Given the situation that we are in - I suppose we will have to rely on a SSW then like we have done last year and year before last?
We seem to get colder than average winters when we have one of the following weak La Nina's and when we are in an easterly QBO and when there is colder than average SST's in the NE pacific.
Below are the last Average or Colder than average winters.
Winter 08/09
Winter 09/10
Winter 10/11
Winter 12/13 - The year we had a Tripole in the N. Atlantic
Winter 17/18
All of those winters had one more more of the following above. 1. (Weak La Nina) 2. (Easterly QBO) 3. Colder than average SST's in the NE pacific.
Whilst the winter of 17/18 wasn't that much colder than average and most of the cold came later in the winter - I recall it had all of the 3 above = weak La Nina, easterly QBO and colder than Average SST's in the NE pacific.
Most recent winters esp last few 18/19 and 19/20 we have had none of the above during the winter
We have had weak El Nino last winter and before. The QBO has been westerly last winter and the winter before (transitioning to westerly). Also winter over past two years has seen not only record breakingly cold stratospheric temperatures but record breaking strong zonal winds at 10hpa and we have NOT seen any cooling of SST's in the NE pacific hence why it's been so mild and or zonal.
Still time for things to change but we all know La Nina favours front loaded winters so given that this November looks exceptionally mild from the models then we had better hope December provides something of interest. Otherwise like last year and the year before we have to rely on a SSW to occur to bring a chance of developing HLB.
I guess the million dollar question which many don't or may not know the answer to is if the PV is strengthened/enhanced by record breaking cold temperatures in the stratosphere, then what are the causes of these cold stratospheric temperatures every winter?
Average temperatures should be around -60c at 30hpa and they are currently -75c @ 30hpa!? This is 15c below average and what is the cause of this because it's driving the PV to go into over-drive!?
(I remember starting a topic on this and the QBO and how it effects out weather patterns earlier in the year).
Edited by user
09 November 2020 22:50:25
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Reason: Not specified
Home Location - Kellands Lane, Okehampton, Devon (200m ASL)
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Sean Moon
Magical Moon
www.magical-moon.com