttering sound of the building that he had never heard before. He checked the speed indicated by the recorder trace, about 105 mph, and knew that the winds were much faster than that. He realized that rime ice must be accreting around the anemometer. While the rest of the team slept, Steve went outside with a wooden club and climbed a ladder to the roof of the building to deice in winds exceeding 150 mph!
Figure 3: MWO Observers Alexander McKenzie (left) and Sal Pagliuca (right) check the tension of the guy wires on the Heated Number 2 anemometer.
Figure 4: MWO Observer Wendell Stephenson is packed with gear and provisions at the bottom of the Mount Washington Carriage Road prior to ascending the mountain.
Winds remained strong all morning. Because of this, McKenzie, the communications expert, decided to leave their radio transmitting across New England all day. Colleagues in Exeter, New Hampshire and at Blue Hill Observatory just south of Boston often listened and communicated to the MWO Observers. In the early afternoon is when the winds peaked. Sal, a former electrical engineer with General Electric, was the observer who timed the record wind gust. He used a stop watch to measure the time between the clicking sounds of the anemometer recording device, which made clicks every 1/10th mile of wind that blew by. He timed 1.17 seconds between clicks, and shouted the time twice so Arthur could write it down. With much anticipation they converted the time to a corrected wind speed of 231 mph!
Gusts of 231 mph were measured twice, and frequent gusts of 220 to 229 mph were also recorded. The fastest 5-minute average wind speed was an astonishing 188 mph.
Redundant measurements are critical for confidence and fidelity in scientific measurements, and Sal was not the only person recording the timing between clicks. During the event, the other observers took turns with the stop watch timing the click when the wind was screaming at over 150 mph. In addition, Dr. Charles Brooks, the first MWO President, professor at Harvard, and Director of Blue Hill Observatory, was timing the clicks he heard over the radio at Blue Hill during the hour leading up to the record wind gust. Everybody’s measurements were in close agreement and left no doubt that what they were witnessing was real.
Only a couple months later, the now famous Heated Number 2 anemometer was carefully transported off the mountain to the U.S. Weather Bureau headquarters in Washington, D.C. The Chief of the U.S. Weather Bureau (now the National Weather Service), Charles Marvin, performed tests on the anemometer to calibrate it and ensure it was still operating within acceptable tolerances. This calibration test was one of the last projects Marvin performed before retiring later that year after 22 years of work at the Weather Bureau. The calibration of the anemometer was very close to the calibration performed in November 1933; the Heated Number 2 spun about 3% slower than it did in November – possibly a sign of slight wear on the bearings. The fact that it spun slower implies that the actual wind speed during that infamous day may have actually topped 231 mph.
Figure 5: Charles Marvin, Chief of the U.S. Weather Bureau from 1913-1934, stands next to a triple register device similar to the one attached to the Heated Number 2.
Charles Marvin stated in his documentation of the calibration test, “Great confidence is justified in the verity of these results…” Proper calibration procedures to validate the 231 mph wind speed record were followed perfectly. The anemometer was calibrated just 5 months before and 2 months after the record wind speed and careful attention were paid to the instrument during the storm to ensure it did not become encased in ice. Redundancy of the measurements of the high wind gusts by multiple people also lends the utmost confidence in the record. So, to answer the Observers’ question from that fateful day in 1934: “Yes, they believe it.”
Eric Kelsey, MWO Lead Research Scientist