Monday, November 19, 2012

A Case for a Cold Stormy Winter

A combination of a Negative NAO and Negative AO in October has a strong correlation to Eastern US cold and/or snow.  Those who want to roll the dice on a cold, stormy winter can look to 2002-03, 2009-10 during this decade.   I do have to mention that the indices were strongly positive in October preceding legendary winters like 1977-78.  It is interesting that snowy winters like 1981-82, 1968-69, and 1960-61.  I discounted 1974 because it was a blazing La Nina year.  2006 is an oddity because it was a promising El NIno Winter which the phenomena simply shut down.

So, we have an argument for cold, stormy winter.   The fact that the legendary winters were excluded might be an indicator of the correlation working in 
+AMO (Warm North Atlantic) situation but not so much when it is negative.  There is no such thing as a perfect linear correlation in weather.

Data Source: NOAA Earth Science Laboratory

This composite Temperature anomaly from the NOAA Earth Science Laboratory covers the bonafide El Nino Winters featuring a -NAO/-AO below -1.00 in October (I excluded 2006).  The pattern of cold is what I believe will resemble the upcoming winter.

This is a composite of Sea Level Pressure anomaly.  Take note of the lowest pressure being at the 50N/50W position that argues for my idea that the upcoming season can be dubbed the Winter of the Nor'easters.  50/50 Lows favor snow/ice in NC and VA.  This data is also from the NOAA Earth Science Research Laboratory.

This plot is not dissimilar to the PNA
      That's all for now.  Later this week it will be time to discuss a potentially really cold start to December.

Wednesday, November 14, 2012

Finally! The Winter 2012-13 Forecast

To El Nino or not, Is that really the question?

Here in NC and VA many El Nino winters are loved because they do tend to be colder an usually contain a few good winter storms.  La Nina, on the other hand, is maligned for warm, dry, winters that lead to hot summers full of bugs and pests.   Therefore, the first question usually asked is whether to label a winter as an El Nino or La Nina.

Occasionally we see the crazy La Nina's like 1976-77 and 2010-11 which blocking develops in NE Canada and leads to endless cold.  There are also occasional El Nino's that feature warmth closer to South America that lead to endless gray 40-50 degree rainy days.  Thus, while the labels have some reliable generalities, I think it is a good idea to analyze the whole globe for clues. The fact is that it takes a moderate to strong El Nino or La Nina to rule the roost.

What are the Oceans telling us?

There is always the question of whether the ocean temperatures are being driven by the atmosphere, "Top-Down" , or vice versa (Bottom Up).   A good winter El Nino features plenty tropical storminess near the Dateline.  I find another feature even more interesting.  Look at the Ocean Temp anomalies below:

  1. Warm east of Hawaii, Cold Gulf of Alaska:  This feature appears to be stable and promotes a -EPO.  An indicator of a cool to cold Winter if the signal holds through the season.
  2. Warm pool near Mexico:  Promotes low pressure at that location.  This promotes drainage of cold air from the north and a subtropical jet stream.
  3. Oops!, I skipped 3 but do not want to re-do the Chart :>)
  4. El Nino?:  Sort of.... warm water in the right place to promote low pressure and feed the all important Jet Streams.  I think just enough but not too much.
  5. Cold Water near Darwin, AU:  Tropical cold water promotes High Pressure.  At that location it would mean a downhill slide to #4.
  6. Cold Southeastern Seaboard:  This can be an indicator of cold to come if the water is caused by rain and cool Autumn.It can also be a bummer that promotes NC and parts of VA being skipped instead of targeted by Nor'easters.
  7. Neutral Water near Greenland, ice already east, but warm further south: Too much -NAO snows on LA, MS, AL, FL, GA, and SC, while skipping us.   That signal is very mixed in regards to the NAO.  Winters with plenty of fluctations seem to be the most exciting.  Tough read...
The oceans seem to be indicating a much different Winter than the non-winter of 2011-12.  There are definitely ingredients for a season that is biased cold with enough "El Nino" around to send storms into the Gulf of Mexico to the East.  The cold water near the SE Coast is not something Winter lovers want to see unless it is being caused by the atmosphere ("Top Down") and not given a chance to feedback.   Hurricane Sandy and 2 Nor'easter non-effects on NC and limited in VA has me worried that a Confluence (Skip Zone) might be out there.

Other Signs and Wonders

The beautiful colorful sunsets this autumn and feverish Squirrel activity are 2 observations also supporting a cool to cold winter.  I don't think an acorn from our Oak Tree has even hit the ground!

More Seriously...

While I have my concern,,,,  this appears to be a 2003-04 type winter that  featured 2 snows and a mega-icestorm.  There will be plenty of back and forth swings in the SOI, plenty of frontal passages, and a base state that is cooler than average in the east (-EPO).  I am also impressed by blocking in the West Polar Pacific (called the -WPO) which, if it is stable through winter would provide an ample supply of Siberian air.

So, in a nutshell:

  • At least 2 degrees colder than average.
  • Plenty of storm, opportunities should yield 2-3 disruptive winter storms.  Hopefully the traditional school calender does not end in late June 2013.
  • If we go through December and see NC and VA being skipped by Nor'easter, it will be time to lower expectations about snow,