06:14 Thu Apr 19, 2018
An Epic Storm Summary
As this past shift elapsed, our eyes turned to an impending storm that looked to bring a mess of wintry precipitation and STRONG winds Saturday through Tuesday. We became especially excited through the weekend as the storm setup looked eerily similar to the storm that brought the summit a 231 mph wind gust in 1934. The only difference was going to be the strength of the high and low pressure systems in play, so we knew that it would not be breaking any records, BUT we had a feeling the winds were going to roar. In the days leading up to the storm, the forecast personally had me pulling my hair out (I am bald now) (but not really). The issue was a strong temperature inversion that was going to set up beneath the summit, or so I thought. The colder air at the surface was the result of high pressure to the north sending a backdoor cold front into New England. I mistakenly forecasted for the summit to remain above the inversion and in a layer of air that would be above freezing, thus expecting our dominant precipitation type to be rain during the worst of the storm. As you are likely aware of now, this was not the case…
3 foot long rime ice feather plucked off of the tower!
Rain, freezing rain, sleet and snow fell on Friday heading into the weekend and the ice already began to accrue atop the Rockpile. Plain rain fell late Friday night, and that was the last time we would have any non-freezing precipitation through Tuesday. One inch of snow and sleet accumulated on Saturday as a warm front lifted through New England (although that warm air remained above the summits). The result was wet snow, sleet and some freezing drizzle. The front stalled out on Sunday and the day was very similar to Saturday, although precipitation fell more as freezing rain and sleet this go around. Sunday was when the hair pulling really took off as my forecast for Monday was determining just how high that temperature inversion would set up as the worst of the storm barreled through.
The wind forecast was okay! The temperature and precipitation type were not. I went to bed Monday morning, already a little exhausted from battling glaze ice that had been accruing on our instrumentation for a few days straight. My anticipation was to wake up and hear the winds roaring, and heavy rain falling, assuming the mercury had risen above freezing. I woke up to what felt like an alternate reality if I am being perfectly honest. Upon waking up in the afternoon, Adam informed me that the temperature was in the teens and VERY heavy sleet had been falling through the afternoon. When it came time for my first observation at the start of my shift, I climbed to the top of the tower where it felt as though I was under fire from an army wielding BB guns. It was not JUST heavy sleet (and I mean HEAVY), it was very large sleet, forming in a convective nature. These large balls of sleet were coming at me at category 1 hurricane strength and occasionally hitting me along a gust over 100 mph. This may “sound” awful, but it was truly remarkable to experience… After my second observation, Adam and I went to the observation deck door to film a quick video to give everyone a taste of what was going on. As we were filming the video, we opened the door and realized the heavy sleet had transitioned to very heavy freezing rain that was causing glaze ice to form at a tremendous rate. The second that my phone was exposed to the freezing rain, wind and cold, it unfortunately died so we could not get the footage we were hoping for. To give you an idea of how hard the freezing rain was coming down, after being outside for a few minutes I came back inside and was covered in glaze ice myself.
I took this right after coming inside from one of my observations. I was outside for a few minutes and became encased in glaze ice!
After filming the video, we came back down to the weather room to watch it. In the middle of it, the building began to shake amidst a loud roar as a rogue gust of wind seemed to come out of nowhere. Adam shouted “WHAT WAS THAT?!” as we both looked towards the Hays Chart and saw the needle pushing towards the outer edge of calibration. We ran over and realized that we hit 131 mph!
Hays Chart showing our peak gust of 131 mph at 8:19pm EDT.
Adam is okay, so I figure I share this next part because looking back on it now is very funny. He ran downstairs to get our intern Jill, and summit volunteer, John. In a fit of joy and rapid motion, he slid all the way down the stairs to where John was waiting at the bottom and saw the whole thing. The stairs were actually covered in sleet that had blown through the door, so this is understandable. Full of adrenaline, he came back upstairs and we all enjoyed the loud roars of wind gusts consistently hitting 110-120 mph for the next couple of hours before they began to diminish. Freezing rain continued for several more hours before finally transitioning to snow showers by the wee hours of Tuesday morning. By daybreak, it was a fascinating sight atop the Rockpile as every surface was covered in FEET of hard rime and glaze ice. In addition to all of the ice, over 3 inches of liquid precipitation had fallen on Monday, which was composed of freezing rain and 6.7” of sleet! So much sleet was accruing and being lifted up by the winds causing us to report blowing snow, which was actually composed solely of sleet. As you walked through the drifts of sleet, each step you took resulted in a splash as the tiny beads of ice displaced outward. It was another epic storm that I will undoubtedly remember for the rest of my life!
