04:43 Tue Sep 19, 2023
Meteorological Summer 2023 By The Numbers
Looking at our calendar, we are only days away from autumn which will land on Saturday, 23 September 2023. This date refers to the astronomical autumn season, which is based on Earth’s tilt on its axis as it is orbiting around the sun. Therefore, the seasons of autumn and spring would land on the equinoxes (when day and night are roughly of equal length) and summer and winter would land on solstices (when day/night are of their greatest lengths, longest day in summer, longest night in winter). However, for those of us studying weather/climate, we are already in an autumn frame of mind.
Meteorological seasons typically occur three weeks earlier than astronomical seasons. Meteorological seasons are based on the annual temperature cycle – winter is cold, summer is warm, and fall/spring are the transition between the warmth and cold. So using the annual temperature cycles, meteorological autumn would be Sept, Oct, and Nov (winter – Dec, Jan, Feb; spring - March, April, May; and summer – June, July, August). Meteorological autumn therefore occurred 1 September 2023 and will run until 30 November 2023. Why do meteorologists and climatologists do this? This is done for consistency – by dividing up the seasons by calendar dates they are nearly even varying between 90 to 92 days. And the other reason is for less variation between seasonal and monthly statistics from year to year.
No matter which fall you choose to recognize and/or celebrate, the key thing to remember is that September is the start of our transition season from summer into winter which means that our warmest weather is generally behind us, more icy/snowy weather lies ahead (we received our first few flakes of the season in late August), and winds start to roar back to life as stronger pressure gradients develop (by October, statistically speaking, 1 out of every 2 days will see hurricane force winds and 1 out of every 4 will see gusts of 100 mph higher). So, make sure to check out the Higher Summits Forecast
so that you are prepared for whatever the mountain might throw your way.
While meteorological fall has arrived, I figured it might be worthwhile reflecting back on meteorological summer 2023. Looking back at weather stats, if I had to summarize summer 2023 weather conditions on the summit, they would be - rainy, snowy, foggy/cloudy, and “calm”. To find out why these words were chosen, let's look back at some of the stats from last year:
In terms of total liquid precipitation, from 1 June to 31 August 2023, the summit of Mt Washington received 48.39 inches, which was 23.15 inches above the 1991-2020 30-year normal for our location. This makes summer 2023 our second wettest season in our dataset (1932-present) behind the wettest season which is winter (Dec-Jan-Feb) 1969 when 50.26 inches of precipitation was collected. June 2023 was the 2nd wettest June in our dataset with 17.30 inches falling. July 2023 was our wettest July in our dataset with 17.08 inches falling. And August 2023 was our 2nd wettest August in our dataset with 14.01 inches falling.
From 1 June to 31 August of 2023, the summit received 8.4 inches of snow, which was 7.0 inches above the 1991-2020 30-year normal for our location. While a trace of snow fell in August 2023, the rest fell in June with that 8.4 inches in June making it the snowiest June ever in our dataset.
Our average summer temperature for 2023 was 47.8°F (8.8°C), which is 0.2°F below the 1991-2020 30-year normal for our station. When broken down by months, June was a cool month as it was 0.8°F below the 1991-2020 30-year normal for our station. July was a hot month as it was 2.8°F above the 1991-2020 30-year normal for our station. As such, July 2023 wound up being our 7th warmest July in our dataset and the 8th warmest month ever in our dataset. August on the other hand was 2.6°F below the 1991-2020 30-year normal for our station. As such, August 2023 wound up tying for the 14th coolest August in our dataset. Our warmest temperature recorded in summer 2023 was 66°F (18.9°C), which occurred on July 6th. Our coldest temperature recorded in summer 2023 was 26°F (-3.3°C), which occurred on June 4th.
In terms of winds, for summer 2023 our average was 23.5 mph, which was 2.1 mph below the 1991-2020 30-year normal average for our location. Of note was June 2023 which was our 3rd least windy (or “calmest”) June in our dataset and was the 11th least windy (or “calmest”) month ever in our dataset. Our highest gust recorded for summer 2023 was 94 mph, which occurred on August 19th. From 1 June to 31 August 2023, we had 10 days which had gusts of 73 mph or greater and of those days, 0 days had gusts that were 100 mph or greater.
