The Winter Weather Pattern as seen from Mid-October

The global situation does not mix a recipe for a cold winter here in NC. We do have some open doors for some dramatic attacks of cold weather. There are also a couple of wildcards which can place our area in play for winter weather. Despite the ability for winter to strike I believe that 2/3 of days will be above average in terms of temperature and that precipitation will continue much below average through at least mid-February.

The reason for this is the expected moderate La Nina which will border on strong. Here are the current global sea surface temperatures relative to known averages . Here are the problem areas for those wanting a long, cold, snowy.icy winter:

1. Warm Atlantic near Greenland causes storms to explode there, keeping pressure low and cold trapped in the Arctic. This is a Positive NAO Signal.
   
2. Ice Cold Gulf of Alaska with a warm spot south of the Aluetians. A low placed over the warm spot is Positive EPO signal and portends a stormy cold winter for the US West Coast. (Note: The East Pacific Oscillation measures the difference in pressure east and west of Hawaii.

There are some wildcards on the playing field that can make our winter interesting at times:

1. Should the cold water stay concentrated along the Pacific South American Coast (Nino 1+2) that would actually be a more neutral signal for our region. Neutral in NC is still warmer than average BUT the probabilities of winter incursions rise sharply.
   
2. There is a clear Negative WPO (West Pacific Oscillation). This feature in both monster Positive and Negative phases controlled last year's winter. This mechanism in a negative phase can force Siberian air into our weather pattern as it did in our promised min-winter last year. However Siberian air is very dry and without a negative NAO to lock it in there is little hope for significant snow or ice. The cold spot north of Japan is the signal/
   
3. Warm Gulf of Mexico - La Nina Winters typically send storms up the Ohio Valley, frustrating us here in NC. However Dec 1998 (4.3"), Jan 2000 (20"), Nov 2000 , and Jan 2002 (11.5") are examples of breakout storm situations. History shows lower but more consistent snowfall in cold Atlantic years but in its warm phase there are spikes from these types of situations (breakouts) amidst the years devoid of wintery precip.
   
4. The UK Met Office is predicting a Neutral overall NAO in an Ocean pattern which encourages the positive phase. Could their pretty good model be seeing some strong spikes down in an overall positive dominated winter?

The Bottom Line

* At this time it appears that more than 2/3 if Winter will feature above average temperatures.

* Overall precipitation is expected to be very dry overall. November and after Feb 15 right now appear to be the best chances for above average.

* November appears to be cooler than average actually beginning a little earlier than expected (late Oct). I tried to hold on to the heat through Halloween but the cold is coming. In fact a sharp SOI drop to -24 today places a weather event on or near Halloween. Will it be a trick or treat?

* December and January will likely features 20 days of warm to very warm and 10 days of neutral or less for each month. We will watch closely in the Arctic to see if it gets so cold that the Jet Stream breaks out. In my experience the cold days can be very cold, even challenging records at times.

* Once mid to late February kicks in there may be a window of opportunity there for some old fashioned winter weather. We need to see how the forces which govern our weather pattern function. If the La Nina gets past peak by late January then we will watch for mid to late February.

* Raleigh-Durham averages 7" of snow per year with a Standard Deviation of approx 6". With a normal range of 1-13" accurately prediction snowfall seems to be more foolish than possible, particularly in warm Atlantic years.


Dean