Caleb Meute, Weather Observer / Meteorologist
20:08 Tue Apr 17, 2018
Spring Around the Corner?
With how cool the weather has been across much of the country,
many are looking ahead to see when more spring like conditions will begin. First, why has much of the eastern United States
been seeing such cool weather when we had such warm conditions in February and
early March? Well in the overall synoptic flow (Large scale weather patterns
larger than 1000km across) there has had consistent blocking high pressure over
Greenland, which creates a deep trough (Dip in the jet stream) resulting in
cooler than average temperatures. Figure 1 below is a plot of the 500 millibar
height anomalies for the northern hemisphere over the past month. The warm
colors over Greenland and the colder colors over Canada are a good indicator of
the persistent blocking that we have been seeing over the last month.
Figure 1: 500 mb height anomalies in the northern hemisphere over the last month.
Higher than average snowfall in March and early April has recovered the snowpack lost in the February melt and then some. In Figure 2 and 3 below, snow covers much of the interior North East as well as the Great Lakes region to the Hudson Bay. With northwest flow due to the persistent blocking pattern, air masses are originating from over the deep snow pack. The snow helps insulate cold air as it moves south by both reflecting incoming solar radiation with any heating from the sun going into melting the snow, keeping temperatures near freezing. If there was bare ground, the air mass would heat up during the day as the sun warms the ground and transfers that heat to the atmosphere above it. With how strong the sun is at this time of year, any snow free ground would quickly warm a polar air mass and take away its chill.
Figure 2: Current snow depth across the United States
Figure 3: Current snow depth across the North East
The good news about this map is that there is not much snow to the south and southwest of New England. Once the weather pattern changes and we get a few days of southerly or southwesterly flow, the snow in the North East will quickly melt, exposing the bare ground to the sun to really start our spring season. We would need a weather pattern with southerly flow to bring in the warm air with sunny skies to last long enough to melt a vast majority of the snow in the Great Lakes region and southern Canada. This will give us a good buffer from the colder air masses as they travel out of the Polar Regions. Losing all that snow won’t necessarily mean that we will be free from the cold weather but the amount of time that it will stick around will be greatly reduced.
Looking ahead in the short term, we will have another colder storm coming in keeping below normal temperatures into the weekend, but beyond that is much more promising for warmer weather. In Figure 4, I have a plot of the 500 mb height anomalies expected early next week. It is a long way out so I am using an ensemble of model to get more of a mean out of a bunch of different model runs with different parameterization to help reduce error in the long range. Looking at anomalies also gives a better idea on if we are going to see a better chance of warmer or colder weather rather than looking at specifics like precipitation or expected high temperatures.
Figure 4: Forecasted 500 mb height anomalies for early next week
With those darker oranges over New England, there is good agreement that a warm up is on its way. We will have to see how much snow and ice this warm up will melt! This late into spring, it is possible that after this weekend southern and coastal regions of New England will have seen the last of below freezing temperatures until fall! Up here on the Rockpile, we are prepared to see winter for another few months of winter! We can see snowfall up here in any month of the year!
Adam Gill, Weather Observer/IT Specialist
13:02 Thu Apr 12, 2018
Big Wind Day
It’s hard to believe, sitting here amidst the hum of computers, the whir of a humidifier running continuously,
and the occasional phone call that 84 years ago to the day, in a one-room wooden cabin chained to the mountaintop
where cats outnumbered people, a group of intrepid explorers and scientists experienced, observed, and recorded a
humbling wind gust of 231 mph… surviving not only to tell of their experience, but also to verify the accuracy of
their measurement. A measurement which stood as the fastest surface wind speed recorded for nearly 62 years, and
remains to-date the fastest surface wind speed experienced by man.
In reflecting on the event, and its significance to the Observatory, I thought it would be fun to look at the
historical weather maps as well as a few snippets of documentation from the observer log books.