As for our weather during 1 June to 31 August 2023, we averaged 24% of the possible sunshine. The summit had 0 days (sunrise to sunset) that were noted as clear or mostly clear, and there were 8 partly sunny days, with the remaining 84 days being filed under mostly cloudy, cloudy, or obscured (fog). We had 88 days with at least some amount of fog recorded during a 24-hour period. We had 70 days with rain and 10 days with snow.
Late summer sunrise looking down the Mt. Washington Auto Road at the summit
Ryan Knapp, Weather Observer/Staff Meteorologist
19:08 Fri Sep 08, 2023
El Niño and Its Influences on Weather
As we enter the fall season, it's clear that 2023 has been a year filled with meteorological buzzwords. Phrases like "polar vortex," "heat dome," and "bomb cyclones" have inundated the public with an overwhelming amount of weather terminology. One particular term that has gained prominence this year is "El Niño."
Although technically more of a climate phenomenon, "El Niño" has become a familiar figure in meteorology, akin to that eccentric uncle everyone knows. Whether you're a high-ranking expert at the National Oceanic and Atmospheric Administration (NOAA) or just tuning in to your local TV meteorologist's idiosyncrasies, "El Niño" seems to be everywhere. But as its popularity has grown, so have the misconceptions and misattributions surrounding it. From clickbait articles predicting meteorological doomsday to overly confident amateur winter weather enthusiasts swearing that "El Niño" guarantees a record-breaking East Coast winter, it appears that "El Niño" has become the scapegoat for meteorological events in 2023.
In this blog, I aim to explain the drivers of El Niño and, more broadly, the El Niño Southern Oscillation (ENSO). We'll delve into its current state, where it's heading, and the million-dollar question: what does it mean for winter in the United States?
ENSO has a lengthy and impactful history. Human beings have observed its effects for at least the last 499 years. In 1524, Spanish conquistador Francisco Pizarro's expedition faced strong southeasterly winds, which hindered their progress along the west coast of South America. The following year, they encountered more favorable northeasterly winds that allowed them to journey farther south. As they moved inland, they discovered wetter than usual conditions in otherwise arid parts of Peru and Ecuador. Little did they know that they were witnessing El Niño's wet signature along the western coast of South America. However, ENSO hasn't always brought favorable outcomes. The late 1800s saw a series of global famines, some attributed to disruptions in atmospheric circulations caused by El Niño. These disruptions, particularly in the monsoon circulation, led to the deaths of millions in China and India.
You might be tempted to believe the extreme headlines suggesting that El Niño is a menacing force destined to bring catastrophic events. But before anyone panics, let's take a closer look at this climate control mechanism. ENSO can be summarized as a regular cycle of sea surface temperature changes across the equatorial Pacific, occurring every two to seven years.
These temperature changes are driven by shifts in sea-level air pressure patterns over the tropical Pacific. The Southern Oscillation Index (SOI) measures these pressure changes by comparing air pressure differences between weather stations in Darwin, Australia, and Tahiti. When Darwin experiences lower air pressure, it creates an east-to-west airflow that draws warmer surface ocean water towards Australia. The movement of water allows for deeper and colder waters to fill the partial void left by the stronger winds. This process, known as upwelling, results in colder-than-average temperatures across the equatorial Pacific, a condition known as La Niña.
Conversely, during El Niño, the east-to-west trade winds slow or even reverse, reducing upwelling and warming the ocean's surface layer in the equatorial Pacific.
You might wonder why we monitor a narrow band of ocean temperatures thousands of miles away. The answer lies in the ocean's impact on convection, or thunderstorm activity. The tropics are a hotbed for thunderstorms, and during an El Niño event, warmer waters supercharge convection over the tropical Pacific. Changes in the concentration of convection can significantly alter the jet stream's configuration, affecting precipitation patterns and drought development.
Schematic diagram showing the difference in air movement and convection between El Nino and La Nina events. Bureau of Meteorology image.
