El Nino brings mixed winter outlook
Don Day mentions that this winter will be very interesting due to the reversal of climate drivers compared to the previous year. He explains that for the last three years, there was a strong La Nina, which resulted in colder temperatures in the subtropical Pacific. However, this year, the Pacific Ocean is in an El Nino phase, where temperatures are warmer.
Don emphasizes the significance of the Pacific Ocean in driving weather patterns and highlights the coupling between the atmosphere and the oceans. He mentions that the field of meteorology has only recently started to investigate the interactions between the ocean and the atmosphere.
During a La Nina phase, the Pacific Ocean tends to be stingy with water, resulting in drought conditions in Central and Western North America. However, with the shift to El Nino, Don predicts a different set of parameters that will impact the upcoming winter season.
When asked about the ski areas, Don suggests that the Sierra Nevada, the mountains of Colorado, Nevada, Utah, Arizona, and New Mexico will have a good snow year. However, areas like Montana, northern Wyoming, Idaho, and the Pacific Northwest may not receive as much snow.
Don explains that historically, El Ninos tend to bring warmer and drier conditions to the northern border of the US and southern British Columbia. He expresses concern about this area during late winter and spring but mentions that there may be some moisture in the short term.
El Nino affects weather patterns
According to the southern meteorologist, understanding historical weather trends is crucial in forecasting future weather patterns. Historically, certain areas tend to be warmer and drier, and this is likely to continue. However, the strength of the current El Nino is not as strong as forecasted, which may result in less severe weather patterns.
The interaction between El Nino and the jet stream is particularly important in guiding precipitation in the continental US. In agriculture in the Central and Western North America, paying close attention to El Nino and La Nina can provide a heads up on upcoming weather patterns. La Nina tends to be droughty because it reduces the amount of water vapor in the Pacific, leading to a stronger and faster jet stream. This causes a more flat and less waviness in the jet stream, resulting in windier conditions. The down slope off the Continental Divide leads to higher evaporation rates and the Chinooking effect, which can cause storms to dissipate and result in dry conditions in the southern and central plains.
El Nino, on the other hand, drives more water west of the divide, resulting in wetter conditions in certain areas. It weakens the jet stream and leads to the formation of two jet streams. One jet stream goes across the northern tier, but it is not as strong, and there is less downsloping. Another jet stream forms in the vicinity of central Southern California and goes along the Southern tier of the US, causing a wet pattern. This wet pattern extends from Southern California to the Southeastern US, with a gradient of decreasing precipitation from South to North.
However, it is important to note that El Nino is not the only factor that affects weather patterns. Other variables and factors, such as the quad biennial oscillation (QBO) in the stratosphere, also play a role. The QBO refers to the alternating 14-month periods of wind direction near the equator in the stratosphere. These stratospheric circulations can have an impact on weather patterns and need to be considered in weather predictions.
Winter forecast: stormy and cold
He discusses the winter forecast for the upcoming season. Don mentions that this winter could be very interesting due to several factors, including El Nino, the Quasi-Biennial Oscillation (QBO), and solar activity.
El Nino can have a significant impact on weather patterns around the world. El Nino adds more moisture to the atmosphere, which can lead to increased energy and storm activity. This means that there is a higher possibility of Arctic oscillations sending polar vortexes south, resulting in colder temperatures and more snowfall.
The QBO is another factor that influences winter weather. It refers to the movement of winds in the stratosphere, which can cause perturbations in the troposphere where we live. Don explains that when the QBO is in a negative phase, it tends to result in a negative Arctic oscillation, which is associated with the polar vortex. Therefore, during negative QBOs, there is a higher tendency for polar vortexes to occur.
Solar activity is also considered in the winter forecast. He mentions that there is a correlation between solar minimums and strong La Nina events. Solar minimums occur approximately every 11 years, and they are periods of decreased solar activity. He notes that severe droughts in the US have occurred at or just after solar minimums. As solar activity increases and reaches its maximum, El Nino events tend to become more frequent.
Considering all these factors, Don predicts that the upcoming winter will be stormy and cold. The additional moisture from El Nino, combined with the negative QBO and solar activity, creates a volatile mix. This means that there is a higher likelihood of snowfall and colder temperatures across the country.
Ocean conditions affect weather patterns
He explains that certain regions in the United States, particularly those far away from water sources, heavily rely on ocean interactions for their water supply. The Pacific Ocean plays a crucial role in providing water vapor that leads to precipitation in these areas. Therefore, any changes in the Pacific's behavior, such as during a La Nina event, can significantly impact weather patterns and result in drought or other extreme weather conditions.
He also discusses the concept of solar cycles and their influence on weather. Solar maximum and solar minimum refer to levels of energy input into the Earth's atmosphere from the sun. During periods of high solar activity, characterized by an abundance of sunspots, there tends to be less cloud cover and warmer temperatures. Conversely, during solar minimum, cloud cover increases, leading to cooler ocean basins and reduced water vapor release.
The connection between solar cycles and ocean conditions is still a topic of debate among scientists, but the speaker finds it compelling. They explain that higher cloud frequency over the ocean basins during solar minimum can naturally cool these regions and result in less water vapor. However, it is important to note that these interactions can be regional and not uniform across the entire globe.
Don also introduces the Pacific Decadal Oscillation (PDO), another cycle in the Pacific Ocean. The PDO refers to periods of overall warmer or colder temperatures in the Pacific Basin, lasting approximately 25 to 30 years. The current PDO is negative, which means the Pacific has been colder since 1999. This negative PDO has led to a higher frequency of La Nina events, contributing to the severe droughts experienced in the Western United States over the past 30 years.
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