Figure 1. Daily Weather Map for Tuesday, April 10th, 1934
Washington, D.C., Tuesday April 10, 1934 – 8 A.M. (E.S.T.)
“A disturbance that was central over Minnesota Monday morning has moved eastward to Lake Huron, Alpena, Mich.,
29.40 inches. Another disturbance is central about 300 miles east of Cape Hatteras, Hatteras, N. C., 29.62 inches.”
Figure 2. Daily Weather Map for Wednesday, April 11th, 1934
Washington, D.C., Wednesday April 11, 1934 – 8 A.M. (E.S.T.)
“A disturbance of considerable intensity is central over the lower Lake region, Erie, Pa., 29.22 inches.”
Figure 3. Daily Weather Map for Thursday, April 12th, 1934
Washington, D.C., Thursday, April 12, 1934 – 8 A.M. (E.S.T.)
“A disturbance of great intensity is central this morning over Connecticut, New Haven, 29.26 inches. Pressure is high from
the Rocky Mountain region eastward to the Mississippi Valley, Rapid City, S. Dak., 30.54 inches.”
Note how in each of the weather summaries, the verbiage describing the system increases in severity, from simply a disturbance, to one of
considerable, and then great intensity. Even with the lack of operating weather stations at the time, enough data was available to discern
that a very strong system was set to impact the area.
The following paragraph is a snippet from the observer log books:
"I dropped all other activities and concentrated on observations. Everyone in the house was ‘mobilized’ as during a war attack and assigned
a job. The instruments were watched continuously so that they may give a continuous and accurate record of the various meteorological
elements at work. The anemometer was particularly watched. A full tank of gasoline made us feel good." -Log Book entry, Sal Pagaliuca
Figure 4. Observers Alex McKenzie, Bob Monahan, Joe Dodge, and Sal Pagliuca
One of the most remarkable aspects of this storm was that the gust to 231 mph wasn’t an isolated event. As the afternoon wore on, frequent values of 220 mph
were recorded, including several gusts to 229 mph. For reference, a Category 5 hurricane has wind speeds of greater than 156 mph.
The observers at the time captured just how unbelievable this event was in their log book:
"'Will they believe it?' was our first thought. I felt then the full responsibility of that startling measurement. Was my timing correct? Was the method OK?
Was the calibration curve right? Was the stopwatch accurate?"
-Log Book entry, Sal Pagliuca
As we now know, the measurement was in fact accurate, with the anemometer being sent down for confirmation of its accuracy and repeatability after the event.
That astonishing value, 231 mph, became the highest surface wind speed ever observed by man, and solidified the importance and value of having a manned
weather station atop the summit, a feature which continues to this day.
Taylor Regan, Weather Observer
10:42 Fri Apr 06, 2018
Vernacular Confusion (The Sequel!)
“We’ll never survive!”
“Nonsense! You’re only saying that because no one ever has!”
Wesley and Buttercup, The Princess Bride
It’s time for more Vernacular Confusion! Don’t worry; it’s not going to be as scary as it sounds. Maybe I should have led with a different quote…
Vernacular Confusion is where I go over meteorological terms that might be misunderstood or misused. Part 1 of Vernacular Confusion had a definite winter vibe to it, so this time I’m going to go over some warmer terms. It is Spring, after all (whether or not it feels that way up here at the Rockpile is unimportant). Let’s get to it!
Pineapple Express/Atmospheric Rivers
Just to start things off, I want to clarify that Seth Rogen and James Franco have nothing to do with this. In meteorological terms, the Pineapple Express is an example of a strong atmospheric river. According to NOAA, atmospheric rivers are “narrow regions in the atmosphere that transport much of the moisture from the tropics to the northern latitudes”.
The Pineapple Express is an atmospheric river that transports moisture from the tropical Pacific (near Hawaii) to the West Coasts of Canada and the United States. The Pineapple Express can drop up to five inches of rain on California in a single day. Not all atmospheric rivers are strong, and their precipitation can prove beneficial to water supplies, but those with the strongest winds and largest moisture contents can cause severe flooding due to extreme rainfall.
Diagram of the Pineapple Express from WeatherNation.
Let’s move to the East Coast and talk about the Gulf Stream. The Gulf Stream is a current of tropical water that starts in the Caribbean and flows up along the Atlantic Coast. It wraps around Florida and follows the coastline up to the North Carolina Outer Banks, where it takes a more eastward path farther out to sea.