Now that we've covered the basics of ENSO, let's examine its current status. At the time of writing this blog, ENSO is firmly in El Niño territory, with temperature anomalies continuing to rise. The warmest sea surface temperature anomalies are currently near the west coast of South America, where water temperatures are a remarkable 3°C (5.4°F) above average
Loop of weekly Sea Surface Temperature (SST) anomalies around the equatorial Pacific (Jun-Aug).
Climate and Society (IRI) predict a 90-100% chance of El Niño conditions through at least January. The probability remains above 50% through March before dropping to 37% by April. The Climate Prediction Center (CPC) also maintains at least an 80% chance of El Niño through next spring. The crucial point in both forecasts is the expectation of El Niño conditions throughout the winter. The next section will address what this might mean for winter weather in the United States.
To predict how an El Niño winter might unfold, let's examine past events. We'll start by looking at the jet stream, located high in the troposphere at about 40,000 feet (200mb). The behavior of the jet stream is essential because it influences everything from storm tracks to precipitation and temperature patterns. When analyzing the zonal (west-to-east) jet stream anomalies during the last ten El Niño events, we see that, on average, the northern or Polar jet weakens compared to normal. Conversely, the southern or subtropical branch of the jet stream becomes stronger during El Niño, driven by increased convection across the Pacific. This can lead to an active storm track across the southern United States, occasionally resulting in Nor'easters for the Northeast. In contrast, during La Niña, the polar jet tends to be slightly stronger than normal, while the subtropical jet weakens.
200mb wintertime zonal wind anomalies for El Nino (left) and La Nina (right).
Another crucial factor for understanding seasonal behavior is the 500mb heights, which describe the atmospheric height at the 500mb level. Higher heights indicate warmer atmospheric conditions, while lower heights signify cooler conditions and stormier weather. During an El Niño winter, the lowest 500mb anomalies are typically found across the southern and western United States, with a concentration of lower heights in the mid-south. These anomalies result from the active subtropical jet, which spawns frequent storms moving from west to east across the southern US. Further north, a weakened polar jet can lead to higher heights and warmer temperatures, particularly in the upper Midwest and New England. La Niña reverses this pattern, with higher heights and temperatures in southern areas and lower values in the northern US and the Pacific Northwest.
500 mb wintertime geopotential height anomalies for El Nino (left) and La Nina (right).
The most noticeable impacts on wintertime precipitation anomalies occur along a belt stretching from California to the Southeast and roughly along the I-95 corridor on the eastern seaboard. During an El Niño winter, the increased southern storm track leads to more regular precipitation, particularly in the southeast, where anomalies can range from 1 to 5 inches above normal. Conversely, parts of the Pacific Northwest and Ohio tend to experience drier conditions as most storm tracks are south of these areas. La Niña flips these patterns, with precipitation anomalies shifting locations and magnitude.
Winter anomalies become more evenly distributed from north to south, with storm tracks once again playing a significant role. The southern US, experiencing wetter and stormier conditions, is more likely to see cooler-than-average temperatures, while the northern US generally leans toward warmer temperatures. The warmest anomalies are typically found in the upper Midwest, northern New England, and the Pacific Northwest. Warmer temperature departures dominate most of the country during a La Niña event, except for the western US and some parts of the upper Midwest.
Wintertime precipitation anomalies for El Nino (left) and La Nina (right).
Wintertime temperature anomalies for El Nino (left) and La Nina (right).
Francis Tarasiewicz, Weather Observer & Education Specialist
In summary, what do all these variables imply for the upcoming winter? Where will storms track, and will there be blizzards or a salvageable ski season?
It's essential to note that NOAA won't issue its annual winter outlook for another two months. While we can speculate about increased storm activity and possible warmth in the northern US, making a definitive forecast at this point is challenging due to the numerous variables at play. Moreover, ENSO's primary impact tends to be on the west coast, whereas our seasonal variability on the east coast is largely influenced by the North Atlantic Oscillation (NAO).
