Difference between EL Nino & EL Nino Modoki temperature wise:
EL Nino- Mainly below normal readings across the entire country (Depending on the strength of EL Nino)
EL Nino Modoki/ “Almost EL Nino”- Temperatures are mainly colder across the central and eastern half of the country due to abnormal ridging out west.
EL Nino: Given the Strength, above normal Precip looks to be in the west due to the storm jet being out there frequently throughout the winter. Near/Slightly Below normal Precip readings for the central and eastern half of the United States.
EL Nino Modoki/ “Almost EL Nino”- above normal Precip looks to be across the southern and eastern half of the united states as below normal readings are mainly focused across the western half due to abnormal ridging.
To get cold air south, you want to see a few things, a negative AO and NAO and a Positive PNA. The stronger these readings the more likely you are to see colder air.
Difference between Positive NAO and Negative NAO:
Positive NAO means lower pressures are occurring near Iceland so as a result, ridging is allowed to take place across the southern half of the united states resulting in warmer than normal temperatures across our area.
Negative NAO means that ridging is taking place across Iceland so as a result, cold air is allowed to funnel south and east resulting in huge cold fronts and well below normal temperatures across our area.
Difference between Positive AO and Negative AO:
Positive AO means that lower pressures are occurring across the Arctic region so as a result, this will keep the cold air north and allow ridging to take place across the mainland United States.
Negative AO means that higher pressures are occurring across the Arctic region so as a result, this will force artic air to funnel southward resulting in well below normal readings across the central/eastern half of the united states.
Difference between Positive PNA and Negative PNA:
Positive PNA means that ridging is taking place across Alaska so as a result, this creates a hill type effect and helps send cold air down to the mainland United States.
Negative PNA means that lower pressures are taking place across the western half of the united states and Alaska so as a result, this will not help send cold air south and will result in ridging to take place across the eastern half of the united states.
This is our Temperature Outlook for Winter 2018-19:
Look for temperatures to be well below normal across the central/eastern half of the united states. This will be due to frequent cold shots from the arctic through the winter. Temperatures will be near normal across the northern plains for this winter as their averages is a lot colder than ours here in the Natural State. This does mean that we will see chances for colder air here across the state as well. As it stays cold up north, snow falls meaning that cold air doesnt modify as fast as it moves south. Out west, look for temperatures to be well above normal as ridging looks to dominate the winter out there. Now there will be times that the west is below normal and the east be above normal but we think that overall that the east will be colder than the west this upcoming winter
Look for well above normal Precip stretching from the southwest through the northeast. This will be due to an amplified subtropical jet that will be frequent storm systems across this area. We are forecasting above normal snowfall in this area as well especially from Texas to Maine. Across the northern plains, Precip chances will be near normal as we expect some snowstorms throughout the winter up there. Unfortunately, out west, Precip looks to be below normal due to abnormal ridging taking place out there. This does not mean they won’t see any rain/snowfall. This means that throughout the season, they will be below their normal rain/snow amounts. One more thing to note on this as well, we could see a few more ice/sleet events than usual as well and would not be surprised to see these during the early winter weeks.
~Chief Forecaster Derek
~Long Range/Senior Forecaster Cameron