Extreme Temperature Diary-November 29, 2018/ Topic: Jet Split Flow…A Sign of El Nino

Thursday November 29th… Dear Diary. The main purpose of this ongoing post will be to track United States extreme or record temperatures related to climate change. Any reports I see of ETs will be listed below the main topic of the day. I’ll refer to extreme or record temperatures as ETs (not extraterrestrials)😊. 

Jet Split Flow… A Sign of El Nino

Today I’m going to put my meteorological hat back on, letting all know of more weather signs that indeed El Nino may be developing. Met models are forecasting a typical El Nino pattern brewing across the CONUS with some climate change ramifications going into December. The bottom line here is that early December will be colder than average for most of the CONUS with strong systems alleviating drought in California, which will also produce some heavy precipitation that could lead to some flooding across portions of the South, and systems reinforcing biting chill across the northern tier of states with more lake effect snow. Across the central states we may see a wintry mix of ice and snow. The climate link here? Even though the jet pattern may be much more typical for December watch for heavier than usual precipitation.

Here is the typical El Nino weather pattern for winter:

Meteorologically what we also look for is a “slit flow” between the northern and southern portion of the polar jet. The subtropical jet running to the south of the southern branch of the polar jet supplies both energy and juice for southern U.S. storms. The split southern portion of the jet typically ushers in storms into California through the South. The northern portion usually is located much further north than a “phased” jet; thus, allowing temperatures to be warmer than average across most of the northern tier of states. The northern branch in a typical El Nino winter sometimes dips into the Northeast producing average chilly conditions there and producing the “wedge” of cold air funneling southward through the Mid-Atlantic and South, creating episodes of  icy messes: 

So what similarities to a typical El Nino pattern do we have on the latest met models from Thursday? By 12/6/18 we see an eye opening forecast at 500 millibars:

The jet is definitely split with two strong systems poised to move into California, one just off the coast and another well south of the Gulf of Alaska as denoted by the blue lobes on the Pivotal chart in the Pacific. The northern branch is pumping cold air into the Northeast. Here is what is forecast by the GFS at the surface:

 Eventually the storm system over California may produce an icy cold, wet system for much of the South and Middle Atlantic: 

As a reminder on all of my posts when I present models going out more than 5 days the proverbial devil is in the details. Forecast busts are likely on presented individual panels and graphics, so I am just showing “trends.” In any case the trends that are very important going into December I’m seeing are a parade of wet systems pounding California, producing mudslides in burn scar zones, and some wicked storm systems traversing the South. I pray that we won’t see more fatalities in California. I do see some good news since the Sierra and southern Rockies snow pack will be replenished greatly this coming season.  Just today:

The next short term weather system that may produce havoc is more spring like, potentially producing some severe weather across the South with some snow in the norther Plains as November flips to December on the old calender:   

Lastly, what do current sea surface temperatures look like in the Pacific?

At least a weak El Nino signature is definitely there off the west coast of South America. Throw in global warming and I bet there will be several surprises across the United States through the winter of 2018/19. We’ll bring these up one by one on the Extreme Temperature Diary as we go through time.


Here are more of Thursday’s climate and weather news items: 

(As usual, this will be a fluid post in which more information gets added during the day as it crosses my radar, crediting all who have put it on-line. Items will be archived on this site for posterity.)

Great news! Mother nature is increasing that snowpack:

From snow on one area of the planet to fire on another:

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The Climate Guy

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