The NAO describes the relationship between air pressure in the Arctic and mid-latitudes where most of us live. Unlike ENSO, the NAO alternates between positive and negative phases on a weekly to monthly basis. The negative phase, characterized by lower pressure and colder polar regions, often results in colder weather and more active winters.
Forecasts for the NAO are difficult to make beyond a few weeks, and its fluctuations have a more substantial impact on the weather in the northeastern United States than ENSO. In conclusion, there's much uncertainty, but one thing is certain: Mount Washington will experience extreme weather this winter, regardless of what unfolds in the Pacific.
17:59 Fri Sep 08, 2023
Views from the Top: Summer Intern Signing Off
This summer, I had an incredible opportunity to intern at Mount Washington Observatory. I learned a lot in the process. Being from Prince George’s County, MD, just 20 minutes from D.C., I wasn't very familiar with New Hampshire or the mountains before coming to the summit. Through the course of my internship, I was able to view the beautiful higher summits, all while learning a ton of meteorological knowledge.
During my undergraduate years at the Pennsylvania State University, I had never taken a forecasting course. However, this summer I worked alongside Jay Broccolo and Alex Branton, who encouraged me to pursue writing the Higher Summits Forecast. I learned the importance of notifying hikers of the weather above tree line, in addition to incorporating advice in advance to support their outdoor pursuits. This was extremely interesting and fulfilling.
I took many walks around and cloud gazed during my time on the summit. I was able to soak in all the higher summit views. Luckily, I had the chance to run in the Mount Washington Road Race, approximately 8 miles up the Auto Road! This was super fun and another key highlight of my summer. I will forever remember running the daunting Auto Road.
The following week, I shared the responsibility of giving weather station tours during Seek the Peak. I loved meeting hikers as they shared their excitement and interest in the Observatory. This was extremely cool learning about the organization’s culture and how hikers prepared to climb the summit. At the base, I joined the Après Hike Party and learned a ton about what to pack for a hike.
Another summer highlight was the early morning rising and radio calls to local huts nearby. Every morning, I would educate the local huts about the nighttime observers forecasts for the next 48 hours. Radio calls and tours effectively helped me to communicate science, interpreting complex atmospheric science processes to give the public an understanding of what’s happening in the higher summits. It was cool seeing an almost 30-degree temperature difference some days on the summit. The valley would be at 70 °F, while the higher summits were in the upper 40s, with winds making it feel a lot cooler. I found the importance of listening out for this radio call and checking the forecast before climbing in the alpine zone.
The winds. The winds. The winds. As we are known for our extreme weather, I learned a lot about our maximum winds and averages on Mount Washington. And I was able to stand outside in 60-70 mph winds. This was super fun as I had never experienced winds that fast. I also enjoyed giving visitors tours up to the instrument tower. They too played in the winds and were amazed by our gusts and wind speeds here on Mount Washington.
I also had the incredible opportunity to meet the renowned Willem Lange, a distinguished host of "Windows to the Wild” and an outdoor adventurer. Apart from being a New England contractor, Mr. Lange is also a gifted writer and master storyteller, making our encounter even more enriching. The experience of being interviewed by his team was truly enjoyable. I had a delightful time, sharing laughter and anecdotes about our adventures while filming and exploring various places.
"Windows to the Wild" host Willem Lange visited the Observatory in mid-July to interview Myah. The episode is planned for Sept. 2024.
Mr. Lange shared some valuable advice with me, suggesting that I should always inquire about someone's origins to spark engaging conversations. I am eagerly anticipating the release of the episode in the coming year. I cannot wait to relive the moments we shared during our adventure.
Myah Rather, Summit Intern
My last highlight of my summer internship was the research on the Rain on Snow project and presenting data for the August edition of Science in the Mountains. This too helped me with my Python skills and critically making an analysis for Mount Washington Observatory’s climatological record. After this summer, I feel a lot better with presenting science analysis, and in addition, continuing to educate people about science. Luckily, I will be sharing my knowledge at the American Meteorological Society (AMS) in January.
Alongside the beautiful views, I too enjoyed the great team that assisted me this summer, including Jay, Alex, Alexis, and Stephanie. I was truly able to enjoy every moment and look forward to returning for a visit.