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Thursday, January 22, 2009

Sudden Stratospheric Warming

Welcome to our visitors from The Wx Outlook - TWO Community Wx Forum...NetWx...and UKWxWorld. Good discussions and information about this unusual event.

(updated below)

240-hr ECMWF: complete disruption / reversal of the polar vortex ==> MAJOR stratospheric warming.



Major winter stratospheric warmings preferentially occur during the easterly phase of the QBO (Holton and Tan (1980))...so this event is notable since QBO is currently west ~10 m/sec...as seen on the latitide-height x-section in the 30 - 50 mb layer over the Equator.



As would be expected...AO tanks...too.



All a consequence of the huge mid-month +PNA / Rossby wave propagating into the ignore-o-sphere?



Sig wx ahead?

UPDATE

Chart below shows just how unusual SSW is during QBO-west and solar minima.



(h/t TWO Community Weather Forum from across the pond)

Tropospheric after-effects of SSW lag by ~4 weeks and can last for many weeks afterward. A warm stratosphere means the tropopause has lowered which in turn means lower heights in the troposphere and low trope heights mean cold conditions at the surface.

"Pronounced weakenings of the NH wintertime stratospheric polar vortex tend to be followed by episodes of anomalously low surface air temperatures and increased frequency of occurrence of extreme cold events throughout densely populated regions such as eastern North America, northern Europe, and eastern Asia that persist for ~2 months." (Thompson et. al. - 2002)

EDIT: corrected reference to present QBO phase.

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