United States Winter 2018-19 Forecast

Written by on November 3, 2018 in United States of America with 0 Comments

The 2018-19 winter forecast is based on and factoring in all atmospheric/oceanic drivers currently in play. This year’s forecast will take into consideration the Pacific and Atlantic sea surface temperature anomalies, continued development of an El Nino as well as solar cycle status.

Background

Here are the main factors taken into consideration for the upcoming 2017-18 winter for the United States. Global SSTA’s can and do have significant influence on the atmosphere above, especially in the mid to late winter pattern.

What’s very striking in the below SSTA chart is the warm Pacific, cool Atlantic and development of a modoki or central Pacific based El Nino. Another likely aid to a colder central and eastern winter will be the return of the ‘warm blob’ over the Gulf of Alaska.

Credit: Tropical Tidbits

Other factors to consider

The global temperature is slowly coming down following the Super El Nino from a couple of years ago. Each super El Nino drives the global temperature up (in the form of increased water vapour into the atmosphere), a La Nina (cooling of the equatorial Pacific) typically follows a strong El Nino often helping drop the global temperature from above to below normal.

However the global temperature has risen further with each of the last 3 Super El Ninos. The 1997-98 Super El Nino had a higher start point for cooling than the 1982-83 Super El Nino and it would appear we have an even higher start point for cooling now following the 2014-15 Super El Nino compared to 1997-98. Point is we are beginning the cooling from a warmer ‘start point’ and this is essentially leading to less global cooling with each passing Super El Nino.

What will be interesting to see over the next 6 months will be how much of a drop in global temperature shall we see this winter?

Eurasian snow cover during October was low while high over North America. This could help build the cold on the North America side of the arctic quicker, leading to a head start to winter for the US in November and more so December.

Other, more complex and long term factors worth considering

Other players which are more complex and more challenging to read in the long term but is linked to the current status and behavior of solar cycle. The Quasi-biennial oscillation (QBO) is a measure of equatorial zonal winds within the tropics.

A more typical westerly QBO usually correlates to a stronger westerly flow through the mid latitudes and less amplification. This tends to be stronger around solar maximums whereas an easterly QBO is the reversal in the upper winds and often aids the development of high latitude blocking. This becomes more common around solar minimums.

Also, there is the Maddan Julian Oscillation (MJO), a pulse of increased convection which circles the equatorial region of the planet. The MJO often has greater influence during low solar years with more amplification of upper air pattern.

We are currently nearing the end of solar cycle 24 with the minimum expected by 2020. This can and will affect all of the above drivers, even controlling the cooling and heating of our vast oceans.

With the lowest sunspot activity in some 80 years and the approach of a solar minimum, one has to assume that our planet is ready to turn down the thermostat.

Ocean feedback effects on the atmosphere

There is a great deal of uncertainty this far out as to how the stratospheric polar vortex will behave this winter, however low solar, low arctic sea ice and the aid of a warm North Pacific all points to a level of weakening which would allow outbreaks of polar air southwards.

Modoki El Nino

The warm Gulf of Alaska could be key for the US as this has proven to boost heights over Alaska and the western (North Am/Siberia) side of the Arctic. The warm N Pacific and modoki El Nino combined suggest a colder winter for the eastern side of the US. With warmth off the Atlantic Coast combined with the central Pacific El Nino should enhance the southern storm track (subtropical jet stream) signaling a stormier/snowier than normal winter in the East.

While a warm West, cold East winter is likely, predicting the timing of cold, snowy spells is impossible. However, if we look at the current and possible strengthening of the polar vortex during November, this suggests milder times later November and through the first half of December.

December looks average to above average for much of the US but towards Christmas through January and February, there is increased likelihood for a colder, snowier pattern developing from the Northern Plains to Southeast including the Northeast as feedback from the warm central and north Pacific kicks in.

The Canadian model indicates a classic winter for the East with February looking coldest with a strong -AO/NA in control.

Michael Ventrice

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