NASA image of Sea Surface Temperatures in the Atlantic Ocean. The Gulf Stream is the curl of warmer temperatures along the East Coast.
Ocean-air interactions are a vital area of the study of weather. As stated by LiveScience, “the Gulf Stream affects the climate of the areas closest to the current by transferring tropical heat towards the northern latitudes”. Just as atmospheric rivers transport moisture from the ocean, the Gulf Stream transports heat. This keeps the coastline waters of the southeastern states much warmer than those of the West Coast.
Sometimes, particularly in the summer, you might see lightning without hearing the accompanying boom of thunder afterwards, or notice a flash without seeing a cloud-to-ground bolt. The term ‘heat lightning’ is often attributed to this phenomenon. NOAA posits that the term arose because this phenomenon happens most often on warm summer days.
In actuality, ‘heat lightning’ is no different than the lightning from any other storm. As stated by NOAA, “it is possible that you might see lightning and not hear the thunder because it was too far away”. The sound of thunder can only be heard at a distance of about 10 miles from the flash. Seeing a muted flash instead of a lightning bolt is due to interference from ground features or the curvature of the earth. Instead of seeing the bolt, you merely see the bolt’s reflection off the clouds.
Distant lightning captured by FOX 25 Storm Tracker Bobby Hines from okcfox.com.
A rose by any other name would still smell sweet, however, so a lightning show by any other name will still be pretty! Just take care to watch these natural shows from the safety of a secure building.
Sarah Schulte, Summit Intern
14:20 Thu Apr 05, 2018
One Windy Day
Although not quite the storm I was hoping for, the storm that has affected the summit over the past 24 hours has still been very impressive due to the duration of our high winds. For 10 hours straight we observed winds equivalent to a category 3 hurricane (111 mph or greater), with 16 consecutive hours of 100 mph or greater winds. Despite the long duration of winds of this magnitude, our peak gust from the storm was “only” 120 mph, meaning these were extremely steady, but very strong winds. We’ll take a look below at the overall set up for this storm, why we were so excited for high wind potential, and one theory as to why the summit did not see higher winds.
It was anticipated that the highest winds with this storm would occur on the tail end of the system, as high pressure situated over the Southern Appalachians began building into New England from the southwest.
GFS Lamp model numbers for Mount Washington roughly 18 hours ahead of the highest expected winds. Highlighted are gusts that were expected to reach or exceed 112 mph for 7 consecutive hours!
GFS Model showing the expected surface features across the U.S. Note strong low pressure (974 mb) over eastern Canada and a 1024 mb high pressure system. Image courtesy of Tropical Tidbits.
A very tight pressure gradient between the strong storm system that tracked through the Saint Lawrence Valley and this high pressure set the stage for widespread high winds across New England. This type of set up has resulted in some of the highest wind events ever recorded on the summit (gusts of 154 mph in 1996 and 175 mph in 1942 come to mind, to name a few), but for a system to produce winds of that caliber, a few other factors need to align. Firstly, the location of the high pressure is extremely critical to the strength of the winds (by setting up the steep pressure gradient between the passing Low and the building High pressure systems). Additionally, the atmospheric profile must show a few key elements as well.
Surface weather features for Dec 3rd, 1942. Note the similarities in the location of high and low pressure to our most recent storm. Low pressure on this date was significantly stronger than the more recent storm, however, and resulted in a peak gust of 175 mph!
Forecast sounding around the time of highest winds on the summit. The red line (temperature) shows a sharp increase starting near 800 mb. Mount Washington was at about 785 mb during this time, or within this temperature inversion, likely contributing to a more steady, less gusty wind.
These factors are where our current passing system met its downfall, in terms of generating impressive wind gust values. The summit was situated in a very strong and relatively deep temperature inversion, which likely dampened our gust potential. This inversion, or increase in temperature with height seen in the forecast sounding above diminished the air turbulence within that layer and resulted in a very steady wind. This is at least my leading theory on why we did not see higher gusts as one would typically expect with winds of this strength. Still, this was one of the more impressive storms of the winter season, and one I won’t soon forget!
Tom Padham, Weather Observer/Education Specialist