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After watching and closely observing the conditions across the globe, but more specifically in the Pacific and Atlantic oceans, I am going to do a somewhat short “mid-term” updated forecast from my preliminary forecast which I issued now about 2 months ago back in late July. I am just going to update my thoughts on the ENSO, as well as the other indices and their correlation with each other but without writing too much, as I am going to save my 5 page write-up fro my final winter forecast which should be out sometime in early-mid November likely(within the first 2 weeks hopefully). So without further ado here is my updated winter forecast:
ENSO:
As I have explained, or tried to explain many times there are many different ways of measuring the ENSO, from daily values, to 5 day values, to weekly values, to monthly values, to bi-monthly values and finally to the most “official” measurement; trimonthly values. However, my preferred mode of measurement for the ENSO state overall are the monthly numbers, so I will be generally using those in this forecast along with future forecasts (although in some more detailed forecasts; I will likely mention most of them; if not all of them). Anyways, if you look at the latest official monthly values from CPC(Climate Prediction Center) in the equatorial Pacific we are currently in a moderate La Nina with a monthly reading in region 3.4(the official ENSO measuring region) of -1.20. However as many have stated including myself, this is not the only thing of concern when looking at a specific ENSO state. Something else worth noting is the base of the ENSO, whether it be east-based, central based, basin-wide or some kind of mix of these. Currently though per the monthly readings we would be considered in an east to possibly central based moderate-strong La Nina with the coldest waters in the month of August in region 1+2(the furthest east region in the equatorial Pacific) with an official monthly reading from CPC of -1.53, followed by region 3.4(the western of the two central regions) with a reading of -1.20, then followed by region 3(the eastern of the two central regions) with a monthly reading of -1.09, and lastly is region 4(the furthest west region) with a monthly reading of -0.98. Therefore overall, if you were to consider all the different regions; we could be considered in a basin-wide moderate La Nina right now based on the latest monthly numbers. However over the past few weeks, some interesting things have started to occur over the equatorial Pacific, but to keep it short, the latest weekly readings on all four region were greater or equal to an anomaly of -1.40, with region 1+2 and still the coldest at -1.9, region 3.4 and region 3 at -1.5 and region 4 staying steady at -1.4, which therefore means that current conditions across the equatorial Pacific suggestthat we are now in a strong La Nina, but these conditions will need to persist for a few more weeks in order to be reflected that way in the monthly numbers, which I basically can expect, at least for the next few weeks likely. Now in terms of where I expect this La Nina to go from here, it gets a little tricky particularly from November onwards due to the likely evolvement of certain indices(either going positive potentially or negative), as well as the uncertainty present in some of the forecast models for the ENSO. Overall based on current and expected conditions I would expect this La Nina to peak sometime between the October-December monthly numbers and with a peak monthly reading in region 3.4 of between -1.5 to -1.9 likely, which would therefore mean that unofficially this La Nina should peak in strong status per the monthly numbers; unofficially because the trimonthly numbers are the “official” representation of the ENSO state/ONI, which could be very close to being in strong status as I expect the peak in the ONI/trimonthly readings to be between -1.2 to -1.8 likely either in the October, November December trimonthly or the November, December, January trimonthly. Now on to something trickier to forecast, in which I mentioned earlier in this forecast; the base of the La Nina. As stated earlier we are currently in an east-central based moderate-strong La Nina per the monthlies, and current weekly conditions suggest we are in an east-based strong La Nina, with a moderate-strong basin-wide La Nina. It is very tough to say at the moment how conditions will evolve, particularly in regions 1+2 and 3(the easternmost regions) which have made a surprise “comeback” so far this month, in terms of competing with regions 3.4 and 4 for the top spot as the coldest region compared to normal. This was not really expected by many (myself as well), however I think that both regions 1+2 and 3 could slowly start to warm back up again, but not by much possibly over the next couple months which leads to then the possibility of a basin-wide moderate-strong La Nina by the winter time, slowly trending to a moderate La Nina by the end of winter likely. It is too uncertain to say right now, so I will not go out and say either way for the base of this La Nina as I think it is possible we could either have basin-wide moderate-strong La Nina conditions for the winter, or possibly slightly west-based(biased) moderate-strong La Nina conditions for the winter time-period. I will have much more though on the base of the La Nina in my final forecast .Anyways, at which ever state, whenever this La Nina peaks and which ever base it takes for the winter it should likely steadily but yet gradually weaken throughout the winter, and I think that it is possible we see a return to neutral conditions across the equatorial Pacific by the northern hemispheric mid to late-spring or summer 2011. Either way, basically from December through until March across the eastern 1/3 or so of North America should feel the effects of a moderate-strong La Nina with likely more moderate La Nina conditions occurring in the months of December and March with more strong La Nina conditions occurring likely in January and likely moderate-strong La Nina conditions occurring in February (for the most part). I will have much more on the ENSO, and likely a much better handle on things as it is possible that by the time I issue my final forecast the La Nina may have already peaked.
As I said before, I’d rather not make this forecast 5 pages long, so as far as the other indices are concerned, I will leave my thoughts on that for my final winter forecast, as not only will that be a more detailed winter forecast, but also I will likely have a much better idea on all the indices, particularly ones such as the PNA, EPO, AO, NAO, etc. However, just to clarify my current thoughts on certain indices and so people see what my maps contain and can figure out how these indices create our weather patterns across North America:
AO: On average for the winter, I would expect the AO to be slightly negative (but not as negative as it was last winter at times), and I think that it is quite possible that the AO goes positive at times, particularly in January and maybe occasionally in February as well, but a +AO would likely be more probable in January this winter.
NAO: On average for the winter, I would expect the NAO to generally be slightly negative as well as the AO(partly due to their fairly strong correlation with each other particularly in the winter, and also due to the “long-term” –NAO pattern we are currently in), but I think that possibly more +NAO time-periods are possible than +AO periods, however again I would expect the most of the +NAO conditions to occur in the month of January and possibly into February as well.
AMO: On average for the winter I would expect a generally positive AMO, which would then definitely aid in keeping the NAO for the most part negative due to their negative correlation, however times of –AMO could be possible as well.
QBO: On average for the winter I would say more positive then negative, if not positive throughout the whole of the winter season.
PNA: On average for the winter, I would expect the PNA to generally be slightly negative due to its fairly strong correlation in the winter time with the PDO, which should/could be quite negative during the winter this year. However I would expect some times of both +PNA are also possible throughout the winter (i.e. some fluctuation could occur throughout the winter with the PNA). also from toronto
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also from over on accuweather
this is temps