Hot Off the Press! Beginnings of a Sudden Stratospheric Warming (SSW) Event (5:30pm, Tue, 1/26/16)

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imageFigure 1. The SSW event is forecast begins this week (Jan 26) as warm air at 10 hPa moves over the North Pole, elongating and displacing the stratospheric reflection of the Polar Vortex (PV).

Dear Growers, Agents, Agronomists & Others,

So this is “hot off of the presses” so to speak.  It is too early to go to far with this information, but is appears that Northern Hemisphere is in the beginnings of a Sudden Stratospheric Warming (SSW) event. SSW almost always result in at least one good push of arctic air into the eastern half of the of the US.

Here is what typically happens with a SSW. The Polar Vortex (PV) is weakened and either splits or is displaced in a manner that would lead to cross-polar flow into the central and eastern United States. Additionally, the corresponding strong ridging near Alaska, that will likely occur, is a very strong signal for a strong very cold Arctic high pressure to build over northwestern Canada, which greatly increase the risk of Arctic air outbreaks over the eastern United States.

A split of the PV would typically result in the most severe and persistent below normal temperature anomalies in the eastern US. Right now too early to tell if it will be a split or just a displacement of the PV. If the SSW actually occurs, the most likely timing on the Arctic air moving in the US would be sometime in the 2/5 – 2/20 time period.  So just wanted to give everyone a heads up that we are now starting to see changes that could cause a more extreme cold event for strawberry growers across our region as we get into mid Feb time frame.

We will see how this unfolds over the next 5 days. There are a lot of mitigating factors that could come into play to limit the intensity of the cold air that actually makes into our region.

Another factor in the latest long range model runs to consider, is that meteorologists are beginning to see a negative bias in the Arctic Oscillation (AO) for much of February, so if the PV splits; the negative AO could persist into the first half of March as well.  So we’re glad we stuck with the over all colder than normal trend to the temperatures in the outlook after Feb 5.

Written By

Photo of Dr. Barclay PolingDr. Barclay PolingFormer Professor and Extension Specialist, Strawberries and Muscadines (919) 515-5373 (Office) barclay_poling@ncsu.eduHorticultural Science - NC State University
Updated on Jan 26, 2016
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