16:23 Mon Aug 10, 2020
A Brief Geologic History of The Whites
After hearing word of a North Carolina earthquake that occurred this past Sunday I was reminded of my second passion, Geology. I started diving into the “shakemap” from the USGS website and was able to see where the earthquake was felt and read some reports of first hand experiences from this 5.1 magnitude earthquake. I found myself asking the questions of “Does North Carolina have a geological reason for having earthquakes?”, “How was North Carolina geologically formed?”. These questions inevitably lead to “How was Mount Washington formed?”.
Thanks to a paper written by R. Buchwaldt and F. Dudas I was able to dive into the evolution of Mount Washington and some geologic forcing that developed our beloved Appalachian Mountains. Below I will summarize some of the key elements to how Mount Washington came to be.
As the supercontinent Pangea formed, there were many collisions of other plates that molded the geology of the Whites. About 450 to 250 millions of years ago (Ma), the continent called Gondwana (Current day Europe and Africa combined) crashed into North America. During this collision, some of the Earth was thrusted upward causing a large elevated region. While the Appalachian Mountains at one point rose more than 4.5 miles high, forces of erosion weathered it down. There was a second collision of continents about 400 Ma between North America and a micro continent f Avalonia. The rocks were crushed together with a series of folding and faulting. Under the intense heat and pressure of this event, many of the sedimentary minerals of the earth were transitioned into different minerals through the process of metamorphism. Some of the infamous granite of the granite state was produced in this event where the heat and pressure was so strong that it melted the previous rock into granite.
A secondary type of geologic event that is responsible for most of the features we see today is glaciers. Approximately 0.08 Ma or 80,000 years ago the Wisconsinan glaciation occurred. It is estimated that back then there was an estimated 1km thick of ice on top of Mount Washington. “The deposited sediments have been dated by the Carbon method and indicate that the local ice had retreated from the lower elevations by 13,500 years and that the Presidential Range was ice free by about 11,500 years ago” said Buchwaldt and Dudas. Glaciers tend to hold onto and “eat up” rocks as they move. So, as they melt and recede they will leave behind some of their deposits in their wake. The White Mountains attribute some of their features to this process.
I found this paper very informative and fascinating. I have always wondered how Mount Washington came to be and now many of my questions have been answered! I hope you have learned some new geology about how our beloved white mountains were formed over time!
Information from R. Buchwaldt and F. Dudas paper titled: DEAPS 2013: Geology of the Mt. Washington area, New Hampshire, a glimpse into the evolution of the Appalachian Mountains
Nicole Tallman, Weather Observer/Education Specialist
17:21 Wed Aug 05, 2020
AuGUST Lives Up to It's Name: New Monthly Wind Record!
What an evening we had yesterday! For my first real storm/wind event of my MWOBS career I’d say I got an exciting one! As Tropical Storm Isaias (ees-ah-EE-ahs) raced up the eastern seaboard these past few days it brought heavy rain and serious winds to much of the region including a record breaking wind gust to the summit.
During the afternoon hours leading up to the closest passage of the storm, the other observers and I patiently waited and monitored the progress as Isaias battered its way through southern New England. I wondered what my new personal wind record would be as it was previously just barely over hurricane force at 77 mph, and forecasts were suggesting triple digits. As the day went on the winds started ramping up and bands of showers moved into the area. I could sense the growing excitement in the room as we discussed our peak wind guesses for the night, and communicated with relatives to our south where tornado warnings were popping up here and there. Since I am so new to how different summit weather is compared to the valley I did not know how to base my guess, so I went in between the other observers at 121 mph.
The storm drew closer to us as we neared the evening hours, with the center track being west of the summit, traveling north through the middle of Vermont. Winds quickly climbed to 70, 80, then 90 mph smashing through my personal record and amazing me with the rate of increase in speeds due to Isaias being such a fast mover. During the 6 o’clock hour we crested 100 mph, and I was able to go outside and experience the mayhem. It was a humbling experience being pushed around, although I was told the southeast winds we were experiencing are generally less menacing out on the observation deck since we are situated on the northwest side of the summit. A short while later a gust of 123 mph made quite the roar and my guess was looking A-OK at that point. At about the same time, heavier bands of rain started passing through which dumped an appreciable amount of rain in a short period. I was downstairs cooking some dinner when suddenly the stove vent water drain bottle overflowed all over the counter, with the feed tube having a steady stream of water exiting it. My engineering mind rushed to find some hose so that the drain could feed right to the sink. Normally the drain bottle could be emptied every once in a while but the heavy rain bands overwhelmed the system at the time. I was happy to be able to find a solution to the problem quickly or the bottle would have had to be emptied every 5 minutes it seemed, which would have taken away my opportunity to storm watch with the crew!
