Winter 2018 2019 Preliminary Outlook Part 3

I'm writing this on the last night of Summer 2018. Astronomical fall begins Saturday at 9:54 PM. Typically as we transition from Summer to Fall we experience big swings in temperatures and often times storminess as the fall air masses interact with the summer air masses.  The strong cold front coming through later tonight is the beginning of that process.

As the fall pattern evolves we will see activity increase in the Tropical Atlantic for the end of September into Mid October. We are now seeing a major pattern change to fall. Summer 2018 hit hard in July and stayed with us all summer. We're going to see a similar setup for Fall 2018.

I talk about Sea Surface Temperature (SST) and teleconnections all the time.  Looking at Those warm SST off the East Coast. Trough will develop over the Great Lakes, Northeast , and into the Middle Atlantic in October. Indeed that is what the models are now showing. But looking beyond the next couple of weeks, we have to widen our scope and look at other areas of the globe. 

The Indian Ocean is important to our coming winter. why is that?  SST west of Australia are cooler than average. This means air is sinking in Indian Ocean.  So north and west of there we will see a lot less convection. But that will lead to more convection in the Central tropical Pacific. This setup increases eastward upper level motion over the tropical Pacific.   So the MJO phases 8,1,2, and 3 would be more likely than the warm phases. This is all cause and effect. The setup in the Indian and Pacific Oceans is saying to North America pump the western ridge and deepen that eastern trough. 

The air mass in Canada is increasingly below average. We have an active northern jet. As the western ridge develops, we will see frontal systems slide down the ridge, into the Great Lakes, Northeast and Middle Atlantic Region. The frontal systems will allow that cold Canadian air to invade the northern tier of the CONUS.  As we move into October we will  defiantly feel that fall chill.

 Some of the factors that reinforce the thoughts I've been having for quite some time. 

The  Quasi-Biennial Oscillation (QBO):

The QBO deals with easterly and westerly stratospheric equatorial zonal winds. These winds typically switch from westward to eastward based on a two year cycle. The changes happen in the stratosphere, with time the influence moves lower and lower in the atmosphere. The QBO is all about how atmospheric waves propagate vertically and how this motion effects the mean wind flow involving speed and direction.  

On average, an East Based (negative) QBO results in a cold winter pattern for the Northeast. Last winter we had an negative based QBO that was trending more negative.  In spite to the warm mid January to mid February last winter's temperatures averaged  well below average.  As this winter approaches we have a negative QBO that is trending toward neutral ( or less negative.  Here is a look at a chart that will explain this to better understand. 

. “A” denotes winter seasons when the QBO is both negative and trending more negative. “B” denotes winter seasons when the QBO is negative but trending in a positive direction. “C” denotes winter seasons when the QBO is positive, but trending negative. “D” denotes winters when the QBO is positive and trending more strongly positive. Winter seasons tend to be coldest when the QBO is in regime “A” and warmest when in regime “D”. Also, when the QBO is trending in a negative direction the western US tends to be warmer than the eastern US, and when the QBO is trending in a positive direction, the eastern US tends to be warmer than the western US

The El Nino - Southern Oscillation (ENSO) and Southern Oscillation Index (SOI):

The SOI  is an index used to indicate the development and intensity of El Nino or La Nina events. This is calculated using the pressure differences between Darwin and Tahiti. These pressure differences effect the strength of the Pacific equatorial trade winds.  Negative  values favor El Nino, while positive values favor La Nina.

On my Facebook weather pages, I've been talking about how the pressure setup in the Southern Pacific Ocean will cause the SOI to crash. Looking at the latest SOI values we can see that is now happening.

Here are the SOI Values from September 19, 2018    

Average SOI for last 30 days .... -3.43

Average SOI for last 90 days .... -3.12

Daily contribution to SOI Calculation .... -6.59

Here are the latest SOI Values from September 21, 2018

Average SOI for last 30 days .... -3.13

Average SOI for last 90 days .... -3.21

Daily contribution to SOI calculation .... -14.38

So things are heading in the direction I indicated.

A little on the ENSO:

The drop in the SOI, is going to help Jumpstart the developing Modoki El Nino

When we look at SST (From Tropical Tidbits) in the tropical Pacific; we see surface water temperatures in the Nino region 1+2 and 3 are below average, while surface water temperatures  are average to slightly above average in the central Pacific north of the equator. But looking at the subsurface temperatures things are a lot different. These warmer temperatures are just under the surface; it won't take a lot to bring them to the surface.

The SOI crashing should increase the odds of bringing the warm water under the surface up to the surface.  

The JMA ( Japan Meteorological Organization) has very good and fairly reliable climate models. Here is a look at the JMA December, January, and February temperature anomalies.    

We're already seeing a huge increase in Greenland snow cover.  This along with the abnormal cold building in Canada and the developing snowpack are both a good sign as well.

Based on my thoughts of a weak Modoki El Nino developing. When you look at the years that had a weak Modoki, this is what you end up with.

When you take weak Modoki El Nino and add in years that had a QBO that was trending west; you end up with this.

Here is a look at one of my main analog years. You can see it is quite cold.

I've revised my thoughts a little on temperatures for the upcoming winter.

Here is a look at the temperature chart I drew back in the beginning of August.

Here is a chart showing my revised December - February temperatures.

If you want to read the two other winter outlook post.

Part 1

Part 2

Winter like weather is going to start early this year. October into November will be overall cold, with bouts of snow here and there. December is iffy for a lot of cold. But with 1977 as one of the analogs, mean I could be wrong about that. With the pattern staying active December could end up quite rainy. There is also the risk for overrunning events that could bring ice.  If I'm right about the setup....winter could also hang on into the spring. Well that is about all want to cover. I will be releasing my Official winter 2018-2019 outlook end of  October or first part of November.