A Cirque-us Around Mount Washington

2020-04-20 13:42:40.000 – AJ Grimes, Weather Observer

Continuing on last week’s theme of extreme ice, let’s talk about glaciers! If you’ve ever gone skiing at Tuckerman Ravine or climbing at Huntington Ravine, you may have wondered what force created these spectacular formations. Or, perhaps you’ve stood at the crest of the Gulfside Trail and wondered at the Great Gulf. Would you believe that there used to be massive ice sheets there that carved these awe-inspiring sights?

 

View of Mount Washington from Wildcat Mountain, with Tuckerman Ravine on the left and Huntington Ravine on the right.

Each of these formations is a glacial cirque: a geologic formation that occurs when glaciers carve out an amphitheater-like valley.* The headwall is the highest boundary; two other cliffs encircle the basin. A lip, the lowest side, offers an outflow path. Snow accumulates and packs in this basin, and a glacier develops. Through a few different processes, the area is then scraped down. Erosion happens as the glacier moves, rotates, wears through and mechanically abrades, and breaks off pieces of bedrock (called “plucking”). Also, freeze-thaw weathering can occur when water enters into cracks and faults in a surface, expands with freezing, then melts and contracts, thus weakening the bedrock. This is similar to what happens on roads, resulting in ice heaves and potholes, something I am sure all New Englanders are familiar with. When the glacier finally melts, it leaves behind this amphitheater-shaped valley.

 

Looking into Tuckerman Ravine from above.

Tuckerman and Huntington Ravines are two of the most famous cirques surrounding Mount Washington, but a few others might catch your eye when you visit: Oakes Gulf, Gulf of Slides, Ammonoosuc Ravine, and of course, the Great Gulf.

 

The view into the Great Gulf from the Gulfside Trail.

While this might seem surprising, the height of Mount Washington allowed for it to retain its glacial cover for longer than nearby areas – it was under glacial ice 15,000-20,000 years ago. Additionally, the makeup of the bedrock is more easily eroded and “plucked”. As a result, Mount Washington is an excellent place to see a number of magnificent cirques!

*While arguments have been made that continental glaciers contributed to the local geography of the mountain, the sharp sides of Tuckerman Ravine and Huntington Ravine are believed to be evidence of an additional process involving local glacier formation and recession.

AJ Grimes, Weather Observer

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 1/10^th 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

A Note About Our Afternoon Forecasts

2020-04-03 16:22:08.000 – MWO Staff, Mount Washington Observatory

New Higher Summits Forecast intro

MWO Staff, Mount Washington Observatory

METAR Code: How it led to a Unique Social Distancing Selfie

2020-03-23 21:08:24.000 – Rebecca Scholand, Summit Operations Manager

My Selfie With My Father Flying Overhead

My Father’s Point of View as He Flew Overhead

Rebecca Scholand, Summit Operations Manager

First Week on the Summit!

2020-03-03 21:06:19.000 – David DeCou, Weather Observer

Greetings from the Summit of Mount Washington!

My name is David DeCou, and I am the new Night Observer in training here at the Observatory. I originally grew up in Grand Rapids, Michigan, and spent the last few months of my life working in Antarctica at the Amundsen-Scott South Pole Station as a Weather Observer. It has been an exciting week of many firsts for me, and I don’t think anything could have prepared me for my amazing experiences here during my first time on the Summit.

On Wednesday, it was my first time taking a ride in a snowcat, my first time ascending the Auto Road, and my first day in the clouds at the Observatory. As I joined the crew during my first ascent (I was lucky enough to ride in the front!), I was in a constant state of amazement, despite the view being cut short by a wall of cloud that seemed to follow us the entire way. It took some days before I had my first real view from the summit. While visibility was low, conditions were relatively calm the day I arrived. This was not the case the following day.

Conditions on the Summit can change quickly from being in the clear to being shrouded in passing fog. This was largely my view for my first couple of days here!

At the South Pole, while temperatures are extremely cold, actual weather conditions are pretty calm year round – the strongest winds I experienced there reached about 30 mph, but are 10-15 mph on average. On Thursday morning at Mount Washington Summit, I awoke to the sound of rattling, from sustained 100+ mph winds buffeting the building. Antarctica was nowhere near enough to prepare me for the winter weather at the Observatory. I went outside with Ian and Caleb, micro-spikes on our boots, to replace and collect the precipitation can for the morning synoptic observation. At that time, winds were around 115 mph from the East, and we received a maximum gust of 132 mph sometime that morning. The moment we left the front rotunda door, it was chaos. Every time my feet left the precious ground to take a step forward, the roaring winds punched my legs forward and into the air, while flinging countless shards of ice debris all around us. It felt like an endless stream of frozen paintballs, and there was the constant danger of being toppled over. There were brief moments where we had to brace ourselves during a strong gust and wait for an opening to continue moving. On our short (but difficult) journey back to the door, we had to move against the wind, with the added challenge of needing to keep the filled precip can upright. It was as fun as it was scary. Count 100+ mph winds as another first for me (on only day 2)!!

During my first week, I’ve had a wonderful time working with and getting to know Ian, Jay, and Caleb, as well as our two fantastic volunteers this week, Sue and Sandra (thank you for all the wonderful food!!!). I have begun to learn the daily routine, shadowing Ian and Caleb for observations, daily checks, forecasts, and various tasks like de-icing the instruments on the Observatory tower, where rime ice accumulates frequently during winter weather.

Rime ice built up on the Observatory tower during an unexpected spell of clear skies on Tuesday.

  West view from the observation deck on my first clear day at the Observatory! It may not look it, but the powerful unobstructed NW winds made it very difficult to take this photo.

 Undercast skies to the West made my first-ever sunset at the Observatory an unforgettable one. It was well worth the wind chill on the tower!

 Northeast-facing windows of the Observatory rotunda on the first clear day of this shift.

David DeCou, Weather Observer