The winds started to decrease a bit, with the peak gust still remaining at 123 and it looked like it was trending downwards. My guess seemed to still be holding up well! Was the heaviest part of the storm over? Nearing the 8 o’clock hour David Decou, our shift night observer, came in from taking an observation and said it felt like the winds were getting stronger again. Our usual wind speed recording device, the famous hays chart, was unfortunately not in service so sadly we could not watch the red ink line to observe the trends. Luckily, we were able to pull up a computer program that mimics the hays chart so we had the next best thing to view and check the spikes from strong gusts. Suddenly at 8PM sharp, the chart spiked showing a gust of 147 mph! The wind database was cross referenced and sure enough, it showed a peak gust of 146.7 mph from the southeast! Our crew celebrated the feat as it set all of our personal records and we then shared the news with the state park crew who also had a few new personal records set. We soon discovered that besides personal records, it also set a new all-time wind record for the month of August! The previous record was 142 mph set back in August of 1954.
My final thoughts on my first storm is just wow. The thrill and excitement being up here, monitoring the weather and experiencing the power of nature first hand is incredible. I look forward to many more storms, especially those with snow involved (too early for this?). Definitely glad to have nearly doubled my record, and experienced 100+ mph winds but I have a feeling 147 will probably hold for a bit, who knows.
If you enjoy learning more about the weather and the Mount Washington Observatory consider joining us on Tuesday for our Second Science In The Mountains program on Thunderstorms, Lightning & Lightning Safety. To learn more and sign up for the virtual presentation visit this link below:
Sam Robinson, Weather Observer/Engineer
19:33 Mon Aug 03, 2020
A Little Bit of White Mountain Tornado History
This past week, I spent some time researching tornadoes in preparation for a distance learning program on tornado development. Aside from learning some fun facts for the presentation, I got rather curious about tornado history in New Hampshire...
While Mt Washington isn’t exactly known for its tornadic activity (to my knowledge there has never been an observed tornado on Mt Washington), but New Hampshire does average around a tornado a year, and tornadoes have been observed in every state in the US.
After exploring some of the historical tornadoes throughout the state, it seems that most of them occurred in the southern half of the state, which is no surprise considering the impeding effects the mountain terrain would have on the required vorticity.
I also learned about another F0 tornado that touched down on the south side of Pequawket Pond in Conway Village on June 23, 1965, and a little further south, Tamworth experienced two F1 tornadoes both in the month of August of 1972 and 1976. The 1972 tornado was 77 yards wide and tracked northwest from just east of Chocorua village to just north of Silver Lake. The 1976 Tamworth tornado touched down just north of the center of town with 5 reported injuries, the only injuries reported of the mentioned tornadoes.
For anyone in need of a refresh on the Fujita scale, the metric for classifying tornadoes is based on wind speed and its associated damage. The Fujita scale is named after the prominent Japanese American severe storms researcher Tetsuya Theodore Fujita.
Also not too far away was the August 1969 F3 tornado that tracked up the Interstate 93 corridor from around Thornton to just south of Woodstock. An F3 tornado classifies a tornado as having wind speeds ranging from 158 to 206 mph, and I find it remarkable to think that while we experience winds of that magnitude every once in a while, tornadic events could potentially bring such violent winds to a fairly wide range of locations.
At the dinner table this evening, weather observer David Decou and I chatted about the idea of whether or not a tornado could touch down on Mount Washington. We both agreed that it is fairly unlikely, but not impossible. One of the common misconceptions about tornadogenesis is that tornadoes can’t form over mountains because of the effect the mountain would have on the twister. This isn’t exactly the case... The reason tornadoes don’t often form over mountains has more to do with how they impede the convective and cyclonic development needed for tornadogenesis. Essentially, it often proves to be a bit of a scrambler for clouds that might ordinarily have conditions favorable for tornado development.
So I’m not sure that we’ll ever see a tornado up here, but if it were to happen, we’ll surely be keeping an eye out.
Nate Iannuccillo, Weather Observer/Education Specialist