The Tuesday before Thanksgiving, we released our winter weather outlook for central Indiana, which can be seen in the video above. For those who may have missed it, we outlined a potential shakeup to the upper-air pattern and circled the calendar for a significant change by or about December 12. This still looks to be on track.
Recent Decembers have been lacking snow. Less than 5" had accumulated each of the past five Decembers, and we are overdue.
Winter temperatures have averaged above normal for four straight years.
While the National Weather Service's December outlook calls for a higher probability of above normal temperatures and precipitation, our feeling is that a new pattern will emerge by mid-month.
The connection to ocean temperatures have a profound impact on winter weather patterns across North America and yield some clues as to how the winter season may evolve. Over recent years, a newer class of hybrid computer models incorporate more of the ocean's impact on the upper-air patterns (coupled models) attempting to better resolve the the pattern long range. Connections to upper-air patterns in other regions of the planet (tele-connections) have also yielded some success, along with tie-ins to solar cycles. Hands down, there are many sophisticated approaches to season outlooks, but there is one giant hurdle.
The faster and more powerful computer model forecasting that have improved forecasts for the past six decades is susceptible to one large variable: water.
70% of the planet is water, and we are still data deficient over the oceans.
Newer, more powerful satellite technology has allowed for weather gathering in remote corners of the planet and have aided in unlocking more of the mysteries that lie out in the oceans, improving forecasts now and for many more decades to come.
So what is happening in the Pacific? No El Nino (warmer ocean temperatures), No La Nina (colder ocean temperatures). This year, ocean temperatures are slightly above normal in the central Pacific, which classifies as "neutral" conditions. While scanning weather records that compare to similar winters that were considered neutral, we found that two of the top three snowiest seasons occurred under neutral conditions. That doesn't mean we are again on track for such a status, but it gives us higher confidence that a snow surplus could be in the works. Stay tuned.
While there are limitations, we can issue outlooks well in advance of the upcoming season that are useful for preparations entering the season.
A "wavy" and more volatile weather pattern could lead to quick temperature swings and shots of much colder air. Over the past 10 days, we've been tracking the possible changes and the first in a series will emerge starting next week.
Below, the default weather pattern for the upcoming winter favors chilly air in January and February. While this pattern will not be persistent and will stray from time to time, ultimately, the colder flow will win out.
Above normal snowfall could be in the works as an upper-air pattern pattern emerges from mid-December on, and it would lend to the overall above normal snowfall forecast for the entire season. On average, Indianapolis sees 25" of snowfall from October through May. This year, we could surpass 30".