Saturday, 5 January 2013

Sudden Stratospheric Warming Event Intensifying

A major stratospheric warming event is taking place across northeast asia and expanding northeastwards towards the north pole. The most notable warming is taking place between 1mb and 30mb in the upper stratosphere.
Notice the sudden stratospheric warming at 10mb:

This warming is beginning to work its way down to the 50 and 70mb levels. The effects of the SSW event are causing an expansion in the stratosphere which suppresses and cools the troposphere. This event also weakens the polar jet stream which allows the cold air bottled up across the arctic to move southwards into mid latitudes. Currently a positive arctic oscillation(strong polar jet stream) is in place but that should change soon as the stratosphere continues to warm and weaken the vortex. Their are three reasons why I believe that the stratospheric warming event will continue to intensify throughout the next week which will cause the sensible weather across north america to become very cold for the end of january and into february.

Part 1: East Asian Mountain Torque Spike

East Asian Mountain Torque Values are increasing and have spiked positive which will help to strengthen planetary wave breaking events across east asia. In simpler english, the current warming that is taking place across east asia will continue to feed warmth towards the north pole. Weakening of the polar vortex has already taken place from our current warming and the negative phase of the QBO. Further warming in the next seven days will be too much for the PV to withstand. You can see the rapid warming in the upper stratosphere on the loop below.
Current warming will cause a complete split in the polar vortex which is shown on the european stratosphere forecast for day 3. Notice one piece of the vortex is centred across north america with a weaker piece in central europe. This weakening of the vortex will cause a huge amount of arctic air to get transported underneath into central and eastern north america. A 2-3 week lag time occurs between the SSW event and cold air transport to the surface which means that we can expect the cold to reach eastern north america by the 20th-25th of january. Very cold air will last until the beginning of february with this setup.
Part 2: West Pacific Kelvin Wave 

Latest observations point towards another kelvin wave formation across the western pacific. Kelvin waves are pockets of warmth that move eastwards along the thermocline(subsurface boundary between cold and warm water) in the equatorial pacific. Kelvin waves contain westerly wind bursts aloft which cause two major implications on our weather pattern. 1) Transport warm water from the western pacific into nino regions 3 and 4(central pacific), further enhancing the el nino and subtropical jet disturbances. 2)  It Causes major drops in the SOI by transporting major warmth into the upper atmosphere. The atmosphere always need to balance itself out so it therefore cools north america as a result of the SOI drop. Relating this back to out stratospheric warming event the kelvin wave helps to transport additional warmth into the upper atmosphere which disrupts the polar vortex even further. Take note of the kelvin wave located near 140 east longitude and 100 meters below the surface.
 All of these atmospheric factors point towards a major stratospheric warming event continuing to intensify which will weaken the polar vortex and transport arctic air into north america from mid january to the beginning of february. The cold will invade the west and northern plains first with the frigid air moving in between the 12th and 20th. The cold should progress east by the 20th as is natural when a large amount of arctic air is pushing eastwards and spreading out into an upstream ridge.  The core of the cold will be focused at the ohio valley, midwest, great lakes and northern new england as opposed to the mid-atlantic states.
GFS temperature anomaly forecast from the 15th to 20th of january:

 This cold weather pattern will continue into the beginning of february and perhaps beyond if more stratospheric warming events continue to occur. The GFS and ECMWF forecast models believe that another warming will happen in about 7-10 days.


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