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2018-2019 Winter Weather Forecast

My official winter weather forecast has been issued for North Carolina and the United States. Long range forecasting is very difficult and is subject to many factors; therefore, a seasonal forecast provide a “best guess” of what to expect.

Many hours and days of studying different computer models, analog years, current conditions, and oscillations have went into developing this forecast. Below you will find the summary of the forecast, a list of analog years used in the forecast, and the rationale behind this forecast. I believe this forecast is the most likely outcome this season; however, please understand it is a forecast that is subject to change.

Winter Forecast

Temperature Forecast

Below average temperatures are expected across much of the Carolinas this winter; however, I am not expecting temperatures to be much below average. I expect periods of above and below average temperatures; however, my official forecast is for temperatures to be below average this year (blue shading). The areas in blue are expected to be 1°-2° below average. Coastal areas will see seasonal temperatures, mainly due to warm air moving northward during stormy times.

Precipitation Forecast

Above average precipitation is expected to continue across the Carolinas as El Nino begins to affect our weather. Numerous areas of low pressure are expected to develop and move northward, bringing periods of heavy rain or wintry weather. The mountains, foothills, and piedmont areas could see 25-50% more precipitation than normal. Many areas in the Carolinas have already seen their wettest years on record, and these areas are expected to continue receiving precipitation throughout the upcoming winter.

Snowfall Estimates

With the primary track of low pressure being to our south and east, and with the expected below average temperatures, above average snow accumulations are expected across the Carolinas. My official forecast shows 10-25% more snow than average, especially across western NC.

This is the best forecast at the moment for the upcoming winter. Remember long range forecasts are subject to change due to multiple factors; therefore, I will be continually providing updates throughout the winter season.

The Rationale Behind The Forecast

El Nino – Southern Oscillation (ENSO)

The winter weather forecast for this year was based heavily on the developing El Nino. El Nino and La Nina refers to warming of the waters in the Pacific Ocean near the Equator. In El Nino, increased precipitation and cooler temperatures are expected in the southeast. In La Nina, drier conditions and warmer temperatures are expected in the southeast.

This year, we are moving from El Nino – Southern Oscillation (ENSO) neutral conditions to a weak El Nino. The Climate Prediction Center has a 70-75% chance of El Nino remaining until the end of winter this year.

Model predictions show a weak to moderate El Nino developing and lasting through winter.

The El Nino this year is a different from a normal El Nino because the warmest waters are expected to be located in the central Pacific Ocean. This is referred to as a “El Nino Modoki”. Historically, an El Nino Modoki phase typically bring cooler than average temperatures and above average precipitation.

El Nino Modoki index published by the Japan Agency for Marine Earth Science and Technology. Read More about El Nino Modoki at http://www.jamstec.go.jp/frcgc/research/d1/iod/enmodoki_home_s.html.en

ENSO remains one of the most important oscillations in my winter weather forecast in terms of precipitation and temperature.

Pacific Decadal Oscillation (PDO)

The PDO index affects the weather pattern in the United States during the winter months as well. The PDO is similar to ENSO; however, the PDO phases usually last for longer periods of time. The PDO is a function of the water temperature in the Pacific Ocean.

Right now, the PDO is in between a warm phase and a cold phase and is trending towards a negative (cold) phase. The negative phase favors above average temperatures for the southeast United States.

Snowfall Across Siberia

A ridge of high pressure across Siberia this October has resulted in lower snowfall totals than in previous years. Recent studies have shown that the October snowfall across Siberia can help determine the weather downstream. Research on the Siberian snowfall remains low, but this general trend would lead to above average temperatures.

NAO, AO, and PNA

The affects of the AO, NAO, and PNA on the weather across the United States during winter is well documented. These three oscillations vary from week to week and can not be accurately forecasted more than a couple of weeks out. These are the annual wild cards that can affect the winter forecast greatly.

The Analog Years Used In The Forecast

Each year I gather analog years that are similar to the weather expected this season. This year, I focused on years when the ENSO was moving into a positive direction from a negative or weak positive phase. I also focused on years when temperatures were near average to slightly above average.

Temperatures this year during July – September were slightly above average and precipitation was above average across much of the eastern United States. 

I selected the following years as Analog Years to help determine the temperature forecast for this year in the southeast United States.

  • 2014-2015
  • 2006-2007
  • 1986-1987
  • 1976-1977
  • 1968-1969

These analog years helped me determine my temperature forecast for the upcoming winter. Most of the winters had below average temperatures; however, a few did feature above average temperatures. The confidence in the temperature forecast remains low.

Precipitation forecasts were derived using analog years of weak to moderate El Ninos. In general, with El Nino, precipitation is usually greater than average across the southeast. I expect this El Nino will be no different, and I expect above average precipitation.

Final Summary

  • Above average precipitation expected across the Carolinas, medium to high confidence.
  • Slightly below average temperatures expected across the Carolinas, low to medium confidence.
  • I expect average to above average snow accumulation across NC. The best chance of above average snow accumulation will be north of I-85 across the mountains, foothills, and western piedmont.

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